Feasibility Study of Anaerobic Digestion and Biogas - Lewis County

manuremanagement.cornell.edu

Feasibility Study of Anaerobic Digestion and Biogas - Lewis County

Feasibility Study of Anaerobic Digestion and Biogas Utilization

Options for the Proposed Lewis County Community Digester

Cooperative Extension

Lewis County

Final Report

June 2010 (updated)

www.manuremanagement.cornell.edu


Feasibility Study of Anaerobic Digestion and Biogas Utilization

Options for the Proposed Lewis County Community Digester

By:

Curt Gooch, P.E. 1 , Senior Extension Associate

Jennifer Pronto 1 , Research Support Specialist

Brent Gloy, Ph.D 2 , Professor

Norm Scott, Ph.D 1 , Professor

Steve McGlynn 1 , Research Support Specialist

Christopher Bentley 1 , Undergraduate Student

1 Biological and Environmental Engineering Department

2 Department of Applied Economics and Management

334 Riley-Robb Hall

Cornell University

Ithaca, New York 14853

June 11, 2010

Updated June 30, 2010


Foreword

The Feasibility Study of Anaerobic Digestion and Biogas Utilization Options for the Proposed Lewis

County Community Digester project is not a feasibility study in its strictest definition, but rather an

assessment of the farm and non-farm biomass resources available in and around the village of Lowville,

an investigation into the available options for co-digesting them (various combinations of materials and

site locations), an estimation of the biogas that could be produced by the various scenarios, the resulting

energy produced, and net energy available for use, and an economic profitability assessment for each of

the options investigated. The scope of work for this project was somewhat dynamic as adjustments

were continually made based on progress of evaluating the information at hand. This report was

written to provide the findings and recommendations of the feasibility study to the client, the Lowville

Digester Workgroup, and also to serve as an educational tool for the stakeholders of this and future

proposed centralized anaerobic digester projects.

The proposed Lewis County Community Digester project exemplifies the full potential of a centralized

anaerobic digester. Manure and, waste biomass materials (processing byproducts from multiple

sources), are mixed together and heated to produce biogas; a locally generated, clean burning,

renewable energy. Waste biomass is generated daily by food processing plants and restaurants, public

facilities and institutions such as schools and hospitals, and at private residences. Co-digesting manure

and these materials reduces the burden on landfills and reduces greenhouse gas (GHG) emissions. The

U.S. dairy industry has formally committed to reducing its GHG emissions by 25% by 2020 and this

project is an example of how this can be effectively accomplished, from a technical/applied perspective.

In fact, the Lewis County Community Digester project demonstrates the vision behind “Dairyville 2020”

– the Innovation Center for U.S. Dairy’s Dairy Power Initiative flagship project. The major shortcomings

at this point are high capital costs and less than required energy purchase prices needed to make such

systems economically feasible.


Acknowledgements

This document is the culmination of a team effort by the authors and many others who provided their

assistance and support. The authors wish to acknowledge and thank the following individuals/groups

for their contributions:

Senator Joseph Griffo, 47 th District in New York State, for funding this project and for his continued

interest.

The dairy farmers of Lewis County who completed the farm surveys.

Representatives for the non-farm biomass suppliers who completed the non-farm surveys.

Drs. Dave C. Ludington and Michael B. Timmons, Professor Emeritus and Professor, respectively, of

Biological and Environmental Engineering at Cornell University for their efforts in reviewing drafts of the

feasibility study and for their constructive inputs and suggestions.

Members of the Lowville Digester Workgroup for their confidence in the Cornell team to provide a

feasibility study that would contain unbiased information and for their teamwork and collaboration

while the feasibility study was being conducted.

Ms. Christine Ashdown (Cornell Office of Sponsored Programs) for her timely efforts in developing the

contract for this project and for her continued support to funded project opportunities pursued by

members of the Cornell PRO-DAIRY program.

Ms. Michele Ledoux (Cornell Cooperative Extension – Lewis County) for her trust in the Cornell team

and for her work in securing the funding and performing contract administration tasks that resulted in a

workable means to performing this work.

Ms. Norma McDonald (North American Sales Manager, Organic Waste Systems, Inc.) for providing key

information on energy crop digesters suitable for U.S. applications needed to perform the annual

economic profitability analysis for the energy crop digester scenarios investigated.


Mr. Todd Vernon (Senior Sales Manager, GE Energy – Jenbacher) for providing key information on the

Jenbacher engine-generator sets needed to perform the annual economic profitability analysis.

Mr. Frans Vokey (Cornell Cooperative Extension – Lewis County) for his overall leadership of the

Lowville Digester Workgroup and Cornell collaboration, and for all of his efforts in planning and running

project meetings.

Mary Beth Anderson (community resident) for her assistance in collecting samples from non-farm

biomass suppliers and for work on distributing and collecting non-farm biomass surveys.

Mike Durant (Soil and Water Conservation District) for designing the project map.


Table of Contents

Foreword

Acknowledgements

Table of Contents

Table of Figures

Table of Tables

Abbreviations and Acronyms

Executive Summary p. 1

Introduction p. 15

Chapter 1. Basics of Centralized Dairy Manure-based Anaerobic Digestion, Biogas Utilization, p. 23

and Nutrient Recovery Systems

Chapter 2. Literature Review of Centralized AD Projects p. 39

Chapter 3. Farm and Community Biomass Survey p. 49

Chapter 4. Biomass Sample Collection and Analysis p. 61

Chapter 5. Biomass Transportation p. 71

Chapter 6. Preliminary Investigation of Five AD Scenarios p. 77

Chapter 7. Final AD Scenario Selection and Details p. 93

Chapter 8. Next Steps and Recommendations p. 115

References p. 117

Appendix

A. Glossary of terms p. 121

B. Farm-based Survey p. 127

C. Non Farm-Based Survey p. 131

D. Substrate Sampling Report p. 133

E. Biochemical Methane Potential; Laboratory Procedure p. 137

F. Projected Farm Survey Responses p. 139


Table of Figures

Figure 1. New York State map showing location of project-site ................................................................. 16

Figure 2. Typical CAD system process flow diagram ................................................................................... 23

Figure 3. A CAD in Jutland, Denmark .......................................................................................................... 24

Figure 4. Danish above-grade complete mix vertical digesters in background .......................................... 29

Figure 5. Thermal to electric conversion efficiency of six NYS on-farm engine-generator sets. (Source:

Gooch, Pronto, Ludington, Unpublished, 2010) ......................................................................................... 32

Figure 6. Basic process flow diagram for advanced biogas clean-up for biomethane production. ........... 34

Figure 7. Advanced digestate treatment to segregate and concentrate nitrogen, phosphorus, and

potassium. ................................................................................................................................................... 38

Figure 8. Landfill tipping fees ($/ton) by region of the U.S. (Repa, 2005) .................................................. 47

Figure 9. Landfill tipping fees ($/ton), developed from Figure 8 (Repa, 2005). ......................................... 47

Figure 10. Lowville regional map with collaborating dairy farms superimposed along concentric circles of

various radii centered on downtown Lowville............................................................................................ 54

Figure 11. Quantity (millions lbs/yr.) of substrates (wet weight). ............................................................. 57

Figure 12. Biochemical Methane Potential (BMP) data (cumulative biogas yield) for substrate 4. ........... 62

Figure 13. Graphical representation of biochemical methane potentials for all substrates tested. .......... 63

Figure 14. Estimated annual minimum, maximum, and average methane production by substrate. ....... 66

Figure 15. Estimated aggregated annual minimum, maximum, and average methane production of nonfarm

biomass substrates and manure. ....................................................................................................... 66

Figure 16. Nutrient concentrations for pre- and post-digestion conditions for N, P, K.............................. 70

Figure 17. Diagram of estimating a break-even tipping fee for non-farm biomass substrate suppliers. ... 75

Figure 18. CAD Site 1 for Scenario Nos. 1 and 2. ........................................................................................ 78

Figure 19. Remote AD Site 2 for Scenario Nos. 3, 3a, and 3b. .................................................................... 79

Figure 20. Remote AD Site 3 for Scenario Nos. 3, 3a, and 3b. .................................................................... 80

Figure 21. Process flow diagram for Scenario No. 1 using the average annual total volume of the seven

non-farm biomass substrates. .................................................................................................................... 81

Figure 22. Process flow diagram for Scenario No. 2 using the average annual total volume of the three

non-farm biomass substrates. .................................................................................................................... 83

Figure 23. Process flow diagrams for Scenario No. 3 using the average annual total volume of the three

non-farm biomass substrates for Site 2 and Site 3. All manure and digestate are trucked. ..................... 85

Figure 24. Process flow diagram for Scenario No. 3a using the average annual total volume of three nonfarm

biomass substrates for Site 2 and Site 3. Manure and digestate are pumped and trucked. ............ 87

Figure 25. Process flow diagram for Scenario No. 3b using the average annual total volume of three nonfarm

biomass substrates for Site 2 and Site 3. ........................................................................................... 89

Figure 26. Final Scenario No. 2 process flow diagram. ............................................................................... 94

Figure 27. Energy crop anaerobic digester process flow diagram. ............................................................. 94

Figure 28. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received,

by farm. ....................................................................................................................................................... 96

Figure 29. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received,

by farm, taking into account each farm's nutrient balance situation....................................................... 112

Figure 30. Image of residential food waste sample collected. ................................................................. 134

Figure 31. Meat and butcher waste from substrate number 4. ............................................................... 135

Page


Table of Tables

Table 1. Typical fuel-to-power efficiency values (adapted and updated from Wright, 2001). .................. 33

Table 2. St.Albans/Swanton, VT project statistics ...................................................................................... 39

Table 3. LREC project statistics ................................................................................................................... 41

Table 4. Dane County, WI (Waunakee cluster) project statistics ............................................................... 42

Table 5. Cornell project statistics ................................................................................................................ 43

Table 6. York, NY project statistics .............................................................................................................. 43

Table 7. Salem, NY project statistics ........................................................................................................... 44

Table 8. Perry, NY project statistics ............................................................................................................ 45

Table 9. Port of Tillamook project statistics................................................................................................ 46

Table 10. Summary of current (2009) farm survey data ............................................................................. 51

Table 11. Summary of nutrient balance information as provided in farm surveys ................................... 53

Table 12. Summary of non-farm biomass survey results............................................................................ 56

Table 13. Select Lewis County crop farm data ............................................................................................ 58

Table 14. BMP analysis results for all substrates tested ............................................................................. 63

Table 15. Biogas production potential of non-farm biomass substrates and manure ............................... 65

Table 16. Potential biogas production of available energy crop acreage ................................................... 65

Table 17. CES lab results for each non-farm biomass substrate: nutrients ................................................ 67

Table 18. CES lab results for each non-farm biomass substrate: solids...................................................... 67

Table 19. Estimated annual mass of nitrogen series for raw AD feedstock .............................................. 68

Table 20. Estimated annual mass of phosphorus and potassium series for raw AD feedstock ................ 68

Table 21. Predicted annual mass of nitrogen for post-digested AD feedstock ......................................... 69

Table 22. Predicted annual mass of phosphorus and potassium for post-digested AD feedstock ........... 70

Table 23. Capital and annual cost estimates for a project-owned trucking fleet ....................................... 72

Table 24. Contracted trucking fleet example schedule .............................................................................. 73

Table 25. Scenario No. 3a means of manure and digestate transport ....................................................... 87

Table 26. Comparison of the five AD scenarios .......................................................................................... 91

Table 27. Scenario No. 2 participating farms and associated manure generation ..................................... 94

Table 28. Scenario No. 2 feedstock volumes .............................................................................................. 97

Table 29. Potential methane and biogas production volumes for each feedstock in Scenario No. 2 CAD 98

Table 30. Capital costs ($) for Scenario No. 2 CAD system, engine-generator set, and biogas clean-up

system, and totals for two different energy sale options ............................................................... 101

Table 31. Annualized capital costs ($) for the Scenario No. 2 CAD system based on minimum, maximum,

and average biogas production quantities...................................................................................... 102

Table 32. Scenario No. 2 CAD, annual operating and maintenance expenses ($) .................................... 103

Table 33. Scenario No. 2 CAD, total annual costs ($) ................................................................................ 103

Table 34. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various biomethane sale prices

and biogas production volumes (no tipping fees received) ............................................................ 104

Table 35. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various electrical energy sale

prices and biogas production volumes (no tipping fees received) ................................................. 104

Table 36. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various biomethane sale prices

and biogas production volumes, including current tipping fee paid by substrate supplier #8 ...... 105

Table 37. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various electrical energy sale

prices and biogas production volumes, including current tipping fee paid by substrate supplier #8

......................................................................................................................................................... 105

Page


Table 38. Scenario No. 2 CAD net annual economic profitability ($) 2 for various biomethane sale prices

and tipping fee revenues ................................................................................................................ 106

Table 39. Scenario No. 2 CAD, net annual economic profitability ($) 2 for various electrical energy sale

prices and tipping fee revenues ...................................................................................................... 106

Table 40. Annualized capital costs ($) for energy crop digester system .................................................. 108

Table 41. Net annual economic profitability ($) for various electricity prices and feedstock costs ......... 109

Table 42. Capital cost estimate for construction of on-farm short-term manure storage per farm ........ 111

Table 43. Scenario No. 2 CAD nitrogen series annual masses by feedstock source and totals ................ 111

Table 44. Scenario No. 2 CAD phosphorus and potassium series masses by feedstock source and totals

......................................................................................................................................................... 111

Table 45. Farm survey responses based on projections for two years ..................................................... 139

Table 46. Farm survey responses based on five year projections ............................................................ 140


Abbreviations and Acronyms

AD

BMP (1)

BMP (2)

Btu

CAD

CAFO

cfm

CCE-LC

CIP

CMMP

CNMP

CBM

CH 4

CHP

CNG

CO 2

COD

Decatherm

ESP

FOG

ft 3

gal

GE

GHG

GWh

GWP

gpm

H 2

H 2 S

HRT

kg

kW

kWh

L

LCE

LWWTP

Lb(s)

LNG

m 3

mmscf

MW

MWh

N 2

N 2 O

NH 3

Anaerobic digestion

Best Management Practice

Biochemical Methane Potential

British thermal unit (mmBtu = 1 x 10 6 Btu), (TBtu = 1 x 10 12 Btu)

Centralized anaerobic digester

Concentrated Animal Feeding Operation

Cubic feet per minute

Cornell Cooperative Extension of Lewis Count

Clean-in place wastewater

Cornell Manure Management Program

Comprehensive Nutrient Management Plan

Compressed biomethane

Methane

Combined heat and power

Compressed natural gas

Carbon dioxide

Chemical oxygen demand

= 1 million Btu

Electrical service provider

Fats, oils, and greases

Cubic foot

US gallon (3.8 liters)

General Electric Company

Greenhouse gas

Giga-Watt hours

Global Warming Potential

Gallons per minute

Hydrogen

Hydrogen sulfide

Hydraulic retention time

Kilogram

Kilowatt

Kilowatt-hour

Liter

Lactating cow equivalent

Lowville Wastewater Treatment Plant

US pound

Liquefied natural gas

Cubic meter

Million standard cubic feet

Megawatt

Mega-Watt hours

Nitrogen

Nitrous oxide

Ammonia


NPK

NRCS

NYS

OLR

O&M

PPA

REC

RNG

STP

TSS

SCFM

SLDM

SLS

SPDES

VFA

VS

VSS

yd 3

Nitrogen, phosphorus and potassium content of fertilizer/organic matter

Natural Resources Conservation Service

New York State

Organic loading rate

Operations and maintenance

Power Purchase Agreement

Renewable energy credit

Renewable natural gas

Standard Temperature and Pressure

Total suspended solids

Standard cubic feet per minute (adjusted for temperature and pressure)

Sand-Laden Dairy Manure

Solid-liquid separator

State Pollutant Discharge Elimination System

Volatile fatty acids

Volatile solids

Volatile suspended solids

Cubic yard


Executive Summary

The region surrounding Lowville, New York has multiple existing large scale renewable energy systems,

including wind and hydro-power. In the spirit of broadening the area’s renewable energy systems,

members of the Lowville Digester Work Group (comprised of representatives from Cornell Cooperative

Extension of Lewis County (CCE-LC), Kraft® Foods, Lewis County Economic Development Office,

residents, dairy farmer representatives, Lewis County Farm Bureau, and the Soil and Water Conservation

District) desire to develop a locally-owned and operated biomass-based renewable energy system. The

energy produced would stay local and the system would provide direct benefits to Lewis County

farmers, businesses, and residents. This desire prompted an investigation of anaerobic digestion

technology and its application in a centralized anaerobic digester (CAD) system that would use both

farm and non-farm biomass feedstock sources as input materials.

The Lowville Digester Work Group, in June of 2009, commissioned Cornell University (Ithaca, New York)

to conduct this feasibility study through funding provided by Senator Joseph Griffo of the 47 th District in

New York State. Cornell worked closely with the Lowville Digester Work Group to develop the feasibility

study scope of work and key parts of its implementation.

The scope of the feasibility study consisted of multiple biomass related components including: resource

assessments, sampling and laboratory analyses (biochemical methane potential and nutrient

concentration investigation), methane production estimations and trucking analyses. The scope of work

also included biogas to energy conversion quantifications, digester site option investigations, and

economic profitability analyses. The major findings pertinent to each of these areas investigated are

provided below; the report contains additional information and details.

Biomass Resource Assessment

Many potential sources of farm and non-farm biomass in and around Lowville were initially identified by

members of CCE-LC. Project specific surveys, one for use in assessing the dairy farms and one for

assessing the non-farm biomass sources, were developed by Cornell University and CCE-LC. Identified

farms were surveyed by members of CCE-LC while non-farm biomass sources were surveyed by the

Lewis County Economic Development office.

1


The farm survey results revealed that there are 25 dairy farms (herd size ranges from 62 to 787 cows)

within an 18-mile radius of downtown Lowville with a total of 5,327 lactating cow equivalents (LCEs). All

of these farms have long-term manure storages (6-month or longer), and use organic bedding material

to bed their cow stalls. Five of the farms reported they have excess organic nutrients (nitrogen,

phosphorus, and potassium), while nine farms indicated that they are nutrient deficient, and 11 are in

balance. An opportunity exists for this project to help farms better manage their nutrients and lessen

the need to purchase commercial fertilizers. The survey responses also showed that the number of LCEs

would increase by approximately 675 cows over two years, and then by 150 more cows after five years.

It should be noted that the actual change in cow numbers in the future (increase or decrease) will be

driven primarily by dairy farm profitability.

The non-farm survey results revealed there are 11 potential sources of biomass (local food processors,

food vendors and residents were surveyed) in the local area that could be aggregated and co-digested

with manure. The minimum estimated useable quantity of substrates from the six non-farm biomass

sources with the highest volumes, was 110 million lbs/year, and the maximum quantity of useable

substrate was 160 million lbs/year. Two of the potential sources (whey mixed with CIP water and postdigested

sludge) provide the bulk (largest volume) of the non-farm biomass available for digestion.

Initial survey results prompted investigation into additional sources of biomass for co-digestion to

further increase potential biogas production. This included manure from sand-bedded dairy farms,

which was ruled not to be an option at this time due to the small farm sizes and comparatively large

capital equipment cost to effectively separate bedding sand from manure. Potential biomass sources

from Fort Drum, a nearby United States Army base, Reed Canary grass from fallow ground along the

Black and Beaver Rivers, and sludge from the Lowville Wastewater Treatment plant (LWWTP) were also

considered and investigated but due to availability, harvesting, and handling issues, all were deemed not

feasible for inclusion at this time, and therefore were not included in further analysis.

Energy crops (corn silage and haylage) fed directly to an energy crop digester were also considered. Two

farms, one north of Lowville and the other south of Lowville, that are currently solely cash crop farms

were included, but kept separate, in the overall analysis.

2


Biomass Sampling and Laboratory Analysis

Based on the information available from the 10 completed non-farm biomass surveys 1 , the decision was

made to obtain samples from five of the 10 potential feedstock sources, with one source having two

different materials analyzed, for a total of six potential feedstock materials analyzed. These included

waste grease, meat processing by-products, mixed food scraps, post-digested sludge, and diluted whey.

Sub-samples of the collected materials were analyzed in triplicate at the Cornell Agricultural Waste

Management Laboratory to quantify the biogas and methane (CH 4 ) produced by these materials, on a

unit basis. As expected, the laboratory results showed that the waste grease material produced the

highest unit yield (363 L CH 4 /kg raw substrate 2 ) and the diluted whey the least (2 L CH 4 /kg raw

substrate 2 ). Sub-samples were also analyzed at an EPA certified laboratory, to quantify their nutrient

composition.

Biogas and methane production estimates for dairy manure were obtained from previous work

conducted at the Cornell Agricultural Waste Management Laboratory where several manure samples

had previously been obtained from commercial New York State dairy farms and analyzed using the same

procedure (Labatut and Scott, 2008).

Methane Production Estimation

The methane (CH 4 ) production for dairy manure and each identified non-farm biomass substrate was

estimated by multiplying the methane production (on a unit mass basis) by the annual estimated

biomass quantity provided in each of the completed surveys. Using this approach, the estimated

minimum annual methane production was 10 thousand ft 3 CH 4 /yr for waste grease (due to its

comparative low quantity available) and the maximum was 157 million ft 3 CH 4 /year for manure (due to

the comparatively high quantity available).

Energy crop methane production estimates were developed using typical yields (wet tons/acre) for corn,

grass, and alfalfa silage for Lewis County, applied to the cropland currently farmed by the two

potentially collaborating cash crop farmers (2,000 and 400 acres). Total biomass yields were multiplied

by unit methane yields for each crop; overall, the estimated annual methane yield from the energy crop

digester was 97 million ft 3 CH 4 /year.

1 Substrate supplier #11 was not initially surveyed; it was discovered subsequent to the conclusion of the survey period.

2 Expressed on a wet weight basis

3


Energy Potential Quantification

Assuming that manure from 15 selected farms 3 and the three non-farm biomass substrates with the

highest volumes are co-digested, and using the average estimated gross and parasitic electrical energy

values, the resulting potential net electrical energy available from the CAD facility would be

approximately 8,880 MWh/year. Assuming a typical residence uses 7,250-kWh/year, approximately

1,225 homes could be powered by the CAD facility. If all net energy available were used for biomethane

sale, the CAD facility would be capable of producing 80,800 million Btu’s, which would have a residential

value (at a price of $13.81/1,000 ft 3 natural gas) of $1,115,900.

Trucking Analysis

The proposed project would encompass facilitating the transport of raw manure to the centralized

anaerobic digester (CAD) facility (30 million gallons per year), and CAD effluent (42-48 million gallons per

year), back to the collaborating farms at no cost to the collaborating farms. The CAD effluent is a higher

volume than the manure proportion of the influent due to the inclusion of non-farm biomass substrates

at the CAD facility, which would be transported to the CAD by each substrate supplier at their cost. Two

options for the transport of manure and CAD effluent were analyzed; initiating a project-owned trucking

fleet, or contracting with an existing trucking company. A 6,000-gallon manure tanker truck was

assumed for all trucking-related analyses.

The analysis of a project-owned trucking fleet, with an estimated initial capital cost of $1.5 million and

estimated annual expenses of more than $420,000, was deemed not economically feasible at this time.

Contracting with an existing trucking company is the recommended option to pursue in order to simplify

the overall CAD facility start-up by lessening the capital cost and reducing the risks. Although this option

entails higher annual costs, (estimated to be $1.3 million dollars in total annual expense), the projectrun

fleet is a possibility to pursue at any time following project start-up.

3 These 15 farms referred to are the selected farms under Scenario No. 2

4


Digester Site/Configuration Scenarios Investigated

Five different digester site/configuration scenarios were initially analyzed and presented, along with

other interim project findings, to the Lowville Digester Work Group at a December 2009 meeting. The

five scenarios explored were:


Scenario No. 1: Co-digest manure from all (25 farms) dairy farms surveyed, and seven (out

of 11 total) non-farm biomass substrates at a central location adjacent to the LWWTP.

This option makes use of all manure and most non-farm biomass substrates discovered by

the completed surveys.


Scenario No. 2: Co-digest manure from 14 dairy farms, and three non-farm biomass

substrates at a central location adjacent to the LWWTP. This option was explored to

reduce trucking costs by reducing the number of collaborating farms.


Scenario No. 3: Co-digest manure from only 12 dairy farms, and one non-farm biomass

substrate at one of two remote sites, and co-digest manure from four dairy farms and two

non-farm biomass substrates at a second remote site. This option was explored to

determine the impacts of having multiple, smaller, regional digesters to further reduce

trucking costs.


Scenario No. 3a: Identical to Scenario No. 3, except that 33% of the manure would be

piped to each remote digester site, and the remainder would be trucked. This option was

also pursued to determine impacts on trucking costs.


Scenario No. 3b: Identical to Scenario No. 3, but includes 400 acres of energy crops

digested at one remote site and 2,000 acres of energy crops digested at the second

remote site. This option was explored to investigate the impacts of including an energy

crop digester on overall biogas production and profitability.

The Lowville Digester Work Group chose Scenario No. 2 CAD, as described above, for complete

investigation at the December, 2009 meeting, and it was decided that one additional farm would be

included in the scenario before performing an economic profitability analysis.

5


The remainder of the Executive Summary provides details and the results of a complete analysis

performed for the Scenario No. 2 CAD, and since the Lowville Work Group also requested a detailed

analysis of an energy crop digester co-located with the Scenario No. 2 CAD manure and non-farm

biomass digester, this information is also provided below.

Scenario No. 2 CAD System Overview

The estimated annual average volume of non-farm biomass substrates available for co-digestion by

three local suppliers was 16 million gallons per year (range 13 to 19 million gallons per year) and the

manure volume available from the 15 targeted collaborating farms was 30 million gallons per year.

Therefore, the CAD should be sized to handle at least on average 122,400 gallons of influent per day.

Using a digester hydraulic retention time of 22.5 4 days, the digester treatment volume needed was

calculated to be 2.8 million gallons. A digester configuration of one or multiple tanks can be used to

accomplish this overall size requirement. The average estimated capital cost for a complete mix digester

system of this size was $5.89 million (range $4.73 to $7.14 million).

The annual cost to transport manure to the CAD site (adjacent to the existing LWWTP) and digester

effluent back to the collaborating farms was estimated to be on average $1.12 million annually (range

$1.07 million to $ 1.17 million). It was assumed that the trucking cost for the non-farm biomass material

to the CAD site would be paid by the substrate suppliers, as is currently the case.

The average estimated gross volume of biogas produced was 188 million ft 3 /year (range 140 million to

237 million ft 3 /year). Using a biogas methane concentration of 60%, the annual estimated volume of

methane produced was 113 million ft 3 /year (range 84 million to 142 million ft 3 /year).

4 22.5 days is the average of 20 and 25 days, which are common retention times for similarly sized systems

6


Two of the most commonly implemented biogas utilization options were investigated:

1) Use biogas to fuel a reciprocating engine-generator set 5

2) Sell cleaned biogas as renewable natural gas, biomethane, by first removing

impurities (carbon dioxide, hydrogen sulfide, and moisture) using pressure-swing

adsorption gas clean-up technology 6 .

For option 1, it was assumed that thermal energy harvested from the engine-generator set would be

used to meet all of the digester heating requirements (warming the CAD influent to target operating

temperature and then maintaining it); field experience has shown that this is an appropriate assumption

to make. For option 2, it was assumed that 20 percent of the biogas produced by the digester would be

needed to meet this demand; this assumption needs to be confirmed, based on information about the

design of each digester system considered, specifically, how well the vessel is insulated and the

exposure it has to winter wind and temperature. The overall estimated annual parasitic heating

requirement was 20,200 million Btu’s per year (range 15,000 to 25,500 million Btu’s per year). Using the

average estimated parasitic heating requirement, the annual cost to provide this heat ranged from

$81,000 to $282,000 per year for a natural gas purchase price range of $4 to $14 per decatherm,

respectively.

For parasitic electrical requirements, for both biogas utilization options, the average estimated parasitic

electrical energy requirement of the CAD system was determined the same way. Calculations were

performed using data from vendor information obtained for other similar sized systems to determine

the electrical energy requirement per gallon of influent material; the results were that the average

electrical energy requirement was found to be 0.0313 kWh per gallon of influent 7 (range 0.0121 to

0.0505 kWh per gallon of influent). Applying these energy values to the CAD system, the estimated

average annual parasitic electrical energy requirement was 1,400,000 kWh per year (range 540,000 to

2,257,000 kWh per year). Using the average estimated parasitic energy requirement, the estimated

annual cost to provide this energy ranged from $112,000 to $252,000 for an electrical energy purchase

price range of $0.08 to $0.18 per kWh, respectively.

5 Other, less commonly used methods exist for converting biogas to electrical energy (e.g. microturbines)

6 Other methods are available for scrubbing biogas to make biomethane (e.g. membrane separation, regenerative amine wash)

7 Influent is defined as the biomass on the in-flow side of a treatment, storage, or transfer device

7


Nutrient Management Implications

Assuming the non-farm biomass imported for co-digestion supplies excess nutrients to the postdigestion

product that would be available for sale to area crop farms, the project could potentially

receive $226,000/year in total revenue. Of the $226,000/year, $86,000/year would be derived from the

sale of nitrogen, $121,000/year would be derived from the sale of phosphorus, and $19,000/year would

be derived from the sale of potassium.

Economic Profitability Analysis- Scenario No. 2 CAD

A net annual economic profitability analysis was performed for the Scenario No. 2 CAD to determine if

this scenario was economically viable considering the options of: 1) selling electrical energy at a price

range of $0.08 to $0.18 per kWh, or 2) selling biomethane (cleaned biogas) at a price range of $4 to $14

per decatherm. For both of these options, separate net annual economic profitability analyses were

performed, which included a tipping fee equal to the tipping fee being paid by one of the three nonfarm

biomass suppliers whose substrate was selected for co-digestion (the other two tipping fees were

not provided by the completed surveys).

For all of the analyses, the cost of capital (discount rate) used was 5%, the economic life of the digester

was 20 years, and the replacement cycle of the engine-generator set was 10 years. Trucking costs to

haul manure to the CAD site and effluent to collaborating farms was included as an annual cost. Other

annual costs included operation and maintenance of (1) the CAD system (based on data obtained from

vendor quotes for other similar systems), (2) the engine-generator set ($0.018 per kWh) and (3) the

biogas clean up system.

The results of the net annual economic analysis showed that for all energy sale options investigated it

was more costly to own and operate the system each year, than the system would receive in revenue

annually. In other words, no option was found to be economically profitable.

Based on these results, a final net annual economic profitability analysis was conducted to determine

the tipping fees needed for the two energy sale options investigated to result in a Scenario No. 2 CAD

financially break-even situation. For the option of selling electrical energy at a price ranging from $0.08

to $0.18 per kWh, the break-even tipping fee range was determined to be $21 to $9 per ton,

8


espectively. For the option of selling biomethane at a price range of $4 to $14 per decatherm, the

break-even tipping fee range was determined to be $29 to $16 per ton, respectively.

The calculated break-even tipping fee ranges were substantially below the average tipping fee of over

$70 per ton currently charged by landfills for the northeastern U.S., but somewhat higher than the

calculated tipping fee currently being paid by the non-farm biomass supplier considered for this

project with the most biomass available annually.

Energy Crop AD System Overview

The proposed Lowville energy crop digester is an anaerobic digester designed to process high solids

energy crop materials (corn silage and/or haylage). Such digesters are widely used in Germany and

other European countries and produce about eight times the biogas as digesters fed manure only

(Effenberger, 2006).

Silage corn and grass hay would be harvested and ensiled as if they were going to be fed to dairy cattle.

Sufficient quantities would be stored to enable the energy crop digester feed hopper (usually a walking

floor bin) to be filled once-a-day, year round, normally with a pay loader. Several times per day, the

control system would automatically transfer a portion of the feedstock into the digester; screw

conveyors (augers) are normally used due to the high solids content of corn silage and haylage.

The energy crop digester economic analysis performed for this feasibility study used “in-the-bunk” silage

prices ranging from $30 to $55/ton, meaning that the costs to grow and harvest the crops and ensile

and store them are covered by the purchase price.

In addition to the energy crop feedstock, a small portion of manure is also normally added to the energy

crop digester, about 10 percent by weight, to help stabilize digester pH and to provide some dilution

water to lessen the power required to provide in-vessel mixing.

Energy crop digester effluent, laden with organic nutrients, is the consistency of digested manure. For

this feasibility study, it is assumed the effluent would be stored on-site for a short period of time and

periodically trucked to the energy crop source farms for longer-term storage and for subsequent use as

fertilizer to grow the next rotation of energy crops. Some of the surplus nutrients from the Lowville CAD

9


system could also be trucked to the collaborating farms to meet the overall fertilizer requirements for

the crops grown on those farms.

Economic Profitability Analysis - Energy Crop AD System

The same net annual economic profitability analysis was performed for the energy crop AD system. For

this analysis, the only energy sale option investigated was the sale of electrical energy 8 , using a sale price

range of $0.08 to $0.18 per kWh with varying feedstock (fermented corn silage and haylage) prices

between $30 and $55 per wet ton.

Again, the cost of capital (discount rate) used was 5 percent, the economic life of the digester was 20

years, and the replacement cycle of the engine-generator set was 10 years. Trucking costs to haul

digester effluent to collaborating farms was included as an annual cost, as it would be paid by the

project. Other annual costs included operation and maintenance of: (1) the CAD system (based on data

obtained from industry vendors), (2) the engine-generator set ($0.018 per kWh) and (3) biogas clean up

system.

The results of the net annual economic analysis showed that for all digester feedstock and energy sale

price options investigated it was more costly to own and operate the system each year than the

system would receive in revenues annually. This is the same result that was found for the Scenario No.

2 CAD options investigated.

Recommendations and Future Work

The recommendation for a CAD system is based on conducting thorough and complete technical and

economic feasibility analyses, as well as the vision of the Lowville Digester Work Group. Based on this,

the recommendation is to further investigate one centrally-located complete mix AD, sited adjacent to

the LWWTP that would co-digest manure from 15 targeted collaborating dairy farms and targeted nonfarm

biomass substrates (currently the following three substrates: whey, post-digested sludge, and

glycerin) that are by-products generated nearby.

8 Biogas clean-up to biomethane was not investigated, since economic profitability analysis results for the Scenario No. 2 CAD

showed little difference in the bottom line when compared to electrical energy sales.

10


The future net annual economic profitability behind this recommendation is encouraging, given that, (1)

the calculated tipping fee needed for the system to break-even is well below the average tipping fee

charged in the northeastern U.S. and many predict regulations will be instituted in the near future

restricting the land-filling of organic matter, (2) future regulations aimed at reducing the impact of fossilfuel

derived energy (specifically GHG emissions and climate change) would likely positively impact

renewable energy projects, (3) energy produced from such projects would have less price volatility than

fossil fuel-based energy products, and (4) the annual economic profitability will improve with reductions

in capital cost by receiving grants and/or premium payments for renewable energy.

If future efforts are put forth to further investigate one CAD, it is recommended that the two major

areas provided below be addressed in the order presented below and that the bullet items under each

be included.

A. Address Economic Barriers to Project Implementation








Identify other potential sources of non-farm biomass that are currently being landfilled

or otherwise disposed of that could be received by the CAD with a tipping fee

paid by the supplier.

Continue the education and outreach efforts concerning this project and the goals and

objectives of local community members, targeted at collaborating and noncollaborating

dairy farmers and non-farm biomass substrate suppliers to develop

project support targeted towards securing public funding.

Secure grant funding or subsidies that could help offset the capital cost of the CAD

and/or supplement the revenue(s) received for system outputs (raw biogas,

electricity, biomethane, and/or organic nutrients).

Validate the trucking analysis and farm biomass pick-up options determined under

this effort.

Investigate the willingness of non-farm biomass suppliers to enter into reasonable

long-term contracts , with a negotiated tipping fee.

Investigate the willingness of the end user(s) of the net energy produced by the CAD

facility to enter into reasonable long-term contracts.

Explore the potential for selling raw biogas to a local end user.

11


Investigate the possibility of the sale of CAD surplus heat combined with woody

biomass heat to local industry or the community (district heating).

B. Advanced Project Due Diligence














Perform more complete laboratory testing of the targeted substrates mixed

proportionally with manure to better solidify the quantity of biogas that would be

produced by the system.

Perform a value engineering/economic analysis that includes looking at the digester

treatment volume vs. biogas production potential.

Conduct an in-depth site and environmental impact assessment for the targeted

construction site.

Investigate the legal issues for various digester ownership options.

Determine the permit(s) that will be required by the New York State Department of

Environmental Conversation (NYSDEC) 9 .

Conduct an in-depth investigation into the site improvements that will be required at

each farm in order to participate in the project, and develop an associated budget.

Investigate contracting with an existing trucking company to provide transportation of

farm biomass.

Assess renewable energy credits (RECs) and carbon credits as applied to centralized

digesters.

Conduct a net energy analysis for the proposed system.

Develop a request for proposals (RFP) package to be distributed to AD system

designers.

Validate the economic profitability analysis using the results of the proposed RFP.

Continue investigation into future opportunities, such as manure nutrient extraction

equipment and resulting product marketing opportunities for organic nitrogen,

phosphorus, and potassium.

Continue assessment of alternative biogas market opportunities such as the sale of

biomethane as a vehicle fuel.

9 There are currently no operating dairy manure-based CAD systems in NYS, and an initial inquiry made by Cornell to NYSDEC on

behalf of this project revealed that NYSDEC is not readily prepared to state what permit(s) is/are needed.

12


Nomenclature

Effort was made to make terminology throughout this report consistent to allow for a more clear

understanding of the information presented. Please refer to this list as necessary.

Centralized Anaerobic Digester (CAD) facility

Energy crops

Feedstock

Lewis County Community AD project

Lowville Digester Work Group

Manure

Methane production potential

Non-farm biomass substrates

Non-farm biomass substrate suppliers

The term used to describe the proposed manure

and substrate co-digestion AD system, and all of

the integrated components.

Field crops grown specifically as a feedstock source

for an energy crop AD system

Describes the entire influent to the CAD

The name of the proposed project

The local volunteer group of decision-making

stakeholders on behalf of the project

Effluent from a dairy housing barn made up of cow

urine and feces, bedding, and other minor

components such as gravel, undigested feed,

and/or milking system gray water.

Quantification of a biomass substrate to produce

methane

Organic by-product material from local processors

of farm products; otherwise referred to as food

waste

Local food processors and vendors who have,

upon initial survey, shown interest in supplying

organic material for co-digestion; otherwise known

as food waste sources

13


Introduction

The proposed Lewis County community anaerobic digester (AD) project (see Figure 1) was initiated in

early 2008. Cornell University was contracted to perform a feasibility study of the proposed project in

May 2009, with a targeted completion of December 2009. Three interim project meetings were held by

the Cornell team to present interim project findings and assess progress in October and December, 2009

and March, 2010. After some changes in scope of the project, the final feasibility report was completed

in May 2010.

Lowville goals and objectives

Interest in a community AD from several Lewis County, NY constituents grew from the initial set of goals

developed from multiple community viewpoints. The Lowville Digester Work Group was formed from a

group of local stakeholders interested in determining the application of anaerobic digestion technology

to meet the goals set forth, and to oversee development of the proposed project. The following are the

initial project goals developed by the Lowville Digester Work Group (committee document, 2008):

Goals for the community:




Encourage continued economic growth

Lessen the negative impact of farms on county residents (e.g., farm-based odor)

Reduce the environmental footprint

Goals for the region’s dairy industry:




Provide greater flexibility in manure handling and nutrient management that results in an

economic advantage versus today

Reduce odor associated with manure storage and land application

Allow a greater number of animals per unit of land area with less environmental risk

Goals for local industry:


Gain access to sustainable energy at lower (versus today) cost.

15


Figure 1. New York State map showing location of project-site

Scope of Work

The following questions were posed in the scope of work document developed prior to the beginning of

the feasibility study, and used throughout the study by Cornell University and the Lowville Digester

Work Group to guide the project.

Biomass

1) What is the annual on-farm (manure) and Village of Lowville non-farm biomass potentially

available for anaerobic digestion, by source

2) How much biomass can be secured, by source

3) How many farms are currently prepared (on an infrastructure basis) to store raw manure

short- term and digester effluent long-term

4) What infrastructure upgrades are needed for those farms not currently prepared to store

raw manure short-term and/or digester effluent long-term

Biomass/biogas transportation

5) What options exist for transporting manure from the farms to the digester location(s) and

digestate back to the farms and what is the estimated cost associated with this

16


6) What options exist for transporting non-farm biomass to the digester location(s) and what

is the estimated cost associated with this

7) What are the results of an economic sensitivity analysis on biomass transportation cost

8) What is the feasibility of transporting biogas or biomethane (processed biogas) to a

utilization site

Anaerobic digestion

9) What are the AD technology options available

10) Which option is best suited for the application

11) What are the estimated capital and operating and maintenance costs associated with the

AD and associated equipment

12) Is it best to truck all biomass destined for digestion to one site or to have an array of

digesters strategically located within the county

Biogas/energy conversion

13) How much biogas can potentially be produced with the secured biomass

14) Is biogas clean-up required and if so what option is best

15) How much energy can be extracted from the biogas

16) What are the results of a sensitivity analysis performed on the sale price for the energy

Nutrients

17) What is the expected nutrient value of the manure once digested (tons total-N, ammonia-

N, total-P, ortho-P, and potassium)

18) What is the anticipated increase in digester effluent volume and nutrient composition

with the importation of securable non-farm biomass sources

Impacts on the community

19) How many truck loads of manure will be transported to the digester site(s) per day

20) What labor force is anticipated to operate the overall facility

17


Economics

21) What is the estimated total annual cost for various digester/biogas utilization scenarios

Designated responsibilities

In addition to the questions set forth in the scope of work, the same document designated which tasks

each group involved in the project would be responsible for. It was decided that the Cornell Manure

Management Program Team (CMMPT) would provide leadership and overall project coordination to

facilitate the completion of the feasibility study. CMMPT developed and maintained a project schedule

identifying specific tasks, responsible parties and targeted completion dates. Specific responsibilities are

outlined below.


CMMPT

o

Deliverables: CMMPT will complete and provide the following items to Cornell

Cooperative Extension of Lewis County:

• Initial Findings (written report and oral presentation)

• Interim Report (written report and oral presentation)

• Final Report (written report and oral presentation)

o

The work tasks and components of the feasibility study include:

• Gather information from existing centrally located community ADs or

completed feasibility studies that are relevant.

• Develop a survey for completion by select dairy farms within Lewis County

• Develop a survey to all potential substrate suppliers within Lewis County

• Aggregate and analyze results of the above surveys

• Perform all calculations required to answer the questions outlined above

• Prepare all reports and make oral presentations


Lewis County Cornell Cooperative Extension (CCE)

o

o

Identify farms within a specified radius of possible digester site(s)

Implement the farm survey and provide reports/summaries to CMMPT

18


o

Organize project meetings


Lewis County Soil and Water Conservation District (SWCD)

o

o

Using data provided by the Cornell Cooperative Extension, create a map identifying all

potential participating dairy farms within the selected radius of the Village of Lowville

Wastewater Treatment Plant (LWWTP) and other potential digester sites. Incorporate

information on road infrastructure into map so that feasible transportation routes can

be considered.

Using data provided by the Cornell Cooperative Extension, create a map identifying all

potential substrate suppliers within the selected radii of the LWWTP and other

potential digester sites.


Village of Lowville

o

o

Implement a survey to quantify all potential non-farm biomass substrates within Lewis

County

Provide completed surveys and results to CMMPT for analysis and use


Lowville Digester Work Group

o

o

o

Assist with the identification of potential sites for the proposed central AD

Assist in identifying potential buyers of final products

Inform community about the project and generate support

Project approach

Cornell University, in agreeing to perform the feasibility study for the Lewis County community AD,

responded to the Lowville Digester Work Group’s request with the following plan of action:

Develop a plan of necessary work to be accomplished on the local level

Aggregate and analyze results of local work

Calculate total quantity and characteristics of digester inputs

o

Farm

19


o

o

Kraft

Other

Assist local creation of a map of cooperating farms and other biomass sources

Calculate costs and feasibility of farm-based biomass transportation

Measure biogas producing potential of assumed substrate inputs and calculate projected

biogas production

Review biogas clean up options

o

o

o

Cost

Scale

Availability

Determine the best use of biogas produced

o

Generation of electricity

• Cost of interconnection

• Sale to grid or private

o

Sale of cleaned biogas

• Sale to Kraft

• Sale to community

• Sale of energy back to farms

• Used to power vehicles/farm trucks

o

o

Market price of each option

Cost of implementing each option

Analyze all final products from digester and determine marketability

o

Solids

• Bio-security issues

20


o

o

o

o

o

o

Heat

Electricity

Nutrient-laden liquid effluent

Compost

Other

Determine revenue from each potential sale

Devise a strategy to return organic material/nutrients to farms

o

o

o

Solids and/or liquids

Transportation

Delivery infrastructure feasibility on a farm level

Overall cost benefit analysis for project

Formulate questions for Lewis working group before proceeding, based on initial findings

Incorporate new visions to final recommendation

Develop a mid-study interim report

Develop a final feasibility study report

21


Chapter 1. Basics of Centralized Dairy Manure-Based Anaerobic

Digestion, Biogas Utilization, and Nutrient Recovery Systems

A centralized dairy manure-based anaerobic digestion and biogas utilization system is one where dairy

manure, the system’s stable feedstock, is aggregated from multiple farms, blended together, and codigested

in a heated vessel for 15 to sometimes more than 30 days. In many cases, non-farm biomass

substrates such as food processing and bio-fuel processing by-products, organic industrial wastes, and

culled and leftover human foods are co-digested with dairy manure. Digestate (digester effluent) is

generally stored short-term on-site at the centralized facility, and then transported back to source farms

for storage until it is used to replenish cropland with nutrients (nitrogen (N), phosphorus (P), and

potassium (K)) and organic matter. Digestate can be further treated, as described later in this chapter,

to achieve various undigested fiber recovery and nutrient conservation and management goals and

objectives. A typical process flow diagram for a centralized digestion system is shown in Figure 2.

Figure 2. Typical CAD system process flow diagram

Centralized digesters are best located where they are strategically placed to minimize transportation of

manure and non-farm biomass substrates and to maximize output energy and digestate utilization. CAD

23


can effectively improve fertilization of cropland by returning CAD effluent to a strategically located site

at the farm, for ease of use in spreading on cropland.

Centralized digestion systems are common-place in Denmark and other European countries; a

centralized digester in Jutland, Denmark is shown in Figure 3.

Figure 3. A CAD in Jutland, Denmark

Overall, centralized digestion of manure provides the opportunity for economies of scale to come into

play that generally cannot happen on individual farms. The capital and operating costs per unit of

influent treated (i.e., cents per gallon) is generally less in larger systems than smaller systems. Another

reason centralized digestion is given due consideration is that it is likely to have the size needed to

justify and pay for a full-time crew to operate the facility. Further, centralized digestion provides the

opportunity for more efficient use of organic nutrients by the collaborating farmers. Digestate can be

sampled more frequently than on-farm, thus better quantifying the nutrients sent back to each

collaborating farm. Also, anaerobic digestion provides a steady and consistent material that is well

suited for secondary or tertiary treatments that can include enhanced nutrient management by

farmers.

24


A common concern with centralized anaerobic systems is biosecurity (disease control). Commingling

of source farm manure and non-farm biomasses is part of the centralized digestion model that

cannot be avoided. Farmers can be especially concerned about biosecurity since manure that may

contain infectious disease causing organisms can be brought onto their farms. However, the risk of

this is lessened when manure is digested; further risk reductions occur when influent or digestate is

pasteurized before being returned to the farm.

Additional information about dairy manure-based centralized digestion systems is provided in this

chapter with the goal of preparing the reader for the following chapters where the work and feasibility

study findings are presented. More in-depth information about on-farm and centralized anaerobic

digestion can be obtained by reviewing the references cited herein.

Centralized digester feedstock materials

Centralized digesters are generally fed two or more of the three different types of biomass materials.

The three types are categorized based on availability, specifically those that are:




Continuously available such as manure, certain food processing wastes like whey, etc.

or at least almost continuously (e.g. some slaughterhouse waste sources)

Seasonally available such as grape puree, onion tops, carrot skins, etc.

Available year-round but not consistently such as processed foods that have exceeded

their shelf life

Manure

For most centralized digestion systems, manure is the stable feedstock material. Not only is it

continuously produced by dairy cattle, it also provides a key role in co-digestion with other, more

biologically convertible materials as it moderates pH due to its buffering capacity.

The average U.S. dairy cow produces 150 lbs. of raw manure per day that contains 20 lbs. of total

solids (TS), 17 lbs. of volatile solids (VS), 1 lb. of (N), 0.17 lbs. of (P), and 0.23 lbs. of (K) per day while

a dry cow and a replacement (heifer) produces measurably less (ASABE, 2005). A portion of the

manure VS are biologically converted to biogas. Digestion of raw manure from a dairy cow produces

on average, 80 ft 3 biogas per cow-day (Ludington, 2008).

25


Non-farm biomass sources

Any biomass can be digested. Digestion of various biomass materials is largely a function of materials

handling (conveying material from storage into a digester), biodegradability, maintaining a balanced

state within the digester vessel, and economics. Many of the suppliers of non-farm biomass substrates

available for anaerobic digestion currently pay significant tipping fees to the local landfill authority in

order to dispose of their unwanted processing by-products.

In New York State, many farmers are interested in mixing non-farm biomass substrates with manure

due to:

1. The increased biogas production potential the mixture produces

2. The associated tipping fees for allowing substrate suppliers to unload their by-product

on the farm.

Non-farm biomass can have lower solids content than raw manure, so when combined with manure

the resulting mixture needs to be mixed within the digester to keep the solids in suspension.

Some materials, like fats, oils, and greases readily break down in an AD while others like corn silage take

much longer to fully do so. Many non-farm biomass substrates have the potential to produce several

orders of magnitude of biogas per unit of influent mass compared to manure. An example of biogas

production from co-digesting manure with food wastes is between 368 and 560 ft 3 biogas per cowday,

as found on one New York State dairy farm (Gooch et al., 2007).

Like manure, non-farm biomass generally contains measurable levels of nutrients (N, P, and K) that

must be considered when assessing the impact centralized digestion will have on a collaborating

farm’s ability to comply with their Comprehensive Nutrient Management Plan (CNMP).

A centralized anaerobic digester (CAD) that looks to co-digest measurable volumes of non-farm

biomass substrates needs to have reasonable assurance that these are available and securable by

long-term contract or are able to be replaced with alternate biomass sources. This is important

because the capital cost of the centralized digester will be directly affected by the volume of nonfarm

biomass sources digested and the associated biogas production potential.

26


Anaerobic Digestion

Direct environmental benefits of an anaerobic digestion system include conservation and phase

transformation of manure nutrients (N), (P), and (K) during digestion resulting in an effluent rich in

organic, crop available-nutrients needed to grow feed for livestock and people alike. Since the digestion

process significantly reduces odors associated with untreated biomass stored long-term, digestate can

more effectively be used to fertilize crops. This reduces the need to purchase synthetic fertilizers that

require large amounts of fossil fuels to produce, thus reducing the greenhouse gas (GHG) emissions

associated with crop production. Improvements in water quality are also associated with less use of

synthetic fertilizers.

Anaerobic digesters can be thought of as an extension of a cow’s stomach. Both rely on operative

microbes that flourish in the absence of oxygen to transform foodstuff into useable energy. Operative

microbes are most successful at doing this when they are consistently fed a diet that meets their

nutritional needs and the digester temperature and pH are maintained at target values.

The anaerobic digestion process overall involves three groups of anaerobic microbes. First, hydrolytic

bacteria initiate a process called hydrolysis. These bacteria use extra cellular enzymes to convert

organic insoluble fibrous material into soluble material; however, inorganic solids and hard-to-digest

organic material are not able to be converted.

Next, acid forming bacteria convert the soluble carbohydrates, fats, and proteins to short-chained

organic acids. The acids produced in step two become the food source for the methanogens, which

produce methane gas in the third step.

Various methanogenic species grow in different temperature regimes.

1. Psychrophilic methanogens grow in the lowest of the temperature ranges, less than 68°F.

Methanogens in this range grow slowest and produce the least biogas per unit of time.

Covered lagoon systems, especially those in northern climates, will be in this range much

of the year (Wright, 2001).

27


2. Mesophilic methanogens grow in an optimum temperature of about 100°F which is the

most common operational temperature for digesters in the U.S.

3. Thermophilic methanogens grow in an optimum temperature of about 130°F. The higher

operating temperature increases the rate of biomass degradation, increases pathogen

reduction, and allows for shorter retention times thus reducing the capital cost of the

digester vessel.

Digester Types

In the U.S. there are basically three different types of anaerobic digestion systems used today to process

dairy manure. They are: plug-flow, complete mix, and covered lagoon. Of these three, a complete mix

system is the system of choice for use in a centralized digester because the likelihood of co-digestion of

dairy manure with non-farm biomasses is very high. (Digester influent concentrations less than 10

percent total solids are common when co-digesting manure with most food processing by-products

and require mixing to minimize solids settling.)

Complete mix digesters can be either horizontal flow or vertical flow systems. Each is briefly discussed

below.

Complete Mix Digester, Horizontal Flow System

Horizontal-mix digesters incorporate agitation systems in digester vessels. The mixing system is

mainly utilized in scenarios that have influent total solid concentrations greater than 12 percent (not

common with dairy manure-based systems) or less than 10 percent.

Complete Mix Digester, Vertical System

Vertical mixed digester tanks can be either below-grade (atypical) or above-grade (typical) as shown

in Figure 4. Cast-in-place concrete, welded steel, bolted stainless steel, and bolted glass-lined steel

panels are all used to construct vertical tanks.

The mixing process is achieved by various methods, depending on the preference of the system

designer and the overall goals of the system. In one method, an external electrical motor (about 10-

20-Hp) turns a vertical shaft, concentric with the digester tank, which has several large paddles

28


attached. The shaft speed is about 20 RPMs. This system is common for solid top tanks.

Another method uses submersed impeller agitators each driven by either an electrical motor or a

centrally located hydraulic motor. These systems have a much higher blade speed, perhaps 1,750

RPMs, and can be used with both flexible top and solid top applications. One clear advantage of the

first method is the electrical motor is easy to service and replace.

Vertical tanks are insulated during the construction process to reduce the maintenance heating

requirement (heat to maintain digester operating temperature). Significant heat can be lost from

vertical tank digesters if they are not properly insulated. Applicable insulation options are to spray

the tank with foam insulation or to use rigid board insulation attached to the tank and then covered

with metal cladding.

Figure 4. Danish above-grade complete mix vertical digesters in background

Biogas

Anaerobic digestion produces a continuous supply of biogas in quantities sufficient to not only power

the digestion plant but also to utilize the excess in various ways. Producing electricity and/or thermal

29


heat from biogas results in a net reduction of greenhouse gases (GHG). Anaerobic digestion of dairy

manure also mitigates methane emissions otherwise caused by traditional manure handling and storage

practices.

Production of biogas is dependent mainly on the digester hydraulic retention time (HRT), digester

operating temperature, and the biochemical energy potential of the influent. Higher biomass

conversion efficiencies by thermophilic (~135°F) methanogens allow for shorter hydraulic retention

times and consequently reduced capital costs as compared to mesophilic (~100°F) systems. Biochemical

energy of an influent material is most accurately evaluated by conducting long-term (6-month) benchtop

reactor tests (Angenent, 2009) but is generally estimated by measuring the VS content in the

influent. Biochemical methane trials can also be conducted in the laboratory to estimate the biogas

production potential of a biomass sample. Jewell (2007) reported that an appropriate estimation of the

methane (CH 4 ) production is to use a value of 0.5 L CH 4 /gram of VS degraded. If the dry biogas is 60

percent CH 4 this is equivalent to 13.4 ft 3 biogas/lb. of VS degraded.

Composition and energy value

On-farm digester monitoring has shown that biogas is comprised mainly of ~60% methane and ~40%

carbon dioxide (CO 2 ), with trace levels of 0.2 to 0.4 percent hydrogen sulfide (H 2 S). Even though H 2 S

concentrations are low, biogas is highly corrosive and prudence is needed to avoid pre-mature biogas

transport and utilization equipment failures.

Pure (dry) methane has a low heating value of 896 Btu/ft 3 (at standard temperature and pressure: 68°F

and 1 atm) (Marks, 1978). Since biogas is only ~60% methane, its heating value is ~40% lower or about

540 Btu/ft 3 . Raw biogas is considered to be saturated with water vapor.

Utilization: fuel source for engine-generator sets

Using biogas as an energy source to fuel on-site engine-generator set(s) is the most common use of

biogas today. Large engines that had been adopted for landfill biogas years ago are now widely

available for use at centralized digestion sites. Most are spark-ignited systems with a few compression

ignited systems that also use about 10 percent diesel fuel concurrently as a fuel source.

30


Overall, these “low Btu or dirty gas” engines work well with the exception of difficulties arising from

hydrogen sulfide (H 2 S). Hydrogen sulfide is very corrosive at low temperatures since it converts to

sulfuric acid. To date, most on-farm biogas-fired engines combat the corrosiveness by running the

engine nearly continuously (keeps the temperature high) and changing oil more frequently than for

cleaner fuel source scenarios.

Recently, some U.S. farmers have implemented methods to reduce H 2 S concentrations from biogas prior

to utilization. Methods include chemical reaction and biological reduction systems. Scrubbers are

mainstream equipment on European digester systems.

Overall, there are two basic types of generators:

1. Induction generators run off the signal from the utility and are used to allow parallel hook

up with the utility. Induction generators cannot be used as a source of on-farm backup

power since the system needs the signal from the utility line to operate properly.

2. Synchronous generators could be run independently of the utility but matching the

utilities power signal would be very difficult so these types of generators would be used if

the system were not connected to the utility grid.

Most generator systems manufactured today have controls that will allow the engine-generator set to

synchronize with the utility’s electrical frequency and still operate in island mode when there is a

disruption of the grid power. These systems can be set up to “black start” if desired.

Thermal-to-electrical conversion efficiencies for biogas-fired internal combustion engine-generator sets

are less than desirable, but are about the same as other fuels. On-farm digester monitoring has shown

that the conversion efficiency ranged from 22 to 28 percent, as shown in Figure 5.

The electricity production depends on the amount and quality of gas as well as the efficiency of the

engine-generator. Typically, 33-38 kWh/day will be produced per 1,000 ft 3 /day of biogas produced

(Koelsch et al., undated and EPA, 1997). Some engine-generator set manufacturers show biogas-toelectrical

energy conversion efficiencies as high as 42% in their advertisement literature. As with all

31


large capital purchases, careful evaluation of those systems is needed to ensure they are economically

feasible.

As already mentioned, engine water jacket heat, and sometimes exhaust heat as well, is harvested and

used as the primary means to heat the digester. In the winter, most if not all of this harvested heat is

needed, while in the summer a good portion of it is dumped to the ambient via forced-air/water heat

exchanger.

Figure 5. Thermal to electric conversion efficiency of six NYS on-farm engine-generator sets.

(Source: Gooch, Pronto, Ludington, Unpublished, 2010)

Utilization: fuel source for microturbines

Two New York State dairy farms have microturbines in operation to power generators to produce

electricity. The main interest in microturbines is the premise that they require less maintenance on a

daily basis and also on a long-term basis, and most recently that they potentially produce less exhaust

emissions. Biogas pressure needs to be increased from typical digester pressure values to about 60 psi

before being injected into a microturbine. Corrosion-resistant small-scale compressors are available to

compress raw biogas to this pressure thus lessening the need for an H 2 S scrubber.

The typical fuel-to-power efficiencies of various biogas utilization options are shown in Table 1. These

efficiency figures do not account for increases due to the use of co-generated heat.

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Table 1. Typical fuel-to-power efficiency values (adapted and updated from Wright, 2001).

Prime Mover Type

Efficiency

Spark ignition engine 18-42%

Compression ignition

engine (Diesel)

30-35% above 1 MW

25-30% below 1 MW

Gas turbine

18-40% above 10 MW

Microturbine

25-35% below 1 MW

One source states the operation and maintenance cost of $0.015 per kWh are estimated for enginegenerators

(EPA, 1997). On-going engine-generator set service contracts are offered by one company

that sells them for $0.015 to $0.02 per kWh produced depending on the pre-existing maintenance

performed on the set and presence of an H 2 S scrubber.

Utilization: fuel source for boilers

On-farm biogas utilization by a boiler is the second most popular use of the energy. Natural gas boilers

can be modified to use biogas as a fuel source. The main modification involves increasing the pipe

delivery size and orifices in the burners to accommodate the lower density fuel. Decreasing the

concentration of H 2 S in the biogas can extend the life of the boiler equipment. Boilers are mainly used

to provide primary or secondary heating of the digester and in some cases also to provide domestic

heating of farm offices and lounge areas. One farm used boiler heat to heat a calf barn, but this use is

limited.

Utilization: fuel source for other uses

Raw biogas can also be used as a fuel source for drying equipment such as grain dryers, separated

manure solids dryers, evaporators, etc. Other possible uses fall under the category of those needing

fully cleaned (scrubbed) biogas, commonly known as “biomethane”. These possible uses include any

that currently use natural gas (almost pure methane) and as a vehicle fuel. There are two primary

methods to process biogas into biomethane. They are: 1) chemical and, 2) physical removal of

impurities (CO 2 , H 2 S, and water vapor). Details of these processes are beyond the scope of this report

but the general flow process diagram is shown in Figure 6.

33


Figure 6. Basic process flow diagram for advanced biogas clean-up for biomethane production.

Advanced Centralized Digester Information

Specific information on a CAD system is presented below.

System electrical demand

Modern CADs require electrical energy to operate with the highest electrical demand normally

associated with the pumps and agitation equipment. The electrical energy used to operate a system

is known as parasitic electrical energy. With all centralized digester systems it is important to

implement a design that is energy efficient. Electrical energy efficiency can be expressed in various

ways including as a function of the: 1) influent volume (annual kWh/annual influent), 2) vessel

treatment volume (annual kWh/tank size), and 3) energy production (kWh consumed/kWh

produced). All systems that are not electrically efficient result in reduced sale of electrical power

and/or increased purchase of electrical energy from the utility.

System thermal (heat) demand

Anaerobic digesters require a controlled heating system for operation. There are two different heat

demands in most systems; they are: 1) differential heat, and 2) maintenance heat. Differential heat is

the heat needed to raise the influent temperature to digester target operating temperature and

34


epresents by far the largest heating requirement of the system. Maintenance heat is needed in

most, but not all systems, to maintain digester contents at target operating temperature.

When an engine-generator set is used to convert biogas to electricity, the heat of combustion is

harvested from the engine and used to heat the digester. In this scenario, the heating efficiency of

the digester heating system is less important than if heat is provided by a biogas-fired boiler. Under

the later scenario, a primary goal of the digester system is normally to sell raw or processed biogas

and thus the need exists to minimize the parasitic heating requirement. Installations where heat

sales are important can utilize digester effluent/influent heat exchangers can be used to minimize the

parasitic heating requirement by preheating digester influent.

Biosecurity/disease control

Dairy manure is known to contain various pathogens that survive outside the cow. Not all cows on all

farms have the same contagious pathogens. The centralized digestion model involves commingled

digested manure and non-farm feedstock(s) being returned to the source farms resulting in justified

biosecurity concerns.

The hydraulic retention time (HRT) of complete mix digesters varies at the microscopic level from

manure particle to manure particle. Some manure particles will remain in the digester for greater

than the theoretical HRT while some will short-circuit due to the agitation process and exit sooner.

Data collected from one New York State dairy farm that co-digested dairy manure with several nonfarm

biomass sources using a complete mix digester showed that the average reduction of the

commonly measured fecal coliform (an indicator organism) and Mycobacterium paratuberculosis

(Johne’s disease) was 98.4 and 94.8 percent, respectively (Wright et al., 2003).

In Denmark, mixing of non-farm biomass materials with manure is common practice and when this is

done, the Danish government requires the food waste/manure mixture to be pasteurized (70°C for

one hour) prior to being land applied in order for the farm to be in compliance with standard manure

application laws. Observation has shown that pasteurization normally occurs at the centralized

digester site, prior to digestion.

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Operational considerations

Experience has shown that well-designed centralized digesters can be operated successfully for long

uninterrupted periods of time continuously (24 hours per day, seven days per week, and 365 days per

year) when adequate management and maintenance is provided. Centralized digesters are complex and

involve:




Physical systems including containment vessels and influent /effluent pits

Mechanical systems including pumps, agitators, and sensors

Biological systems including methanogens

The daily success of such a system is deeply rooted in personnel who take “ownership” in the system

and are provided the resources needed to make it successful.

General operational challenges for a CAD system include:


Changes in influent composition; Adding variable qualities or quantities of influent can

allow the acid-forming bacteria to out-produce the methanogens. Acidic conditions can

then develop, compromising the stable environment and production of methanogens.


Foaming; Foaming can occur when rising biogas bubbles do not pop when reaching the

manure/biogas headspace interface in the AD. Foaming can be a major issue when

feedstock composition or feeding rates change, most notably on farms when new corn

silage and/or haylage is fed to cows. Excessive foaming can plug the biogas outlet or enter

the biogas line and gum up pressure regulators or other equipment.


Temperature; Maintaining the temperature of the AD is critical to ensure efficient,

operative microbes and consequently consistent quantity and quality (composition) of

biogas. Attention to design of the digester heating system is important to the success of

the overall system.


Frozen manure; Slushy or frozen manure is common in much of the winter in New York

State. Tremendous energy (about 144 Btu’s/lb) is needed to thaw frozen manure and

then to increase the temperature from 32°F to digester operating temperature (~68

Btu’s/lb manure for a mesophilic digester operating at 100°F). In fact, the requirement

36


can be so high that there is not enough heat to bring the manure up to operating

temperature. With lowered temperatures, biogas production decreases, resulting in even

less heat being available. In a CAD system, frozen manure should not pose any problems,

since the manure must be able to be picked up and transported from the farms to the

CAD, within one day.


Control systems; Automatic controls are essential for continuous performance of a

centralized digester system. Proper control equipment selection will allow the system to

be monitored remotely thus providing the opportunity for employees to have a rotating

schedule of weekends off and being “on call”. The digester should have a preventative

maintenance schedule that includes monitoring equipment that creates input data for the

automated control system.


Safety; Centralized digester employees and managers need to be properly trained for the

safety hazards present in the system. There are safety issues of asphyxiation, fire, and

explosion associated with the production of biogas. Methane can explode when mixed

with air in concentrations of 5 to 15% and a fire hazard exists when there are leaks

present in biogas containment materials. Dangerous levels of ammonia and hydrogen

sulfide may also be present. The same hazards associated with large engines and

electrical generation equipment are also present in these systems.

Digestate nutrient recovery

As previously mentioned, anaerobic digestion provides excellent pre-treatment for subsequent

processes to separate and concentrate N, P and K as shown in Figure 7. A centralized anaerobic digester

system can provide more economies of scale thus presenting increased opportunity to do this over

individual farm-based anaerobic digesters.

Separating nutrients into concentrated materials can provide farmers more flexibility in selecting

nutrients that are needed for specific crops and soil conditions. This will further the environmental

benefit of the project by providing such fertilizers in a form that the farmer can more efficiently apply to

cropland and result in higher crop utilization and less environmental impact. Higher application

efficiencies can be obtained by way of 1) reduced trips to the field, thus decreasing the time required to

37


apply organic fertilizer to cropland, and 2) increased timeliness of application resulting in reduced

nutrient loss to the environment.

Figure 7. Advanced digestate treatment to segregate and concentrate nitrogen, phosphorus, and potassium.

Technologies originally developed for treating municipal wastewater are readily available for

removing excessive phosphorous from manure (and a manure- non-farm biomass blend), but the

economics of the implementation of such systems on-farm are not well established.

38


Chapter 2. Literature Review of Centralized AD Projects

A literature review was conducted to assess and identify centralized (AD) feasibility studies for projects

of similar scope as the proposed Lewis County project. There are a number of existing studies that have

been performed to assess the feasibility of large-scale AD projects; a synopsis of the eight most relevant

reports is presented below. The values presented in this chapter for energy production, cow numbers,

and economics, among others, were taken directly from the feasibility reports and were not verified by

those reviewing them. Some of the values taken from these studies do not follow the logic used to

develop these same values throughout the remainder of this report.

St. Albans/Swanton, Vermont Cooperative Dairy Manure Management Project

The St. Albans/Swanton, Vermont area has a high concentration of dairy farms, and was also the site of

Vermont’s Northwest State Correctional Facility. These key considerations, in addition to environmental

concerns such as a need to improve manure-based odors and reduce nutrient run-off (namely

phosphorous reduction) prompted an investigation into the feasibility of a centralized anaerobic

digestion system (Bennett, 2003). This project has not yet been initiated; the results of the feasibility

study have been circulated for additional input. Basic statistics determined in the feasibility study are

included in Table 2.

Table 2. St. Albans/Swanton, VT project statistics

Proposed input material quantity

Proposed number of farms involved

Proposed number of cows involved

Estimated electrical energy production

Estimated capital cost

Expected cash flow

226,000 1 tons dairy manure/year

26 farms

10,200 cows

2,000 kWh/day

$6,000,000 ($581/cow)

+ $0.71/ton of manure

1 this number, taken directly from the report calculates to 121 lbs manure/cow-day, and a value of 150 lbs/cowday

was used for this work done in this feasibility report

This project was initially proposed with a specific end user identified. The nearby Northwest State

Correctional Facility housing 250 inmates, consumed 1.28 million kWh/year of electricity at a cost of

$122,000 per year, and used nearly 11.55 billion ft 3 of natural gas per year. The report states:

“At first glance, the transportation cost exceeds the value of the electricity produced by the

digester. Only when all the benefits and revenues are compared to the expenses can this project

be fully appreciated. Then, the large environmental and public impacts are added to the

electricity, heat, and by-products to make this a compelling project.”

39


The project feasibility study considered four general designs:

One central digester

Three mini-central digesters (each serving between 2,000 to 5,000 cows)

Several local cooperative digesters (for farms with over 300 animal units 10 )

Individual farm digesters

The report advocated one central digester for “best economies of scale and knowledge sharing”, and

because it best fit the needs of the end user in terms of energy usage. Transportation costs were

paramount in making this assessment. The report stated that: “reaching additional farms would involve

dramatic increases in mileage with minimal increases in electricity generated; transportation is a major

on-going expense.” Project trucking requirements estimated nine truck drivers, 6-10 facility personnel,

and 2-3 administrators for a total of 17-22 new jobs created by the project (Bennett, 2003).

Lane Renewable Energy Complex

The Lane Renewable Energy Complex (LREC) was a municipal biogas plant and centralized AD facility

proposed in light of environmental and economic concerns in the Eugene and Springfield, Oregon areas

(Weisman, 2008). The LREC was proposed to be “The United States’ first Kyoto-compliant municipal

biogas power plant and public transportation refueling facility.” In addition to biogas, the AD facility was

proposed to provide organic fertilizer for 200,000 acres throughout Lane County and Oregon. The LREC

project has not yet been implemented; adequate funding is currently being sought.

Pollution in the Willamette River and high fertilizer prices were key concerns to be addressed through

the reduction of runoff from un-incorporated manure. In addition, electricity and a nutrient-laden

fertilizer are claimed to be produced by the AD facility. Basic statistics determined in the feasibility

study are included in Table 3.

10 An ‘animal unit equivalent’ or ‘animal unit’ is generally defined as 1,000 pounds of live animal weight. Note: this is an out of

date method of expressing animal equivalents; for dairy applications, expressing parameters on a lactating cow basis is

appropriate.

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Table 3. LREC project statistics

Proposed input material quantity

400 tons 1 of agricultural waste, food waste (commercial and

residential), and municipal wastewater

Estimated gross biogas production 5.5 million ft 3 biogas/year

Estimated electrical energy production 8,300 kWh/day

Estimated capital cost $256,000,000

Projected O&M costs

$8,400,000/year

Projected annual net revenue $19,500,000

1 No units of time provided in report, i.e. tons/year

The proposed biogas plant would consist of 15 two-stage, 1 million-gallon mesophilic digesters with

slurry recirculation. Biogas would be scrubbed to reduce hydrogen sulfide (H 2 S) and siloxanes (siloxanes

may originate from municipal sources) before being sent by a blower to five Caterpillar 3520 enginegenerator

sets, each with a generating capacity of 1,660-kW, or to a vehicle fuel upgrading system.

The proposed project was planned to be a collaboration between: Lane County, EPA, U.S. Economic

Development Administration, USDA, Oregon Department of Energy, Lane Transit District,

ENERGYneering Solutions Inc., Swedish Biogas International, Union Pacific, Lane Community College,

and the Biogas Institute of the Ministry of Agriculture in Chengdu, Sichuan, People’s Republic of China.

It was anticipated the facility would take 24 months to come online, and it was estimated the project

would create 125 high-quality, full-time positions and 400 construction jobs (Weisman, 2008). The

proposed site for the LREC has several important advantages: it is publicly owned, zoned industrial,

located near a natural gas transmission pipeline, and has an existing 5.5 mile sewage pipeline for

wastewater transfer. The project anticipated receiving $65 million in state and federal grants for the

project.

Dane County, Wisconsin Community Manure Facilities Plan

The feasibility study for the Dane County, Wisconsin project examined two clusters of farms in

Waunakee and Middleton, Wisconsin. Within these clusters, two options were considered: anaerobic

digestion and combustion. The County decided to move forward with plans for the anaerobic digestion

option for the Waunakee cluster (Strand, 2008). Basic statistics determined in the feasibility study for

the Waunakee cluster approach are included in Table 4.

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Table 4. Dane County, WI (Waunakee cluster) project statistics

Proposed input material quantity 152,000 gallons per day

Proposed number of farms involved 5

Proposed number of cows involved 6,000 animal units

Estimated electrical energy production 9,700 kWh/day

Estimated capital cost 1 $6,400,000

Projected O&M costs 1 $1,000,000

Estimated GHG reduction

19,800 TCO 2 e/year

1 Based on the lowest levels of phosphorus removal

The Waunakee cluster included five farms with a total of approximately 6,000 animal units. The farms

were located within approximately one-half mile of each other, with additional farms located nearby.

The main goals of the study were “to strengthen the livestock industry in the county and to protect

water quality as related to manure management.” The scope of the study included a survey of area

farms, identification and selection of farms to be used in the analyses as well as a selection of

management alternatives to be studied, technical and economic analyses of these alternatives, and

discussions of financing methods, non-monetary evaluation, and potential business structures of the

proposed project.

In March 2009, Wisconsin Governor Jim Doyle announced that he would allocate $6.6 million to the

Waunakee area digester and a second digester in Middleton. This is in addition to the $1.2 million

already allocated in the 2009 County budget for construction costs associated with the project.

Additional federal money is currently being sought.

Cornell University’s Proposed Anaerobic Digester

The feasibility study examining an AD facility at Cornell University was completed as part of an

undergraduate class research project examining sustainable development on the Cornell University

campus in Ithaca, New York. This study considered two options for biogas use: introduction to a natural

gas pipeline or use of the biogas to power a hydrogen fuel cell. The report advocates the more

expensive fuel cell option over a natural gas pipeline, for its environmental benefits as well as its

educational opportunities on the Cornell University campus (Casey et al., 2007). “While this project may

represent only a small reduction in Cornell’s actual carbon emissions it provides an important early step

on the long and difficult journey to carbon neutrality,” the report states. Basic project statistics

determined in the feasibility study are included in Table 5.

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Table 5. Cornell project statistics

Proposed input material quantity

Estimated biogas production

Estimated capital cost

6,300 tons organic waste/year, including veterinary school

manure, greenhouse wastes, and dining hall food waste.

1.45 x 10 7 ft 3 biogas/year

$5,500,000 (over 20 years)

Cornell University hired Stearns & Wheler GHD to further develop the findings of the report, and the

firm has published their feasibility study findings in, Cornell University Renewable Bioenergy Initiative

(CURBI) Feasibility Study.

Evaluation of Anaerobic Digestion Options for Groups of Dairy Farms in Upstate New York

This feasibility study assessed the potential viability of constructing a CAD in York, New York in

Livingston County, to serve several small farms in the region. The suggested measures of the study were

never implemented, the reason(s) is not known. Basic project statistics determined in the feasibility

study are included in Table 6.

Table 6. York, NY project statistics

Proposed input material quantity 164,000 tons manure/year

Proposed number of farms involved 16 farms

Proposed number of cows involved 4,700

Estimated electricity production 650 kWh/day

Estimated capital cost $1,550,000

Projected O&M costs

$317,000/year

Projected annual revenue

$235,000/year

While several potential project sizes were examined, the projections above consider 4,700 cows

supplying manure to the CAD, since this resulted in the lowest estimated transportation costs. Breakeven

benefit at 4,700 cows was $150/cow, derived from the sale of post-digestion products. Since the

value of these products per cow ranged from $200 - $400, revenue was estimated to be $50/cow,

assuming the conservative $200 value per cow ($235,000/year profit in 1997) (Jewell et al., 1997).

Effects of economies of scale were examined in this report. “As the dairy size decreased to 600 milk

cows, the net cost of managing manure increased to over $200 per cow per year (net cost or value

equals fertilizer value less the cost of land application),” the report states. The study recommended

construction of a 4,000 - 6,000 - cow facility as a first step in the York, NY area. Initially, stabilized waste

would be returned to farms. The report advocated for efforts that would reclaim other by-products,

such as fiber, in a cost-effective manner. The report projected a total annual value of the recovered

43


fiber for bedding to be $50 - $200/cow-year (Jewell et al., 1997).

Feasibility Study of a Central Anaerobic Digester for Ten Dairy Farms in Salem, NY

A Salem-based dairy farmer group contracted with Stearns & Wheler, LLC, and Dr. Stanley A. Weeks to

conduct a feasibility study for constructing a centralized AD to cost-effectively treat manure from 10

dairy farms in Washington County New York (Bothi and Aldrich, 2005). Basic project statistics

determined in the feasibility study are included in Table 7.

Table 7. Salem, NY project statistics

Proposed input material quantity 113,000 tons dairy manure/year

Proposed number of farms involved 10 farms

Proposed number of cows involved 3,700 cows

Estimated electricity production 6,600 kWh/day

Estimated capital cost $2,105,000

Projected O&M costs

$1,043,000/year

The study considered three design options:

1. Pre-treatment with solid-liquid separation, digestion and separated solids composting

2. Option one with the addition of a centrifuge process to remove additional solids and

nutrients prior to digestion

3. Solid-liquid separation and digestion with no on-site composting

The report recommended option number three, since the per-cow costs were lowest for this option.

Construction of a centralized AD was deemed not economically feasible at the time the report was

written. Trucking costs were a significant component of the total annual cost for all scenarios. Within

each alternative, several options for material transport were examined. The costs of trucking manure

for these scenarios ranged from $384,000/year for one-way trucking (given that the effluent was

pumped off-site to 6-month storage) to $604,000/year for raw manure trucking and effluent trucking

(given 5 days on-site storage) (Bothi and Aldrich, 2005). Furthermore, the potential energy generation

was beyond the electrical needs of the target end-user. Finding a use for the excess power generated

could improve the economic feasibility of this project.

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Feasibility Study of Anaerobic Digestion Options for Perry, New York

The New York State Energy Research and Development Authority (NYSERDA) provided partial funding

for a feasibility study to assess anaerobic digestion potential among four of the larger neighboring dairy

operations in the Town of Perry, Wyoming County, NY. Wyoming County is the largest milk-producing

county in New York State. The four CAFOs involved in the study cited odor reduction as their primary

goal in pursuing an alternative manure management system (CCE, 2002). Basic project statistics

determined in the feasibility study are presented in Table 8.

Table 8. Perry, NY project statistics

Proposed input material quantity 90,400 gallons dairy manure/day

Proposed number of farms involved 4 farms

Proposed number of cows involved 3,804 lactating cow equivalents

Estimated biogas production 323,500 ft 3 biogas/day

Estimated electricity production 519 kW

Estimated capital cost $1,187,000

Projected annual revenue $91,490

The study examined four options: (1) one centralized digester shared by all farms, (2) one digester

shared by two nearby farms, (3) one digester on each farm with collaboration in other ways, such as

through collaborative marketing or joint composting, and (4) collaboration to recruit an independent

business to provide digestion services for farms. The project statistics presented in Table 8 represent

the centralized digestion option considered. The economic analysis for this option was the least

feasible, due to logistical concerns, low energy benefits, and high transportation costs. The report noted

that if electricity could be sold back to the grid as a premium, the economics of the study would change

significantly. The option considering one digester installed on each farm was found to be the most

economically and logistically feasible option at the time of the study. Two digesters were constructed in

2006, one at Sunny Knoll Farm and one at Emerling Dairy (CCE, 2002), and remain operational today.

Feasibility Study for a Port of Tillamook County Dairy Waste Treatment and Methane

Generation Facility

This report was assembled for the Tillamook Methane Energy and Agricultural Development Policy

Committee. In light of the Tillamook Creamery’s capacity to double its cheese production, local dairies

sought to improve manure waste management. Pathogens, water quality issues, and public health

issues resulting from mostly nitrogen-based pollution were cited as important motivators for a

45


eassessment of manure management practices (Edgar, 1991). Basic project statistics are provided in

Table 9.

Table 9. Port of Tillamook project statistics

Proposed input material quantity 57-128 tons dairy manure solids/day

Proposed number of farms involved 191 dairies

Proposed number of cows involved 25,996 cow-units

Estimated electricity production 123,600 kWh/day; 5.15 MW

Estimated capital cost $1,300,532— $5,739, 674

Projected annual O&M $25,558— $1,233,186

Projected annual revenue $52,300

Initial inquiries into accepting sludge from waste treatment plants at both the City of Tillamook and the

Tillamook Creamery found that regulatory complications outweighed the marginal production benefit of

this added waste stream. The report considered several scenarios with varying degrees of three key

variables: percent total solids of the raw waste being hauled (10% or 13%), the extent of manure

collection (50%, 100%), and the percent of the total number of cows’ manure collected (15%, 25%, 50%,

100%, 200%). The report also considered varying scenarios involving one, two, or three digesters.

Ultimately, the best case for net cost was two plants (Edgar, 1991). The facility was ultimately built and

is in operation under the direction of George DeVore at the time of this writing. In 2007, it seemed the

project had transitioned to using heat produced by the system to dry solids and then to sell organic

material (Scott, 2010).

Economic Feasibility Study for a Centralized Digestion System

A web-based model was developed to be used in performing an economic sensitivity analysis for

centralized anaerobic digester projects (Minchoff, 2006). The model found that tipping fees were a

crucial component of overall CAD economic viability.

Average landfill tipping fees ($/ton) for

different regions in the United States are presented in Figure 8, and the data is also presented

graphically in Figure 9. As of the last survey, the Northeast had the highest tipping fees when

compared with the rest of the country, at $70.53/ton (Repa, 2005).

46


Figure 8. Landfill tipping fees ($/ton) by region of the U.S. (Repa, 2005)

Figure 9. Landfill tipping fees ($/ton), developed from Figure 8 (Repa, 2005).

Summary

The centralized digester feasibility studies reviewed were mostly initiated due to local concern over

improved manure management, odor reduction, and/or improved nutrient management. For the

studies that involved co-digestion of dairy manure with non-farm biomass substrates, the amount of

energy produced was higher per dollar of capital investment. While many of the studies were not

deemed economically feasible or were otherwise not implemented, several mentioned that valuation of

environmental benefits could potentially improve the economic outlook for some projects, depending

47


on initial goals of the project. Of the feasibility studies reviewed here to look at the practice and

economics of centralized digestion, the common findings of these feasibility studies were:


Economics: Many of the proposed systems were not found to be economically feasible

at the time the studies were conducted. Manure trucking costs were a prohibitively

large component of the estimated annual operating cost. However, the approaches

taken to analyze transportation expenses generally did not include a line item for

tipping fees received by the digester from non-farm biomass suppliers. Several studies

also found the need to develop a valuation system for benefits that are not readily

perceived, i.e., odor reduction or water quality improvement. Many centralized

digester projects take advantage of additional biomass, beyond manure, for codigestion

which greatly enhances energy production and can usually generate a tipping

fee for the project. Most of the projects described in this chapter were never pursued,

as many sought grant funding to cover capital costs.


Energy production: Most projects reviewed here planned to generate electricity for

sale to, in most cases, one end user/buyer.


Odor: Concern was expressed about the potential for significant odor emissions from

trucking raw manure to the centralized digester site, and the potential of on-site odors

from the centralized digestion facility. Experience has shown that odors associated

with influent materials stored short-term can be mitigated with systems that collect the

off-gases and process them in a bio-filter. Odor reduction was one of the most

common reasons for pursuing centralized AD.


Biosecurity concerns: There is no way to prevent the commingling of sourced manure

and centralized digester effluent needs to be returned to the source farms. Here it is

important to point out that research has shown that anaerobic digestion of dairy

manure significantly reduces viable populations of two tested pathogens that are a

concern for cattle and humans (Wright et al., 2003).

48


Chapter 3. Farm and Community Biomass Survey

The Lowville community AD project was conceived through discussions about what could be done locally

to preserve and preferably to increase the strength of the agriculture industry in Lewis County. A

community manure treatment and processing center was proposed, including an AD centrally located in

Lowville, New York with the goal of providing benefits to three key groups in Lewis County: dairy

farmers, local industry, and residents.

In order to accurately assess the needs of these key groups and to determine the feasibility of meeting

those needs, two surveys were developed by Cornell University’s Manure Management Program and

Cornell Cooperative Extension of Lewis County (CCE-LC).

The dairy farm manure and non-farm biomass surveys served three purposes:

1. Determine the useable quantity, availability, and general composition of existing

biomass (waste) streams

2. Assess the willingness to cooperate among local farmers and businesses

3. Make contacts and compile data for future community involvement

The first survey, distributed by CCE-LC, was a survey of dairy farms that: (1) fell within a 20-mile radius of

Lowville, (2) did not use sand bedding, and (3) had long-term storage. The presence of a long-term

storage at each farm was a key item that was used to select collaborating farms, as farms with a longterm

storage could participate in the project with little additional capital expense.

CCE-LC representatives administered the dairy farm-based surveys by mail in fall 2008. To improve the

response rate, the farm-based surveys were administered again face-to-face in Spring/Summer 2009.

The second survey was a non-farm biomass survey distributed to select local businesses by the Village of

Lowville. Officials from the village of Lowville administered the non-farm surveys in-person in

Spring/Summer 2009. A blank copy of each survey is provided in Appendix B and C.

49


Dairy farm survey

While it was ultimately decided that those farmers who took the time to fill out a survey could be

considered interested or supportive simply because of their decision to participate in the survey, most

of the farmers responded to the “perspective questions” with caution. “If it benefits me,” was a

common reply of the respondents' willingness to provide the proposed CAD project with their manure.

Delivery of nutrient-laden effluent back to each participating farm will likely prove to be an important

determinant of the project’s ultimate success with the farmers. Overall, willingness to cooperate is

heavily dependent on perceived benefits to the farmer.

A summary of the data obtained through the farm survey is shown in Table 10. Information regarding

each farm’s existing manure storage(s), road access, and bedding type(s) is included. Storage, access,

and bedding are all farm characteristics needed to help determine the degree to which a dairy farm

would be able to participate in a community digester project.

50


Table 10. Summary of current (2009) farm survey data

Farm ID

number

Distance

from

center of

Lowville

(miles)

Number

of

mature

cows

Number

of

heifers

Lactating cow

equivalents

(LCE) (total

solids basis) 1

Days of

shortterm

storage

available

Months

of longterm

storage

available

Bedding type

1* 2 200 150 262 3-4 6

Bedded

pack/shavings

2 6 0 150 62 1 6

Chopped

hay/shavings

3 6 66 10 70 1-3 5 chopped hay

4 7 105 75 136 0 7 chopped hay

5 7 420 40 436 0 2

mattresses, hay

shavings

6* 7 85 70 114 1-3 6 chopped hay

7* 8 150 100 191 1 6

mattresses,

sawdust

8 8 80 80 113 0 6 chopped hay

9 8 620 407 787 2 4

sand, chopped

hay

10 9 145 115 192 1-3 6 chopped hay

11 9 190 160 256 0 6 Sawdust

12* 9 195 160 261 1-3 5 sand, sawdust

13 9 155 150 217 1 6 chopped hay

14* 9 175 80 208 0 5 flat hay

15 10 70 30 82 0 6 Hay

16 10 62 62 87 0 4 chopped hay

17 11 80 70 109 3 12

chopped hay

(sawdust)

18* 11 500 150 562 2 24 dust hay

19 11 400 430 576 0 10 Sawdust

20 12 54 36 69 0 6 chopped hay

21 13 91 60 116 0 6 mattresses, hay

22 13 91 60 116 0 6 chopped hay

23 15 130 35 144 0 6 Sawdust

24 15 85 10 89 0 6 Sawdust

25 18 50 60 75 0 16 Hay

SUM 4,199 2,750 5,327

Farms with an asterisk (*) next to their ID number have either gravel, stone, or paved road access. No asterisk indicates the

presence of a dirt road.

All farms in the table have on-farm long-term storage.

1 LCE values were not provided on the surveys, but were calculated using survey data.

51


Using information provided in the American Society of Agricultural and Biological Engineering (ASABE)

Practices Standard (ASABE, 2005) along with information from the farm surveys, estimates were made

of the daily mass of manure production and composition by farm.

In order to account for the fact that dry cows and heifers produce less manure and volatile solids per

day than lactating cows, the manure quantity and composition produced by each animal management

group is expressed on a lactating cow equivalent (LCE) basis. ASABE Standards (ASABE, 2005) were used

to establish the baseline manure and total solids production for each management group and

adjustments were made for the dry cow and heifer management groups in such a way that their manure

production and total solids were expressed on a lactating cow equivalent basis.

The survey inquired not only about the present situation of each farm, but also requested answers to

each of the questions based on projections of two years (2011) and five years (2014). Based on

responses from the 25 farms that completed the survey, the number of LCEs is projected to increase by

675 cows over two years, and 150 more after five years. When considering a project such as a CAD with

a significant project life (in this case 20 years), it is important to consider the availability of all feedstocks

on a long-term basis. The overall dairy population in Lewis County is expected to increase over the next

two to five years (Vokey, 2010). The survey results based on two and five year projections are provided

in Appendix F.

The survey also asked farms to describe their nutrient balance situation; the responses regarding

nutrient balance are provided in Table 11. The responses showed that nine farms lack the three key

nutrients (N, P, and K), eleven farms have a balanced nutrient situation, and five farms have excess of at

least one of the three key nutrients. Farms with a lack of nutrients, for example, would likely be more

interested in the nutrient-laden effluent produced as a by-product of anaerobic digestion. Select survey

results from the 25 dairy farms who responded to the survey are superimposed on a map of Lewis

County, NY and shown in Figure 10.

52


Table 11. Summary of nutrient balance information as provided in farm surveys

Farm ID number Nitrogen (N) Phosphorus (P) Potassium (K)

1 lack lack lack

2 lack lack lack

3 lack lack lack

4 lack lack lack

5 balanced balanced balanced

6 lack lack lack

7 excess excess excess

8 excess excess excess

9 balanced balanced balanced

10 lack lack lack

11 excess excess excess

12 balanced balanced balanced

13 lack lack lack

14 lack lack lack

15 balanced balanced balanced

16 balanced balanced balanced

17 balanced balanced balanced

18 lack lack lack

19 excess excess excess

20 balanced balanced balanced

21 balanced excess balanced

22 balanced balanced balanced

23 balanced balanced balanced

24 excess excess excess

25 balanced balanced balanced

53


Figure 10. Lowville regional map with collaborating dairy farms superimposed along concentric circles of various

radii centered on downtown Lowville.

54


Non-Farm Survey

The non-farm biomass survey asked businesses what type and how much of each waste stream they had

available, and what they currently pay to dispose of it. Also asked in the survey, was how much

contamination (non-biodegradable materials, i.e., plastic forks or aluminum foil) might be found in each

waste stream, which is important to consider when aggregating non-farm biomass for co-digestion.

Eleven local food processors and businesses responded to the survey; however only a few were found to

have a measurable supply of food waste. Results from all eleven respondents are shown in Table 12,

with sources italicized to indicate they were later sampled for laboratory analysis.

A graphical representation of the annual quantity available from select non-farm biomass substrates,

manure from the 25 dairy farms, and manure from the 15 farms selected for the final scenario, is shown

in Figure 11. It is apparent from the figure that the quantity of most of the non-farm biomass substrates

is insignificant when compared to the quantity of manure available. The two non-farm biomass

substrates with the most meaningful quantities are substrates 8 and 10.

55


Table 12. Summary of non-farm biomass survey results

Non-farm

biomass

ID

1

2

Biomass Description

mixed food, milk,

napkins, paper plates,

straws

mixed food, liquid, paper

plates

Quantity

3 yd 3 /day,

September-June

40 gallons

pre-consumer/day,

225 gallons

post-consumer/day

Estimated annual quantity

available (lbs/year)

Minimum

Maximum

Approximate

disposal costs

($/year)

1,009,000 1,009,000 5,000

790,000 806,000 19,400

3 mixed food, oil, grease 25 lbs/day 9,100 9,100 4,100

4 meat, fat, guts

5A

mixed food

800 - 2,000 lbs/week

December-October

1-5 gallons

pre-consumer/day,

5-10 gallons

post-consumer/day

17,000 72,000 N/A

13,200 37,500

4,200

5B waste grease 8 gallons/week 2,200 3,750

6 flowers, stems, petals

7 mixed food

8

9

50 lbs/week, more in

December, February,

May

3 gallons/week, more in

Summer

2,400 2,700 N/A

1,000 1,250 N/A

whey/water

28,800 to 36,000

gallons/day

62,400,000 109,500,000 251,000

Clean in Place (CIP)

Wastewater

14,400 gallons/week 4,400,000 6,200,000 26,000

oil 5 gallons/week 2,000 2,000

vegetables 2 gallons/week 800 800

meat 1 gallons/week 400 400

mixed product 5 gallons/week 2,000 2,000

10 post-digested sludge

11 1 glycerin

5,037,261

gallons/year

150 gallons/day,

5 days/week

2,300

41,900,000 41,900,000 N/A

339,000 409,000 N/A

Totals 110,000,000 160,000,000 $312,000

Italicized sources denote samples tested for biochemical methane potentials

1 The source for non-farm biomass substrate 11 was discovered further along in the project and the information in the table was

provided directly by the substrate supplier

56


Figure 11. Quantity (millions lbs/yr.) of substrates (wet weight).

Additional biomass sources

The lower than expected quantity of manure discovered in the completed dairy farm surveys, prompted

investigation of additional sources of biomass for co-digestion, in order to increase the gas producing

potential of the AD system. Co-digestion with additional non-farm biomass substrates provides more

benefits to project economics than additional dairy manure. The other biomass sources investigated are

outlined below. Currently, non-farm surveys have been distributed to other local businesses in an

attempt to supplement the currently low available quantities of non-farm biomass substrates.

Sand-bedded and daily-spread dairy farms

The Lowville Digester Work Group inquired about the inclusion of sand-bedded farms in the area, as

potential candidates to increase manure available for digestion. However, for almost all of the farms in

the region of the proposed CAD project, the economies of scale are not present to allow for sandmanure

separation systems to be economically feasible, and for those that it does, sand-manure

separator effluent is too dilute to warrant transporting to a CAD site.

Several relatively small farms within a 15-mile radius of the proposed digester site in downtown Lowville

were not included since they currently practice daily manure spreading and do not currently have

manure storage capabilities.

57


Residential food waste

Residential food waste was considered as a potential non-farm biomass substrate, but serious

investigation was postponed in light of the lack of technologies to make this option feasible. Feasibility

of the large-scale collection of residential organic waste would need to be assessed independently, as it

is outside the scope of this project.

Fort Drum

Fort Drum, a large military base north of Lowville, NY is a potential source of organic substrates that was

investigated; however, a phone conversation with a Fort Drum official revealed that they intend to

develop their own waste management system to handle food waste from their centralized dining

facilities.

Energy crops

The availability of growing energy crops for inclusion to the CAD system was also investigated. Lewis

County has few strictly crop farms; those that do exist total approximately 2,400 acres (Lawrence, 2009).

Details about the two farms surveyed are included in Table 13.

Table 13. Select Lewis County crop farm data

Crop farm Farm acreage Crops grown Location relative to central Lowville

A 2,000

1,000 acres corn

500 acres grass

15 miles north

500 acres alfalfa

B 400

150 acres corn

50 acres soybeans 1

200 acres alfalfa/grass

12 miles south

1 Not considered as an energy crop for this study; the 50 acres of soybeans were added to the acreage of corn, for

estimates associated with this study.

Lowville Wastewater Treatment Plant

The Lowville Wastewater Treatment Plant (LWWTP) was suggested as a potential site for the Lewis

County community AD system; therefore, output solids from the LWWTP were investigated as a possible

organic waste input for the CAD facility. The plant has two aerobic lagoons, one with 23 million gallons

of capacity and the second with 21 million gallons of capacity. The average influent to the LWWTP is 1.1

million gallons per day (gpd), but can be as high as 5 million gpd during high precipitation events (Tabolt,

2009). Lagoon number one was drained in 1998, and 2,860 tons of sludge was removed. The plant

58


manager estimated the sludge removal process would take place approximately every 26 years.

According to previous sludge sample analysis, the sludge contains high concentrations of heavy metals

such as lead (Tabolt, 2009). Due to the intermittent availability, heavy metal concentration, and

unknown impact on the AD process, the solids from the LWWTP were not considered to be feasible for

inclusion to the AD facility.

Fallow Ground

Finally, the possibility of digesting several hundred acres of reed canary grass that grows along the Black

and Beaver Rivers in Lewis County was considered. Historically, this acreage has been harvested for

bedding hay, however, difficulties that prevent utilizing this land base on a reliable basis include:

flooding, debris, fragmented ownership, accessibility, timeliness of harvesting and logistics (Lawrence,

2009). For these reasons, this option was ultimately not included in final biomass source estimates.

59


Chapter 4. Biomass Sample Collection and Analysis

In this chapter, the collection and analysis of the non-farm biomass samples is described in detail. After

these samples were collected, they were used in analyses to determine their biochemical methane

potential (BMP). In addition to the BMP analysis, sub samples were sent to a laboratory in Syracuse, NY

for nutrient analysis. The results from both analyses are presented, as well as the implications of the

laboratory results. Laboratory test results from BMP analysis were translated to total volume of biogas

that can be expected to be produced by digesting each of the feedstocks available on an individual basis.

These values are important in assessing energy production capabilities and digester vessel sizing

estimates. Also, nutrient implications are presented based on the laboratory nutrient results. Values

such as the annual mass of nutrients returning to collaborating farms are important for nutrient

management and therefore overall digester facility design.

Sample collection

In order to quantify the methane production potential of available non-farm biomass substrates,

samples were collected from the substrate suppliers on July 15, 2009. Six select non-farm biomass

substrates (2, 4, 5A, 5B, 8, and 10) with the highest available volumes, based on survey results, were

chosen to perform biochemical methane potential (BMP) tests. Samples were stored in 1L plastic screwtop

containers, and placed on ice until refrigerated. All efforts were made to obtain a representative

sample under normal operating conditions. A full substrate sampling report is available in Appendix D.

Laboratory Biochemical Methane Potential test (BMP trials)

Six select non-farm biomass substrates from five sources 11 were analyzed for biochemical methane

potential (BMP) at Cornell University’s Agricultural Waste Management Laboratory. All samples

collected were analyzed in triplicate for 30 days, with the exception of substrate 4, which was analyzed

with six replicates, due to the high variability of the substrate sample, resulting in seven individual BMP

trials conducted, as listed below. A synopsis of the laboratory procedures for conducting the BMP trials

are provided in Appendix E developed from Labatut and Scott (2008).

11 Substrates 5A and 5B are from the same source

61


Substrate 2

Substrate 4 (six replicates)

Substrate 5A

Substrate 5B

Substrate 8

Substrate 10

Results

An example of the biogas production data from a 30-day BMP assay depicting biogas yield for substrate

4 is shown in Figure 12. The results from the BMP trials are shown in Table 14 in liters of CH 4 per kg of

raw substrate for each of the non-farm biomass substrates, and also represented graphically in Figure

13. The minimum and maximum values are one standard deviation below and above the mean,

respectively. The same information (L CH 4 /kg substrate) was found for manure from “Experimental and

Predicted Methane Yields from the Anaerobic Co-Digestion of Animal Manure with Complex Organic

Substrates” (Labatut and Scott, 2008).

Figure 12. Biochemical Methane Potential (BMP) data (cumulative biogas yield) for substrate 4.

1 only four of six replicates shown; other two replicates contained outlying data points.

62


Table 14. Cornell University Agricultural and Waste Management Laboratory BMP analysis results (2009) for all

substrates tested

Non-farm biomass

substrate ID

Non-farm biomass substrate

description

Yield (L CH 4 /kg raw substrate)

Minimum Maximum Average

5B Waste grease 258 468 363

4 Meat, fat, guts 149 177 163

5A Mixed food scraps 110 118 114

2 Mixed food scraps, liquid 78 85 81

Raw manure 1 Dairy farm manure 20 33 27

10 Post-digested sludge 5 10 7

8 Diluted whey and CIP 2 3 2

1 Data from Labatut and Scott, 2008

As can be expected, the grease and meat substrates have the highest methane producing potential.

Pre- and post-consumer food scrap wastes were the second highest producers. As observed through

many manure sampling analyses, the biogas producing potential of manure is expected to be low as

compared with many organic substrates. The whey sample was very dilute, which accounts for the low

methane yields, and the post-digested sludge has already undergone a digestion process, which

accounts for the low methane yields from that substrate.

1

Figure 13. Graphical representation of biochemical methane potentials for all substrates tested.

1 Data from Labatut and Scott, 2008.

After the BMP trials concluded at day 30, two of the substrates showed indications that biogas

production could continue – substrates 2 and 5B. The number of days that CH 4 was produced by each

substrate is listed below. Although it is unlikely that a community digester would have a hydraulic

63


etention time of more than 30 days, it is worth noting the additional biogas producing capabilities of

certain non-farm biomass substrates.

Substrate 8: 28 days CH 4 production complete

Substrate 5A: 30 days CH 4 production complete

Substrate 5B: CH 4 production could continue past 30 days

Substrate 2: CH 4 production could continue past 30 days

Substrate 4: 28 days CH 4 production complete

Substrate 10: 22 days CH 4 production complete

It should be noted that co-digestion of certain organic substrates with manure has the potential to

create a synergistic effect on biogas production; therefore, simply adding the biogas producing potential

of raw manure and each substrate may underestimate potential total biogas production. However,

there can also be antagonistic effects of non-farm biomass substrates as well, due to inhibitory

characteristics that might disrupt the function of the methanogens, responsible for methane production.

Therefore, minimum, maximum, and average values are presented to show a potential range of biogas

producing capabilities. More in-depth laboratory analyses, such as co-digestion studies using benchscale

reactors, are necessary to determine the expected behavior of each substrate in an operational

CAD.

Glycerin

Non-farm biomass substrate 11 – glycerin – was discovered after the BMP trials had already been

performed. Therefore, the methane potential of glycerin was calculated using theoretical values and

the following values from Lopez (2009): 1,010 g COD/kg substrate, 292 ml CH 4 /g COD removed, and 85%

biodegradability of glycerin.

Biogas production estimates

The potential quantity and availability of each of the AD feedstocks along with laboratory analyses were

used to calculate the potential total annual biogas production volume. The results of this analysis,

including minimum and maximum values for biogas production, are shown in Table 15.

The results presented in Table 15 for the biogas production projections of each non-farm biomass

substrate, is shown graphically in Figure 14. Non-farm biomass substrates 8 and 10, although low in

64


methane yields, are high in available quantity and therefore result in the highest overall biogas

production potential on an annual basis for the non-farm substrates. The aggregated minimum,

maximum, and average annual biogas production potential for these seven non-farm biomass substrates

and for manure from 25 farms are shown in Figure 15. It is apparent from

Figure 15 that the impact of the non-farm biomass substrates on overall biogas production is very small

in relation to manure, not due to methane yields per unit of influent, but due to the sheer volume

available.

Table 15. Biogas production potential of non-farm biomass substrates and manure

Methane production potential

(million ft 3 /year)

Feedstock source ID Minimum Maximum Average

2 0.99 1.10 1.04

4 0.04 0.20 0.12

5A 0.02 0.07 0.05

5B 0.01 0.03 0.02

8 1.86 4.77 3.15

10 3.42 6.60 5.01

11 1.36 2.89 2.13

Raw manure 94 156 125

Energy crops

A total of 2,400 acres of energy crops, including alfalfa, grass hay, and silage corn, are estimated to be

available for use in co-digesting with manure for the proposed Lewis County community AD system. A

summary of the biogas production information is presented in Table 16.

provided by Norma McDonald at Organic Waste System, Inc.

Unit biogas yields were

Table 16. Potential biogas production of available energy crop acreage

Tons per year

Unit biogas yield 1 Annual biogas production

(scf/ton as fed)

(million ft 3 /year)

Corn 22,200 5,550 128

Alfalfa and grass 5,400 5,780 30

1 Source: McDonald (2010)

65


Figure 14. Estimated annual minimum, maximum, and average methane production by substrate.

Figure 15. Estimated aggregated annual minimum, maximum, and average methane production of non-farm

biomass substrates and manure.

66


Laboratory nutrient testing

Sub samples of the six substrates analyzed for co-digestion were sent to the Certified Environmental

Services Laboratory (CES), an EPA certified lab, in Syracuse, NY for nutrient analysis. The laboratory

results are shown in Table 17 and Table 18.

Table 17. CES laboratory results for each non-farm biomass substrate: nutrients

Non-farm biomass

substrate ID

TKN 1

(mg/kg)

NH 3 -N 1

(mg/kg)

Constituent

Organic N 1

(mg/kg)

TP 1

(mg/kg)

OP 1

(mg/kg)

K 1

(mg/kg)

2 5,024 496 4,528 571 181 1,234

4 20,493 8,551 11,941 975 979 2,200

5A 14,394 1,200 13,194 1,295 375 2,334

5B 4,122 291 3,831 393 117 1,096

8 195 28 179 187 78 143

10 3,931 796 3,235 1,971 83 593

1 TKN: Total Kjeldhal Nitrogen, NH 3 -N: Ammonia, Organic N: by subtraction (TKN-NH 3 -N), TP: Total Phosphorus, OP:

Ortho Phosphorus, K: Potassium

Table 18. CES laboratory results for each non-farm biomass substrate: solids

Glycerin

Constituent

Non-farm biomass substrate ID

TS 1 TVS 1

pH 1 VAAA 1 COD 1

(%) (%) (mg/kg) (mg/kg)

2 16 15 4.05 1,602 201,192

4 25 22 6.95 13,317 382,992

5A 35 31 4.29 2,075 385,416

5B 97 92 6.00 653 187,860

8 0.51 0.35 5.22 98 3,636

10 6 4 7.83 359 44,844

1 TS: Total Solids, TVS: Total Volatile Solids, VAAA: Volatile acids as acetic acid, COD: Chemical oxygen

demand

Since this non-farm biomass substrate was not identified until after the testing phase of the project was

completed, the total annual mass of N, P, and K imported to the CAD site from this material was

estimated by using nutrient concentration data from an un-publishable source. Since glycerin products

vary widely depending upon source and purity, further analysis of the glycerin product specific to this

project is recommended. Nutrient concentrations for the three key nutrients, N, P, and K in glycerin

used in this analysis were: 100, 1, and 0 pounds per 8,000 gallons glycerin, respectively.

67


Manure

Manure nutrient concentrations were estimated using ASABE standard manure production values, as

provided in Chapter 1. The mass of the three key nutrients, N, P, and K in manure are: 0.99, 0.17, and

0.23 pounds per cow per day, respectively (ASABE, 2005).

Nutrient implications

The estimated minimum and maximum quantities available (Table 12) and the laboratory data for each

non-farm biomass substrate were used to determine the total mass of each nutrient parameter in the

raw non-farm biomass substrates on an annual basis. The total number of LCEs available from the 25

farm surveys received was used in conjunction with the standard values for nutrient concentrations in

manure. The resulting mass of nutrients from both manure and non-farm biomass sources, on a predigestion

basis, are provided in Table 19 for the N series, and Table 20 for the P and K series.

Table 19. Estimated annual mass of nitrogen series for raw AD feedstock

Raw Substrate TKN Raw Substrate Ammonia-N

Non-farm biomass

(lbs/year)

(lbs/year)

substrate

Raw Substrate Organic Nitrogen

(lbs/year)

Minimum Maximum Minimum Maximum Minimum Maximum

2 3,980 4,050 390 400 3,580 3,650

4 350 1,480 150 620 200 860

5A 190 540 16 45 170 500

5B 10 15 1 10 15

8 13,050 22,600 1,870 3,240 11,980 20,740

10 165,100 33,430 135,920

11 490 - -

Raw manure 1 1,925,000 - -

1 manure from 25 farms

Table 20. Estimated annual mass of phosphorus and potassium series for raw AD feedstock

Raw Substrate Total

Raw Substrate Ortho

Non-farm biomass

Phosphorus (lbs/year) Phosphorus (lbs/year)

substrate

Raw Substrate

Potassium (lbs/year)

Minimum Maximum Minimum Maximum Minimum Maximum

2 450 460 140 150 980 1,000

4 20 70 17 70 40 160

5A 20 50 5 14 30 90

5B 1 0 2 5

8 12,540 21,700 5,220 9,040 9,590 16,600

10 82,790 3,470 24,930

11 5 - 0

Raw manure 1 330,500 - 447,160

1 manure from 25 farms

68


Since the values shown in Table 19 and Table 20 are for raw non-farm biomass substrates, estimates

must be used to quantify the post-digestion concentration of the same nutrients; these values are

shown for the nitrogen series in Table 21 and for the phosphorus and potassium series in Table 22. The

values for post-digested nutrient concentrations were estimated using a percent change value for each

nutrient parameter from previous manure and substrate sampling and monitoring of five digester

systems including one co-digestion system (Gooch et al., 2007). Results indicate that on average,

ammonia-N increases in concentration by 23.4%, organic nitrogen decreases in concentration by 15.9%

and ortho-phosphorus increases in concentration by 14.4% (Gooch et al., 2007). It is assumed that the

mass of total nitrogen, total phosphorus and potassium do not change as a result of the anaerobic

digestion process. A comparison of pre- and post-digestion nutrient concentrations is shown in Figure

16 for the N, P, and K nutrient series for the non-farm biomass substrates. As can be observed there is

no change in the concentration of the major forms of these nutrients, however, for ammonia-N, organic

nitrogen, and ortho-phosphorus, there is a slight increase in concentration due to the digestion process.

Table 21. Predicted annual mass of nitrogen series for post-digested AD feedstock

Non-farm biomass

substrate

Post Digestion TKN

(lbs/year)

Post Digestion Ammonia-

N (lbs/year)

Post Digestion Organic-N

(lbs/year)

Minimum Maximum Minimum Maximum Minimum Maximum

2 3,980 4,050 480 490 4,150 4,230

4 350 1,480 180 760 230 1,000

5A 190 540 20 60 200 570

5B 10 15 1 10 15

8 13,050 22,590 2,310 4,000 13,880 24,020

10 165,140 41,240 157,460

11 490 - -

Raw manure 1 1,924,730 - -

1 manure from 25 farms

69


Table 22. Predicted annual mass of phosphorus series and potassium for post-digested AD feedstock

Non-farm biomass

substrate

Post Digestion Total

Phosphorus (lbs/year)

Post Digestion Ortho

Phosphorus (lbs/year)

Post Digestion

Potassium (lbs/year)

Minimum Maximum Minimum Maximum Minimum Maximum

2 450 460 160 170 980 1,000

4 20 70 20 80 40 160

5A 20 50 10 20 30 90

5B 1 0 2 5

8 12,540 21,700 5,970 10,340 9,590 16,610

10 82,790 3,970 24,930

11 5 - 0

Raw manure 1 330,510 - 447,160

1 manure from 25 farms

Figure 16. Nutrient concentrations for pre- and post-digestion conditions for N, P, K.

70


Chapter 5. Biomass Transportation

The literature search performed for existing centralized digester feasibility studies (see Chapter 1)

revealed that transportation costs are usually the largest operating cost component of a CAD. The

approach used in these studies to determine the overall transportation costs were 1) unit cost per gallon

and 2) unit cost per gallon-mile.

For the purposes of this feasibility study, transportation of material to and from each participating farm

and the CAD facility was explored in two different ways, through the use of a project-owned and

operated trucking fleet, and by contracting with an existing trucking company. Each option was

investigated for the proposed Lewis County CAD facility feasibility study and is discussed below. Overall,

it was determined that the best option would be to contract with an existing trucking company.

Transportation costs were based on a methodology that used the estimated time required to pump and

to load or unload a 6,000-gallon truck with a 500 gallon per minute (gpm) truck-mounted pump. The

comparison of trucking options presented is based on participation of all 25 dairy farms who responded

to the survey, however, regardless of which final digestion scenario is chosen, the final determination

remains the same, that it is less costly to contract with an existing trucking company for the proposed

project.

Whether choosing a contracted or an owned trucking fleet, the process and assumptions that are made

for transporting manure from the farms and CAD effluent back, are the same. Manure is picked up from

the short-term storage at each farm, and transported to the CAD facility, at a cost to the project; this

service would be of no cost to the farms. Non-farm biomass substrates incorporated for co-digestion

are not transported through the same means as manure from farms. It is assumed that the substrate

suppliers would continue to be responsible for trucking their waste and paying a tipping fee to the

project. Effluent from the CAD facility would be trucked by the project back to the participating farms,

and deposited in a long-term storage at each farm. The return trucking volumes would consist of both

the manure and non-farm biomass substrates delivered by the substrate suppliers. There is the

possibility to further explore delivery of CAD effluent to satellite storages for each farm, where the

effluent would be delivered to a location more central to the farm’s cropping activities.

71


Owned Trucking Fleet

The first option regarding material transportation to and from participating farms is to create an inhouse

trucking division to be owned and operated by the project. In order to handle the manure from

participating dairy farms, it was determined that six 6,000-gallon truck-mounted tanker trucks would be

needed with a 500 gpm truck-mounted pump, with a capital cost of $165,000 per truck (Mack Trucks,

2009), for a total initial cost of $990,000. In addition, it would cost approximately $450,000 (estimated

at $30/ft 2 ) to construct a 15,000 ft 2 building to house a maintenance shop, clerical support, employee

amenities (locker and break rooms), and $75,000 (estimated at $5/ft 2 ) for start-up equipment, tools and

computers.

Necessary staff includes six drivers, one clerical person, and one maintenance person for a total of eight

project-related jobs that would be created. Annual labor expenses for the in-house fleet drivers were

calculated using a draft schedule for collection and delivery to/from each farm and the proposed CAD

facility located in downtown Lowville. Costs for fuel, truck maintenance, parts, utilities, insurance and

general overhead are also included in the annual operating cost estimate, which is shown in Table 23.

Table 23. Capital and annual cost estimates for a project-owned trucking fleet

Capital cost ($) Annual Cost ($)

One 6,000 gallon truck 165,000 8,500

6 trucks 990,000 51,000

Fuel cost 19,500

Maintenance Building 450,000 12,000

Equipment/Furnishings 75,000

Driver salary 45,000

6 drivers 270,000

Administrative salary (1) 30,000

Maintenance person salary (1) 40,000

Total $1,515,000 $422,500

In summary, the capital cost estimate for the project-owned trucking fleet scenario is $1,515,000 and

annual operating costs are estimated to be $422,500.

72


Contracted Trucking Fleet

The second option regarding material transport to and from participating farms is to enter into a

contract with a private waste hauler. Shue Trucking based in Port Leyden, NY was contacted to obtain

cost estimates and to provide technical feasibility information. Shue provided a quote of $82 per hour

for a driver and truck with all required accessories. The annual cost projections were based upon a

6,000-gallon truck with a 500 gpm truck-mounted pump. Projected total annual volumes of manure and

non-farm biomass substrates were utilized to determine the number of trips required per year to service

all 25 participating farms. The same loading and unloading time requirements were used as for the

project-owned fleet calculations in determining the necessary annual trucking time. An example used to

calculate costs for the contracted fleet scenario is shown in Table 24.

Table 24. Contracted trucking fleet example schedule

Volume

Volume

Distance

influent No. of trips

manure

Farm from

to from farm to

to

ID digester

digester digester

digester

(miles)

annually annually

(gal/day)

(gal/year)

miles

influent

trucked

annually

Hours

per

trip

Hours

per

year

Cost

($/hour)

Annual

cost to

transport

influent 1

to AD

($/year)

1 2 4,710 1,804,680 300 600 0.75 230 $82 $18,500

2 6 1,110 424,430 70 420 1 70 $82 $5,800

5 7 7,860 3,011,710 500 3,510 1 500 $82 $41,160

7 8 3,440 1,318,140 220 1,760 0.75 170 $82 $13,510

1 Only influent trucking costs represented in this table

In summary, there is no trucking-related capital costs associated with the contracted trucking fleet

scenario. The estimated annual operating cost based on 25 farms for the contracted fleet scenario is

$1,260,000 if using the minimum volume of manure and non-farm biomass substrates available (110

million lbs/year). The estimated annual operating cost based on 25 farms for the contracted fleet

scenario is $1,350,000 if using the maximum volume of manure and non-farm biomass substrates

available (160 million lbs/year).

Manure and Digestate Trucking

The location of the 25 collaborating farms can be revisited in Figure 10. When developing scenarios with

a reduced number of farms, the criteria used was whether those farms produced at least 3,000 gallons

of manure per day. It was assumed that a mass of 3,000 gallons of manure stored for one day in the

winter would not be likely to freeze, whereas a smaller amount might, as indicated by several of the

73


farm-based surveys. Collaborating farms would not be charged a transportation fee for trucking

material between their farm and the digester; this cost would be covered by revenue (tipping fee)

received from non-farm biomass disposed of at the digester site.

It is important to note that a 5% increase in the calculated volume of manure associated with each farm

was assumed, to account for washwater and other biomass co-mingled with manure at the farm prior to

project pick-up. Also, the assumption was made that there is a 3% reduction of overall influent volume

due to the digestion process, and that effluent from the CAD would consist of digested manure and nonfarm

biomass substrates. Assuming less than a 3% reduction would result in higher trucking costs. The

CAD effluent would be a higher volume than the manure initially trucked to the CAD facility, and each

participating farm would receive a weighted amount of this additional volume as digester effluent. The

resulting aggregated volume would be trucked back to participating farms.

Non-farm Biomass Substrate Trucking

It is assumed that substrate suppliers would provide transportation of their biomass by-products from

their business location to the AD facility at their expense. This is a safe assumption to make since the

substrate suppliers currently have to pay trucking costs to transport their organic by-products to a

disposal site. Tipping fees, needed to cover manure transportation expenses, are intended to be

charged to substrate suppliers only, and not to participating farms, as can be seen in Figure 17.

74


Figure 17. Diagram of estimating a break-even tipping fee for non-farm biomass substrate suppliers.

75


Chapter 6. Preliminary Investigation of Five AD Scenarios

One apparent reason for many proposed CAD facilities not being implemented is the cost to transport

manure and digestate between collaborating farms and the CAD site. Therefore, the following five

scenarios were developed based on the survey data from the initial feasibility investigation with specific

emphasis on transportation costs, biogas production, and biogas utilization options. The information

contained in this chapter was presented as an interim report to the Lowville Digester Work Group at a

December 2009 meeting.


Scenario No. 1: co-digest manure from 25 dairy farms (see Figure 10), and seven non-farm

biomass substrates (2, 4, 5A, 5B, 8, 10, 11) at a central location (Site 1) adjacent to the

Lowville wastewater treatment plant (see Figure 18)


Scenario No. 2: co-digest manure from 14 dairy farms, and three non-farm biomass

substrates (8, 10, 11) at a central location (Site 1) adjacent to the Lowville wastewater

treatment plant (see Figure 18)


Scenario No. 3: co-digest manure from 12 dairy farms, and one non-farm biomass

substrate (8) at Site 2 (see Figure 19), and co-digest manure from four dairy farms and two

non-farm biomass substrates (10, 11) at Site 3 (see Figure 20)


Scenario No. 3a: identical to Scenario No. 3, except that at Site 2 manure from five of the

12 farms would be piped to the digester site, and at Site 3 manure from two of the four

farms would be piped to the digester site

Scenario No. 3b: same as Scenario No. 3 with 400 acres of energy crops digested at Site 2

and 2,000 acres of energy crops digested at Site 3

Each scenario and the investigation results were the core of an interim project report presented to the

Lowville Digester Work Group on December 18 th , 2009 (details in the remainder of this chapter). As a

result of that presentation, the Lowville Digester Workgroup decided that Scenario No. 2 should be

more fully investigated and the results of that complete investigation are detailed in Chapter 7.

77


The remainder of this Chapter provides baseline information used in evaluating all five scenarios,

additional details about each scenario analyzed, and analysis results (transportation cost, biogas

production, and biogas utilization options) used in part to select one scenario to perform a full economic

evaluation. The corresponding process flow diagram(s) for each scenario includes average feedstock

and effluent volumes, trucking cost, biogas production, electricity and heat generation that represent

the average of the minimum and maximum values.

Proposed

CAD site

Figure 18. CAD Site 1 for Scenario Nos. 1 and 2.

78


Proposed

CAD site

Figure 19. Remote AD Site 2 for Scenario Nos. 3, 3a, and 3b.

79


Proposed

CAD site

Figure 20. Remote AD Site 3 for Scenario Nos. 3, 3a, and 3b.

Background for All Scenarios

In each scenario, biogas produced could be used as:




A thermal heat source to fuel a boiler to produce hot water

A fuel source for an engine-generator set to produce electrical power

A renewable alternative to natural gas after being scrubbed

For the centralized scenarios (Scenario Nos. 1 and 2), biogas that has been processed by gas-clean up

equipment could also potentially be injected into a natural gas pipeline as biomethane. Any of the

resulting forms of energy could be sold to one or more buyers; however, for the de-centralized regional

digesters scenarios, sale of energy to one main buyer may not be practical. Biogas production volumes

were determined at STP (0°C and 1 atm), and heat content was calculated using the lower heating value

of methane at STP which is 896 Btu/ft 3 and a concentration of 60% CH 4 (Marks, 1978).

80


Scenario No. 1

Scenario No. 1 consists of one CAD system located at Site 1, adjacent to the Lowville Wastewater

Treatment Plant (LWWTP) in downtown Lowville, as shown in Figure 18. Manure from 25 nearby dairy

farms would be trucked by the project from each farm to the proposed Lewis County community CAD

facility (See Table 10 for details of the 25 farms). Seven non-farm biomass substrates with the highest

volumes (2, 4, 5A, 5B, 8, 10, 11) out of the 11 non-farm biomass sources initially surveyed would be codigested.

Figure 21 shows a simplified process flow diagram for Scenario No. 1.

Figure 21. Process flow diagram for Scenario No. 1 using the average annual total volume of the seven non-farm

biomass substrates.

The following are additional project values determined according to the details of Scenario No. 1:

Average annual mass of non-farm biomass substrates: 134 million lbs/year (16 million gallons/year)

o

o

Minimum: 110 million lbs/year (13 million gallons/year)

Maximum: 160 million lbs/year (19 million gallons/year)

Average annual total AD feedstock mass: 440 million lbs/year (53 million gallons/year)

o

o

Minimum: 416 million lbs/year (50 million gallons/year)

Maximum: 465 million lbs/year (56 million gallons/year)

81


Average annual manure influent and CAD effluent transportation costs: $1,305,000

o Minimum: $1,260,000

o Maximum: $1,350,000

Average annual volume biogas produced: 228 million ft 3 /year

o

o

Minimum: 170 million ft 3 /year

Maximum: 287 million ft 3 /year

Average annual volume methane produced: 137 million ft 3 /year

o Minimum: 102 million ft 3 /year

o Maximum: 172 million ft 3 /year

Substrate tipping fee needed: $0.08 per gallon

Scenario No. 2

Scenario No. 2 consists of a centralized digester located at Site 1, as in Scenario No. 1, however with

select farms and select non-farm biomass substrates. Instead of the 25 dairy farms, Scenario No. 2

would involve digesting manure from 14 surveyed dairy farms, chosen for those farms’ ability to

produce at least 3,000 gallons of manure per day. The three non-farm biomass substrates with the

highest volumes (8, 10, 11), out of the 11 sources initially surveyed, would be co-digested with the

manure. Figure 22 shows a process flow diagram for Scenario No. 2. For complete details on the final

Scenario No. 2, please also see Chapter 7.

82


Figure 22. Process flow diagram for Scenario No. 2 using the average annual total volume of the three non-farm

biomass substrates.

The following are additional project values determined according to the details of Scenario No. 2:

Average annual mass of non-farm biomass substrates: 134 million lbs/year (16 million gallons/year)

o

o

Minimum: 109 million lbs/year (13 million gallons/year)

Maximum: 158 million lbs/year (19 million gallons/year)

Average annual total AD feedstock mass: 372 million lbs/year (45 million gallons/year)

o Minimum: 348 million lbs/year (42 million gallons/year)

o Maximum: 397 million lbs/year (48 million gallons/year)

Average annual manure influent and CAD effluent transportation costs: $1,120,000

o Minimum: $1,070,000

o Maximum: $1,170,000

83


Average annual volume biogas produced: 188 million ft 3 /year

o

o

Minimum: 140 million ft 3 /year

Maximum: 237 million ft 3 /year

Average annual volume methane produced: 113 million ft 3 /year

o

o

Minimum: 84 million ft 3 /year

Maximum: 142 million ft 3 /year

A substrate tipping fee needed: $0.07 per gallon

Scenario No. 3

Scenario No. 3 consists of two decentralized regional digesters, one located north of Lowville (Site 2) and

one located south of Lowville (Site 3). Site 2 would digest manure trucked by the project from 12 of the

25 dairy farms, chosen for their proximity to AD Site 2. Site 3 would digest manure trucked by the

project from four of the 25 dairy farms chosen for their proximity to AD Site 3. Site 2 would co-digest

substrate number 8, the highest volume non-farm biomass substrate that is closest to AD Site 2. Site 3

would co-digest substrate numbers 10 and 11, the highest volumes of non-farm biomass substrates, in

proximity to AD Site 3. A simplified process flow diagram for Scenario No. 3 is shown in Figure 23.

84


Figure 23. Process flow diagrams for Scenario No. 3 using the average annual total volume of the three non-farm

biomass substrates for Site 2 and Site 3. All manure and digestate are trucked.

The following are additional project values determined according to the details of Scenario No. 3:

Minimum annual mass of non-farm biomass substrates for both sites: 109 million lbs/year (13 million

gallons/year)

o

o

Site 2: 67 million lbs/year (8 million gallons/year)

Site 3: 42 million lbs/year (5 million gallons/year)

Maximum annual mass of non-farm biomass substrates for both sites: 158 million lbs/year (19 million

gallons/year)

o Site 2: 116 million lbs/year (14 million gallons/year)

o Site 3: 42 million lbs/year (5 million gallons/year)

85


Minimum annual manure influent and CAD effluent transportation costs for both sites: $684,000/year

o

o

Site 2: $477,000/year

Site 3: $207,000/year

Maximum annual manure influent and CAD effluent transportation costs for both sites: $740,000/year

o

o

Site 2: $533,000/year

Site 3: $207,000/year

Average annual volume biogas produced for both sites: 191 million ft 3 /year

o Site 2: 125 million ft 3 /year

o Site 3: 66 million ft 3 /year

Average annual volume methane produced for both sites: 114 million ft 3 /year

o

o

Site 2: 75 million ft 3 /year

Site 3: 39 million ft 3 /year

Average substrate tipping fee needed:

o

o

Site 2: $0.05 per gallon

Site 3: $0.04 per gallon

Scenario No. 3a

All aspects of Scenario No. 3a are identical to Scenario No. 3, except that Scenario No. 3a utilizes

a combination of pumping and trucking manure and digestate to/from collaborating farms and

the remote digester sites. Certain farms appear near enough to the proposed remote AD sites

to logically envision that manure may be piped, with the hopes that overall transportation cost

would be lessened by pumping approximately 33% of the total available manure. Table 25

shows which farms would potentially pipe and truck manure according to Scenario No. 3a.

Figure 24 shows a process flow diagram for Scenario No. 3a.

86


Table 25. Scenario No. 3a means of manure and digestate transport

Remote Site 2 (Northern site)

Remote Site 3 (Southern site)

Farm ID lbs/day 3a. Transport Farm ID lbs/day 3a. Transport

5 65,460 Trucked 4 20,363 Trucked

6 17,055 Trucked 9 118,031 Trucked

7 28,650 Piped 10 28,823 Piped

8 16,920 Piped 11 38,340 Piped

12 39,090 Piped 205,556

13 32,475 Piped

14 31,170 Piped

17 16,305 Trucked

18 84,225 Trucked

19 86,445 Trucked

21 17,340 Trucked

23 21,653 Trucked

456,788

Figure 24. Process flow diagram for Scenario No. 3a using the average annual total volume of three non-farm

biomass substrates for Site 2 and Site 3. Manure and digestate are pumped and trucked.

87


The following are additional project values determined according to the details of Scenario No. 3a, a

hybrid scenario of manure both piped and trucked from 16 farms to two regional digesters in different

locations.

Minimum annual manure influent and CAD effluent transportation costs for both sites: $539,000/year

o

o

Site 2: $375,000/year

Site 3: $164,000/year

Maximum annual manure influent and CAD effluent transportation costs for both sites: $599,000/year

o Site 2: $435,000/year

o Site 3: $164,000/year

A substrate tipping fee needed:

o

o

Site 2: $0.04 per gallon

Site 3: $0.03 per gallon

The costs associated with piping manure and digester effluent between selected farms, shown in Table

25, were not calculated prior to the Dec. 18, 2009 project meeting, and based on the selection by the

Lowville Digester Workgroup to focus on Scenario No. 2, no effort was subsequently made to finish out

the preliminary investigation of this option.

Scenario No. 3b

Scenario No. 3b was developed to examine the effect of including a separate energy crop digester at

each of the two regional digester sites. The same dairy farms and non-farm biomass substrates would

be used to provide material to each of the decentralized regional AD locations as was outlined in

Scenario No. 3. Field crops from crop farm A would be ensiled and digested at Site 2, while field crops

from crop farm B would be digested at Site 3. There would be two digester systems at each decentralized

site. Figure 25 shows a simplified flow diagram for Scenario No. 3b, with some details

removed for clarity; these details are provided in bullet form following the figure.

88


Figure 25. Process flow diagram for Scenario No. 3b using the average annual total volume of three non-farm

biomass substrates for Site 2 and Site 3.

The following are additional project values determined according to the details of Scenario No. 3b; all

other substrate volumes are identical to Scenario No. 3:

Average annual volume of effluent for Site 2: 35 million gallons/year

o

o

Manure/substrate AD: 31 million gallons/year

Energy crop AD: 4 million gallons/year

Average annual volume of effluent for Site 3: 15 million gallons/year

o

o

Manure/substrate AD: 14 million gallons/year

Energy crop AD: 1 million gallons/year

89


Minimum annual manure influent and CAD effluent transportation costs for both sites: $704,000/year

o

o

Site 2: $491,000/year

Site 3: $213,000/year

Maximum annual manure influent and CAD effluent transportation costs for both sites: $759,000/year

o

o

Site 2: $546,000/year

Site 3: $213,000/year

A substrate tipping fee needed:

o Site 2: $0.05 per gallon

o Site 3: $0.04 per gallon

A summary of the initial investigation of the five scenarios is provided in Table 26. As was mentioned at

the beginning of this chapter, the Lowville Digester Work Group selected Scenario No. 2 to perform

additional investigation and a complete economic analysis. The two main reasons that Scenario No. 2

was selected by the Workgroup were, it provided:

1. Increased opportunities for energy utilization produced by the CAD system, and

2. Increased opportunities for post-digestion treatment of effluent that would benefit

collaborating farms.

There is less risk involved with a centralized AD option as opposed to the de-centralized regional

digesters described in Scenario No. 3, since the project could likely still proceed even if a few of the

farms decided at some point to discontinue participating. Scenario No. 2 would allow for energy

capture from one system, which could be sold to one main buyer. Also, if it is discovered that nutrient

concentrations in the effluent stream need to be adjusted, this scenario allows there to be one point

where this could be done. The Work Group requested that an energy crop digester, located at Site 1 be

included in the full analysis.

90


Table 26. Comparison of the five AD scenarios

Scenario

No.

No. of feedstock

sources

Average AD

feedstock mass

(million

lbs/year)

Average

volume biogas

produced

(million

ft3/year)

Average raw

manure and

CAD effluent

transportation

costs

Tipping

fee

needed

($/gallon)

1

2

25 farms,

7 non-farm biomass

substrates

14 farms,

3 non-farm biomass

substrates

440 228 $1,303,000 $0.08

372 188 $1,120,000 $0.07

3

3a

Site 2: 12 farms, 1 nonfarm

biomass substrate

375 191 $684,000 $0.05

Site 3: 4 farms, 2 nonfarm

biomass substrates

Same as Scenario

No. 3 375 191 $599,000 1 $0.04

3b

Site 2: 12 farms, 1 nonfarm

biomass substrate,

crop farm A

Site 3: 4 farms, 2 nonfarm

biomass substrates,

crop farm B

1 Does not include cost to pump manure and digestate.

420 344 $732,000 $0.05

91


Chapter 7. Final AD Scenario Selection Analysis and Results

Overview

As mentioned in the previous chapter, the Lowville Digester Work Group decided during the December,

2009 interim report meeting that Scenario No. 2 was the best scenario of those initially developed and

investigated based on the initial goals they had outlined at the onset of the project (see Introduction)

and the findings developed to date for presentation at that meeting.

Scenario No. 2 as described in the previous chapter was slightly altered to include one additional farm

for the final analysis (15 total farms). During the December meeting, the Lowville Digester Work Group

also requested an analysis of an energy crop digester (co-located at the same site but as a separate

system, due to AD design specifications based on material handling requirements) be performed to

determine the increase in biogas available from the facility. Both the Scenario No. 2 manure/non-farm

biomass CAD and the energy crop digester analysis are based on two separate systems co-located at Site

1, adjacent to the LWWTP.


Scenario No. 2 manure/non-farm biomass CAD is based on manure from the 15 identified

collaborating dairy farms (listed by farm ID in Table 27) and 3 non-farm biomass

substrates with the highest volumes available (8, 10, and 11) out of the 11 surveyed. The

15 farms were chosen for their ability to produce at least 3,000 gallons of manure per day

(justification in Chapter 5). A process flow diagram for Scenario No. 2 is shown in Figure

26.


The energy crop digester is based on two crop farms (A, B) that would supply corn silage

and grass and alfalfa to the site and ensile it for use in constantly feeding the energy crop

digester. A process flow diagram for the energy crop digester is shown in Figure 27.

93


Figure 26. Final Scenario No. 2 process flow diagram.

Figure 27. Energy crop anaerobic digester process flow diagram.

Table 27. Scenario No. 2 participating farms and associated manure generation

Farm ID LCEs lbs/day

1 262 39,225

2 62 9,225

5 436 65,460

7 191 28,650

9 787 118,031

10 192 28,823

11 256 38,340

12 261 39,090

13 217 32,475

14 208 31,170

16 87 13,113

18 562 84,225

19 576 86,445

21 116 17,340

23 144 21,653

4,355 653,264

94


Transportation

The Lowville CAD project includes transporting manure from collaborating dairy farms to the CAD site

and digestate back to the farms. Non-farm biomass substrates would be trucked to the CAD facility at

the supplier’s expense. The initial transportation assessment for the project centered on whether to

contract with an existing trucking company, or to initiate a trucking division as part of the overall

centralized AD project (details in Chapter 5). It was determined that initially contracting with an existing

trucking company would be more cost effective to the project and provide lower financial risk. At some

point after project start-up, when the economic implications of the project are clear, it will be prudent

to re-evaluate the option of a project-owned trucking fleet to transport material between the farms and

the Scenario No. 2 CAD site.

Based on contracting with an existing fleet, the trucking costs were estimated based on transporting

manure from the dairy farms to the CAD site, and effluent back to participating dairy farms. The

estimated annual trucking costs for Scenario No. 2 manure/non-farm biomass CAD are between

$1,100,000 (minimum substrate assumed) and $1,200,000 (maximum substrate assumed).

As explained in Chapter 5, each dairy farm would receive a higher volume of CAD effluent as compared

with the manure volume provided, as determined by using a weighted basis calculation for each farm;

this is shown in Figure 28.

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Figure 28. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received, by farm.

It is important to consider the impacts of additional traffic a project of this magnitude would have on

the community. For the manure and non-farm biomass CAD, there would be an estimated 13,000 loads

per year brought by the 6,000-gallon manure tankers; this amounts to approximately 35 loads per day

transported through town. It is not known at this time the specific impacts to certain routes, or

upgrades that would be necessary to local infrastructure, i.e., bridges.

96


Anaerobic Digestion

The feedstock volumes for Scenario No. 2 are shown in Table 28. Under Scenario No. 2 manure/nonfarm

biomass CAD, there are three non-farm biomass substrates that would be co-digested with manure

from 15 collaborating farms. The mass of feedstock available for inclusion to the proposed energy crop

digester was proposed to be co-digested with a portion of the manure (10% of that in the manure/nonfarm

biomass CAD), and is also presented in Table 28. Minimum and maximum potential substrate

volumes for all feedstocks were quantified in order to develop a range in quantities available.

Table 28. Scenario No. 2 feedstock volumes

Potential quantity

(gal/day)

Potential quantity

(lbs/day)

Availability

(days/year)

Potential quantity

available

(million lbs/year)

Feedstock

source

Min Max Min Max Min Max Min Max Ave

8 31,000 38,000 257,000 317,000 260 365 66.8 115.7 91.2

10 13,800 13,800 115,000 115,000 365 365 42 42 42

11 150 150 1,300 1,600 1 260 260 0.34 0.41 0.37

Subtotal 110 160 135

crop farm A 100,000 100,000 365 365 37 37 37

crop farm B 20,000 20,000 365 365 7.4 7.4 7.4

Subtotal 44.4 44.4 44.4

100% Manure 78,000 78,000 653,000 653,000 365 365 238 238 238

Total 392 441 416

1 Based on varying specific gravities, since the purity of the glycerin substrate is unknown

Table 29 contains the minimum, maximum and average values for the potential methane and biogas

production for each individual feedstock, as well as for the total substrate quantity, in the Scenario No. 2

manure/non-farm biomass CAD. The CAD in this scenario is projected to produce on average, 113

million ft 3 of methane annually with a thermal value of 101,000 million Btu’s.

97


Table 29. Potential methane and biogas production volumes for each feedstock in Scenario No. 2 CAD

Feedstock source

Minimum

methane

(million

ft 3 /year)

Maximum

methane

(million

ft 3 /year)

Average

methane

(million

ft 3 /year)

Minimum

biogas

(million

ft 3 /year)

Maximum

biogas

(million

ft 3 /year)

Average

biogas

(million

ft 3 /year)

8 1.9 4.8 3.3 3.1 8 5.5

10 3.4 6.6 5 5.7 11 8.4

11 1.4 2.9 2.1 2.3 4.8 3.5

Total substrate 6.7 14.3 10.4 11.1 23.8 17.2

Raw manure 77.1 127.8 102.4 128.5 212.9 170.7

Total 83.8 142 112.7 139.6 236.7 187.9

CAD facility sizing

The Scenario No. 2 manure/non-farm biomass CAD was sized based on providing a 22.5 day 12 hydraulic

retention time to co-digest the aggregate daily manure volume from the 15 collaborating farms and the

average daily volume of the three non-farm biomass substrates.

It was assumed all manure and

substrates generated at each source would be made available for co-digestion.

Ideally, the system would include a separate influent holding tank for each substrate.

A heated

substrate holding tank would be needed if any fats, oils or greases (FOG) were secured in the future for

co-digestion. The size of the substrate holding tank(s) needs to be determined based on each supplier’s

need for disposal of biomass.

The energy crop digester sizing estimates were based on:

1. Farm data for the two identified energy crop farms

2. Average yields for corn, alfalfa and grass hay for the types of farms provided by the

Lewis County Field Crops Educator (Lawrence, 2009)

3. Energy crop digester specifics from a representative of Organic Waste Systems, Inc.

(McDonald, 2010), a company that is currently engaged in the energy crop digester

business.

12 22.5 days is the average of 20 and 25 days, which are the most common retention times for similarly sized systems

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Economics

An economic analysis was conducted to estimate the annual profitability of the Scenario No. 2

manure/non-farm biomass CAD system using data developed by this study and other available

information needed to perform the calculations. The economic analysis considered the costs and

revenues that would be generated by the system. The major cost categories include capital costs,

operating and maintenance costs, and feedstock transportation. The capital costs were converted to

annual economic costs using an annual equivalent cost approach (includes economic depreciation),

using Equation (1).

Equation (1): AEC = PV/ ( 1/r – 1/(r*(1+r)^n) )

With AEC = annual economic cost

PV = present value (initial capital investment)

r = interest rate

n = time (years)

This approach uses discounted cash flow principles to annualize the up-front investment costs. After

annualizing these costs, a series of annual budgets for the system were developed by estimating the

annual income and expenses associated with the project. The analysis did not consider any potential

grants or direct subsidies; these would have the impact of improving the economic results. Similarly, the

analysis did not include items such as insurance or tax implications.

As previously stated, the Scenario No. 2 manure/non-farm biomass CAD and the energy crop digester

system were analyzed independently, since they are mutually exclusive digester systems. The biogas

produced by the two systems could be combined immediately after production to gain economies of

scale for pre-utilization/utilization equipment, but our analysis was not performed with this assumption.

The economic analysis of each system is presented below, starting with the Scenario No. 2 CAD system.

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Scenario No. 2 Manure/Non-Farm Biomass CAD

Capital costs

The capital costs for the three main components of the Scenario No. 2 CAD system are shown in Table

30; these costs were determined by multiplying values for project specific items by a unit cost for each

of the items. The unit costs for the digester system were based on analyses of competitive proposals

received between 2007 and 2009 for previous digester system projects of a similar size and adjusted for

inflation. The unit cost used was $1.84 (minimum), $2.43 (maximum), and $2.14 (average) per gallon of

digester treatment volume. The capital cost for the Scenario No. 2 CAD system is also based on a HRT of

22.5 days 13 .

The engine-generator set capital cost is based on a unit cost of $800/kW for all GE Jenbacher enginegenerator

sets (Vernon, 2010). The size of the engine was determined based on projected quantity and

quality of biogas produced and the nearest sized engine-generator set available 14 that best matched the

projections. Other manufacturers of engine-generator sets that are also well-suited for biogas plant

applications exist and data for their systems could also be used in the analysis. The capital costs for the

engine-generator sets shown in Table 30 are for minimum, maximum, and average projected biogas

production volumes.

The capital cost for a biogas clean-up system (hydrogen sulfide and carbon dioxide removal) to produce

pipeline quality biogas (biomethane) was provided by a vendor representative for Guild Associates, Inc.

(Mitariten, 2009) for their Molecular Gate® technology SPEC plant that we understand is appropriate for

all ranges of projected biogas productions for this CAD project, at $796,000.

13 22.5 days is the average of 20 and 25 days, which are the most common retention times for similarly sized systems

14 The theoretical size of the engine-generator set needed was compared with that commercially available, which was not an

exact match

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Table 30. Capital costs ($) for Scenario No. 2 CAD system, engine-generator set, and biogas clean-up system, and

total cost for two different energy sale options

CAD system

Total Cost: Total Cost:

Engine-generator Biogas clean–up

biomethane sale electricity sale

set

system

option 1

option 2

Minimum 4,730,000 678,000 A 796,000 5,526,000 5,408,000

Maximum 7,140,000 1,146,000 B 796,000 7,936,000 8,285,000

Average 5,887,000 905,000 C 796,000 6,683,000 6,792000

1 Assumes total biogas production used in production and sale of biomethane; no electricity sale

2 Assumes total biogas production used to generate electricity; no biomethane sale

A For a 848-kW GE Jenbacher Type 3 engine-generator set

B For a 1,432-kW GE Jenbacher Type 6 engine-generator set

C For a 1,131-kW GE Jenbacher Type 4 engine-generator set

The estimated total capital costs of the Lowville CAD system ranged from $4.7 million to $7.1 million.

Annualized capital costs

The total capital investment was converted to an annual equivalent capital investment based upon the

total investment required, the cost of capital invested in the project, and the expected life of the

equipment. The cost of capital was estimated at 5 percent. The cost of capital reflects the opportunity

cost for funds invested in the project. The approach used in this analysis was to treat the discount rate

as a “real” discount rate. In other words, this discount rate does not include the impact of inflation. As

a result, no-inflation factors were applied to the future cash flows. Consistent with the request of the

Lowville Digester Work Group, the 5% cost of capital is relatively low. Increases to the discount rate

would have the impact of increasing the annual economic capital costs of the project. There are two

large capital investments associated with the project, one for the digester itself and one for either the

electrical generation equipment or the biogas clean-up equipment.

The estimated life of the digester system was assumed to be 20 years, and the estimated life of the

engine-generator set and biogas clean-up system were assumed to be 10 years, meaning the set was

replaced on a 10-year replacement cycle and for this analysis the set was replaced at the same price as it

was when the first purchase was made. In other words, the real costs of the generator are expected to

remain the same. The analysis did not inflate cash flows associated with income and expenses. This

approach is consistent with using a relatively low discount rate (5%) that is meant to reflect the real cost

of capital. A future analysis could incorporate inflation expenses into the replacement of the electrical

generation equipment. Similarly, a future analysis could shorten or lengthen the replacement cycle for

the electric generation equipment. In general, lengthening the replacement cycle will improve the

profitability of the system and shortening the cycle will decrease the profitability.

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The annualized capital costs for the Scenario No. 2 CAD system are shown in Table 31. Energy sales via

electricity and biomethane were considered for the three scenarios of minimum, maximum, and

average biogas production quantities. The total annual capital costs for the entire system necessary for

each energy sale option are shown in the two furthest right columns of Table 31. The costs of the

electrical generation equipment are annualized based upon a 10-year replacement cycle. The annual

total capital costs for the system under electrical energy generation range from $468,000 to $721,000.

The total annual capital costs for the system under biomethane production range from $483,000 to

$676,000.

Table 31. Annualized capital costs (ACC) in dollars for the Scenario No. 2 CAD system based on minimum,

maximum, and average biogas production quantities.

Total ACC:

Total ACC:

CAD Engine-Generator Gas Clean-Up

biomethane electricity sale

system

set

system

sale option 1

option 2

Minimum 380,000 88,000 A 103,000 483,000 468,000

Maximum 573,000 148,000 B 103,000 676,000 721,000

Average 472,000 117,000 C 103,000 575,000 589,000

1 Assumes total biogas production used in production and sale of biomethane; no electricity sale

2 Assumes total biogas production used to generate electricity; no biomethane sale

A For a 848-kW GE Jenbacher Type 3 engine-generator set

B For a 1,432-kW GE Jenbacher Type 6 engine-generator set

C For a 1,131-kW GE Jenbacher Type 4 engine-generator set

Annual operating and maintenance costs

Estimates for the annual operating and maintenance (O&M) costs were calculated for the Scenario No. 2

CAD, the engine-generator set, and the biogas clean-up system and the results are shown in Table 32.

The O&M costs for the engine-generator set were estimated using 1.7¢/kWh of energy produced for a

GE Jenbacher unit (Vernon, 2010). The O&M costs for the gas clean-up system were estimated

assuming 5% of capital expenses for annual maintenance and repair costs. The average total O&M costs

assuming biomethane production and sale were estimated at $227,000, and assuming electricity

production and sale, were estimated at $348,000.

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Table 32. Scenario No. 2 CAD, annual operating and maintenance expenses ($)

O&M Digester O&M Generator Biogas Clean-Up

Total: biomethane Total: electricity

sale option 1 sale option 2

Minimum 87,000 120,000 A 40,000 126,000 207,000

Maximum 301,000 203,000 B 40,000 341,000 503,000

Average 188,000 160,000 C 40,000 227,000 348,000

1 Assumes the net biogas production (20% of total for parasitic heating) used in production and sale of biomethane; no

electricity sale

2 Assumes total biogas production used to generate electricity; no biomethane sale

A For a 848-kW GE Jenbacher Type 3 engine-generator set

B For a 1,432-kW GE Jenbacher Type 6 engine-generator set

C For a 1,131-kW GE Jenbacher Type 4 engine-generator set

Total annual cost

The total annual cost, based on total annualized capital costs and annual O&M costs, are shown in Table

33. The average total annual costs assuming biomethane production and sale were estimated at

$803,000, and assuming electricity production and sale, were estimated at $937,000.

Table 33. Scenario No. 2 CAD, total annual costs ($) for options of selling biomethane and electricity

Total:

Total:

Digester Engine-Generator Biogas Cleanbiomethane

sale electricity

system

set

Up system

option 1 sale option 2

Minimum 466,000 208,000 A 143,000 609,000 674,000

Maximum 874,000 351,000 B 143,000 1,016,740 1,225,000

Average 656,000 277,000 C 143,000 803,000 937,000

1 Assumes the net biogas production (20% of total for parasitic heating) used in production and sale of biomethane; no

electricity sale

2 Assumes total biogas production used to generate electricity; no biomethane sale

A For a 848-kW GE Jenbacher Type 3 engine-generator set

B For a 1,432-kW GE Jenbacher Type 6 engine-generator set

C For a 1,131-kW GE Jenbacher Type 4 engine-generator set

Net economic profitability

The total annual costs (annual capital costs plus annual O&M costs) were compared to the estimated

revenues that could be generated by the Scenario No. 2 CAD system, and are presented for varying

biogas production volumes and revenues for biomethane sale in Table 34 and for electric power sale in

Table 35. The values in both tables indicate the annual economic gain or loss (when the numbers are in

parenthesis) associated with the system. For the option of biomethane sale, the analysis assumes that

20% of the energy generated by the system will be used to meet the parasitic heat needs of the Scenario

No. 2 CAD.

These results indicate that there is no reasonable gas or electricity price at which currently projected

biogas production volumes would allow for the revenue needed to meet capital and O&M costs. The

103


annual profitability of the system is highly negative under even the most optimistic energy price

scenarios. This includes the sale of biomethane associated with non-farm biomass co-digested with

manure; it was assumed that the substrate suppliers would cover costs associated with non-farm

biomass transportation from the business to the CAD facility. It is important to note that these are

annual economic costs. In other words, operating the digester with electricity production and sale at

$0.10 per kWh and average gas production would result in an annual economic loss of nearly $1.3

million dollars.

Table 34. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4 for various biomethane sale prices and

biogas production volumes (no tipping fees received)

Biomethane sale 1 price

($/Decatherm)

4 6 8 10 12 14

Low Biogas Production (1,971,000) (1,861,000) (1,752,000) (1,642,000) (1,532,000) (1,423,000)

High Biogas Production (1,819,000) (1,605,000) (1,391,000) (1,177,000) (963,000) (749,000)

Average Biogas Production (1,906,000) (1,745,000) (1,583,000) (1,421,000) (1,260,00) (1,098,000)

1 Assumes net biogas production (20% of total for parasitic heating) used for biomethane sale; no electricity sale

2 Assumes average capital and O&M cost estimates

3 Includes manure and CAD effluent transportation costs

4 Does not include pipeline injection costs

Table 35. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4,5 for various electrical energy sale prices

and biogas production volumes (no tipping fees received)

Electric sale 1 price

($/kWh)

0.08 0.10 0.12 0.14 0.16 0.18

Low Gas Production (1,620,000) (1,507,000) (1,394,000) (1,281,00) (1,167,000) (1,054,000)

High Gas Production (1,231,000) (1,021,000) (811,000) (600,000) (390,000) (179,000)

Average Gas Production (1,431,000) (1,271,000) (1,111,000) (951,000) (791,000) (630,000)

1 Assumes total biogas production used to generate electricity; no biomethane sale

2 Assumes average capital and O&M cost estimates

3 Includes manure and CAD effluent transportation costs

4 Does not include interconnection costs

5 Assumes no revenue from the sale of engine-generator set surplus thermal energy

The above results show that the Scenario No. 2 CAD is not economically viable for either energy sale

option, even with the most optimistic energy sale prices.

When tipping fees currently paid are included, the economic profitability overall becomes less negative;

this is shown in Table 36 and 37. For this analysis, an annual tipping fee of $277,000 ($6/ton) 15 was

used, which represents the annual cost for non-farm biomass substrate supplier #8 to dispose of their

by-products. The other two non-farm substrate providers whose by-products were included in this

analysis did not provide the current tipping fees they pay to dispose of their processing by-products.

15 An updated value provided in May 2010 to correct a wrong value shown in the non-farm biomass survey

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Table 36. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4 for various biomethane sale prices and

biogas production volumes, including current tipping fee paid by substrate supplier #8

Biomethane sale 1 price

($/Decatherm)

4 6 8 10 12 14

Low Gas Production (1,694,000) (1,585,000) (1,475,000) (1,365,000) (1,256,000) (1,146,000)

High Gas Production (1,542,000) (1,328,000) (1,114,000) (900,000) (686,000) (472,000)

Average Gas Production (1,630,000) (1,468,000) (1,306,000) (1,145,000) (983,000) (821,000)

1 Assumes total biogas production used for biomethane sale; no electricity sale

2 Assumes average annual capital and average O&M cost estimates

3 Includes manure and CAD effluent transportation average cost and tipping fee paid to project

4 Does not include pipeline injection costs

Table 37. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4,5 for various electrical energy sale prices

and biogas production volumes, including current tipping fee paid by substrate supplier #8

Electric sale 1 price ($/kWh) 0.08 0.10 0.12 0.14 0.16 0.18

Low Gas Production (1,343,000) (1,230,000) (1,117,000) (1,004,000) (891,000) (778,000)

High Gas Production (955,000) (744,000) (534,000) (323,000) (113,000) 97,000

Average Gas Production (1,155,000) (995,000 (834,000) (674,000) (514,000) (354,000)

1 Assumes total biogas production used to generate electricity; no biomethane sale

2 Assumes average capital and O&M cost estimates

3 Includes manure and CAD effluent transportation costs and tipping fee paid to project

4 Does not include interconnection costs

5 Assumes no revenue from the sale of engine-generator set surplus thermal energy

Since the economic profitability of the Scenario No. 2 CAD remained negative even when including the

tipping fee paid by non-farm biomass substrate supplier #8, and realizing the other two suppliers also

already pay a tipping fee to dispose of their by-products, we determined the tipping fees needed to

result in a break-even economic profitability for both energy sales options. The results of these analyses

are shown in Table 38 and 39.

The tipping fee revenue (column 1) represents the range in aggregated annual tipping fees received and

the correlating fee in ($/ton). The price per ton was determined by dividing the tipping fee received

(column 1) by the average total mass of all non-farm biomass received from substrates 8, 10, and 11. If

biogas prices received were $10 per decatherm, the net annual tipping fee revenues required to make

the project break-even would be $1,421,000 per year, at $21/ton. If electrical energy prices received

were $0.14 per kWh, the net annual tipping fee revenues required to make the project break-even

would be $951,000 per year.

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Table 38. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various biomethane sale prices and

tipping fees charged for non-farm biomass substrates

($/year)

Biomethane sale 1 price ($/decatherm)

Tipping Fee 4 6 8 10 12 14

($/ton)

0 0 (1,906,000) (1,745,000) (1,583,000) (1,421,000) (1,260,000) (1,098,000)

200,000 3 (1,706,000) (1,545,000) (1,383,000) (1,221,000) (1,060,000) (898,000)

400,000 6 (1,506,000) (1,345,000) (1,183,000) (1,021,000) (860,000) (698,000)

600,000 9 (1,306,000) (1,145,000) (983,000) (821,000) (660,000) (498000)

800,000 12 (1,106,00) (945,000) (783,000) (621,000) (460,000) (298,000)

1,000,000 15 (906,000) (745,000) (583,000) (421,000) (260,000) (98,000)

Breakeven

1,906,000 1,745,000 1,583,000 1,421,000 1,260,000 1,098,000

($/year)

Breakeven

29 26 24 21 19 16

($/ton)

1 Assumes total biogas production used for thermal energy sale; no electricity sale

2 Assumes average capital and O&M cost estimates

3 Assumes no revenue from the sale of engine-generator set surplus thermal energy

Table 39. Scenario No. 2 CAD, net annual economic profitability ($) 2,3 for various electrical energy sale prices and

tipping fees charged for non-farm biomass substrates

($/year)

Electric sale 1 price ($/kWh)

Tipping Fee 0.08 0.10 0.12 0.14 0.16 0.18

($/ton)

0 0 (1,432,000) (1,271,000) (1,111,000) (951,000) (791,000) (630,000)

200,000 3 (1,232,000) (1,071,000) (911,000) (751,000) (591,000) (430,000)

400,000 5 (1,032,000) (871,000) (711,000) (551,000) (391,000) (230,000)

600,000 8 (832,000) (671,000) (511,000) (351,000) (191,000) (30,000)

800,000 11 (632,000) (471,000) (311,000) (151,000) 9,000 169,700

1,000,000 13 (432,000) (271,000) (111,000) 49,000 209,000 369,700

Breakeven

1,432,000 1,271,000 1,111,000 951,000 $791,000 630,299

($/year)

Breakeven

21 19 17 14 12 9

($/ton)

1 Assumes total biogas production used to generate electricity; no thermal energy sale

2 Assumes average capital and O&M cost estimates

3 Assumes no revenue from the sale of engine-generator set surplus thermal energy

The above shows that the Scenario No. 2 CAD can be economically viable when a moderate tipping fee

is charged to the suppliers of the non-farm biomass that is significantly less than that charged by the

local landfill, which was reported to be approximately $60/ton by the Lowville Digester Work Group but

more than the calculated tipping fee being paid by non-farm biomass substrate supplier #8. It appears

that a tipping fee range of $17 to $24/ton is needed to break-even, depending on the energy sale option

chosen.

106


Energy Crop AD System

The Lowville energy crop digester would be an anaerobic digester designed to process high solids energy

crop materials (corn silage and or haylage). Such digesters are widely used in Germany and other

European countries and produce about eight times the biogas as digesters fed manure only

(Effenberger, 2006).

Silage corn and grass hay would be harvested and ensiled as if they were going to be fed to dairy cattle.

Sufficient quantities would be stored to enable the energy crop digester feed hopper (usually a walking

floor bin) to be filled once-a-day, year round, normally with a pay loader. Several times per day, the

control system would automatically transfer a portion of the feedstock into the digester; screw

conveyors (augers) are normally used due to the high solids content of corn silage and haylage. The

energy crop digester economic analysis performed for this feasibility study used “in-the-bunk” silage

prices ranging from $30 to $55/ton, meaning that the costs to grow the crops and harvest and ensile

them are covered by the purchase price.

In addition to the energy crop feedstock, a small portion of manure is also normally added to the energy

crop digester, about 10 percent by mass, to help stabilize digester pH and to provide some dilution

water to lessen the effort required to provide in-vessel mixing.

Energy crop digester effluent, rich in organic nutrients, is the consistency of digested manure. For this

feasibility study, it is assumed the effluent would be stored on-site for a short period of time and

periodically trucked to the energy crop source farms for longer-term storage and for subsequent use as

fertilizer to grow the next rotation of energy crops. Some of the surplus nutrients from the Lowville CAD

system could also be trucked to the source farms to meet the overall fertilizer requirements for the

crops grown on those farms.

Capital Costs

The total capital cost of the energy crop digester was estimated to be $4.5 million dollars. This price was

developed using the same fashion as the capital cost of the Lowville CAD system was determined; unit

price information calculated from data provided by a company involved in energy crop digesters,

Organic Waste Systems, Inc. (McDonald, 2010), was used in conjunction with project specific

information.

107


The estimated total capital cost for the GE Jenbacher Type 4 engine-generator set that most closely

matches (1,131 kW) the biogas available to fuel the set is $904,800. For this option, the biogas clean-up

to biomethane was not investigated, since economic profitability analysis results for the Scenario 2 CAD

showed little difference in the bottom line when comparing biomethane sale vs. electrical energy sale.

Annualized capital costs

Using the same procedure and assumptions for determining the annualized capital costs for the Scenario

No. 2 CAD system, the annual capital cost for the energy crop digester and engine-generator set is

$361,000 and $117,000, respectively for a total annual capital cost of $478,000.

Annual operating and maintenance costs

The annual operating and maintenance (O&M) costs were calculated using the same procedure and the

assumptions for the Scenario No. 2 CAD system, with one notable difference being that the energy crop

digester O&M costs were based on the recommendation to use 2.5% of the capital cost of the system

(McDonald, 2010). The energy crop digester and engine-generator set annual O&M costs are $113,000

and $123,000, respectively, for a total annual O&M cost of $236,000.

Digester feedstock cost

The energy crop digester feedstock cost is an important item to consider since it is a major cost of the

system and will have the biggest impact of all costs on profitability. This cost will likely annually be

reflective of the cost to supply corn silage and haylage to dairy cows. Based on farm data and average

crop yields for the area, 27,600 tons of crops would be ensiled at Site 1 and the energy crop digester

project would purchase corn silage and haylage “out of the bunker”. The annual estimated cost for

feedstock is shown in Table 40 for a unit price range of $30 to $55/wet ton.

Table 40. Annualized capital costs ($) for energy crop digester system

Feedstock Unit Cost

($/wet ton) out of a 30 35 40 45 50 55

bunker on-site

Annual Feedstock Cost ($) 828,000 966,000 1,104,000 1,242,000 1,380,000 1,518,000

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Net economic profitability

The net annual economic profitability for the energy crop digester is presented in Table 41 for the

situation only producing electricity for sale, over a range of feedstock and electricity sale prices. The

economic profitability was determined by subtracting the following values from the total average

electricity production: total annual capital costs, total O&M costs, the lowest potential feedstock costs,

and the cost to transport energy crop digester effluent back to collaborating crop farms.

Table 41. Net annual economic profitability ($) for various electricity prices and feedstock costs

Electric sale

price

($/kWh)

Energy Crop

Digester

Feedstock Unit

Cost ($/wet

ton)

0.08 0.10 0.12 0.14 0.16 0.18

30 (967,000) (807,000) (646,000) (486,000) (326,000) (165,000)

35 (1,105,000) (945,000) (784,000) (624,000) (464,000) (304,000)

40 (1,243,000) (1,083,000) (922,000) (762,000) (602,000) (442,000)

45 (1,381,000) (1,221,000) (1,060,000) (900,000) (740,000) (580,000)

50 (1,519,000) (1,359,000) (1,198,000) (1,038,000) (878,000) (718,000)

55 (1,656,000) (1,497,000) (1,336,000) (1,176,000) (1,016,000) (856,000)

The net annual economic profitability is negative for all combinations of feedstock purchase price and

electrical energy sale price considered, meaning that the energy crop digester system would cost more

to own than the value of the annual revenue received. Therefore, consideration of an energy crop

digester is not recommended at this time.

109


Farm Impacts

Capital improvements

In order to successfully implement the Scenario No. 2 CAD system, some of the targeted collaborating

farms will need to make on-farm modifications. Based on the farm survey results (Table 10) seven of

the 15 collaborating dairy farms (Nos. 5, 11, 14, 16, 19, 21, and 23) would need to construct short-term

manure storages in order to hold at least 6,000-gallons of manure to be collected by the 6,000-gallon

manure tanker truck with an on-board pumping system. A short-term manure storage was defined by

the project as a storage with the ability to hold one to three day’s worth of manure generated by that

farm. Constructing a manure storage larger than 6,000-gallons will give a farmer the flexibility to store

manure for additional time, should there be a reason that the manure cannot be picked up from the

farm.

A manure bypass system will also need to be included to be used when the manure tanker truck cannot

access the farm manure storage site; this is unlikely to happen often, but could arise as an issue due to

poor road conditions. The ideal manure bypass system would include a pump capable of pumping

manure not only directly to the farm’s long-term manure storage, but also into the manure tanker for

times when its on-board pumping system may fail and also into the farm’s manure spreader.

Other farm improvements may include access roads and utility upgrades; these are all site specific and

the capital cost associated with them will vary from farm to farm.

The estimated capital cost to construct a 10,000-gallon short-term manure storage with bypass pump is

shown in Table 42. The storage construction cost is based on poured-in-place concrete construction;

the walls are 10” thick and the floor is 6” thick, as recommended by the local Soil and Water

Conservation District office (Durant, 2008). Costs include a manure storage gravel access pad for more

reliable access to the 6,000-gallon manure tanker truck upon collection. These specifications would

require about 40 yd 3 of concrete, at a price of $86/yd 3 (Durant, 2008). The access pad is assumed to be

6” thick concrete (NRCS, 2008). A centrifugal pump is specified for use as the bypass pump, with an

estimated cost of $16,000 (NRCS, 2008).

110


Table 42. Capital cost estimate per farm for construction of a 10,000-gallon on-farm short-term manure storage

Total cost of concrete $3,450

Labor $6,900

Gravel $900

Excavation/site prep $1,500

Pump in short-term storage $16,000

Electrical service/upgrade $2,000

Access road $3,500

Total $34,250

Nutrients

Chapter 4 contains the results of the laboratory nutrient concentration testing of the non-farm biomass

substrates. The raw manure nutrient values shown in Table 43 represent the 15 collaborating farms for

Scenario No. 2. Total post-digestion nutrient mass of nitrogen, phosphorus and potassium series are

provided in Table 43 and Table 44.

Table 43. Scenario No. 2 CAD estimated post-digestion nitrogen series and total annual masses by feedstock

source

Post Digestion TKN Post Digestion Ammonia-N

Digestate

source

Post Digestion Organic-N

(lbs/year)

(lbs/year)

(lbs/year)

Minimum Maximum Minimum Maximum Minimum Maximum

8 17,420 25,230 3,090 4,470 18,520 26,830

10 165,140 165,140 41,240 157,460

11 490 - -

Manure 1,573,710 - -

Total 1,756,760 1,764,570 44,330 45,710 175,980 184,290

Table 44. Scenario No. 2 CAD estimated post-digestion phosphorus and potassium series and total masses by

feedstock source

Post Digestion Total Phosphorus Post Digestion Ortho Post Digestion Potassium

Digestate

(lbs/year)

Phosphorus (lbs/year)

(lbs/year)

source

Minimum Maximum Minimum Maximum Minimum Maximum

8 16,730 24,240 7,970 11,540 12,800 18,540

10 82,790 3,970 24,930

11 5 - 0

Manure 270,230 - 365,610

Total 369,755 377,265 11,940 15,510 403,340 409,080

The land base used to grow the crops for the proposed energy crop digester could be used to receive

the nutrients contained in CAD effluent. Discussions between the Lowville Digester Work Group and

owners of area crop farms have shown the willingness of some crop farmers to receive digested effluent

at their farms to replace some or all of the commercial fertilizers currently used. One of the initial goals

111


of the project was to improve the nutrient balance situation in the region; re-distributing nutrients from

farms with excess to farms that are deficient would significantly advance this goal.

Similar to Figure 28, a comparison of the volume of manure provided to the CAD by each farm and the

volume of digested effluent the farm in turn would receive back is shown in Figure 29; however, in this

case, each farm’s individual nutrient balance situation is taken into account. The farms that have either

a balanced or excess nutrient situation would receive an amount of CAD effluent equivalent to the

amount of manure they provide to the CAD project, contrary to the increased amount of effluent they

would receive in the weighted scenario, shown in Figure 28. Assuming farms receive effluent in this

manner, there would be an estimated 11 million gallons/year of excess CAD effluent available for sale to

area crop farms.

Figure 29. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received, by farm,

taking into account each farm's nutrient balance situation.

112


Assuming the non-farm biomass imported for co-digestion supplies excess nutrients to the postdigestion

product that would be available for sale to area crop farms, the project could potentially

receive $226,000/year in total revenue. Of the $226,000/year, $86,000/year would be derived from the

sale of nitrogen, $121,000/year would be derived from the sale of phosphorus, and $19,000/year would

be derived from the sale of potassium 16 .

16 Based on fertilizer sale prices for N,P,and K of $0.46/lb, $0.51/lb, and $0.40/lb, respectively.

113


114


Chapter 8. Future Work and Recommendations

The recommendation for a CAD system is based on conducting thorough and complete technical and

economic feasibility analyses, as well as the vision of the Lowville Digester Work Group. Based on this,

the recommendation is to further investigate one centrally-located complete mix AD, sited adjacent to

the LWWTP that would co-digest manure from 15 targeted collaborating dairy farms and targeted nonfarm

biomass substrates (currently the following three substrates: whey, post-digested sludge, and

glycerin) that are by-products generated nearby.

The future net annual economic profitability behind this recommendation is encouraging, given that, (1)

the calculated tipping fee needed for the system to break-even is well below the average tipping fee

charged in the northeastern U.S. and many predict regulations will be instituted in the near future

restricting the land-filling of organic matter, (2) future regulations aimed at reducing the impact of fossilfuel

derived energy (specifically GHG emissions and climate change) would likely positively impact

renewable energy projects, and (3) the annual economic profitability will improve with reductions in

capital cost by receiving grants and/or premium payments for renewable energy.

If future efforts are put forth to further investigate one CAD, it is recommended that the two major

areas provided below be addressed in the order presented and that the bullet items under each be

included.

A. Address Economic Barriers to Project Implementation




Identify other potential sources of non-farm biomass that are currently being landfilled

or otherwise disposed of that could be received by the CAD with a tipping fee

paid by the supplier

Continue the education and outreach efforts concerning this project and the goals and

objectives of local community members, targeted at collaborating and noncollaborating

dairy farmers and non-farm biomass substrate suppliers to develop

project support targeted towards securing public funding.

Secure grant funding or subsidies that could help offset the capital cost of the CAD

and/or supplement the revenue(s) received for system outputs (raw biogas,

electricity, biomethane, and/or organic nutrients)

115


Investigate the willingness of non-farm biomass suppliers to enter into reasonable

long-term contracts , with a negotiated tipping fee

Investigate the willingness of the end user(s) of the net energy produced by the CAD

facility to enter into reasonable long-term contracts

B. Advanced Project Due Diligence












Perform more complete laboratory testing of the targeted substrates mixed

proportionally with manure to better solidify the quantity of biogas that would be

produced by the system

Conduct an in-depth site and environmental impact assessment for the targeted

construction site

Investigate the legal issues for various digester ownership options

Determine the permit(s) that will be required by the New York State Department of

Environmental Conversation (NYSDEC) 17

Conduct an in-depth investigation into the site improvements that will be required at

each farm in order to participate in the project, and develop an associated budget

Validate the trucking analysis and farm biomass pick-up options

Investigate contracting with an existing trucking company to provide transportation of

farm biomass

Develop a request for proposals (RFP) package to be distributed to AD system

designers

Validate the economic profitability analysis using the results of the proposed RFP

Continue investigation into future opportunities, such as manure nutrient extraction

equipment and resulting product marketing opportunities for organic nitrogen,

phosphorus, and potassium

Continue reassessment of market opportunities such as the sale of biomethane as a

vehicle fuel.

17 There are currently no operating dairy manure-based CAD systems in NYS, and an initial inquiry made by Cornell to NYSDEC

on behalf of this project revealed that NYSDEC is not readily prepared to state what permit(s) is/are needed.

116


References

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University. Personal Communication.

American Society of Agricultural and Biological Engineering (ASABE) Standards, 52 nd ed. 2005. ASAE

D384.2 Manure Production and Characteristics. ASABE, Joseph, Michigan.

Bennett, S. 2003. Feasibility Report of a Cooperative Dairy Manure Management Project in St.

Albans/Swanton, VT.

Bothi, K.I. and B.S. Aldrich. Fact sheet: Feasibility Study of a Central Anaerobic Digester for Ten Dairy

Farms in Salem, NY. www.manuremanagement.cornell.edu 2005.

Casey, J., L. Gerson, A. Smith, N.R. Scott, and L. Albright. 2007. Cornell’s Proposed Anaerobic Digester.

Cornell Cooperative Extension (CCE) of Wyoming County. 2002. Feasibility Study of Anaerobic Digestion

Options for Perry, New York. Web address:

http://counties.cce.cornell.edu/wyoming/agriculture/programs/anaerobic_digestion/files/Feasa

bilityStudyFinalReport.doc

Durant, Mike. Natural Resources Conservation Service (NRCS). 2008. Draft engineering drawings for onfarm

manure storage.

Edgar, Thom G., and Andrew G. Hashimoto. 1991. Feasibility Study for a Tillamook County Dairy Waste

Treatment and Methane Generation Facility. Department of Bioresource Engineering, Oregon

State University.

Effenberger, Mathias. 2006. Dipl. – Ing. M.Sc. Mathias Effenberger. Bavarian State Research Center for

Agriculture (LfL) Institute of Agricultural Engineering and Animal Husbandry.

Energy Information Administration (a), 2009. How much electricity does a typical American home use

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United States Environmental Protection Agency (USEPA). 1997. A Manual for Developing Biogas Systems

at Commercial Farms in the United States. EPA-430-B-97-015.

Gooch, C.A., S.F. Inglis, and P.E. Wright. 2007. Biogas Distributed Generation Systems Evaluation and

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Research and Development Authority. NYSERDA Project No. 6597. Albany, New York.

117


Gooch, C.A., and J.L. Pronto. 2009. Unpublished graph; Data from NYSERDA Project Nos. 6597 and 9446,

Digester Assessment following the protocol developed by Association of State Energy Research

and Technology Transfer Institutions.

Jewell, W.J. 2007. Professor Emeritus of Biological and Environmental Engineering, Cornell University.

Personal Communication.

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New York. Prepared for: USDA-NRCS.

Koelsch, R.K., E.E. Fabian, R.W. Guest, J.K. Campbell. Undated. Anaerobic Digesters for Dairy Farms.

Agricultural and Biological Engineering Extension Bulletin 458. Cornell University, Ithaca, NY

14853.

Labatut, R.A. and N.R. Scott. 2008. Experimental and Predicted Methane Yields from the Anaerobic Codigestion

of Animal Manure with Complex Organic Substrates. ASABE Paper No. 08-5087.

Lawrence, Joe. 2009. Field crop extension educator, Cornell Cooperative Extension of Lewis County.

Personal Communication.

Lewis County Digester Work Group. 2008. A Partnership of the Supply Chain with Benefits to the

Community and the Dairy Industry. Committee working document.

Lopez, J.A., et al. 2009. Anaerobic digestion of glycerol derived from biodiesel manufacturing.

Bioresource Technology 100 (2009) 5609-5615.

Ludington, D.C. and S.A. Weeks. 2008. The Characterization of Sulfur Flows in Farm Digesters at Eight

Farms.

Mack Trucks, Canada. 2009. Personal communication. .

Marks, L.S. 1978. Mechanical Engineers’ Handbook, 4 th Edition. McGraw-Hill Book Company, Inc.

McDonald, Norma. 2010 North American Sales Manager, Organic Waste Systems, Inc.

Communication.

Personal

Minchoff, CJ, and Kifle G. Gebremedhin. 2006. Economic Feasibility Study for a Centralized Digestion

System. Proceedings of the 2006 ASABE Annual International Meeting. Portland, Oregon, July 9-

12. American Society of Agricultural and Biological Engineers, St. Joseph, Michigan. Paper No.

064198.

Mitariten, Michael. Senior Engineer. Guild Associates, Inc. 2009. Personal Communication.

Public Interest Energy Research. 2006. Glossary of energy terms. Website:

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118


Repa, Edward W. 2005. NSWMA’s 2005 Tip Fee Survey. National Solid Wastes Management Association

Research Bulletin 05-3.

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Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.

Scott, Norm. 2010. Personal Communication.

Strand Associated, Inc. 2008. Community Manure Management Facilities Plan, Dane County, WI.

Tabolt, Mark. Lowville Wastewater Treatment Plant Manager. Personal communication. December 15,

2009.

Weisman, W. 2008. Lane Renewable Energy Complex, Lane County, Oregon.

Vernon, Todd. 2010. Senior Sales Manager, GE Energy - Jenbacher

Vokey, Frans. Cornell Cooperative Extension, Lewis County. Personal communication. 2010.

Wright, P.E. 2001. Overview of Anaerobic Digestion Systems for Dairy Farms. Proceedings of Dairy

Manure Systems, Equipment and Technology Conference; Rochester, New York, March 20-22.

NRAES-143. Natural Resource, Agriculture, and Engineering Service. Cornell University, Ithaca,

New York.

Wright, P.E., Inglis, S.F, Stehman, S.M, and J. Bonhotal. 2003. Reduction of Selected Pathogens in

Anaerobic Digestion. Proceedings of the Ninth International Symposium, Animal, Agricultural

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Agricultural and Biological Engineers, St. Joseph, Michigan.

119


120


Appendix A. Glossary for New York State Manure-Based

Anaerobic Digestion 18

Anaerobic bacteria

Microorganisms that live and reproduce in an environment containing no “free” or dissolved

oxygen.

Anaerobic digester

A vessel and associated heating and gas collection systems designed specifically to contain

biomass undergoing digestion and its associated microbially produced biogas. Conditions

provided by the digester include: an oxygen-free environment, a constant temperature, and

sufficient biomass retention time.

Anaerobic digestion

A biological process in which microbes break down organic material while producing biogas as a

by-product.

Anaerobic lagoon

A holding pond for livestock manure that is designed to anaerobically stabilize manure, and may

be designed to capture biogas with the use of an impermeable, floating cover.

Annual capital cost

The equivalent annual capital cost converts the total capital costs into an annual charge. The

equivalent annual capital cost is calculated according to the formula

EAC= pv/(1/r - 1/(r*(1+r)^n)) where “pv” is the present value or total capital investment in

today's dollars, r is the discount rate, and n is the life of the capital investment.

Barn effluent

Material exiting a barn structure, generally consisting of animal excrement (urine and feces) and

used bedding material, and may contain milking center washwater.

Biogas

For the purposes of this document, the raw and un-cleaned gas produced by an AD, consisting of

mainly methane CH 4 (~60%), carbon dioxide CO 2 (~40%), water vapor, and hydrogen sulfide.

British Thermal Unit (Btu)

The English System standard measure of heat energy. It takes one Btu to raise the temperature

of one pound of water by one degree Fahrenheit at sea level.

18 Reference: (Public, 2006)

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Capital cost

A one-time fixed cost incurred on the purchase of buildings and equipment. A digester’s capital

cost includes the purchase of land the system is on, permitting and legal costs, the equipment

needed to run the digester, cost of digester construction, the cost of financing, and the cost of

commissioning the digester prior to steady-state operation of the digester.

Centralized digester

An anaerobic vessel which uses feedstocks from several farms and/or other biomass sources,

within a relatively proximate distance to the digester location.

Co-generation

The sequential use of energy for the production of electrical and useful thermal energy. The

sequence can be thermal use followed by power production or the reverse, subject to the

following standards: (a) At least 5% of the co-generation project’s total annual energy output

shall be in the form of useful thermal energy. (b) Where useful thermal energy follows power

production, the useful annual power output plus one-half the useful annual thermal energy

output equals not less than 42.5% of any natural gas and oil energy input.

Combined Heat and Power (CHP)

The sequential or simultaneous generation of two different forms of useful energy – mechanical

and thermal – from a single primary energy source in a single, integrated system. CHP systems

usually consist of a prime mover, a generator, a heat recovery system, and electrical

interconnections configured into an integrated whole.

Complete mix digester

An anaerobic vessel that is mixed with one or more mixing techniques.

Dewater

To drain or remove water from an enclosure. Dewater also means draining or removing water

from sludge to increase the solids concentration.

Digestate

Effluent; Material remaining after the anaerobic digestion of a biodegradable feedstock.

Digestate is produced both by acidogensis and methanogenesis, and each has different

characteristics.

Discount rate

The interest rate used in discounting future cash flows.

Distributed generation

A distributed generation system involves small amounts of generation located on a utility’s

distribution system for the purpose of meeting local (substation level) peak loads.

Distribution system (electric utility)

The substations, transformers and lines that convey electricity from high-power transmission

lines to consumers.

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Effluent

Digestate; Material exiting the AD vessel.

Emission

The release or discharge of a substance into the environment; generally refers to the release of

gases or particulates into the air.

End-use sectors

The residential, commercial, transportation and industrial sectors of the economy.

Engine-Generator set

The combination of an internal combustion engine and a generator to produce electricity; may

be single or dual fueled depending on the location and set up.

Flare

A device used to safely combust surplus or unused biogas.

Greenhouse Gas (GHG)

A gas, such as carbon dioxide or methane, which contributes to a warming action in the

atmosphere.

Grid

The electric utility companies’ transmission and distribution system that links power plants to

customers through high power transmission line service; high voltage primary service for

industrial applications; medium voltage primary service for commercial and industrial

applications; and secondary service for commercial and residential customers. Grid can also

refer to the layout of gas distribution system of a city or town.

Hydraulic retention time (HRT)

The length of time material remains in the AD.

Hydrogen sulfide (H 2 S)

A toxic, colorless gas that has an offensive odor of rotten eggs. Hydrogen sulfide has serious

negative implications for the wear of gas handling equipment for an anaerobic digester system.

Hydrolysis

A biological decomposition process involved in the anaerobic digestion of organic material.

Influent

Biomass on the in-flow side of a treatment, storage, or transfer device.

Installed capacity

The total capacity of electrical generation devices in a power station or system.

Kilowatt-hour (kWh)

The most commonly used unit of measure of the amount of electric power consumed over time.

The stand-alone unit indicates one kilowatt of electricity supplied for one hour.

123


Lagoon

In wastewater treatment or livestock facilities, a shallow pond used to store wastewater where

biological activity decomposes the waste.

Lost capital

The portion of a capital investment that cannot be recovered after the investment is made,

usually used to express the immediate loss in value of a purchased or constructed item.

Main tier

Distributed renewable energy systems where the electrical power produced is not used on-site

but rather transported to the grid for use elsewhere. Wind generation generally falls into this

category.

Manure

The combination of urine and feces.

Methane (CH 4 )

A flammable, explosive, colorless, odorless, gas. Methane is the major constituent of natural

gas, and also usually makes up the largest concentration of biogas produced in an anaerobic

digester.

Methanogens

Active in phase 3 of the digestion process, acids (mainly acetic and propionic acids) produced in

phase 2 are converted into biogas by methane-forming bacteria.

Microturbine

A small combustion turbine with a power output ranging from 25- to 500-kW. Microturbines

are composed of a compressor, combustor, turbine, alternator, recuperator, and generator.

Net generation

Gross generation minus the energy consumed at the generation site for use in maintaining

energy needs (heat or electric).

Net Present Value (NPV)

The present value of an investment’s future net cash flow minus the initial investment.

Generally, if the NPV of an investment is positive, the investment should be made.

Operation and Maintenance (O&M) costs

Operating expenses are associated with running a facility. Maintenance expenses are the

portion of expenses consisting of labor, materials, and other direct and indirect expenses

incurred for preserving the operating efficiency or physical condition of a facility.

Plug-flow digester

A design for an anaerobic digester in which the material enters at one end and is theoretically

pushed in plugs towards the other end, where the material exits the digester after being

digested over the design HRT.

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Present value

The current value of one or more future cash payments, discounted at some appropriate

interest rate.

Rate of return

The annual return on an investment, expressed as a percentage of the total amount invested.

Siloxane

Any of a class of organic or inorganic chemical compounds of silicon, oxygen, and usually carbon

and hydrogen, based on the structural unit R 2 SiO where R is an alkyl group, usually methyl.

Tipping fees

Monies that are paid to a site that is accepting outside sources of organic material (non-farm

biomass).

Ton

Tonne

US short ton equals 2,000 lbs

Metric ton equals 1,000 kg

Treatment volume

Inside volume of an anaerobic digester that, under normal operating conditions would be full of

material undergoing anaerobic decomposition.

Turbine

A device for converting the flow of a fluid (air, steam, water, or hot gases) into mechanical

motion.

Volatile solids

Those solids in water or other liquids that are lost on ignition of the dry solids at 550 degrees

Centigrade.

125


126


Appendix B. Survey data for Lewis County Anaerobic Digester

Feasibility (Farm based survey)

Farm name: ________________________________________

Contact: ___________________________________________

Farm mailing (or street) address: __________________________________________________

Who is your nutritionist _________________________________________________

Do we need permission to contact your nutritionist _______________________

Cow population questions

At the present time, what is the:

Number of mature cows: ________________

Number of heifers: __________________

Housing type for both groups: _______________________________________________

Bedding type for both groups: _______________________________________________

2 years from now, what changes do you expect to see in the:

Number of mature cows: ________________

Number of heifers: __________________

Housing type for both groups: _______________________________________________

Bedding type for both groups: _______________________________________________

5 years from now, what changes do you expect to see in the:

Number of mature cows: ________________

Number of heifers: __________________

Housing type for both groups: _______________________________________________

Bedding type for both groups: _______________________________________________

Do you have off-site heifer manure ________________

If yes, what is the:

Address: __________________________________________________

Population of heifers providing manure: __________________

Age span of off-farm heifers: _____________________________________

127


Manure composition questions

Is milking center wastewater or other extra water included in the manure _________________

Estimated amount of extra water: ________________ (gallons/day)

If water is added, is it possibly to separate it from the manure flow (Y/N) ____________

Does the farm use Rumensin ® for any of the cows (lactating or heifer) ____________________

Does the farm use copper sulfate for foot-baths ___________________________________

Is there a copy of a recent (< 2 years) manure analysis available ________________________

Do you have an excess OR a lack of manure nutrients on your farm ______________________

How much of each of the following do you have in excess, OR are lacking:

N ________________ (lbs/year)

P________________ (lbs/year)

K ________________ (lbs/year)

Manure handling and storage questions

Manure

Storage

Size

(circle

units)

Animal

groups

Wastewater

included

1 Gal/cu ft Yes/No

Describe

access

(paved, dirt

road, etc.)

How is manure

transferred

(pumps, gravity,

etc.)

How often is

this storage

spread on

fields

How many

acres is it

spread

on

2 Gal/cu ft Yes/No

3 Gal/cu ft Yes/No

4 Gal/cu ft Yes/No

5 Gal/cu ft Yes/No

What is the approximate acreage of: (1) Corn: _____ (2) Grass hay: _____ (3) Alfalfa: _____

(4) Other: _____

Is there short-term (1-3 days) storage available ________________________________

Is there long-term storage available _____________________________________

If yes, how many months storage does it provide _______________________

Describe the access to both short-term and long-term storages; is it directly off a paved road If possible,

please provide a rough map describing the layout. _____________________________

______________________________________________________________________________

128


Where, if any, are the existing pumps located in the manure handling system _______________

______________________________________________________________________________

Is dealing with frozen manure an issue at your farm ___________________________________

Does your farm have significant waste feed to dispose of (ex. Feed refusal, spoiled forage, etc.)

_____________________________________________________________________________

Perspective questions

What concerns would you have in spreading manure that you receive back from a common central

anaerobic digester system __________________________________________________

______________________________________________________________________________

Would you be willing to pay for necessary features or additions that are necessary for the

removal/delivery of manure and digested material (this includes storage facilities, pumps, etc.)

______________________________________________________________________________

Would you be interested in discussing the formation of a cooperative to run and manage this centralized

digester

______________________________________________________________________________

Thank you, for taking the time to complete this survey! Feel free to add any additional comments,

concerns or questions in the space below.

129


130


Appendix C. Survey data for Lewis County Anaerobic Digester

Feasibility (Non-farm based survey)

Company name: ________________________________________

Industry type: _____________________

Contact: ___________________________________________

Mailing address: _____________________________________________________

Give a description of the type of organic material you would be disposing of:

_____________________________________________________________________________________

___________________________________________________________

Organic

waste

item

Solid or

Liquid

Fat, oil, or

protein

Pre-consumer

or postconsumer

Quantity

or volume

Frequency of

removal

Frequency of

accumulation

(seasonality) 1

1 This means, do you only produce this waste at a certain time of year

Do you have any lab analysis of the organic material you would be disposing of And could this be made

available _______________________________________________

Do you currently have a method to dispose of the organic material your business produces (Y/N)

___________________

Do you pay someone to provide this service (Y/N) ___________________________

What is the approximate cost of this disposal ________________________________

131


What is the setup of the storage facility for the organic material produced by your business Please

describe any pits, tanks, pumps, or other equipment used in conveying the organic material to disposal.

_____________________________________________

________________________________________________________________________

What are your feelings/concerns about providing this organic material to a common central anaerobic

digester system ____________________________________________

________________________________________________________________________

Thank you, for taking the time to complete this survey! Feel free to add any additional comments,

concerns or questions in the space below.

132


Appendix D. Substrate Sampling Report

This report details the process of collecting samples of non-farm biomass substrates from substrate

suppliers in Lewis County.

Residential food waste

A local volunteer for the Lowville digester project provided food waste samples from her home which

consisted of residential food waste, chopped with a knife and mixed using a food processor, as shown in

Figure 30. There are considerable logistical problems with obtaining a representative sample of

residential food waste, which varies considerably in content and volume throughout the year and from

home to home.

Meat and butcher’s waste

Samples of meat, fat and guts were collected from a local butcher. The offal was deposited in eight oil

drums and included blood, intestines, hides, livers, fat and other assorted butcher wastes, as shown in

Figure 31. To obtain a representative sample, some blood was pooled into a container along with slices

of liver, intestine and fat that had been manually mixed using a power drill. Since the waste was not

uniform throughout the barrels, the sample incorporated elements from several of the barrels. The

owner of the establishment noted that during deer season (October-December), deer bones would be

the sole by-product from the butchering plant.

Dilute whey

A sample of diluted whey and CIP waste water was collected from a dairy processing plant. Employees

explained that waste whey was disposed of every day while CIP wastewater, was disposed of about

every three days. Thus, a representative sample was taken by mixing three parts whey to one part CIP

wastewater. It should be noted that the substrate supplier already pumps this waste to a location to be

trucked off-site; therefore, no additional infrastructure would likely be necessary for collection and

inclusion to the proposed digester project.

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Grocery store scraps

A local grocery chain was unable to provide a food waste sample, since the portion of their usable food

waste is deposited into a catch-all dumpster that accumulates a high degree of contamination, such as

plastic, metal and other indigestible refuse. Produce waste is currently piped through the local sewer

system to the wastewater treatment plant after being sent through a garbage disposal. Collaboration

between the bakery, produce, and meat departments within the grocery store need to improve in order

to coordinate a large scale waste separation process in the future.

Post-consumer scraps

Samples were taken from multiple local restaurants all of which contributed samples of mixed pre- and

post-consumer food waste in addition to samples of fryer grease. For the purpose of the biological

methane potential (BMP) trials, food and grease wastes from two of the restaurants were combined in

proportion to what they normally produce. Similar waste streams were provided by two local

institutions that were comprised entirely of post-consumer scraps. One institution separated waste into

solid and liquid portions – these were re-mixed for the purpose of sampling and analysis.

Florist shop waste

Finally, a sample was taken from a local florist consisting of refuse flower stems, flowers, petals, and

other plant matter.

Figure 30. Image of residential food waste sample collected.

134


Figure 31. Meat and butcher waste from substrate number 4.

135


136


Appendix E. Biochemical Methane Potential Laboratory

Procedure

320-mL bottles are used in the trials, and contain 200 mL of substrate, inoculum, and

nutrient medium. Inoculum is an active anaerobic mixed culture media obtained from an

operating bench scale AD reactor. The nutrient medium is added for the purpose of

providing the necessary nutrients and trace elements for the microorganism to thrive.

Bottles with only inoculum were used in the set up as controls, to account for the

background methane produced in the bottles by the inoculum.

Bottles containing only water were also used in the set up as controls, to correct for

internal pressure variations due to external temperature and atmospheric pressure

fluctuations.

Prior to incubation, bottles were gassed-out with a mixture of 70% N 2 and 30% CO 2 and

sealed immediately.

Sealed bottles were placed in a mesophilic (37±1°C) incubator containing a shaker to

constantly agitate the bottles during the trials.

The biogas production within the bottles was determined by pressure transducers

attached to a hypodermic needle inserted through the septa of each bottle.

Pressure measurements were performed continuously over a period of 30 days using a

data acquisition (DAQ) system connected to a computer. As pressure built-up in the

bottles, it was periodically released by way of a valve in the top of the bottles. The

instances of these pressure release events can be seen in Figure 12 by the presence of the

small dips across the lines on the graph.

Pressure data recorded by the DAQ system were converted to volume of biogas at a

standard temperature and pressure (STP) according to the ideal law of gases (PV = nRT).

STP is defined as 1°C and 1atm.

Temperature inside the incubator was also continuously monitored through the DAQ with

a thermocouple placed inside a control bottle containing water.

Methane and carbon dioxide content in the biogas was determined by a gas

chromatograph (GC) and the methane yield was subsequently calculated.

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138


Appendix F. Projected farm survey responses

Table 45. Farm survey responses based on projections for two years

Farm ID

number

Number

of

mature

cows

Number

of

heifers

Lactating cow

equivalents

(LCE) (total

solids basis)

1* 200 150 262

2 0 150 62

3 66 10 70

4 105 75 136

5 620 80 653

6* 85 70 114

7* 195 195 275

8 80 80 113

9 688 448 872

10 145 115 192

11 190 160 256

12* 195 160 261

13 155 150 217

14* 175 80 208

15 85 35 99

16 75 70 104

17 80 70 109

18* 600 0 600

19 550 430 726

20 54 36 69

21 91 60 116

22 91 60 116

23 150 40 166

24 85 10 89

25 80 100 121

SUM 4,840 2,834 6,002

139


Table 46. Farm survey responses based on five year projections

Farm ID

number

Number

of

mature

cows

Number

of

heifers

Lactating cow

equivalents

(LCE) (total

solids basis)

1* 200 150 262

2 0 150 62

3 66 10 70

4 105 75 136

5 620 80 653

6* 85 70 114

7* 195 195 275

8 80 80 113

9 688 448 872

10 145 115 192

11 190 160 256

12* 195 160 261

13 155 150 217

14* 175 80 208

15 85 35 99

16 62 62 87

17 80 70 109

18* 500 150 562

19 750 430 926

20 54 36 69

21 91 60 116

22 91 60 116

23 150 40 166

24 85 10 93

25 50 60 121

SUM 4,897 2,936 6,151

140

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