Laminaria digitata - Algecenter Danmark

Life Cycle Assessment of biogas
production process from Laminaria
digitata
Merlin Alvarado�Morales
Bioenergy Research group
Department of Environmental Engineering
Technical University of Denmark

� ... \Introduction
� ... \Objective
� ... \LCA framework
� ... \ ○ Goal and scope definition
○ Inventory analysis (LCI)
○ Impact assessment
○ Interpretation \
� ... \ Conclusions
….\Agenda to be followed
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�Objective
….\Introduction
The aim of this work was to perform a Life Cycle
Assessment (LCA) of a biogas process from
Laminaria digitata to identify bottlenecks and to
improve the environmental aspects at various
points in its life cycle.
3

o ISO 14040 (ISO 2006)
o ILCD Handbook (EU-JRC-IES, 2010)
….\LCA framework
4

�Goal and scope definition
o Functional unit
o System boundaries
o Assumptions and limitations
o Impact categories
….\LCA framework
5

�Inventory analysis (LCI)
….\LCA framework
o Inventory of flows from and to environment
o Inputs of water, energy, and raw materials
o Outputs to air, land, and water
o Data flows are related to the functional unit
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�Impact assessment
o Selection of impact categories (global
warming, eutrophication, etc.)
o Selection of characterization models
o Impact measurement
….\LCA framework
7

�Interpretation
o Identification of significant issues
o Evaluation of the study
... \ Completeness
... \ Sensitivity analysis
... \ Consistency check
….\LCA framework
o Conclusions, limitations and recommendations
8

�Goal and scope definition
Functional unit
Cultivation and processing of one tonne of dry
….\LCA framework
seaweed biomass –Laminaria digitata– produced
in Denmark for biogas production.
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�Goal and scope definition
….\LCA framework
To assess the potential environmental impacts of
a seaweed-based biogas process as well as to
identify hotspots in the life cycle where
environmental performance of the system can be
improved.
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�Goal and scope definition
….\LCA framework
o The impact assessment was performed based
on EDIP2003 (Hauschild and Potting, 2003).
o Impact categories: Global warming,
Acidification and Terrestrial Eutrophication.
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�Goal and scope definition
System boundaries – process system description
….\LCA framework
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Assumptions
�Goal and scope definition
….\LCA framework
o The investigated algae processing system was
assumed to be located along the coastline in
Denmark.
o The seaweed cultivation site was situated at
the open sea.
o The biogas production facility was situated at
the seaside on land.
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Assumptions
�Goal and scope definition
o The biogas produced is combusted in a gas
engine with electrical efficiency of 42%.
….\LCA framework
o Heat is also cogenerated but used internally in
the biogas plant.
o The electricity generated is assumed to
substitute coal-based marginal electricity.
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Assumptions
�Goal and scope definition
….\LCA framework
o The digestate generated is used as fertilizer on
agricultural land.
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�Inventory analysis (LCI)
….\LCA framework
Samples of L. digitata were collected in late March
2011, at Ømo, Denmark.
Arbona and Molla (2006) and Edwards
and Watson (2011) , personal
communication with fishermen
Seaweed production
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�Inventory analysis (LCI)
….\LCA framework
Data on biogas potential were generated through
batch experiments at 52 °C for 30 days.
mLCH4/gVS
250
200
150
100
50
Anaerobic digestion
0
S. latissima*
L. digitata*
P. palmata*
U. lactuca**
U. fusca**
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Assumptions
�Impact assessment
o The impact assessment was facilitated in
SimaPro 7.2.4 LCA software (Pre, 2010).
….\LCA framework
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Assumptions
�Impact assessment
Impact Potentials
200
100
0
-100
-200
-300
-400
-500
-600
-700
Characterized Environmental Impact Potentials
Global Warming
(kg CO 2 -eq)
Seaweed Production (SWP)
Mechanical Pretreatment (MP)
Anaerobic Digestion (AD)
Total
Acidification x 10
(m 2 )
Terrestrial Eutrop.
x 10 (m 2 )
….\LCA framework
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Assumptions
�Interpretation
….\LCA framework
o Important benefits for all impact categories
due to savings linked to both the avoided
fertilizer and energy production.
o In fact, 555 kWh of electricity per functional
unit are recovered and delivered to the grid,
thereby displacing coal-based marginal
electricity production somewhere else in the
energy system.
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Assumptions
�Interpretation
….\LCA framework
o Electricity consumption was estimated to be:
118 kWh per one tonne of dry seaweed.
o Electricity production was estimated to be:
555 kWh per one tonne of dry seaweed.
o Net electricity production: 437 kWh per
functional unit.
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Assumptions
�Interpretation
….\LCA framework
o “Electricity, hard coal, at power plant/NORDEL
S”: 0.851 kg of CO 2 per kWh of electricity
produced.
o Therefore, ca. 372 kgCO 2 per tonne of dry
seaweed are avoided.
o 8, 9 and 37 kg of N, P, and K per one tonne of
dry seaweed.
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Assumptions
�Sensitivity analysis
Impact Potentials
0
-100
-200
-300
-400
-500
-600
-700
-800
-900
Sensitivity Analysis Results
Base case S1 S2 S3
Global warming (kg CO2-eq)
Acidification x 10 (m2)
Terrestrial Eutrophication x 10 (m2)
S1: Energy consumption in SWP (-10%)
S2: LCH4/gVS (+10%)
S3: LCH4/gVS (+42%)
….\LCA framework
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�Conclusions
o Sensitivity analysis showed that the system
….\LCA framework
has potential for technological development
and consequently significant improvements.
o Improve the biodegradability of the feedstock
by different pretreatments.
o Metal content in the digestate needs to be
evaluated.
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Life Cycle Assessment of biogas
production process from Laminaria
digitata
Merlin Alvarado�Morales
Bioenergy Research group
Department of Environmental Engineering
Technical University of Denmark
www.capec.kt.dtu.dk

�Inventory analysis (LCI)
….\LCA framework
Resource
consumption
Unit
Seaweed
production
Mechanical
pretreatment
Anaerobic
Digestion
Diesel L 30
Petrol L 30
Electricity kWh 30 38 50
Heat kWh (GJ) 512 (1.84)
Water L 2380 3439
Stock nutrients solution L 0.03
Plantlet nutrients g 189
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�Conclusions
….\LCA framework
o Production of different biofuels has their own
benefits, risks and uncertainties.
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�Conclusions
o In order to ensure net societal benefits of
….\LCA framework
biofuel production, governments, researchers
and companies need to work together to carry
out comprehensive assessments, map suitable
and unsuitable areas, and define/apply
standards relevant to the different
circumstances of each country.
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