Biofuels in Perspective

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Table 12.1 Corn ethanol dry mill: energy use and net energy value with conventional and biomass power for processing Btu/gallon Distillers’ grain for power Biomass power: willow (SRWC) Biomass power: Corn Stover Natural gas & purchased electricity Processing Power Configuration Corn production 21803 21803 21803 21803 Corn transport 2284 2284 2284 2284 Ethanol conversion 487711 16872 11593 05 Ethanol distribution 1588 1588 1588 1588 Total energy used 74446 27362 26834.3 25675 By-product Credit 131154 13115 13115 0 Energy used, net of byproduct credit 61331 14247 13719 25675 Ethanol energy produced 84530 84530 84530 84530 Energy ratio, w/o byproduct credit 1.14 3.09 3.15 3.29 Energy ratio, w/ byproduct credit 1.38 5.93 6.16 3.29 1electricity: 12671 btu/gal power: 36100 btu/gal from coal natural gas Total: 48771 Source: Gallagher and Shapouri (2006) Also assumes 1.1 Kw-hr elec per gal eth, 3413 btu elec per Kw-hr elec, and 0.3 btu-elec per btu input 2harvest: 241 btu/gal Corn Stover harvest energy from GREET model, see Wang fertilizer replacement: 1446 btu/gal fertilizer replacement requirement from Gallagher, Dikemen, and Shapouri (2003) fertilizer energy requirement from GREET model, see Wang. 3plant, harvest, etc. 202.9 btu/gal fertilizer 956.4 btu/gal Plant management energy use from Heller, Keoleian, and Volk (2002). 4 17.6 % of baseline energy used.
226 Biofuels distillers’ grains. So neither input requires a crop production energy allocation. For corn stover, however, some fertilizer is required to replace nutrients in residues left in the field. So replacement fertilizer quantities are calculated (Gallagher et al., 2003). Then the energy embodied in the fertilizer, its production and application are calculated using the GREET model (Wang et al., 1999). Similarly, we include an allowance for external energy expended on stover harvest and machinery use. Our estimate for the fertilizer replacement and harvest, 1687 BTU/gallon in column two, is about one-third higher than the case of a willow crop. But it is still several multiples smaller than the baseline case with fossil energy. Modification of the energy ratio for distillers’ grains is straightforward. First, additional energy investment is not required because the distillers’ grains are already available at the processing plant, with the external energy investment made in other parts of the corn production/processing account. So we place a 0 in the ethanol conversion entry for column 4. We also place a 0 for the by-product credit, because the distillers’ grains are no longer used for a byproduct feed. Now look at the Energy Ratio calculations for each of the power configurations. First, the baseline of column 1 is taken from a recent study (Shapouri et al., 2002). Here, the energy ratio is 1.38 with the byproduct credit, and 1.14 without byproduct credit. Without even introducing the byproduct credit, all of the biomass power alternatives have energy ratios in the 3.0 to 3.3 range. With the byproduct credit for stover and willow, the energy ratio increases by another multiple, to the 6.0 region. DG power gives a smaller improvement than other biomass alternatives when the byproduct credit is taken into account. 12.3 Crop Production and Greenhouse Gas Emissions Corn has potential for atmospheric CO2 reductions because it has a rapid photosynthesis reaction. Field crops are sometimes categorized according to whether they have C3 and C4 photosynthesis pathways. C4 plants, which include the major ethanol feedstocks (corn and sugar), have rapid growth but require substantial nitrogen input to sustain plant growth. C3 plants, which include soybeans, have slower plant growth and require less nitrogen (Fageria et al. 1997, pp. 44–46). Indeed, corn replaced soybeans for the recent US ethanol expansion. So, begin by estimating and comparing net CO2 reduction estimates for corn and beans. In Table 12.2, estimate the total biomass on an acre (column 5) using typical crop yields and biomassgrain ratios. Next, calculate the carbon content for each crop component (column 6) – carbon content estimates used composition data, and relative carbon weights for the protein (amino acid), oil (fatty acid), and starch subcomponents (White and Johnson, 2003; Yu, 2002; Kuiken and Lyman, 1948; Gallagher, 1998). Finally, applying the ratio, 3.66 lb CO2/lb C, to the product of the carbon content estimate of column 6 and the biomass quantities in column 5, gives the CO2/reduction estimate in column 7. This method of calculation of the CO2 reduction is valid because photosynthesis places carbon in the plant gets there through photosynthesis. This procedure is used elsewhere (Heller et al., 2003, p. 157). The downside is that plant growth requires fertilizer, which in turn, generates greenhouse gas emissions associated with machinery use and fertilizer application. To estimate the emission increase we again used the GREET model (Wang et al., 2007). We also confirmed
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Biofuels Biofuels. Edited by Wim So
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Biofuels Edited by WIM SOETAERT Ghe
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Contents Series Preface ix Preface
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Contents vii 6.3 Biomass Gasificati
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Series Preface Renewable resources,
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Preface This volume on Biofuels fit
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Editors List of Contributors Wim So
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1 Biofuels in Perspective W. Soetae
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Table 1.1 Approximate average world
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Table 1.3 Energy yields of bio-ener
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Biofuels in Perspective 7 is burnt
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2 Sustainable Production of Cellulo
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Sustainable Production of Cellulosi
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Figure 2.9 2004 US adoption rates o
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3 Bio-Ethanol Development in the US
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Bio-Ethanol Development in the USA
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Biorefineries in Production (115) B
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Cost of Cellulosic Ethanol, $ per g
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4 Bio-Ethanol Development(s) in Bra
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Bio-Ethanol Development(s) in Brazi
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Share of energy consumption 100% 90
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Table 4.2 Main technological improv
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4.7.4 Use of Fertilizers and Pestic
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78 Biofuels Table 5.1 Biodiesel pro
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80 Biofuels CH 2 O CH O COR R1 + 3
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82 Biofuels short reaction times. 9
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84 Biofuels Table 5.4 Overview on h
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86 Biofuels Table 5.5 Critical cond
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88 Biofuels methoxide as catalyst u
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90 Biofuels KOH Methano Oil/Fat Aci
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92 Biofuels 16. J. Graille, P. Loza
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6 Bio-based Fischer-Tropsch Diesel
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6.2.1.2 Catalysts Bio-based Fischer
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Bio-based Fischer-Tropsch Diesel Pr
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7 Plant Oil Biofuel: Rationale, Pro
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Table 7.1 Market milestones for pla
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Water CO 2 Figure 7.1 Closed CO 2 l
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Plant Oil Biofuel: Rationale, Produ
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130 Biofuels Among the attractive f
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132 Biofuels Table 8.1 Enzymatic tr
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134 Biofuels conversion was maintai
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136 Biofuels (diglycerides) decreas
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138 Biofuels ME content (wt.%) Reac
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140 Biofuels Ratio of initial react
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142 Biofuels (a) 34 kDa 31 kDa 34 k
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144 Biofuels preparation of whole-c
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ability to reduce flocculation (% o
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148 Biofuels 5. R. C. Strayer, J. A
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150 Biofuels 46. H. Fukuda, Immobil
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9 Production of Biodiesel from Wast
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Production of Biodiesel from Waste
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9.3.2 Processing of Crude and Waste
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Heavy layer from alkaline neutralis
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CPO I 1 1 Heating 60°C Reaction st
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References Production of Biodiesel
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10 Biomass Digestion to Methane in
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Cow manure Pig manure Yard manure B
Page 190 and 191: Number of plants 3000 2500 2000 150
Page 192 and 193: Biomass Digestion to Methane in Agr
Page 196 and 197: Table 10.4 Alternative forms of ene
Page 200 and 201: Wet fermentation 3 - 10% TS applica
Page 202 and 203: Rel. Frequency [%] 35 30 25 20 15 1
Page 204 and 205: Steam 2 1 Energy crops (& manure) D
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Page 213 and 214: 198 Biofuels 11.1 Introduction Hydr
Page 215 and 216: 200 Biofuels lactate 6 glucose 1 GA
Page 217 and 218: Table 11.2 Continued Organism Domai
Page 219 and 220: 204 Biofuels NADH is that the react
Page 221 and 222: 206 Biofuels Clostridium thermocell
Page 223 and 224: 208 Biofuels in particular in Cl. p
Page 225 and 226: 210 Biofuels ferredoxin-dependent m
Page 227 and 228: 212 Biofuels Concentration (mM) 45
Page 229 and 230: 214 Biofuels genes of the glycolysi
Page 231 and 232: 216 Biofuels 11. S. Tanisho and Y.
Page 233 and 234: 218 Biofuels 49. M. J. Axley, D. A.
Page 235 and 236: 220 Biofuels 83. P. J. Silva, E. C.
Page 238 and 239: 12 Improving Sustainability of the
Page 242 and 243: Table 12.2 Atmospheric CO2 (equival
Page 244 and 245: Table 12.3 Incremental CO2 equivale
Page 246 and 247: Improving Sustainability of the Cor
Page 248 and 249: Improving Sustainability of the Cor
Page 250 and 251: Index italic entries indicate refer
Page 252 and 253: iorefineries 3, 10, 11, 41 and corn
Page 254 and 255: policy (official) 59-61 production
Page 256 and 257: NADH 200-6, 207, 210 natural gas 1
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