Biofuels in Perspective

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Table 12.2 Atmospheric CO2 (equivalent) reductions associated with plant growth and input use for corn and soybeans (Col. 3) (Col. 4) (Col. 5) (Col. 6) (Col. 7) (Col. 1) (Col. 2) Crop yield Grain:total Biomass quantity Carbon content CO2 reduction Commodity Input (bu/acre) biomass ratio (dwt lb/acre) (ratio) (lb CO2/acre) Corn 142.2 1.000 6728.9 grain 0.459 11304.2 6728.9 residue 0.499 12289.3 13457.8 total total 23593.4 Fertilizer −477.6 fuel, machinery, other chemicals −629.6 net 22486.2 soybeans 28.96 0.978 1563.8 grain 0.527 3016.4 1529.4 residue 0.577 3229.9 3093.3 total total 6246.3 Fertilizer −92.9 fuel, machinery, other chemicals −629.6 net 5523.8
228 Biofuels that the GREET estimate is about the same as the default IPCC estimate for typical fertilizer application and runoff conditions in North America. In both cases, the input based emissions increases are an order of magnitude smaller than the plant based emission reduction estimates. Consequently, substantial net CO2 reductions for an acre on both crops are calculated. Further, the CO2 removed from the atmosphere is reduced by a factor of 4 when 1 acre of corn replaces 1 acre of soybeans. There is considerable discussion and some uncertainty about how unused crop residues decompose. There are N2O emissions that the IPCC recommend estimating at 1.25 % of the nitrogen content of the crop residues. These emissions are relatively minor; we estimate the CO2 equivalent emissions at 477.6 lbs/acre for corn and 92.9 lb/acre for soybeans. Regarding the destination of carbon from decomposing crop residues, some presume that decomposing plant residues remain in the system, increasing carbon content of the soil, and functioning as fertilizer (Heller et al., 2003). Gallagher et al. (2003) review some data suggesting that soil carbon tends to be related to the tillage (conventional vs. no-till) method, but not to the residue practice (silage vs. field decomposition). Also, a recent simulation looks at corn residues following a switch from conventional tillage to no-till farming (Sheehan et al., 2004, p. 126). In this case, leaving the residues appears to increase soil carbon in the transition to a steady state, until about 10 years after the change in tillage practice. But there is a saturation level. Hence, removing crop residues after 10 years of no-till agricultures may not deplete soil carbon. In subsequent analysis we assume no-till crop planting and residue removal. But residues probably shouldn’t be removed prior to the saturation point to ensure sustainable production agriculture. Otherwise, residue burning would return CO2 to the atmosphere that could have been sequestered in the soil. 12.4 CO2 Adjustment in a Changing Ethanol Industry The corn-ethanol industry connects a major CO2 user, corn, to two major CO2 producers, cars and cows. When ethanol expands, adjustments in several resource and product markets means that CO2 balance may improve or deteriorate; the result depends on the extent of factor and product market adjustments. As the ethanol sustainability discussions move from existence to improvement issues, it is important to move beyond the conventional system boundaries of life cycle analysis. To illustrate, we consider the incremental CO2 effects of a one gallon increase in ethanol production for two polar cases. In Table 12.3, corn supply adjusts to provide input for the ethanol industry. In Table 12.4, corn demand adjusts because the corn supply is fixed. For estimates of the incremental CO2 account in Table 12.3, land is diverted from soybeans to corn. The CO2 collection estimates from Table 12.2 are used, but magnitudes are scaled to correspond to a one gallon increase in ethanol supply. Hence, the lost soybean credit (−10.85), at the bottom of the table, is the lost CO2 collection in soybean production. But the soybean collection estimate is scaled by the amount of soybean land that must be replaced with corn to get one gallon of ethanol. The increase in corn CO2 collection is also scaled to a one gallon increase in ethanol. Indeed, the corn credit (19.76) is derived from the carbon content of the corn used for one gallon of ethanol, less the distillers’ grain
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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
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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 240 and 241: Table 12.1 Corn ethanol dry mill: e
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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