Current Methods for Life-Cycle Analyses of Low-Carbon Transportation Fuels in the United States (2022) / Chapter Skim
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9 Biofuels
9 Biofuels
Pages 157-185
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From page 157... ...
Scarcity and price volatility of petroleum fuels provided important early motivation for interest in biofuels, going back for a century and peaking during periods of high oil prices or concerns about continued availability. More recently, concern over climate change caused primarily by the combustion of fossil fuels added a new motivation to seek alternative fuels produced from biogenic feedstocks that can in principle reduce greenhouse gas (GHG)
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From page 158... ...
Ethanol The most common biofuel in use currently in the United States is ethanol, which is produced through microbial fermentation of sugars and is suitable as a blendstock for spark-ignited internal combustion engines. Ethanol production facilities primarily use yeast to convert sugars to ethanol, namely Saccharomyces cerevisiae (also known as brewer's yeast)
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From page 159... ...
or for blending with diesel for use in compression-ignited internal combustion engines. It is produced by reacting fats or oils with short-chain alcohols such as ethanol or methanol in the presence of a catalyst; this process is called transesterification.
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From page 160... ...
. FEEDSTOCKS FOR BIOFUEL PRODUCTION Agricultural Feedstocks Corn and soybeans are the most common feedstocks currently used to produce biofuels in the United States.
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. As a waste material from forest management and wood processing activities, forest residues can be a source of biorefineries for biofuel production.
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Data quality improvements may support improved GHG accounting in biofuel feedstock production, especially should a performance-based LCFS be developed that accounts for spatially-explicit fer tilizer and energy consumption, and land management practices like cover crop planting, land clear ing, overfertilization, manure application, use of nitrification inhibitors, or noncompliance with long-term soil carbon storage incentives. Woody Biomass Production The GHG emissions associated with the production of woody biomass come from multiple sources, including the use of energy and materials (e.g., fertilizers and soil amendments)
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From page 163... ...
The GHG emissions of woody biomass transportation are driven by the weight of biomass, distances, and energy use. The weight of biomass and distances depend on the biomass supply chain design.
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From page 164... ...
Recommendation 9-1: Additional research should be done to assess key parameters and assump tions in forest management practices induced by increased woody biomass demand, including: changes in residue removal rates, stand management and forest productivity, and changes in tree species selection during replanting. Recommendation 9-2: Research and data collection efforts should be carried out for improved data and modeling related to forest feedstock production and storage, including energy use, yield, inputs, fugitive emissions, and changes in forest carbon stock should be supported.
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From page 165... ...
For corn ethanol facilities, distiller's dried grains with solubles and corn oil are common co-products that have clear applications in the animal feed market and can be accounted for through allocation procedures (see Chapter 3)
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From page 166... ...
In systems that produce CH4, fugitive emissions are often most easily and transparently calculated as a fraction of total system throughput, as is common practice in government-sponsored GHG inventories, such as the Environmental Protection Agency (EPA) GHG Inventory3 and the California Air Resources Board's GHG inventory.4 This can be applied to different parts of the supply chain, including production, processing/cleanup, and pipeline transport.
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From page 167... ...
Increases in biofuel production could also lead to changes on the extensive margin by bringing additional land into crop production, by conversion of idle land, pastureland, and forestland to cropland.
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From page 168... ...
Displacement of Fossil Fuels In principle, large scale biofuel production could displace at least a portion of domestic liquid fossil fuels consumption, ostensibly reducing oil demand. If the production of biofuels does reduce the world market price of oil, then it has the potential to increase the demand for oil in the rest of the world.
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From page 169... ...
In addition to induced LUCs and the rebound effect, the existing literature has noted several other indirect effects due to biofuels -- such as co-product impacts on livestock markets, food availability and dietary change -- that may affect GHG implications positively or negatively. Recommendation 9-6: Beyond research on induced land use change and rebound effects, research should be done to identify and quantify the impacts of other indirect effects of biofuel production, including but not limited to market-mediated effects on livestock markets, land management prac tices, and dietary change of food type, quantity, and nutritional content.
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From page 170... ...
These models are suited to analyze the effects of changes in demand for existing crops that are already being produced but not readily adaptable to analyze the effects of introducing new biofuel feedstocks, such as dedicated energy crops that are yet to be commercially produced. Early applications of the FAPRI-CARD model to examine the induced LUC effect of biofuels ignored the potential for conversion of cropland pasture or idle land to crop production before converting forestland.
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From page 171... ...
. In addition to structural differences across the PE and CGE models, they also differ in key assumptions that affect LUC in response to biofuel production.
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From page 172... ...
FIGURE 9-1 Land available for conversion in commonly-used models for assessing land use change in biofuel production. NOTE: ADAGE = Applied Dynamic Analysis of the Global Economy Model; EPPA = European Paper Packaging Alliance model; GCAM = Global Change Assessment Model; GLOBIOM = Global Biosphere Management Model; GTAP-BIO = Global Trade Analysis Project-BIO model.
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From page 173... ...
Estimates of the induced LUC effect are sensitive to the use of the Armington assumption as compared with the integrated world market assumption. With the Armington assumption in the GTAP-BIO model, land conversions are primarily concentrated in the United States and EU while with the integrated world market assumption they are more evenly distributed across the world and the share of global forest land converted to cropland is higher (Golub and Hertel, 2011)
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From page 174... ...
To attribute these GHG emissions to each unit of biofuel produced and compare the induced emissions to the direct flow of carbon savings from using biofuels to displace fossil fuels, studies have amortized the induced LUC emissions over the time horizon that the land is expected to remain in crop production. Conversion of Induced Land Use Changes to GHG Emissions Assessing the effects of induced LUC on carbon emission requires two components: (1)
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From page 175... ...
Recommendation 9-9: To improve understanding of market-mediated effects of biofuels, research should be supported on different modeling approaches, including their treatment of baselines and opportunity costs, and to investigate key parameters used in national and international modeling based on measured data, including various elasticity parameters, soil carbon sequestration, land cover, and emission factors and others. Recommendation 9-10: Because other market-mediated effects of biofuel production, such as livestock market impacts, land management practices, and changes in diets and food availability may be linked to land use and biofuel demand assessed using induced land use change models, additional research should be done and model improvements undertaken to include these effects.
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From page 176... ...
The results of these modeling practices vary widely. As discussed above, the existing literature shows a few key factors that explain most of the differences across models' results: modeling yield improvement, the extent to which biofuel production occurs on the existing idled land or causes extensification, and the extent to which biofuel produced in one country affect land use changes in other countries due to trade.
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From page 177... ...
The CA-LCFS determines the total CI of a biofuel by adding together the supply chain emissions intensity and induced LUC intensity of the biofuel. Each of these policies uses an estimated ILUC factor for each type of biofuel that is treated to be invariant to scale of biofuel produced, time period or location of feedstock produced for that biofuel, within a country.
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From page 178... ...
2012. Mitigation oppor tunities for life-cycle greenhouse gas emissions during feedstock production across heterogeneous landscapes.
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From page 179... ...
and Pape, D., 2017. A Life-Cycle Analysis of the Greenhouse gas emis sions of corn-based ethanol.
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2022. Overlooked emissions: Influence of environmental variables on greenhouse gas generation from woody biomass storage.
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2020. Carbon-negative biofuel production.
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2021. Varied farm-level carbon intensities of corn feedstock help reduce corn ethanol greenhouse gas emissions.
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2018. Land management change greatly impacts biofuels' greenhouse gas emissions.
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2017. Progress in biofuel production from gasification.
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2017. Testing the use of static chamber boxes to monitor greenhouse gas emissions from wood chip storage heaps.
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