Current Methods for Life-Cycle Analyses of Low-Carbon Transportation Fuels in the United States (2022) / Chapter Skim
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Regulatory impact assessments that use CLCA to project the consequences of policy can help assess the extent to which a given policy design with particular carbon intensity estimates will result in reduced GHG emis sions. 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 practices, and dietary change of food type, quan tity, and nutritional content.
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Nevertheless, given the desire to design policies that achieve reductions in GHG emissions, LCA has been increasingly applied to policy development, and energy and biofuel policy in particular, in recent decades. Recommendation 10-4: Analyses estimating the emissions implications of PEV adoption in future power grid scenarios should consider changes in power grid emissions caused by PEV charging in each power grid scenario.
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● Products could include the following: o development of national, open-source, transparent CLCA models for use in LCFS devel opment and assessment o continued development of national, open-source attributional ALCA models from new or existing models o evaluation of different approaches to creating, using, or combining ALCA, CLCA, and ver ification for evaluation of policy outcomes o quantification of variation between marginal and average GHG emissions for various feed stock-to-fuel pathways; and o quantification and characterization of the implications of approximations and proxies in LCA, such as comparisons of marginal and average emissions. DIRECT AND INDIRECT EFFECTS GHG emissions associated with transportation fuels include emissions from producing the fuel, from combusting the fuel, and from the full supply chain for producing and distributing the fuel.
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Recommendation 4-2: Current and future LCFS policies should strive to reduce model uncertain ties and compare results across multiple economic modeling approaches and transparently com municate uncertainties. Recommendation 4-4: When LCA results are used in policy design or policy analysis, the impli cations of parameter uncertainty, scenario uncertainty, and model uncertainty for policy outcomes should be explicitly considered, including an assessment of the degree of confidence that a pro posed policy will result in reduced GHG emissions and increased social welfare.
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Recommendation 5-2: The research and policy communities should develop frameworks and meth odologies for use of satellite data to characterize national and international land use change that may be in part attributable to an LCFS. Examples of framing questions include: Should an LCFS include measures to mitigate undesirable international land use change, or is it sufficient to monitor international land use change that may be due to the LCFS and these GHG emissions to the associated fuel?
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These efforts could align with the recommendations made in the 2019 National Academies report on negative emissions technologies to study soil carbon dynamics at depth, to develop a national on-farm monitoring system, to develop a model-data platform for soil organic carbon modeling, and to develop an ag ricultural systems field experiment network. These efforts should also be extended internationally.
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Recommendation 6-14: For regulatory impact assessment, LCA of transportation fuels and trans portation fuel policy should consider a range of estimates for possible changes in the emissions of vehicle production required to convert transportation fuels into transportation services, and the re sulting changes in vehicle fleet composition. Recommendation 6-15: LCA comparing transportation fuels for weight-constrained applications should present a per-ton-mile functional unit and/or explicitly model the logistical implications of payload effects by fuel type.
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Where relevant, the ap proach to quantifying emissions of upstream natural gas production should align with those used elsewhere in an LCFS for other fuels produced from natural gas. AVIATION FUELS The life-cycle climate impacts of aviation fuels have been evaluated in the literature and as part of regulatory assessments for several fuels policies.
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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 is one of the most abundant feedstock for bioenergy production in the United States.
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Some of the attributional GHG emissions of upstream production of electricity and chemicals used in biomass conversion are available in many life-cycle inventory databases but have large variations depending on the production technologies and market mix. Research articles vary in their assumptions about the potential for carbon sequestration using biorefinery co-products as soil amendments, but many assume 80-85 percent of biochar is stable for at least 100 years whereas digestate and compost are not assumed to result in accumulation of stable carbon in soils.
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From page 11... ...
Recommendation 10-1: Regulatory impact assessment or other analyses estimating the emissions implications of a change in PEV charging load should use a CLCA approach to estimate the impli cations of power grid emissions and clearly characterize uncertainty of estimates due to assump tions, especially for future scenarios. Recommendation 10-2: Research should be conducted to estimate how upstream emissions in the power sector change in response to changes in generation.
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