Greenhouse Gas Accounting Procedures in Low Carbon Fuel Policies Lead to Undervalued Benefits of Miscanthus-based Sustainable Aviation Fuel

Low carbon fuel policies such as the U.S. Renewable Fuel Standard (RFS), Canada Clean Fuel Regulations (CFR), and California Low Carbon Fuel Standard (LCFS) are intended to reduce the greenhouse gas (GHG) emissions from transportation. Cellulosic feedstocks, optimized biorefineries, and favorable farming locations can significantly reduce biofuel carbon intensity (CI). Despite the emergence of field-to-fuel GHG monitoring technologies that could verify such benefits, programmatic constraints in CI accounting procedures may limit fuel producers’ ability to capitalize on these opportunities. To elucidate the implications of this challenge, this work examines a miscanthus-to-sustainable aviation fuel (SAF) pathway (i) to demonstrate how program provisions drive estimates of biofuel CIs and (ii) to explore potential CI and financial benefits of spatially explicit life cycle assessment (LCA). In comparing policy-based vs. spatially explicit CI scores (estimated via DayCent and BioSTEAM) for SAF production from miscanthus via alcohol-to-jet (ATJ), programmatic CI accounting requirements underestimated GHG benefits in 60-99% of simulated scenarios. These underestimates result in policy-induced SAF price differentials of -1.19 [(-)3.46 to (-)0.23], -0.07 [(-)1.06 to (+)0.37], and -0.48 [(-)2.46 to (+)0.16] $·L-1 for the RFS, CFR, and LCFS, respectively. Ultimately, this work demonstrates the importance of LCA methodological specifications in low carbon fuel policies.