Sustainability Assessment of Purpose Grown Sustainable Aviation Fuel Feedstocks in the Contiguous United States

The US government’s Sustainable Aviation Fuel (SAF) Grand Challenge strives to increase annual SAF production to 35 billion gallons by 2050 while decreasing aviation emissions by 50%. This goal has increased domestic interest in purpose-grown bioenergy crops (Miscanthus, algae, etc.); however, limited research exists on the large-scale, country wide feasibility of SAF feedstocks in the US. Therefore, this research evaluates the county-level bioenergy production potential, economics, and environmental impact of SAF feedstocks throughout the Contiguous United States (CONUS) using GIS analysis and multi-objective optimization.

In total, six bioenergy crops (switchgrass, Miscanthus, poplar, algae, corn, and soybeans) and eight land types (barren, deciduous forest, evergreen forest, mixed forest, shrubland, grassland, pastureland, and cropland currently used for bioenergy) were considered for bioenergy production potential. The eight land classifications considered represent 71% of total CONUS land area. GIS mapping techniques were used to partition the CONUS into 200 m by 200 m patches to understand bioenergy production feasibility on various land types while excluding land with low yield, unfavorable terrain (e.g. steep slopes), or a protected status. County-level results include bioenergy land availability, biofuel production potential, minimum fuel selling price, and greenhouse gas emission impacts including direct land use change (dLUC).

Results show that Miscanthus is the most promising bioenergy crop by providing both a competitive fuel selling price ($4.49-$5.18/gal) and low emissions (-0.5–3.8 kg CO_2-eq/gal vs 10.7 kg CO_2‑eq/gal for conventional jet fuel). All feedstocks grown on forestland were found to have a larger environmental impact than conventional jet fuel due to dLUC impacts. Algae was found to have the highest fuel selling price ($9.98-$12.51/gal) and emissions (8.2-9.9 kg CO_2‑eq/gal) but it also has a biofuel productivity (fuel per land area) 10X that of the other feedstocks. Multi-objective optimization results illustrate the tradeoffs between optimizing CONUS SAF production for minimum fuel selling price, emissions, or land use. When minimizing for emissions, 13.4% of total CONUS land is required and Miscanthus is the primary feedstock. However, when land area is minimized only 0.8% of CONUS land is required because high productivity algae is deployed as the feedstock.