Unlocking the Biofuel Power of Cover Crop in Washington State: Enhancing Potential Through Hydrothermal Liquefaction

This peer-reviewed study evaluates cover crops in Washington state as a renewable feedstock for hydrothermal liquefaction (HTL) biofuel production, supported by techno-economic analysis (TEA) and life cycle assessment (LCA). Field trials conducted over three years at Puyallup and Othello tested triticale, hairy vetch, crimson clover, winter pea, and fava bean preceding cash crops. Biomass yields, soil impacts, and economic returns were assessed under multiple removal treatments.

HTL conversion produced 32–37 wt% biocrude, with modeled cradle-to-grave carbon intensities of 26–31 g CO₂e/MJ and minimum fuel selling prices of $6.75–$7.18 per gallon gasoline equivalent. With Renewable Identification Number (RIN) credits, modeled fuel prices dropped below $2.50/GGE. Soil carbon, nitrogen, and subsequent cash crop yields were not significantly affected. Results indicate that cover crops—particularly triticale and hairy vetch—can provide new farm revenue while supporting >70% carbon intensity reductions relative to fossil fuels. Blending with wastewater sludge further improves year-round supply potential.

This work was supported by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office. The work was performed at Pacific Northwest National Laboratory, a multi-program national laboratory operated by Battelle for the DOE under Contract No. DE-AC05-76RL01830, and under the auspices of the WSU–PNNL Bioproducts Institute, a joint research collaboration between Washington State University and DOE’s Pacific Northwest National Laboratory.