Techno-economic assessment of renewable methanol from biomass gasification and PEM electrolysis for decarbonization of the maritime sector in California
At scale, biomass-based fuels are seen as long-term alternatives to conventional shipping fuels to reduce greenhouse gas emissions in the maritime sector. While the operational benefits of renewable methanol as a marine fuel are well-known, its cost and environmental performance depend largely on production method and geographic context. In this study, a techno-economic and environmental assessment of renewable methanol produced by gasification of forestry residues is performed. Two biorefinery systems are modeled thermodynamically for the first time, integrating several design changes to extend past work: (1) methanol synthesized by gasification of torrefied biomass while removing and storing underground a fraction of the carbon initially contained in it, and (2) integration of a polymer electrolyte membrane (PEM) electrolyzer for increased carbon efficiency via hydrogen injection into the methanol synthesis process. The chosen use case is set in California, with forest residue biomass as the feedstock and the ports of Los Angeles and Long Beach as the shipping fuel demand point. Methanol produced by both systems achieves substantial lifecycle greenhouse gas emissions savings compared to traditional shipping fuels, ranging from 38 to 165%, from biomass roadside to methanol combustion. Renewable methanol can be carbon-negative if the CO2 captured during the biomass conversion process is sequestered underground with net greenhouse gas emissions along the lifecycle amounting to −57 gCO2eq/MJ. While the produced methanol in both pathways is still more expensive than conventional fossil fuels, the introduction of CO2eq abatement incentives available in the U.S. and California could bring down minimum fuel selling prices substantially. The produced methanol can be competitive with fossil shipping fuels at credit amounts ranging from $150 to $300/tCO2eq, depending on the eligible credits.