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The U.S. EPA has issued a Notice of Data Availability (NODA) on grain sorghum [PDF] as a bioethanol feedstock under the Renewable Fuels Standard (RFS2) program. The NODA was published in the federal register on June 12, allowing the public to comment on the lifecycle analysis for this new pathway before a final rule is issued.
EPA’s lifecycle greenhouse gas analysis shows that bioethanol made from sorghum grain would meet the 20% threshold required by the Energy Independence and Security Act (EISA) of 2007 for conventional renewable fuel. When sorghum ethanol is produced at plants powered by biogas and combined heat and power (CHP) technology, it could meet the 50% threshold for advanced renewable fuel.
Sorghum is largely used as animal feed at present, and EPA’s modelling assumes perfect substitution between sorghum grain and corn grain in the animal feed market. They thus predict that diverting sorghum to biofuel production would result in more corn being grown in the U.S. for animal fodder. Some of the demand for animal feed would also be met with distiller’s grains, a co-product of ethanol production from sorghum and other grains.
U.S. sorghum exports would decrease to meet the greater demand for biofuel under EPA’s modelling, leading to changes in the international grain market. More sorghum would be grown elsewhere in the world, and more corn would be produced both inside and outside the U.S. Overall, the EPA expects an increase in global cropland to indirectly fill the demand for sorghum—this cropland expansion would cause land use change emissions that are accounted for in the analysis.
When produced at a plant using energy from natural gas, the EPA predicts that sorghum grain ethanol would have greenhouse gas savings of 22–36% compared to gasoline. Substituting natural gas with biogas (methane from biomass) would reduce lifecycle emissions by 20%. Combining use of biogas with CHP technology results in a 52–53% savings compared to gasoline, which would allow sorghum grain ethanol produced at such a facility to qualify as an advanced renewable under EISA.
EPA’s analysis assigns lower lifecycle GHG emissions to sorghum grain ethanol than to corn grain ethanol for the agricultural feedstock production stage, land use change, and fuel production (given the same technology options). By definition under RFS2, advanced renewable fuels may not be produced from corn starch. Sorghum grain ethanol in contrast is eligible as an advanced biofuel, even though diverting it to biofuels results in large increases in corn production.