Applied Energy, Vol.239, 1459-1470, 2019
Process design and economics for production of advanced biofuels from genetically modified lipid-producing sorghum
This study evaluates the potential for making advanced biofuels from genetically modified (GM) lipid producing sorghum. A biodiesel coproduction process is developed to extract, purify, and upgrade lipids to diesel fuel while carbohydrates are utilized for making ethanol through acid thermal pretreatment, enzymatic hydrolysis, and fermentation. To assess the advantages of coproducing biodiesel from GM sorghum, process economics are compared to a cellulosic ethanol biorefinery receiving non-GM sorghum. Minimum ethanol selling prices (MESP) that reach a breakeven point after 30 years of service life are calculated as an economic index to compare the two processes. Results indicate that biodiesel coproduction improves the economics by lowering the MESP from $3.08/gal for the ethanol-only process to $2.46/gal. Sensitivity analyses reveal that increasing sorghum's lipid content, increasing the lipid extraction efficiency, and reducing the solvent-to-solids ratio in lipid extraction columns are the most important process parameters to further enhance technoeconomics. Analyses indicate that a lipid content above 13 wt% (dry basis) or a biomass price less than $65/Mg (dry basis) will result in a 2014 ethanol wholesale price of $2.25/gal for the coproduction process.