BIOMASS FOR ELECTRICITY AND PROCESS HEAT AT ETHANOL PLANTS

Abstract

Biomass can provide electricity and process heat at dry-grind ethanol plants to both reduce costs and improvethe net energy value of ethanol production. Distillers dried grains with solubles (DDGS), which are coproducts of ethanolproduction, can potentially be used for energy. Corn stover is another potential biomass energy source for ethanol plants.Biomass (DDGS and corn stover) alternatives to provide process heat and electricity at corn dry mill ethanol plants areevaluated. Corn dry grind ethanol production using biomass (DDGS or corn stover) to meet process energy needs andgenerate electricity achieves net energy values in the range of 20 to 30 MJ/L (72,000 to 108,000 Btu/gal) of ethanol, whichequals or exceeds previous estimates for biomass ethanol production. There are significant annual energy cost savings/returnsfor a 150 million L (40 million gal) per year plant capacity over a range of natural gas and biomass prices to apply toadditional capital and operating costs required for a biomass energy system. Electricity generation is potentially an importantcontributor to the annual energy cost savings/returns because of the ability to effectively use waste heat from electricitygeneration to meet process energy needs. Important next steps are to evaluate capital and operating costs of biomasscombustion/gasification, emission control, biomass fuel handling, and electricity generation technologies to determineoverall economic feasibility.