Biomass for Electricity and Process Heat at Ethanol Plants

Biomass can provide electricity and process heat at dry-grind ethanol plants to both reduce costs and improve the net energy value of ethanol production. Distillers dried grains with solubles (DDGS), which are coproducts of ethanol production, 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 are evaluated. Corn dry grind ethanol production using biomass (DDGS or corn stover) to meet process energy needs and generate electricity achieves net energy values in the range of 20 to 30 MJ/L (72,000 to 108,000 Btu/gal) of ethanol, which equals or exceeds previous estimates for biomass ethanol production. There are significant annual energy cost savings/returns for a 150 million L (40 million gal) per year plant capacity over a range of natural gas and biomass prices to apply to additional capital and operating costs required for a biomass energy system. Electricity generation is potentially an important contributor to the annual energy cost savings/returns because of the ability to effectively use waste heat from electricity generation to meet process energy needs. Important next steps are to evaluate capital and operating costs of biomass combustion/gasification, emission control, biomass fuel handling, and electricity generation technologies to determine overall economic feasibility.