Use of Distillers By-products and Corn Stover as Fuels for Ethanol Plants

Dry-grind ethanol plants have the potential to reduce their operating costs and improve their net energy balances by using biomass as the source of process heat and electricity. We utilized ASPEN PLUS software to model various technology bundles of equipment, fuels and operating activities that are capable of supplying energy and satisfying emissions requirements for dry-grind ethanol plants of 50 and 100 million gallons per year capacity using corn stover, distillers dried grains and solubles (DDGS), or a mixture of corn stover and “syrup” (the solubles portion of DDGS). In addition to their own requirements, plants producing 50 and 100 million gallons of ethanol are capable of supplying 5-7 or 10-14 MegaWatts of electricity to the grid, respectively. Economic analysis showed favorable rates of return for biomass alternatives compared to conventional plants using natural gas and purchased electricity over a range of conditions. The mixture of corn stover and syrup provided the highest rates of return in general. Factors favoring biomass included a higher premium for low carbon footprint ethanol, higher natural gas prices, lower DDGS prices, lower ethanol prices, and higher corn prices.