Fuel properties of biomass feed streams at ethanol plants

Biomass co-products from the dry-grind ethanol production process and/or corn stover are potential sources for the energy to operate the plant. The ethanol plant co-products alone contain sufficient energy to meet the electrical and thermal needs of the plant as well as to produce excess power that can be sold. Fuel characteristics of co-products of the ethanol dry-grind process [distillers wet grains (DWG), concentrated distillers solubles (referred to as "syrup"), and distillers dried grains with solubles (DDGS)], and corn stover are evaluated. Analyses include proximate, ultimate, selected metals, ash fusion temperatures, minerals in the ash, and thermogravimetric analysis (TGA). Higher heating values for the co-products are greater than for corn stover and for most other biomass materials. The ethanol co-products contain large amounts of nitrogen, sulfur, and chlorine, which will require major control technologies for combustion or gasification systems to meet emissions limits. The alkali metal content (potassium and sodium oxides) of the ash is high (22% to 34%) for co-products and corn stover, which will require careful design to avoid to ash fouling in combustion and steam generation units. Corn stover has more favorable combustion characteristics than the ethanol co-products based on higher ash fusion temperatures and the TGA results (higher combustion reactivity and lower burnout temperature).