Life-cycle analysis of corn ethanol production in the wisconsin context

A variety of independent and site-specific variables determines the life- cycle energy and greenhouse gas assessments of corn-ethanol fuel. Unique aspects of Wisconsin agriculture present opportunities to optimize the energy efficiency and greenhouse gas neutrality of corn ethanol fuel when all aspects of corn and ethanol production and co-product use are tightly integrated. The Biofuel Energy Systems Simulator was used to perform life-cycle analysis on Wisconsin ethanol plants as determined by surveys. A displacement co-product crediting method was developed to reflect the use of distillers grains in dairy rations within the state. We estimate that the ethanol fuel currently produced in Wisconsin has a net energy ratio of 1.58 and reduces greenhouse gas emissions by 46% when compared to gasoline. The net energy ratio increased to 1.92 and emissions decreased by 16% when all co-products were assumed to be fed in wet form to dairy cows within 64 km of the distillation plant. The impact of displacing natural gas with biogas from the digestion of the manure from the cows fed by-product was not significant. Wisconsin corn ethanol life-cycle analysis was decidedly sensitive to lime and nitrogen inputs. Reducing these inputs by applying and crediting the nutrients and potential alkalinity in dairy manure to corn production increased the net energy ratio to 2.00 and further decreased emissions by 9%. Significantly more favorable results were found when ethanol industry standard and average values were used instead of our survey data, highlighting potential errors from non- site-specific analysis. © 2010 ASABE.