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To assess the value of biofuels, the environmental costs of their productionmust be compared with the benefits of displacing fossil fuel. This article focuses on theenvironmental impacts of biofuel cropping systems and calculates net greenhouse gas(GHG) emissions using life cycle analysis. The impacts of corn and switchgrass croppingfor ethanol production were calculated for three states in the US (Iowa, Illinois, andIndiana) assuming three previous land use scenarios: Conservation Reserve Program(CRP) land, pasture land, and land already used for cropping. Although the results weredifferent for the 3 states considered, the impacts of previous land use and croppingsystem were more important than location. Conversion of CRP lands to corn ethanolproduction would result in little net GHG savings compared to burning fossil fuel, greatlyincrease NO3 leaching, and constrain other benefits of CRP land such as wildlife habitat.Conversion of pasture and crop land to corn ethanol cropping show GHG benefits,reductions in leaching for previously cropped systems, and increases in leaching for landspreviously in pasture. Converting CRP land to switchgrass cropping would lessen the rateat which these soils store SOC, increase N2O emissions, and have little impact on NO3leaching. Converting pasture and crop land to switchgrass cropping would increase SOCstorage, decrease N2O emissions, and decrease NO3 leaching. We conclude that currentland management (cropping system, tillage intensity, and fertilizer application), as well asprevious land use, must both be considered to quantify the environmental impacts ofbiofuel cropping systems.
