Nitrogen Use in Biofuel Production: A Case Study of U.S. Corn and Brazilian Sugarcane

Ethanol produced from United States corn and Brazilian sugarcane dominates the liquid biofuels industry. Yet when determining the viability of these two feedstocks as sustainable and environmentally sound investments, the discussion focuses only on the net energy balances, life cycle analyses of greenhouse gas emissions, and food versus fuel debates. The impacts of growing corn and sugarcane for ethanol on the cycling of nitrogen are often overlooked, even though losses from the agroecosystem can create serious environmental issues, including acid rain, eutrophication of surface waters, and stratospheric ozone depletion. This paper seeks to investigate nitrogen use in the cropping systems of corn and sugarcane from the physiological aspects of plant nitrogen nutrition to the movements of nitrogen in the soil-plant system at the landscape scale. Comparing the effects of plant physiology and crop management on nitrogen requirements and subsequent losses to the environment can highlight which feedstock creates the least disturbance to the nitrogen cycle and thus the surrounding environment. The 2008/2009 growing season provides a case study to examine the interdependency of the physiological nitrogen demands, soil nutrient management, and balanced nitrogen cycling on the yield of ethanol.

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