RESEARCH AND ANALYSIS Reevaluation of Energy Use in Wheat Production in the United States Gerhard Piringer and Laura J. Steinberg Summary Energy budgets for agricultural production can be used as building blocks for life-cycle assessments that include agri- cultural products, and can also serve as a first step toward identifying crop production processes that benefit most from increased efficiency. A general trend toward increased energy efficiency in U.S. agriculture has been reported. For wheat cultivation, in particular, this study updates cradle-to-gate pro- cess analyses produced in the seventies and eighties. Input quantities were obtained from official U.S. statistics and other sources and multiplied by calculated or recently published en- ergy coefficients. The total energy input into the production of a kilogram of average U.S. wheat grain is estimated to range from 3.1 to 4.9 MJ/kg, with a best estimate at 3.9 MJ/kg. The dominant contribution is energy embodied in nitrogen fertil- izer at 47% of the total energy input, followed by diesel fuel (25%), and smaller contributions such as energy embodied in seed grain, gasoline, electricity, and phosphorus fertilizer. This distribution is reflected in the energy carrier mix, with natu- ral gas dominating (57%), followed by diesel fuel (30%). High variability in energy coefficients masks potential gains in total energy efficiency as compared to earlier, similar U.S. studies. Estimates from an input-output model for several input pro- cesses agree well with process analysis results, but the model’s application can be limited by aggregation issues: Total energy inputs for generic food grain production were lower than wheat fertilizer inputs alone, possibly due to aggregation of diverse products into the food grain sector. Keywords agriculture carrier mix energy balance grain input-output model process analysis e-supplement available on the JIE Web site Address correspondence to: Laura J. Steinberg Department of Civil and Environmental Engineering Tulane University New Orleans, LA 70118 <lauras@tulane.edu> © 2006 by the Massachusetts Institute of Technology and Yale University Volume 10, Number 1–2 http://mitpress.mit.edu/jie Journal of Industrial Ecology 149