Greenhouse gas mitigation potential of corn ethanol: Accounting for corn acreage expansion

Combustion of corn-based ethanol substantially offsets net Greenhouse Gas (GHG) emissions by the recycling of carbon dioxide (CO2) stored as biomass. However, the GHG mitigation effect may be partially countered by the growth of CO2 emissions from the increased corn production resulting from the increased demand for corn and higher corn prices. This study assesses the effect for a major U.S. crop production region, the Boone River watershed in Iowa. We use economic models on GIS-based land use and soils data for some 8,275 fields in the watershed to estimate the effect of an increase in corn prices on crop rotations and tillage intensity. The associated changes in soil carbon are estimated using the field-scale Environmental Policy Impact Climate simulation model by comparing soil organic carbon content under the baseline with that under the simulated cropping patterns. A corn price increase from $2 to $4 per bushel ($78.74 to $157.47 per t) is predicted to lead to the switch from the corn-soybean rotation to continuous corn and from the mulch to conventional tillage on the most of the watershed. The associated CO2 emissions are estimated at 63,711 tons (57,799 t) per year higher than under the baseline. © Springer Science+Business Media, LLC 2009.