Sustainability of Corn Stover Harvest for Biomass

Off-farm demand for crop residues is expected to grow as bioenergy policies become effective. Demand for residues will provide farmers with an additional source of revenue but it may also trigger losses in soil organic carbon and increases in fertilizer application. This study develops a dynamic economic model of stover harvest that permits conceptualization and quantification of these potential tradeoffs. We parameterize our model based on publicly available studies of soil biophysical relationships in the Corn Belt. Under these parameter values and 2010 corn and fertilizer prices harvesting stover is not economically convenient at prices below $53 per dry ton of stover. Results suggest that the rate of stover harvest may be quite sensitive and negatively linked to corn prices, which means that policies favoring the use of stover for biomass may be overridden by further increases in corn price. The negative link between stover harvest and corn prices, while somewhat counterintuitive, is driven by the fact that removal of stover reduces future grain yield (through reductions in soil organic carbon). Results also seem to indicate that, under plausible parameter values, profit maximizing farmers would increase stover supply in response to increases in stover price. However increases in supply are, according to our simulations, associated with (potentially significant) reductions in soil organic carbon (and hence carbon emissions as these are positively linked) and increases in nitrogen application (and potential runoffs). This result suggests that concerns about adverse environmental implications of harvesting stover may be justified, and more precise quantification of environmental tradeoffs should be pursued by future research.