Etanol.nu

Energy and Environmental Aspects of Using Corn Stover for Fuel Ethanol

Corn stover is the residue that is left behind after corn grain har vest. We have constr ucted a life-cycle model that describes collecting corn stover in the state of Iowa, in the Midwest of the United States, for the production and use of a fuel mixture consisting of 85% ethanol/15% gasoline (known as “E85”) in a flexible-fuel light-duty vehicle. The model incorporates results from individual models for soil carbon dynamics, soil erosion, agronomics of stover collection and transpor t, and biocon- ver sion of stover to ethanol.

Limitations in available data forced us to focus on a scenario that assumes all farmer s in the state of Iowa switch from their current cropping and tilling practices to continuous production of corn and “no-till” practices. Under these conditions, which maximize the amount of collectible stover, Iowa alone could produce almost 8 billion liter s per year of pure stover-derived ethanol (E100) at prices competitive with today’s corn-starch- derived fuel ethanol. Soil organic matter, an impor tant indi- cator of soil health, drops slightly in the ear ly year s of stover collection but remains stable over the 90-year time frame stud- ied. Soil erosion is controlled at levels within tolerable soil-loss limits established for each county in Iowa by the U.S. Depar t- ment of Agriculture.

We find that, for each kilometer fueled by the ethanol por- tion of E85, the vehicle uses 95% less petroleum compared to a kilometer driven in the same vehicle on gasoline. Total fossil energy use (coal, oil, and natural gas) and greenhouse gas emissions (fossil CO2, N2O, and CH4) on a life-cycle basis are 102% and 113% lower, respectively. Air quality impacts are mixed, with emissions of CO, NOx, and SOx increasing, whereas hydrocarbon ozone precur sor s are reduced. This model can ser ve as a platform for future discussion and analysis of possible scenarios for the sustainable produc- tion of transpor tation fuels from corn stover and other agri- cultural residues.