Simulating the production potential and net energy yield of maize-ethanol in the southeastern USA

The interest in producing ethanol from maize has increased during recent years. However, the potential for maize-ethanol production is restricted to the extent of the feedstock production and the feedstock collection radius around an ethanol processing plant. The harvested acreage of maize in Alabama, Florida and Georgia has varied from 115,000 ha to 1.4 million ha during the last 50 years. One basic criterion for a sustainable production of renewable bio-ethanol is a positive net energy yield (NEY), i.e. more energy must be produced than the non-renewable energy that is used in the energy production chain, including the feedstock production and transportation and the biofuel processing. The goal of this study was to evaluate the potential to produce renewable energy the form of maize-ethanol in a region with typical southeastern USA maize cropping conditions. Two maize production acreages, which represent current and historical large acreages, and two feedstock collection radii of 100 and 200 km around an ethanol plant in southwest Georgia were evaluated. Maize growth and yield were simulated with the Cropping System Model (CSM)-CERES-Maize model to account for climate and soil variability. The simulations included weather data for 68 years. The potential ethanol production and NEY were calculated based on the simulated yields and energy requirements for the production. The ethanol production potential was 30–40 times greater for the large production acreage than for the small acreage. The average NEY across all simulated years was positive for all evaluated production acreages and collection radii. However, it was negative for the large production acreage under certain weather conditions. This study showed the potential to provide for an increase in renewable ethanol production from maize in the southeastern USA to meet the demand of the ethanol processing infrastructure.