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Cellulosic Biofuel Potential of a Winter Rye Double Crop across the U.S. Corn–Soybean Belt

Feyereisen, Gary W., Camargo, Gustavo G. T., Baxter, Ryan E., Baker, John M., Richard, Tom L.
Agronomy Journal 2013 v.105 no.3 pp. 631-642
Glycine max, Secale cereale, Zea mays, air temperature, atmospheric precipitation, biofuels, biomass production, continuous cropping, corn, cover crops, crop models, crop rotation, crop yield, double cropping, energy content, energy crops, food crops, grain crops, harvest date, irrigated farming, planting date, regression analysis, rye, soybeans, summer, winter, United States
Interest in renewable energy sources derived from plant biomass is increasing, raising concern over fuel versus food competition. One strategy to produce additional cellulosic biomass without reducing food-harvest potential is to grow winter cover crops after harvest of the primary summer crop. This study estimates biomass accumulation of a fall-planted winter rye (Secale cereale L.) double crop across the USA on corn (Zea mays L.)– soybean (Glycine max L.) croplands. We identify corn and soybean areas by county using USDA NASS data, excluding irrigated land and area already supporting a winter small grain crop. Within this area, we calculate biomass production after corn harvest and prior to the subsequent corn or soybean crop for 30 locations with RyeGro, a cover crop simulation model. Average RyeGro biomass yields for a 14-year period are used to develop a regression model based on temperature and precipitation, which is used to determine rye biomass potential in each county. The spatial analysis indicates that 7.44 million ha (18.4 million ac) in continuous corn and 31.7 million ha (78.2 million ac) in a corn-soybean rotation are suitable for producing winter rye. The average RyeGro biomass yield for the 30 locations for six planting-harvest date scenarios is 4.2 Mg ha-1. The regression modeling results project that from 112 to 151 Tg (120–170 million ton) of rye biomass, with an energy content of 2.0 to 2.6 EJ (1.9–2.5 quadrillion BTU), can be harvested from this land base 14 and 7 d prior to spring crop planting, respectively. The study demonstrates the sizable potential for this strategy to produce cellulosic biofuel without redirecting the primary food crop to fuel.