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Title: Cellulosic biofuel potential of a winter rye double crop across the U.S. corn-soybean belt

item Feyereisen, Gary
item CARNAGRO, G.G.T. - Pennsylvania State University
item BAXTER, R - Pennsylvania State University
item Baker, John
item RICHARD, T - Pennsylvania State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2012
Publication Date: 1/11/2013
Citation: Feyereisen, G.W., Carnagro, G., Baxter, R.E., Baker, J.M., Richard, T.L. 2013. Cellulosic biofuel potential of a winter rye double crop across the U.S. corn-soybean belt. Agronomy Journal. 105(3):631-642.

Interpretive Summary: Interest in producing biofuels in the U.S. on currently cropped lands has raised concern over competition between fuel and food crops. One approach to reduce the concern is to raise cellulosic biomass crops during the fall-through-spring period between the major summer crops. This study estimates the total biomass from a fall-planted winter rye cover crop that could potentially be harvested for cellulosic biofuel prior to the spring planting of the subsequent summer crop. We identify the U.S. cropland dedicated to continuous corn and corn-soybean rotation and use a simulation modeling approach to estimate winter rye biomass potential on a county basis. The spatial analysis shows that 18.4 million ac in continuous corn and 78.2 million ac in corn-soybean rotation, or a totally of approximately one fourth of U.S. cropland, are suitable for producing winter rye. We estimate the average biomass yield for 30 locations within the study region to be 1.9 ton/ac of dry matter. The total potential annual biomass estimated is 120 to 170 million tons, assuming the biomass is harvested 14 days or 7 days prior to the spring planting date, respectively. The energy content of the biomass is 1.9 to 2.5 quadrillion BTU. The research will benefit researchers and policymakers by putting the size of the double crop biofuels opportunity in perspective with other biofuels options in the world’s most populous country.

Technical Abstract: 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.