Potential of Summer Legumes for Thermochemical Conversion to Synthetic Fuel in the Southeast USA.

Fallow periods during the summer in some crop rotations of the Southeast USA could potentially be used to grow feedstocks for energy production. The objective of this study was to evaluate Crotolaria juncea and cowpeas (Vigna unguiculata) as species to be used as feedstocks for thermochemical conversion to biofuels. The legumes were planted in field plots during late July in 2004, 2005, and 2006 and sampled monthly until the first killing frost each year. Gross energy content was determined with an isoperibol calorimeter. Thermal degradation pattern and gaseous end products of the biomass during thermochemical conversion processes was determined with a thermogravimetric/differential thermal analyzer connected to a mass spectrometer. Dry weather during the summer of 2005 limited growth of the legumes in that year. Nitrogen in the plant tissues, a potential catalyst poison precursor, was higher for cowpeas than for C. juncea. Biomass of C. juncea at the first killing frost was 10752 kg ha^-1 in 2004 and 7170 kg ha^-1 in 2006. Cowpea biomass was 3140 kg ha^-1 in 2004 and 5820 kg ha^-1 in 2006.