Researchers from the Coastal Plains Soil, Water, and Plant Research Center of the United States Department of Agriculture, Agricultural Research Service (USDA-ARS) assessed the use of two summer legumes as potential bioenergy crops. Keeping in mind that good bioenergy crops should have high dry matter/energy yields and reduced agricultural inputs, they considered the growing of legumes as biofuel feedstocks during the late summer season in the Southeastern region in the United States. Legumes have high biomass yields with no nitrogen fertilizer requirements, and planting these potential feedstocks during fallow periods could have many of the environmental benefits. The researchers assessed sunn hemp (Crotolaria juncea) and cowpeas (Vigna unguiculata) in terms of biomass yield, energy content/yield, plant mineral concentrations; and pyrolytic degradation characteristics. Results showed that sunn hemp had higher biomass and energy yields compared to cowpea. The energy content in sunn hemp was also 6% higher than cowpea. Sunn hemp was also found to have lower plant mineral concentrations (K, Ca, Mg, S) that are known to reduce thermochemical conversion efficiencies of biomass-to-biofuel conversion processes. The full paper is published in the journal, Biomass and Bioenergy (URL above).