Switchgrass yield on reclaimed surface mines for bioenergy production

Abstract

The high cost of transportation fuels and the environmental risks associated with acquiring and using nonrenewable energy sources have created a demand for developing renewable bioenergy crops. Switchgrass ( L.), a warm-season perennial grass, is a promising feedstock due to its high biomass production under a wide range of growing conditions and its satisfactory forage quality and chemical composition. West Virginia contains vast expanses of reclaimed surface mine lands that could be used to produce switchgrass as a bioenergy feedstock. This study determined dry matter yields of three switchgrass varieties (Cave-In-Rock, Shawnee, and Carthage) during the second to fourth years of production. Two research sites were established on reclaimed surface mines in southern West Virginia: Hobet and Hampshire. The Hobet site was prepared using crushed, unweathered sandstone as the soil material, and yields were significantly lower at 803 kg ha averaged across varieties and years than annual yields at Hampshire. The highest yield at Hobet, with Shawnee in the third year, was 1964 kg ha. The Hamphire site, which was reclaimed in the late 1990s using topsoil and treated municipal sludge, averaged 5760 kg ha of switchgrass across varieties and years. The highest yield, obtained with Cave-in-Rock during the third year, was 9222 kg ha. Switchgrass yields on agricultural lands in this region averaged 12,000 kg ha. Although average switchgrass yields at Hampshire were about 50% lower than agricultural lands, they were greater than a target yield of 5000 kg ha, a threshold for economically feasible production. Yields during the fourth year from a two-harvest per year system were not significantly different from a single, end-of-year harvest at both sites. Reclaimed lands show promise for growing bioenergy crops such as switchgrass on areas where topsoil materials are replaced and amended like that at the Hampshire site.