Biomass resource potential using energy crops.

摘要

Biomass energy crops can provide a significant and environmentally beneficial source of renewable energy feedstocks for the future. They can revitalize the agricultural sector of the US economy by providing profitable uses for marginal cropland. Energy crops include fast-growing trees, perennial grasses, and annual grasses, all capable of collecting solar energy and storing it as cellulosic compounds for several months to several years. Once solar energy is thus captured, it can be converted by means of currently available technologies to a wide variety of energy products such as electricity, heat, liquid transportation fuels, and gases. Experimental results from field trials have generated optimism that selected and improved energy crops, established on cropland with moderate limitations for crop production, have the potential for producing high yields. Both trees and grasses, under very good growing conditions, have produced average annual yields of 20 to 40 dry Mg ha(sup (minus)1) year(sup (minus)1). Sorghum has shown especially high yields in the Midwest. Hybrids between sugar cane and its wild relatives, called energy cane, have yielded as much as 50 dry Mg ha(sup (minus)1) year(sup (minus)1) in Florida. These experimental results demonstrate that some species have the genetic potential for very rapid growth rates. New wood energy crop systems developed by the Department of Energy's Biofuels Feedstock Development Program offer, at a minimum, a 100% increase in biomass production rates over the 2 to 4 Mg ha(sup (minus)1) year(sup (minus)1) of dry leafless woody biomass produced by most natural forest systems. Experimental data indicate that short rotation wood crops established on cropland with moderate limitations are capable of producing biomass yields of 8--20 dry Mg ha(sup (minus)1) year(sup (minus)1) with a present average about 11 dry Mg ha(sup (minus)1) year(sup (minus)1) on typical cropland sites.