Short-rotation woody crop supply systems in the United States: what do we know and what do we need to know?

Short-rotation woody crop (SRWC) supply systems have been proposed over the past 20 years as a means of rapidly producing biomass for fiber and fuels. The U.S. Department of Energy, through the Biofuels Feedstock Development Program and its partners, has selected model species, developed silvicultural systems and created genetically improved clonal planting stock for use in SRWC supply systems. Spacing, fertilizer and pesticide prescriptions have been developed for several species and regions within the U.S. Breeding and genetic improvement projects continue to identify and select plant materials which display increased productivity and pest resistance. Genetic transformation, somaclonal variation and marker-assisted selection are being used to supplement traditional breeding work. Harvesting and handling methods are currently relying on traditional combinations of existing equipment. Nevertheless, technical and environmental issues related to: (1) long-term use of fertilizers and irrigation; (2) deployment of clonal planting stock; and (3) development of customized harvesting equipment remain as unresolved issues related to further deployment and commercialization of SRWC systems. Overall determination of SRWC sustainability will require resolution of these issues.