This report discusses the use of biomass as an energy feedstock, which is emerging as a potentially viable alternative to address U.S. energy security concerns, foreign oil dependence, rural economic development, and diminishing sources of conventional energy. Biomass (organic matter that can be converted into energy) may include food crops, crops for energy (e.g., switchgrass or prairie perennials), crop residues, wood waste and byproducts, and animal manure. This report discusses legislation regarding biomass, the evolving definition of biomass, and the positions of supporters and detractors of biomass as an alternative energy source.