Biomass, as a renewable energy source, refers to living or to recently dead biological material that can be used as fuel or for industrial production. Biomass comes in many different types, which may be grouped into five basic categories of material:

• Virgin wood, from forestry, arboricultural activities or from wood processing.

• Energy crops: high yield crops grown specifically for energy applications, for example, energycane, switchgrass, and miscanthus.

• Agricultural residues: residues from agriculture harvesting or processing.

• Food waste, from food and drink manufacture, preparation, and processing, and post-consumer waste.

• Industrial waste and co-products from manufacturing and industrial processes.

Biomass is a feedstock for chemicals, electricity, and natural gas, not just liquid fuels. It is essential to successfully grow energy crops at large scale. Biotechnology improvements and agronomics are both key to improving yields and low cost biomass will be critical to future energy production.

The US Department of Energy (DOE) and the US Department of Agriculture (USDA) are both strongly committed to expanding the role of biomass as an energy source. In particular, they support biomass fuels and products as a way to reduce the need for oil and gas imports; to support the growth of agriculture, forestry, and rural economies; and to foster major new domestic industries—biorefineries—making a variety of fuels, chemicals, and other products. As part of this effort, the biomass R&D Technical Advisory Committee, a panel established by the US Congress to guide the future direction of federally funded biomass R&D, envisioned a 30 % replacement of the current US petroleum consumption with biofuels by 2030 [4].

Primary forest resources are logging residues from conventional harvest opera­tions and residues from forest management and land clearing operations, removal of excess biomass from timberlands and other forestlands, and fuelwood extracted from forestlands. Secondary forest resources are primary wood processing mill residues, secondary wood processing mill residues, and pulping liquors (black liquors). Ter­tiary resources are urban wood residues—construction and demolition debris, tree trimmings, packaging wastes, and consumer durables.

Primary agricultural resources are crop residues from major crops, for example, corn stover, small grain straw and sugarcane baggase, grains of corn and soybeans used for ethanol, biodiesel, and bioproducts, perennial grasses, and perennial woody crops; secondary agricultural residues are animal manures and food/feed processing residues, and tertiary are municipal solid wastes, post-consumer residues, and landfill gases.

Forest resources (US) 368 million dry tones per year

Agricultural resources (US) 998 million dry tonnes per year

Total (US) 1,366 million dry tones per year