Biomass Energy
Biomass is any organic material derived from plants or animals — essentially all energy originally captured by photosynthesis. Domestic biomass resources include agricultural and forestry residues, municipal solid wastes, industrial wastes, and terrestrial and aquatic "energy crops" grown solely for energy purposes.
Biomass can be converted to other usable forms of energy and is an attractive petroleum alternative for a number of reasons. It is a renewable resource that is more evenly distributed over the Earth's surface than are finite energy sources, and may be exploited using more environmentally friendly technologies.
Agriculture and forestry residues, and in particular residues from paper mills, are the most common biomass resources used for generating electricity and power, including industrial process heat and steam, as well as for a variety of biobased products. Use of liquid transportation fuels such as ethanol and biodiesel, however, currently derived primarily from agricultural crops, is increasing dramatically.
Biopower 
Biopower, or biomass power, is the use of biomass to generate electricity, or heat and steam required for the operation of a refinery. Biopower system technologies include direct-firing, cofiring, gasification, pyrolysis, and anaerobic digestion.
Most biopower plants use direct-fired systems. They burn biomass feedstocks directly to produce steam. This steam drives a turbine, which turns a generator that converts the power into electricity. In some biomass industries, the spent steam from the power plant is also used for manufacturing processes or to heat buildings. Such combined heat and power systems greatly increase overall energy efficiency. Paper mills, the largest current producers of biomass power, generate electricity or process heat as part of the process for recovering pulping chemicals.
Biofuels
Biofuels are any fuel derived from biomass. Transportation fuels — including ethanol, methanol, biodiesel, biocrude, and methane — are made from biomass through biochemical or thermochemical processes.
Agricultural products specifically grown for conversion to biofuels include corn and soybeans. The energy in biomass can be accessed by turning the raw materials of the feedstock, such as starch and cellulose, into a usable form.
Direct Use of Woody Biomass
Trees, scrap lumber and other woody biomass can be burned to provide space and water heating. "Direct use" means that the biomass is not converted to electricity or a biofuel before the energy is harnessed.
Woody biomass is considered a carbon-neutral fuel. While carbon dioxide is emitted when trees or other crops are burned, the same amount of carbon dioxide is absorbed when the plants grow.
For more information on the use of woody biomass, see the following links:
- Wood and Pellet Heating — An introduction from DOE.
- Woody Biomass Utilization — A U.S. Forest Service site that provides in-depth information and references, including a Primer on Wood Biomass for Energy and a Woody Biomass Utilization Desk Guide (PDF 1.7 MB) that includes information on timber extraction methods.
- Where Wood Works: Strategies for Heating with Woody Biomass (PDF 4.1 MB) — Wood chips, pellet fuel, cordwood, cofiring with coal, and other approaches.
- Cleaner Burning Wood Stoves and Fireplaces (U.S. Environmental Protection Agency).
- Harnessing the Power of Local Wood Energy: Ensuring a Sustainable Supply of Woodchips for Your School (PDF 1.0 MB) — Wood chips, pellet fuel, cordwood, cofiring with coal, and other approaches.
Biobased Products
Today, petroleum is refined to make chemical feedstocks used in thousands of products. Many of these petroleum-based feedstocks could be replaced with value-added chemicals produced from biomass to then manufacture clothing, plastics, lubricants, and other products.
Biobased chemicals and materials are commercial or industrial products, other than food and feed, derived from biomass feedstocks. Biobased products include green chemicals, renewable plastics, natural fibers, and natural structural materials. Many of these products can replace products and materials traditionally derived from petrochemicals, but new and improved processing technologies will be required.
DOE's Biomass Program provides an overview and list of publications about biobased products."