Biopower is the use of biomass resources to produce, either singly or in combination, electricity, heat/steam, and cooling. Most electricity produced in the U.S. uses coal or natural gas as the feedstock, but about 1.5% of the total electricity generated is from biomass.
Industrial settings are well-suited to using biomass to produce biopower because their requirements are relatively consistent and the combustion process can be operated at a relatively steady condition. In 2002, the industrial sector utilized 1.56 quadrillion Btus (quads) of biomass, of which 0.48 quads were used to generate electricity and 1.08 quads generated useful thermal output. Currently, the paper and pulp industry is the largest producer of biomass electricity and heat/steam, generating more than 50% of its internal energy needs from black liquor and waste wood. The wood products industry also generates more than 50% of its own energy needs. With the exception of biopower produced from black liquor, most electricity biopower production is on a small scale (<50 MWe, average 20e MWe) compared to fossil-fuel fired power plants (typically 100 to 1300 MWe) due to the dispersed supply of biomass, its relatively low energy density, and its high moisture content.
A number of technologies can be used to produce biopower including direct fire applications (such as the dedicated combustion of biomass resources in utilities; combustion of biomass resources produced as a by-product of the manufacturing process in industrial settings; and co-firing which involves the partial substitution of fossil fuels with biomass resources); gasification which involves the thermal decomposition of biomass resources in an oxygen starved environment to produce combustible gases (syngas), tars, liquids and charcoal; and pyrolysis which is the thermal decomposition of biomass resources into volatile compounds (gases and bio-oil similar to heating oil) and solids (chars) in the absence of oxygen and usually water.
Distributed generation is typically defined as using small-scale production of electricity at or near the user. Many commercial and industrial customers value reliable electricity which can be provided by on-site generation, either solely as electricity or a combined heat and power (CHP) operation. Distributed generation is distinguished from traditional electricity generation by location (at or near the location of use); capacity (small <1 MWe); and ownership (nonutility). Barriers to the greater use of distributed generation include contractual and technical interconnection requirements; surcharges imposed by utilities on operators of distributed generation for standby services; price of electricity received by the distributed generator; and environmental and permitting requirements of local governments.