The term Biomass refers to all the Earth's vegetation and many products and coproducts that come from it. Biomass is the oldest known source of renewable energy--humans have been using it since we discovered fire—and it has high energy content. The energy content of dry biomass ranges from 7,000 Btus/lb for straws to 8,500 Btus/lb for wood.
Domestic biomass resources include agricultural and forestry wastes, municipal solid wastes, industrial wastes, and terrestrial and aquatic crops grown solely for energy purposes, known as energy crops.
Biomass is an attractive energy source for a number of reasons. First, it is a renewable energy source as long as we manage vegetation appropriately. Biomass is also more evenly distributed over the earth's surface than finite energy sources, and may be exploited using less capital-intensive technologies. It provides the opportunity for local, regional, and national energy self-sufficiency across the globe. And energy derived from biomass does not have the negative environmental impact associated with non-renewable energy sources.
Biomass contains energy that has been stored through photosynthesis. That energy content remains when plants are processed into other materials such as paper and animal wastes, and even into forms of energy we use every day, such as electricity and transportation fuel, known as biofuels. The key to accessing the energy content in biomass is converting the raw material (feedstock) into a usable form, which is accomplished through combustion, or biochemical or thermochemical processes.
The U.S. Department of Energy sponsors research programs to determine and develop the most effective processes for converting biomass to energy. The Biomass Power Program focuses on generating electricity from biomass. The Biofuels Program is two-pronged: At the National Renewable Energy Laboratory, research focuses on developing technology to convert various biomass feedstocks into biofuels for transportation. At the Oak Ridge National Laboratory, research in the Biofuels Feedstock Development Program focuses on developing hardy, high-yield crops that are virtually designed for use as feedstocks for biofuels.
The nation's potential biomass resource is great enough to meet a large part of our energy needs, as described in the information about each of these sources of biomass:
More than 86 million metric tons (95 million tons) of agricultural waste are generated in the U.S. each year. This includes agricultural residues such as wheat straw, corn stover and orchard trimmings. Corn alone provides more waste than all other sources of biomass in this country. United States farmers plant about 80 million acres of corn each year, with a potential stover (leaves, stalks, an cobs) harvest of some 120 million dry tons. This is nearly four times greater than the biomass available from wood waste and paper, the next largest feedstock category.
From 90 to 254 million metric tons (100 million to 280 million tons) of forestry wastes could be collected in the United States each year. Forestry waste includes underutilized wood and logging residues, imperfect commercial trees, and non-commercial trees that need to be thinned from crowded, unhealthy, fire-proned forests. Forest thinning is not only necessary to help western softwood forests regain their natural health, but it will also provide a large supply of waste wood that can be converted to biomass power or biofuels.
Municipal solid and industrial waste
By the year 2000, approximately 196 million metric tons (216 million tons) of municipal solid waste will be generated in the United States. Each year, American industry generates about 11 billion metric tons (12 billion tons) of wastes requiring treatment and disposal. Due to the large volume of waste generated by industry and private homes, landfills are becoming increasingly expensive and closely regulated. Many landfills are being forced to close because of more stringent regulations required for their operation. Instead of burying this waste in landfills, much of it could be used to make biofuels or generate biopower.
In the United States, it is estimated that about 77 million hectares (190 million acres) of land could be used to produce energy crops. Energy crops are crops developed and grown specifically for fuel. These include fast-growing trees, shrubs, and grasses, such as hybrid poplars, willows, and switchgrass. Energy crops can be grown on agricultural lands not needed for food, feed, and fiber. In addition, farmers can plant energy crops along riverbanks, around lakeshores or between farms and natural forests or wetlands to create habitat for wildlife, renew the soils, and encourage biodiversity. Trees can be grown for as long as a decade, then be harvested for energy. The U.S. Department of Agriculture estimates that there will be about 100 million acres available for growing energy crops in the 21st century.
Another advantage of energy crops is that they provide diversity of production to farmers, reducing risks from fluctuating markets and stabilizing farm income. The typical modern farm usually only produces one or two major commercial products such as corn, soybeans, milk or beef. The net income of the entire operation is often vulnerable to fluctuations in market demand, unexpected production costs, and the weather, among other factors. Energy crops are also more resistant to disease and pests and relatively inexpensive to grow.