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Biomass Technology Overview
Biomass technologies include numerous ways of using organic matter to directly generate power, heat, be processed into fuels, or converted to organically derived chemicals and other materials.
Since many types of organic matter is constantly renewed, biomass processes offer the benefit of generating oxygen while growing, and their combustion or conversion generates much less carbon and toxins than conventional fossil fuels.
Biomass sources are quite varied, including agricultural food and feed crops, crop waste and residues, wood wastes and residues, dedicated energy crops and trees, aquatic plants, animal wastes, and municipal wastes.
Key elements in making biomass technologies commercially and economically feasible involve details of collection, handling, and distribution of resources to processing plants.
Colorado Biomass Power Resources
from the Renewable Energy Committee report prepared for the Chairman of the Colorado State Senate Majority Ad Hoc Energy Task Force, and approved by the CRES Board of Directors, October 25, 2001.
Recent studies indicate that Colorado has a fair biomass resource potential. An estimated 5.2 billion kWh of electricity could be generated using renewable biomass fuels in Colorado. This is enough electricity to fully supply the annual needs of 521,000 average homes, or 42 percent of the residential electricity use in Colorado. These biomass resource supply figures are based on estimates for five general categories of biomass: urban residues, mill residues, forest residues, agricultural residues, and energy crops. Of these potential biomass supplies and the quantities cited below, most forest residues, agricultural residues, and energy crops are not presently economic for energy use. New tax credits or incentives, increased monetary valuation of environmental benefits, or sustained high prices for fossil fuels could make these fuel sources more economic in the future.
Wood is the most commonly used biomass fuel for heat and power. The most economic sources of wood fuels are usually urban residues and mill residues. Urban residues used for power generation consist mainly of chips and grindings of clean, non-hazardous wood from construction activities, woody yard and right-of-way trimmings, and discarded wood products such as waste pallets and crates. Local governments can encourage segregation of clean wood from other forms of municipal waste to help ensure its re-use for mulch, energy, and other markets. Using clean and segregated biomass materials for electricity generation recovers their energy value while avoiding landfill disposal. Mill residues, such as sawdust, bark, and wood scraps from paper, lumber, and furniture manufacturing operations are typically very clean and can be used as fuel by a wide range of biomass energy systems. The estimated supplies of urban and mill residues available for energy uses in Colorado are 158,000 and 180,000 dry tons per year, respectively.
Forest residues include underutilized logging residues, imperfect commercial trees, dead wood, and other non-commercial trees that need to be thinned from crowded, unhealthy, fire-prone forests. Because of their sparseness and remote location, these residues are usually more expensive to recover than urban and mill residues. The estimated supply of forest residues for Colorado is 720,000 dry tons per year.
Agricultural residues are the biomass materials remaining after harvesting agricultural crops. These residues include wheat straw, corn stover (leaves, stalks, and cobs), orchard trimmings, rice straw and husks, and bagasse (sugar cane residue). Due to the high costs for recovering most agricultural residues, they are not yet widely used for energy purposes; however, they can offer a sizeable biomass resource if supply infrastructures are developed to economically recover and deliver them to energy facilities. An estimated 2,524,000 dry tons per year is available from corn stover and wheat straw in Colorado.
Energy crops are crops developed and grown specifically for fuel. These crops are carefully selected to be fast growing, drought and pest resistant, and readily harvested alternative crops. Energy crops include fast-growing trees, shrubs, and grasses such as hybrid poplars, hybrid willows, and switchgrass, respectively. In addition to environmental benefits, energy crops can provide income benefits for farmers and rural landowners. For Colorado, the production potential for energy crops has not been estimated.
Biofuel Resources. In general, current U.S. ethanol production is based largely on the starch in kernels of field corn, the nation's largest agricultural crop. (The predominant use of field corn is for animal feed. Current ethanol production uses only about 7% of the crop.) Any starch or sugar crop, however, can now be used to make ethanol.
As commercialization of advanced bioethanol technology makes possible ethanol production from biomass other than starch and sugar, vast additional resources will become available to supplement ethanol production from corn kernels. The first advanced bioethanol technology plants will likely use "opportunity" feedstocks such as paper mill or food processing wastes, that are from concentrated sources and now have low value or must be disposed. In the intermediate future, ethanol can be made from agricultural residues such as corn stover (stalks and husks-roughly equivalent in mass to the corn grain crop), or forestry residues such as from lumber mills or from forest thinning to reduce fire danger near urban areas. In the long term, ethanol could be made from dedicated energy crops of fast-growing trees and grasses such as poplars and switchgrass.
Current U.S. biodiesel production is based largely on oil from soybeans and recycled restaurant cooking oils. Both of these are currently in surplus and biodiesel production uses only a very minor fraction of available supply. Any animal fat or vegetable oil, however, can be used to make
biodiesel.
More about
biomass, bioenergy, biofuels, and biochemicals
US DOE Bioenergy website http://eren.doe.gov/RE/bioenergy.html
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