Biomass refers to living and recently dead biological material that can be used as fuel or for industrial production. Most commonly, biomass refers to plant matter grown to generate electricity or produce bio-fuel, but it also includes plant or animal matter used for production of fibers, chemicals or heat. Biomass may also include biodegradable wastes that can be burnt as fuel. It excludes organic material which has been transformed by geological processes into substances such as coal or petroleum. Biomass as used for electrical generation at the Mt. Poso Cogeneration facility will come from both agricultural waste (orchard removals, prunings, etc.) and urban recycling programs.
Although fossil fuels have their origin in ancient biomass, they are not considered biomass by the generally accepted definition because they contain carbon that has been "out" of the carbon cycle for a very long time. Their combustion therefore disturbs the carbon dioxide content in the atmosphere.
Environmental Impact
Biomass is part of the carbon cycle. Carbon from the atmosphere is converted into biological matter by photosynthesis. On death or combustion the carbon goes back into the atmosphere as carbon dioxide (CO2). This happens over a relatively short timescale and plant matter used as a fuel can be constantly replaced by planting for new growth. Therefore a reasonably stable level of atmospheric carbon results from its use as a fuel. It is accepted that the amount of carbon stored in dry wood is approximately 50% by weight.[4]
Though biomass is a renewable fuel, and is sometimes called a "carbon neutral" fuel, its use can still contribute to global warming. This happens when the natural carbon equilibrium is disturbed; for example by deforestation or urbanization of green sites. When biomass is used as a fuel, as a replacement for fossil fuels, it still puts the same amount of CO2 into the atmosphere. However, when biomass is used for energy production it is widely considered carbon neutral, or a net reducer of greenhouse gasses because of the offset of methane that would have otherwise entered the atmosphere. The carbon in biomass material, which makes up approximately fifty percent of its dry-matter content, is already part of the atmospheric carbon cycle. Biomass absorbs CO2 from the atmosphere during its growing lifetime. After its life, the carbon in biomass recycles to the atmosphere as a mixture of CO2 and methane (CH4), depending on the ultimate fate of the biomass material. CH4 converts to CO2 in the atmosphere, completing the cycle. In contrast to biomass carbon, the carbon in fossil fuels is locked away in geological storage forever, unless extracted. The use of fossil fuels removes carbon from long-term storage, and adds it to the stock of carbon in the atmospheric cycle.
Energy produced from biomass residues displaces the production of an equivalent amount of energy from fossil fuels, leaving the fossil carbon in storage. It also shifts the composition of the recycled carbon emissions associated with the disposal of the biomass residues from a mixture of CO2 and CH4, to almost exclusively CO2. In the absence of energy production applications, biomass residue carbon would be recycled to the atmosphere through some combination of rotting (biodegradation) and open burning. Rotting produces a mixture of up to fifty percent CH4, while open burning produces five to ten percent CH4. Controlled combustion in a power plant converts virtually all of the carbon in the biomass to CO2. Because CH4 is a much stronger greenhouse gas than CO2, shifting CH4 emissions to CO2 by converting biomass residues to energy significantly reduces the greenhouse warming potential of the recycled carbon associated with other fates or disposal of the biomass residues.
The existing commercial biomass power generating industry in the United States, which consists of approximately 1,700 MW (megawatts) of operating capacity actively supplying power to the grid (the Mt. Poso Cogeneration facility conversion will add an additional 44MW), produces about 0.5 percent of the U.S. electricity supply. This level of biomass power generation avoids approximately 11 million tons per year of CO2 emissions from fossil fuel combustion. It also avoids approximately two million tons per year of CH4 emissions from the biomass residues that, in the absence of energy production, would otherwise be disposed of by burial (in landfills, in disposal piles, or by the plowing under of agricultural residues), by spreading, and by open burning. The avoided CH4 emissions associated with biomass energy production have a greenhouse warming potential that is more than 20 times greater than that of the avoided fossil-fuel CO2 emissions. Biomass power production is at least five times more effective in reducing greenhouse gas emissions than any other greenhouse-gas-neutral power-production technology, such as other renewables and nuclear. [5]
References
1. ^ T.A. Volk, L.P. Abrahamson, E.H. White, E. Neuhauser, E. Gray, C. Demeter, C. Lindsey, J. Jarnefeld, D.J. Aneshansley, R. Pellerin and S. Edick (October 15-19, 2000). "Developing a Willow Biomass Crop Enterprise for Bioenergy and Bioproducts in the United States". Proceedings of Bioenergy 2000, Adam's Mark Hotel, Buffalo, New York, USA: North East Regional Biomass Program. OCLC 45275154. Retrieved on 2006-12-16.
2. ^ Oh, Chicken Feathers! How to Reduce Plastic Waste. Yahoo News, Apr 5, 2007.
3. ^ Introduction to Renewable Energy Technology. 1996. John Sakalauskas. Northern Melbourne Institute of TAFE / Open Training Services.
4. ^ Forest volume-to-biomass models and estimates of mass for live and standing dead trees of U.S. forests
5. ^ USA Biomass Power Producers Alliance