Biomass refers to plant or animal-based organic material that can be used as fuel or as a feedstock for industrial production. Most commonly, biomass refers to plant matter grown specifically for use as biofuel, but it also includes plant waste left over from other processes. Common biomass crops include miscanthus, switchgrass, hemp, corn, poplar, willow, sugarcane, and oil palm. Production of biomass is a growing industry as interest in sustainable fuel sources is growing. The current push to produce ethanol using corn as the feedstack is one example. However, this seemingly positive development is not without social ramifications as it is drawing significantly on a food crop and already affecting world food prices.
Biomass specifically excludes organic material which has been transformed by geological processes into substances such as coal or petroleum, i.e. fossil fuels. Although fossil fuels have their origin in ancient biomass they contain carbon that has been "out" of the carbon cycle for a very long time. Their combustion releases many millenia of stored carbon and disturbs the carbon dioxide (CO2) content in the modern atmosphere.
Plastics from biomass, like some recently developed to dissolve in seawater, are made the same way as petroleum-based plastics, are actually cheaper to manufacture and meet or exceed most performance standards. But they lack the same water resistance or longevity as conventional plastics.
Simple use of biomass fuel (Combustion of wood for heat).
Processing and uses
Biomass which is not simply burned as fuel may be processed in other ways.
Low tech processes include:
- composting (to make soil conditioners and fertilizers)
- anaerobic digestion (decaying biomass to produce methane gas and sludge as a fertilizer)
- fermentation and distillation (both produce ethyl alcohol)
More high-tech processes are:
- Pyrolysis (heating organic wastes in the absence of air to produce gas and char. Both are combustible.)
- Hydrogasification (produces methane and ethane)
- Hydrogenation (converts biomass to oil using carbon monoxide and steam under high pressures and temperatures)
- Destructive distillation (produces methyl alcohol from high cellulose organic wastes).
- Acid hydrolysis (treatment of wood wastes to produce sugars, which can be distilled)
Burning biomass, or the fuel products produced from it, may be used for heat or electricity production.
Other uses of biomass, besides fuel and compost include:
- Building materials
- Biodegradable plastics and paper (using cellulose fibres)
Environmental impact
Biomass is part of the earth's natural carbon cycle. Plants absorb CO2 from the atmosphere during their growing lifetime by photosynthesis. After its life, the carbon in plants recycles to the atmosphere through some combination of rotting (biodegradation) and opening burning. Rotting produces a mixture of up to fifty percent methane (CH4) while open burning releases primarly CO2. CH4 converts to CO2 in the atmosphere, thus completing the carbon cycle. This happens over a relatively short timescale and plant matter used as a fuel can be quickly replaced by planting for new growth. Therefore a reasonably stable level of atmospheric carbon results from its use as a fuel.
CH4 has a greater Greenhouse Warming Potential or GWP than CO2, meaning that 'molecule for molecule' it is better at trapping infrared (heat) radiation from the sun. Therfore shifting CH4 emissions to CO2 emissions by converting biomass to energy rather than letting it rot significantly reduces the contribution to global warming. 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 (CH4) that would have otherwise entered the atmosphere and because it is assumed that new living plants will replace the harvested biomass, thus recapturing the same amount of carbon.
In contrast to biomass carbon, the carbon in fossil fuels is locked away in geological storage virtually forever, unless extracted and burned, as is common in industrial society. This use of fossil fuels releases this ancient carbon from its long-term storage and adds it to the stock of carbon in the modern atmospheric cycle, creating an the imbalance we now call global warming.
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.
Replacing old growth forests with tree plantations is detrimental to wild life as these mono-crops do not support the diversity of life that the original forest did. Habitat destruction is the single biggest contributor to extinction of specicies. For example, the mountain gorrilla in the dwindling tropical forests of Africa are directly threatened by the illegal - and very profitable - charcoal industry . This biomass industry uses wood from protected forests to create charcoal for use by people living in more urban areas or where wood fuel has become scarce.
Biomass production for human use and consumption
In developing countriies biomass is the most important source of energy, accounting for about 35% of the total. In the world's poorest nations, biomass accoutns for up to 90% pf the energy supply.
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, 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.
Currently, the New Hope Power Partnership, owned by Florida Crystals Corporation, is the largest biomass cogeneration energy facility in the U.S. The 140 MWH facility recycles sugar cane fiber and urban wood waste, generating enough electricity to power its large milling and refining operations as well as renewable electricity for more than 40,000 homes. The facility reduces dependence on approximately 800,000 barrels of oil per year and by recycling sugar cane and wood waste, preserves landfill space in urban communities in Florida.
Biomass resources are abundant in most parts of the world and modern commercial conversion technologies could transform low tech uses of biomass to modern energy. If dedicated energy crops and advanced conversion technologes are introduced extensively , biomass could make a substantiao contribution to the global energy mix and help reduce global warming.
