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Biomass, a renewable energy source, is biological material derived from living, or recently living organisms,[1] such as wood, waste, and alcohol fuels. Biomass is commonly plant matter grown to generate electricity or produce heat. For example, forest residues (such as dead trees, branches and tree stumps), yard clippings, wood chips and garbage may be used as biomass. However, biomass also includes plant or animal matter used for production of fibers or chemicals. Biomass may also include biodegradable wastes that can be burnt as fuel. It excludes organic materials such as fossil fuels which have been transformed by geological processes into substances such as coal or petroleum.

Industrial biomass can be grown from numerous types of plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane[2], and a variety of tree species, ranging from eucalyptus to oil palm (palm oil). The particular plant used is usually not important to the end products, but it does affect the processing of the raw material.

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.

Plastics from biomass, like some recently developed to dissolve in seawater, are made the same way as petroleum-based plastics. These 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.[3]

Contents

Chemical composition

Biomass is carbon based and is composed of a mixture of organic molecules containing hydrogen, usually including atoms of oxygen, often nitrogen and also small quantities of other atoms, including alkali, alkaline earth and heavy metals. These metals are often found in functional molecules such as the porphyrins which include chlorophyll which contains magnesium.

Biomass sources

Biomass energy is derived from five distinct energy sources: garbage, wood, waste, landfill gases, and alcohol fuels. Wood energy is derived both from direct use of harvested wood as a fuel and from wood waste streams. The largest source of energy from wood is pulping liquor or “black liquor,” a waste product from processes of the pulp, paper and paperboard industry. Waste energy is the second-largest source of biomass energy. The main contributors of waste energy are municipal solid waste (MSW), manufacturing waste, and landfill gas. Biomass alcohol fuel, or ethanol, is derived almost exclusively from corn. Its principal use is as an oxygenate in gasoline.[4]

Biomass can be converted to other usable forms of energy like methane gas or transportation fuels like ethanol and biodiesel. Methane gas is the main ingredient of natural gas. Smelly stuff, like rotting garbage, and agricultural and human waste, release methane gas - also called "landfill gas" or "biogas." Crops like corn and sugar cane can be fermented to produce the transportation fuel, ethanol. Biodiesel, another transportation fuel, can be produced from left-over food products like vegetable oils and animal fats.[5] Also, Biomass to liquids (BTLs) and cellulosic ethanol are still under research.[6]

Biomass conversion process to useful energy

There are a number of technological options available to make use of a wide variety of biomass types as a renewable energy source. Conversion technologies may release the energy directly, in the form of heat or electricity, or may convert it to another form, such as liquid biofuel or combustible biogas. While for some classes of biomass resource there may be a number of usage options, for others there may be only one appropriate technology.

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Thermal conversion

These are processes in which heat is the dominant mechanism to convert the biomass into another chemical form. The basic alternatives are separated principally by the extent to which the chemical reactions involved are allowed to proceed:Combustion,Torrefaction, Pyrolysis,Gasification.

There are a number of other less common, more experimental or proprietary thermal processes that may offer benefits such as hydrothermal upgrading (HTU) and hydroprocessing. Some have been developed for use on high moisture content biomass, including aqueous slurries, and allow them to be converted into more convenient forms. Some of the Applications of thermal conversion are Combined heat and power (CHP) and Co-firing. In a typical biomass power plant, efficiencies range from 20-27%.[7]

Chemical conversion

A range of chemical processes may be used to convert biomass into other forms, such as to produce a fuel that is more conveniently used, transported or stored, or to exploit some property of the process itself.

Biochemical conversion

As biomass is a natural material, many highly efficient biochemical processes have developed in nature to break down the molecules of which biomass is composed, and many of these biochemical conversion processes can be harnessed.

Biochemical conversion makes use of the enzymes of bacteria and other micro-organisms to break down biomass. In most cases micro-organisms are used to perform the conversion process: anaerobic digestion, fermentation and composting. Other chemical processes such as converting straight and waste vegetable oils into biodiesel is transesterification.[8] Another way of breaking down biomass is by breaking down the carbohydrates and simple sugars to make alcohol. However, this process has not been perfected yet. Scientists are still researching the effects of converting biomass.

Environmental impact

On combustion the carbon from biomass is released into the atmosphere as carbon dioxide (CO2). The amount of carbon stored in dry wood is approximately 50% by weight.[9] When from agricultural sources, plant matter used as a fuel can be replaced by planting for new growth. When the biomass is from forests, the time to recapture the carbon stored is generally longer, and the carbon storage capacity of the forest may be reduced overall if destructive forestry techniques are employed.[citation needed]

The existing biomass power generating industry in the United States, which consists of approximately 11,000 MW (megawatts) of summer operating capacity actively supplying power to the grid, produces about 1.4 percent of the U.S. electricity supply.[10]

Currently, the New Hope Power Partnership is the largest biomass power plant in North America. The 140 MW facility uses sugar cane fiber (bagasse) and recycled urban wood as fuel to generate enough power for its large milling and refining operations as well as to supply renewable electricity for nearly 60,000 homes. The facility reduces dependence on oil by more than one million barrels per year, and by recycling sugar cane and wood waste, preserves landfill space in urban communities in Florida.[11][12]

The amount of biomass available is usually not as great as stated in the example above. Many times, especially in Europe where large agricultural developments are not usual, the cost for transporting the biomass overcomes its actual value and therefore the gathering ground has to be limited to a certain small area. This fact leads to only small possible power outputs around 1 MWel. To make an economic operation possible those power plants have to be equipped with the ORC technology, a cycle similar to the water steam power process just with an organic working medium. Such small power plants can be found in Europe.[13] [14][15][16]

Despite harvesting, biomass crops may sequester (trap) carbon. So for example soil organic carbon has been observed to be greater in switchgrass stands than in cultivated cropland soil, especially at depths below 12 inches.[17] The grass sequesters the carbon in its increased root biomass. Typically, perennial crops sequester much more carbon than annual crops due to much greater non-harvested living biomass, both living and dead, built up over years, and much less soil disruption in cultivation.

The biomass-is-carbon-neutral proposal put forward in the early 1990's has been superseded by more recent science that recognizes that mature, intact forests sequester carbon more effectively than cut-over areas. When a tree’s carbon is released into the atmosphere in a single pulse, it contributes to climate change much more than woodland timber rotting slowly over decades. Current studies indicate that recapturing carbon released by burning will take minimally hundreds of years.[18]

Using biomass as a fuel produces the same air-pollution challenges as other fuels. Black carbon - a pollutant created by incomplete combustion of fossil fuels, biofuels, and biomass - is possibly the second largest contributor to global warming.[19] In 2009 a Swedish study of the giant brown haze that periodically covers large areas in South Asia determined that it had been principally produced by biomass burning, and to a lesser extent by fossil-fuel burning.[20] Researchers measured a significant concentration of 14C, which is associated with recent plant life rather than with fossil fuels.[21]

See also

References

  1. ^ Biomass Energy Center
  2. ^ 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. 
  3. ^ Oh, Chicken Feathers! How to Reduce Plastic Waste. Yahoo News, April 5, 2007.
  4. ^ Energy Information Administration
  5. ^ Energy Kids
  6. ^ [1]
  7. ^ Owning and Operating Costs of Waste and Biomass Power Plants
  8. ^ http://www.biomassenergycentre.org.uk/portal/page?_pageid=75,15179&_dad=portal&_schema=PORTAL
  9. ^ Forest volume-to-biomass models and estimates of mass for live and standing dead trees of U.S. forests
  10. ^ "U.S. Electric Net Summer Capacity". U.S. Energy Information Administration. July 2009. http://www.eia.doe.gov/cneaf/alternate/page/renew_energy_consump/table4.html. Retrieved 2010-01-25. 
  11. ^ Agreement for Generating Balancing Service
  12. ^ Biomass: Can Renewable Power Grow on Trees?
  13. ^ Use of biomass by help of the ORC process
  14. ^ How False Solutions to Climate Change Will Worsen Global Warming
  15. ^ Biofuel crops may worsen global warming: study
  16. ^ Biodiesel Will Not Drive Down Global Warming
  17. ^ Soil Carbon under Switchgrass Stands and Cultivated Cropland (Interpretive Summary and Technical Abstract). USDA Agricultural Research Service, April 1, 2005
  18. ^ Jobs and Energy
  19. ^ 2009 State Of The World, Into a Warming World,Worldwatch Institute, 56-57, Isbn 978-0-393-33418-0
  20. ^ Science, 2009, 323, 495
  21. ^ Biomass burning leads to Asian brown cloud, Chemical & Engineering News, 87, 4, 31

External links

Further Reading


Simple English

, a hardy plant used in the biofuel industry in the United States]] .]] Biomass is a basic term in ecology, and in the energy production industry.

In ecology, biomass means the accumulation of living matter. It is the total living biological material in a given area or of a biological community or group. Biomass is measured by weight, or by dry weight, per given area (usually measured per square metre or square kilometre).

In the energy industry, it refers to biological material which can be used as fuel or for industrial production. Biomass includes plant matter grown for use as biofuel, and also includes plant or animal matter used for production of fibres, chemicals or heat. Biomass may also include biodegradable wastes which can be burnt as fuel. It excludes organic material which has been transformed by geological processes into substances such as coal or petroleum. It is usually measured by dry weight.

Contents

Energy industry

The term biomass is especially useful for plants, where some internal structures may not always be considered living tissue, such as the wood (secondary xylem) of a tree.

Biofuels include bioethanol, biobutanol, biodiesel & biogas.

Biomass is grown from several plants, including switchgrass, hemp, corn, poplar, willow and sugarcane[1]. The particular plant used is usually not very important to the end products, but it does affect the processing of the raw material. Though biomass is a renewable 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.

Biomass is part of the carbon cycle. Carbon from the atmosphere is converted into biological matter by photosynthesis. On decay or combustion the carbon goes back into the atmosphere. 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.

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.

Other uses of biomass, besides fuel:

  • Building materials
  • Biodegradable plastics and paper (using cellulose fibres)

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 as conventional plastics. [2]

Ecology

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The most successful animal, in terms of biomass, is the Antarctic krill, Euphausia superba, with a biomass of probably over 500 million tons, roughly twice the total biomass of humans.

This is a summary of biomass data.[3]

BIOME ECOSYSTEM TYPE Area Mean Net Primary Production World Primary Production Mean biomass World biomass Minimum replacement rate
(million km²) (gram dryC/sq metre/year) (billion tonnes/year) (kg dryC/sq metre) (billion tonnes) (years)
Tropical rain forest 17.0 2,200 37.40 45.00 765.00 20.45
Tropical monsoon forest 7.5 1,600 12.00 35.00 262.50 21.88
Temperate evergreen forest 5.0 1,320 6.60 35.00 175.00 26.52
Temperate deciduous forest 7.0 1,200 8.40 30.00 210.00 25.00
Boreal forest 12.0 800 9.60 20.00 240.00 25.00
Mediterranean open forest 2.8 750 2.10 18.00 50.40 24.00
Woodland and shrubland 5.7 700 3.99 6.00 34.20 8.57
Savanna 15.0 900 13.50 4.00 60.00 4.44
Temperate grassland 9.0 600 5.40 1.60 14.40 2.67
Tundra and alpine climate 8.0 140 1.12 0.60 4.80 4.29
Desert and semidesert scrub 18.0 90 1.62 0.70 12.60 7.78
Extreme desert, rock desert, sand or ice sheets 24.0 3 0.07 0.02 0.48 6.67
Cultivated land 14.0 650 9.10 1.00 14.00 1.54
Swamp and marsh 2.0 2,000 4.00 15.00 30.00 7.50
Lakes and streams 2.0 250 0.50 0.02 0.04 0.08
Total continental 149.00 774.51 115.40 12.57 1,873.42 16.23
Open ocean 332.00 125.00 41.50 0.003 1.00 0.02
Upwelling zones 0.40 500.00 0.20 0.020 0.01 0.04
Continental shelf 26.60 360.00 9.58 0.010 0.27 0.03
Algal beds and reefs 0.60 2,500.00 1.50 2.000 1.20 0.80
Estuaries & mangroves 1.40 1,500.00 2.10 1.000 1.40 0.67
Total marine 361.00 152.01 54.88 0.01 3.87 0.07
Grand total 510.00 333.87 170.28 3.68 1,877.29 11.02

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