Composting (Encyclopedia of Environmental Issues, Revised Edition)
All living things are part of a natural recycling process. For example, dead trees in a forest slowly break down into a soillike substance that nurtures the growth of new forest plants. Composting is the same process in a slightly controlled environment.
A backyard or garden compost bin is basically a box with holes or slats, to let in air, that is filled with yard and kitchen waste. A fifty-fifty balance of items containing nitrogen and items containing carbon is needed. Items containing nitrogen include grass clippings, eggshells, coffee grounds, and vegetable and fruit peelings. Items containing carbon include dead leaves, evergreen needles, bark chips, and dryer lint. The various items are added in layers and topped with dirt to hold in moisture. As the waste decays, the bacteria present thrive. They feast on the waste, generating energy and more bacteria. The decomposing pile is occasionally turned with a shovel, and more yard or kitchen waste is added. The waste products from the bacteria, together with what is left after they feast on scraps, form a dry mulch that can be used as a natural garden fertilizer.
Trash and garbage collected from the public by sanitation workers is sometimes composted in municipal processing plants. Decomposable materials are sorted from glass, metal, and other inorganic materials, and the organic items are then shredded or broken down into smaller pieces. In this way, local governments can reduce...
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Nardi, James B. “Composting as an Antidote to Soil Abuse.” In Life in the Soil: A Guide for Naturalists and Gardeners. Chicago: University of Chicago Press, 2007.
Scott, Nicky. Composting: An Easy Household Guide. White River Junction, Vt.: Chelsea Green, 2007.
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Background (Encyclopedia of Global Resources)
The decay of dead plants and animals starts when microorganisms in the soil feed on dead matter, breaking it down into smaller compounds usable by plants. Collectively, the breakdown product is called humus, a dark brown, spongy, crumbly substance. Adding humus to soil increases its fertility. compost may be defined in various ways. The Oxford English Dictionary defines it (as a noun) as a mixture of ingredients for fertilizing or enriching land, a prepared manure or mold; Webster’s New World Dictionary defines it (as a verb) as the making of compost and the treatment of soil with it. Compost and composting derive from the Old French composter, “to manure” or “to dung.”
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History (Encyclopedia of Global Resources)
The origins of human composting activities are buried in prehistory. Early farmers undoubtedly discovered the benefits of compost, probably from animal manure deposited on or mixed with soil. In North America, American Indians and then Europeans used compost in their gardens. Public accounts of the use of stable manure in composting date back to the eighteenth century. Many New England farmers also found it economical to use fish in their compost heaps.
While living in India from 1905 to 1934, British agronomist Sir Albert Howard developed today’s home composting methods. Howard found that the best compost pile consists of three parts plant matter to one part manure. He devised the Indore method of composting, alternating layers of plant debris, manure, and soil to create a pile. Later, during the composting process, he turned the pile or mixed in earthworms.
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How Composting Works (Encyclopedia of Global Resources)
Composting is a natural form of recycling that takes from six months to two years to complete. Bacteria are the most efficient decomposers of organic matter. Fungi and protozoans later join the process, followed by centipedes, millipedes, beetles, and earthworms. By manipulating the composition and environment of a compost pile, gardeners and farmers can reduce composting time to three to four months. Important factors to consider are the makeup of the pile, the surface area, the volume, the moisture, the aeration, and the temperature of the compost pile.
Yard waste such as fallen leaves, grass clippings, some weeds, and the remains of garden plants make excellent compost. Other good additions to a home compost pile include sawdust, wood ash, and kitchen scraps, including vegetable peelings, egg shells, and coffee grounds. Microorganisms digest organic matter faster when they have more surface area to work on. Gardeners can speed the composting process by chopping kitchen or garden waste with a shovel or running it through a shredding machine or lawn mower.
The volume of the compost pile is important because a large compost pile insulates itself, holding in the heat of microbial activity. A properly made heap will reach temperatures of about 60° Celsius in four or five days. Then the pile will settle, a sign that is working properly. Piles 0.76 cubic meter or smaller cannot hold enough heat, while piles 3.5 cubic...
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Modern Uses and Practice (Encyclopedia of Global Resources)
Composting remains an important practice. Yard and kitchen wastes use valuable space in our landfills. These materials compose about 20 to 30 percent of all household waste in the United States. Composting household waste reduces the volume of municipal solid waste and provides a nutrient-rich soil additive. Compost or organic matter added to soil improves soil structure, texture, aeration, and water retention. It improves plant growth by loosening heavy clay soils, allowing better root penetration. It improves the water-holding and nutrient-holding capacity of sandy soils and increases the essential nutrients of all soils. Mixing compost with soil also contributes to erosion control and proper soil pH balance.
Some cities collect and compost leaves and other garden waste and then make it available to city residents for little or no charge. Some cities also compost sewage sludge or human waste, which is high in nitrogen and makes a rich fertilizer. Properly composted sewage sludge that reaches an internal temperature of 60° Celsius contains no dangerous disease-causing organisms. One possible hazard, however, is that it may contain high levels of toxic heavy metals, including zinc, copper, nickel, and cadmium.
The basic principles of composting used by home gardeners also are used by municipalities composting sewage sludge and garbage, by farmers composting animal and plant waste, and by some industries...
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Further Reading (Encyclopedia of Global Resources)
Bem, Robyn. Everyone’s Guide to Home Composting. New York: Van Nostrand Reinhold, 1978.
Campbell, Stu. Let It Rot! The Gardener’s Guide to Composting. 3d ed. Pownal, Vt.: Storey Communications, 1998.
Jenkins, Joseph C. The Humanure Handbook: A Guide to Composting Human Manure. 3d ed. White River Junction, Vt.: Chelsea Green, 2005.
Martin, Deborah L., and Grace Gershuny, eds. The Rodale Book of Composting. New, rev. ed. Emmaus, Pa.: Rodale Press, 1992.
Simons, Margaret. Resurrection in a Bucket: The Rich and Fertile Story of Compost. Crows Nest, N.S.W.: Allen & Unwin, 2004.
Cornell Waste Management Institute, Department of Crop and Soil Sciences, Cornell University. Cornell Composting. http://www.css.cornell.edu/compost/Composting_Homepage.html
U.S. Environmental Protection Agency. Composting. http://www.epa.gov/wastes/conserve/rrr/composting/index.htm
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Definition (Encyclopedia of Global Warming)
Composting is a natural biological process that breaks down organic materials into a stable organic substance called compost. Compost is created by combining organic wastes, such as yard trimmings, food wastes, and manures, in piles or containers. Microorganisms, primarily bacteria and fungi, decompose organic matter and form compost, a nutrient-rich material that is also called humus. Humus is dark brown or black in color and is free of most pathogens and weed seeds. Compost can either be added to soil as fertilizer or be used to support plant growth. Composting is used in landscaping, horticulture, and agriculture as an organic fertilizer to enrich soils. Compost is also used for erosion control, wetland construction, and as landfill cover. Industrial composting systems are increasingly being utilized as landfill alternatives, making them an important tool for waste management.
Composting methods range from simple backyard or onsite systems to large, commercial-scale agricultural and worm-composting centers. Composting can be either aerobic (occurring in the presence of oxygen) or anaerobic (without oxygen). Aerobic methods are generally more efficient at decomposing organic matter. Homeowners and other small-quantity generators use backyard composting systems to degrade such wastes as yard trimmings and food scraps. Larger operations utilize aerated, or turned, windrow composting, in which organic waste is piled in rows called...
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Significance for Climate Change (Encyclopedia of Global Warming)
Composting organic material has many environmental benefits, including some that mitigate some of the harmful effects associated with climate change. In general, composting leads either directly or indirectly to a reduction in the amount of greenhouse gases (GHGs) released into the atmosphere. Composting reduces the use of inorganic fertilizers and pesticides, diverts wastes from landfills, restores soil quality, and increases carbon content in soils. By regenerating nutrient-poor soils, compost increases the water-hold capacity of soils and decreases the amount of inorganic fertilizer required to grow healthy crops.
Inorganic fertilizers require a great deal of energy to produce, so reducing the demand for such fertilizers reduces energy production and consumption. Composting, moreover, slows down the depletion of existing organic matter from soils while simultaneously adding organic matter and carbon to the soil. Increasing carbon sequestration within soils contributes substantially to reduced GHG emissions. Composting also helps decrease plant diseases and pests, which reduces the amount of pesticides required. Composting also diverts organic wastes that would otherwise end up in landfills or other disposal sites. Reducing organic wastes in disposal sites reduces the amount of methane, a very potent GHG, emitted from such sites.
Although composting decreases methane emissions from landfills, some...
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Further Reading (Encyclopedia of Global Warming)
Campbell, Stu. Let it Rot! The Gardener’s Guide to Composting. 3d ed. North Adams, Mass.: Storey, 1998. Introduction to composting for general readers. Includes descriptions of how composting works and different composting methods.
Culen, Gerald R., et al. Organics: A Wasted Resource? An Extended Case Study for the Investigation and Evaluation of Composting and Organic Waste Management Issues. Champaign, Ill.: Stipes, 2001. Written for students, this text provides information related to composting and waste management for a foundation in environmental science. Includes case studies and student activities.
Ebeling, Erich, ed. Basic Composting: All the Skills and Tools You Need to Get Started. Mechanicsburg, Pa.: Stackpole Books, 2003. A complete guide to tools and techniques of composting written by composting experts, including information on different composting methods and how to build composting bins.
Lens, Piet, Bert Hamelers, and Harry Hoitnik, eds. Resource Recovery and Reuse in Organic Solid Waste Management. London: IWA, 2007. Provides information on solid waste management using composting to reduce greenhouse effects and other environmental damage. Written at an advanced scientific level.
Scott, Nicky. Composting: An Easy Household Guide. White River Junction, Vt.: Chelsea Green, 2007. Contains a plethora of basic information about how to begin...
(The entire section is 206 words.)