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Biodegradation

Biodegradation


Biodegradation is the decay or breakdown of materials that occurs when microorganisms use an organic substance as a source of carbon and energy. For example, sewage flows to the wastewater treatment plant where many of the organic compounds are broken down; some compounds are simply biotransformed (changed), others are completely mineralized . These biodegradation processes are essential to recycle wastes so that the elements in them can be used again. Recalcitrant materials, which are hard to break down, may enter the environment as contaminants.

Biodegradation is a microbial process that occurs when all of the nutrients and physical conditions involved are suitable for growth. Temperature is an important variable; keeping a substance frozen can prevent biodegradation. Most biodegradation occurs at temperatures between 10 and 35°C. Water is essential for biodegradation. To prevent the biodegradation of cereal grains in storage, they must be kept dry. Foods such as bread or fruit will support the growth of mold if the moisture level is high enough. The microorganisms need energy plus carbon, nitrogen, oxygen, phosphorus, sulfur, calcium, magnesium, and several metals to grow and reproduce. The oxidation of organic substances to carbon dioxide and water is an exothermic (heat-releasing) process. For each mole of oxygen used as electron acceptor (oxidant), about 104 kilocalories (435 kJ) of energy is potentially available. All organisms make use of only part of this energy. The rest is lost as heat. This can be seen in composting when the compost becomes hot. Biodegradation can occur under aerobic conditions where oxygen is the electron acceptor and under anaerobic conditions where nitrate, sulfate, or another compound is the electron acceptor.

Bacteria and fungi, including yeasts and molds, are the microorganisms responsible for biodegradation. Environmental managers want to use biodegradation when it is needed and prevent it when preservation is important. Chemicals are commonly used to treat wood in buildings and other structures to prevent biodegradation. Wooden posts and pilings are treated with creosote or copper compounds to prevent rotting. Compounds that inhibit biodegradation are often added to automobile antifreeze solutions, aircraft deicer formulations, and other products to preserve the original qualities of the product. These products and chemicals can enter the environment and become contaminants. The inhibitors have a negative effect when the product becomes a waste and is to be biodegraded. For example, biodegradation of aircraft deicer formulations in airport runoff is often inhibited because of the benzotriazoles that are present to preserve the formulation.

see also Bioremediation; Solid Waste.

Bibliography

Alexander, Martin. (1994). Biodegradation and Bioremediation. New York: Academic Press.

Gibson, David T., ed. (1984). Microbial Degradation of Organic Compounds. New York: Marcel Dekker.


Internet Resources

Kansas State University. Great Plains/Rocky Mountain Hazardous Substance Research Center Web site. Available from http://www.engg.ksu.edu/HSRC.

Larry Eugene Erickson and Lawrence C. Davis

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Biodegradable

Biodegradable

The term biodegradable is used to describe substances that are capable of being broken down, or decomposed, by the action of bacteria, fungi, and other microorganisms. Temperature and sunlight may also play a role in the decomposition of biodegradable substances. When substances are not biodegradable, they remain in the environment for a long time, and, if toxic, may pollute the soil and water, causing harm to plants and animals that live in these environments. Humans can also be affected by drinking water or eating crops contaminated by these toxic substances.

Common, everyday substances that are biodegradable include food wastes, tree leaves, and grass clippings. Many communities now encourage people to compost these materials and use them as humus (decayed organic material in soil) for gardening. Because plant and animal materials are biodegradable, this is one way to for towns and cities to reduce solid waste.

The development of detergents in the 1950s and the problems their surfactants caused (wetting agents that allow water to dissolve greasy dirt) raised the issue of the biodegradability of these chemicals. It was found that bacteria in sewage systems degraded some surfactants very slowly. This resulted in the chemicals being released into lakes and streams not fully decomposed and forming suds in the water. Environmental concerns led to the development of new detergents that are more easily biodegradable.

In efforts to control the use of nonbiodegradable materials, governments and industries have taken various measures. For example, the plastic rings that bind six-packs of soda and beer pose a danger to wildlife, who can becoming entangled in them; these rings must now be biodegradable by law in Oregon and Alaska. Italy has banned all nonbiodegradable plastics. Certain manufacturers have responded to the issue by experimenting with biodegradable packaging of food. Many garbage bags and disposable diapers are now being made using degradable plastics, with the goal of reducing litter, pollution, and danger to wildlife.

[See also Composting; Recycling; Waste management ]

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biodegradable

bi·o·de·grad·a·ble / ˌbīōdiˈgrādəbəl/ • adj. (of a substance or object) capable of being decomposed by bacteria or other living organisms. DERIVATIVES: bi·o·de·grad·a·bil·i·ty / -ˌgrādəˈbilitē/ n.

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"biodegradable." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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biodegradable

biodegradable Property of a substance that enables it to be decomposed by microorganisms. The end result of decay is stable, simple compounds (such as water and carbon dioxide). This property has been designed into materials such as plastics to aid refuse disposal and reduce pollution.

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"biodegradable." World Encyclopedia. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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biodegradable

biodegradable Applied to substances that are easily broken down by living organisms.

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"biodegradable." A Dictionary of Ecology. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"biodegradable." A Dictionary of Ecology. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/biodegradable

"biodegradable." A Dictionary of Ecology. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/biodegradable

biodegradable

biodegradable Applied to substances that are easily broken down by living organisms.

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"biodegradable." A Dictionary of Zoology. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"biodegradable." A Dictionary of Zoology. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/biodegradable-0

biodegradable

biodegradable See pollution.

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"biodegradable." A Dictionary of Biology. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"biodegradable." A Dictionary of Biology. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/biodegradable-1