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Biodegradation is the process by which organic substances are broken down by the enzymes produced by living organisms. The term is often used in relation to ecology, waste management and environmental remediation (bioremediation). Organic material can be degraded aerobically, with oxygen, or anaerobically, without oxygen. A term related to biodegradation is biomineralisation, in which organic matter is converted into minerals. Biosurfactant, an extracellular surfactant secreted by microorganism enhances the biodegradation process.
Biodegradable matter is generally organic material such as plant and animal matter and other substances originating from living organisms, or artificial materials that are similar enough to plant and animal matter to be put to use by microorganisms. Some microorganisms have the astonishing, naturally occurring, microbial catabolic diversity to degrade, transform or accumulate a huge range of compounds including hydrocarbons (e.g. oil), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pharmaceutical substances, radionuclides and metals. Major methodological breakthroughs in microbial biodegradation have enabled detailed genomic, metagenomic, proteomic, bioinformatic and other high-throughput analyses of environmentally relevant microorganisms providing unprecedented insights into key biodegradative pathways and the ability of microorganisms to adapt to changing environmental conditions.[1]
Anaerobic biodegradation in landfill
Biodegradable waste in landfill degrades in the absence of oxygen through the process of anaerobic digestion. The byproducts of this anaerobic biodegradation are biogas and lignin and cellulose fibres which cannot be broken down by anaerobes (anaerobic microbes)
Engineered landfills are designed with liners to prevent toxic leachate seeping into the surrounding soil and groundwater. Paper and other materials that normally degrade in a few years degrade more slowly over longer periods of time. Biogas contains methane which has approximately 21 times the global warming potential of carbon dioxide. In modern landfills this biogas can be collected and used for power generation.
Methods of measuring biodegradation
Biodegradation can be measured in a number of ways. The activity of aerobic microbes can be measured by the amount of oxygen they consume or the amount of carbon dioxide they produce. Biodegradation can be measured by anaerobic microbes and the amount of methane or alloy that they may be able to produce.
Plastics
Biodegradable plastics made with plastarch material (PSM), and polylactide (PLA) will compost in an industrial compost facility. There are other plastic materials that claim biodegradability, but are more often (and possibly more accurately) described as 'degradable' or oxi-degradable; It is claimed that this process causes more rapid breakdown of the plastic materials into CO2 and H2O.
Indicative lengths of degradation
The following table should be read with the above comments in mind, and care should be taken before accepting claims of biodegradability in view of the (dubious) claims being made.
- Banana peel, 2 – 10 days
- Orange peels, 1 month
- Sugarcane Pulp Products, 1 - 2 months
- Cotton rags, 1 – 5 months
- Paper, 2 – 5 months
- Rope, 3 – 14 months
- Wool socks, 1 – 5 years
- Cigarette filters, 1 – 12 years
- Tetrapaks (plastic composite milk cartons), 5 years
- Plastic bags, 10 – 20 years
- Diapers 10 – 20 years
- Leather shoes, 25 – 40 years
- Nylon fabric, 30 – 40 years
- Tin cans 50 - 100 years
- Aluminum cans 200 - 500 years
- Plastic Bottles 70 - 450 years
- Plastic six-pack holder rings, 450 years
- Styrofoam cup, non-biodegradeable
- Biodegradable Plastic Bags, 75 days
- Biodegradable Paper Cups, 75 days
See also
External links
References
- ^ Diaz E (editor). (2008). Microbial Biodegradation: Genomics and Molecular Biology, 1st ed., Caister Academic Press. ISBN 978-1-904455-17-2.
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