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Decomposition of plastics
- Nov 20, 2018 -

Plastics contribute to approximately 10% of discarded waste. Depending on their chemical composition, plastics and resins have varying

Plastics contribute to approximately 10% of discarded waste. Depending on their chemical composition, plastics and resins have varying properties related to contaminant absorption and adsorption. Polymer degradation takes much longer as a result of saline environments and the cooling effect of the sea. These factors contribute to the persistence of plastic debris in certain environments. Recent studies have shown that plastics in the ocean decompose faster than was once thought, due to exposure to sun, rain, and other environmental conditions, resulting in the release of toxic chemicals such as bisphenol A. However, due to the increased volume of plastics in the ocean, decomposition has slowed down. The Marine Conservancy has predicted the decomposition rates of several plastic products. It is estimated that a foam plastic cup will take 50 years, a plastic beverage holder will take 400 years, a disposable nappy will take 450 years, and fishing linewill take 600 years to degrade.

Microbial species capable of degrading plastics are known to science, and some are potentially useful for the disposal of certain classes of plastic waste.

In 1975 a team of Japanese scientists studying ponds containing waste water from a nylon factory, discovered a strain of Flavobacterium that digested certain byproducts of nylon 6 manufacture, such as the linear dimer of 6-aminohexanoate. Nylon 4 or polybutyrolactam can be degraded by the strands of Pseudomonas sp. found in sludge. This produced γ-aminobutyric acid as a byproduct.

Several species of soil fungi can consume polyurethane. This includes two species of the Ecuadorian fungus Pestalotiopsis that can consume polyurethane aerobically and also in anaerobic conditions such as those at the bottom of landfills.

Methanogenic consortia degrade styrene, using it as a carbon source. Pseudomonas putida can convert styrene oil into various biodegradablepolyhydroxyalkanoates.

Microbial communities isolated from soil samples mixed with starch have been shown to be capable of degrading polypropylene.

The fungus Aspergillus fumigatus effectively degrades plasticized PVC. Phanerochaete chrysosporium has been grown on PVC in a mineral salt agar. Phanerochaete chrysosporium, Lentinus tigrinus, Aspergillus niger, and Aspergillus sydowii can also effectively degrade PVC. Phanerochaete chrysosporium was grown on PVC in a mineral salt agar.

Acinetobacter has been found to partially degrade low molecular weight polyethylene oligomers. When used in combination, Pseudomonas fluorescens and Sphingomonas can degrade over 40% of the weight of plastic bags in less than three months. The thermophilic bacterium Brevibacillus borstelensis was isolated from a soil sample and found capable of using low-density polyethylene as a sole carbon source when incubated at 50 degrees Celsius. Pre-exposure of the plastic to ultraviolet radiation broke chemical bonds and aided biodegradation; the longer the period of UV exposure, the greater the promotion of the degradation.

Less desirably, hazardous molds have been found aboard space stations, molds that degrade rubber into a digestible form.

Several species of yeasts, bacteria, algae and lichens have been found growing on synthetic polymer artifacts in museums and at archaeological sites.

In the plastic-polluted waters of the Sargasso Sea, bacteria have been found that consume various types of plastic; however it is unknown to what extent these bacteria effectively clean up poisons rather than simply releasing them into the marine microbial ecosystem.

Plastic eating microbes also have been found in landfills.

Nocardia can degrade PET with an esterase enzyme.

The fungus Geotrichum candidum, found in Belize, has been found to consume the polycarbonate plastic found in CDs.

Phenol-formaldehyde, commonly known as bakelite, is degraded by the white rot fungus Phanerochaete chrysosporium.

The futuro house was made of fibreglass-reinforced polyesters, polyester-polyurethane, and poly(methylmethacrylate.) One such house was found to be harmfully degraded by Cyanobacteria and Archaea.


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