Degradation of Plastics in the Environment

Plastics and Environmental Sustainability, First Edition. Anthony L. Andrady. 2015 John Wiley Sons, Inc. Published 2015 by John Wiley Sons, Inc. 

Two requirements must be met to obtain biologically-mediated mineralization of a polymer it must be exposed to a biotic environment conducive to degradation and its chemical structure must be amenable to breakdown by the available set of microbial enzymes in that environment. Thus, even the inherently biodegradable starch in grains (barley and wheat) found in Egyptian pyramids was preserved over millennia because of the dry and dark environment they were stored in. 

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As shown in Table I, the plastic component of MSW has increased dramatically. Past development of synthetic plastic formulations has focused on reducing the photo, chemical, and biological degradation of the plastic polymers. However, the persistence of plastics in the environment as litter, potential marine hazard, and with concern for global carbon cycling 1,6) has focused recent attention on the recycling of plastics or development of new biodegradable plastic formulations. 

A number of reviews of topical interest have appeared with degradable plastics making a come back. These include the role of plastics in the environment " and agricultural film , ethylene carbon monoxide copolymers and their analysis. Several other topic reviews of interest relate to the role of titanium dioxide pigments 22 laser ablation and photolysis, degradation and stabilisation of polyolefins , conformation defects in poly(vinyl chloride)and poly(ethylene terephthalate) photooxidation . 

Another example that illustrates the plasticity of genes in the environment is the construction of a 3-chlorobenzoate, 4-chlorobenzoate and 3,5-dichlorobenzoate degrading Pseudomonas species from two distinct Pseudomonas strains (Reineke Knackmuss, 1980). Pseudomonas sp. B13 is able to grow on 3-chlorobenzoate, but cannot grow on 4-chlorobenzoate and 3,5-dichlorobenzoate. P.putida mt-2, however... 

Meaningful research should be carried out into the effects of degradable plastics in the environment. 

Plastics produced from petroleum-based raw materials in the form of single-use consumer products ate of environmental concern, as most of these materials do not degrade when disposed in the environment after their useful life is over . Currently, systematic collection of plastic waste for recycling and/or disposal is expensive and is limited only to certain communities. Particularly, when plastics are contaminated with soil, foods or other chemicals their recycling become rather difficult. As a result, in the last decade, significant efforts have been made to develop environmentally... 

In recent years, biodegradable plastics have attracted as environmentally fHendly materials to solve the problem of the waste plastics. This paper reports the microbial degradation of polyesters in the naarine environments and the properties of extracellular depolymerases from some polyester-degrading microorganisms. 

Environmentally degradable plastics are sometimes referred to as green plastics where the word green is used in an ecological sense. The impact of plastics on the environment is hardly a new theme, but with increased interest in green chemistry and the broader green revolution, the relationship between plastics and the environment is a topic of current interest. 

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