From a chemical point of view, plastics are high molecular weight organic polymers obtained synthetically or semi-synthetically from various substances. Although they are organic compounds by their structure, the artificial polymerization creates bonds between carbon atoms that do not occur in nature, which makes most plastics non-biodegradable.
biodegradation is the decomposition carried out by microorganisms, mainly bacteria. These microorganisms feed on the substance, transform it and incorporate it back into the natural cycle of elements.
Natural carbon polymers, such as cellulose, are rapidly degraded due to the high number of microorganisms in the environment capable of feeding on them. But artificial polymers are not recognized by the enzyme systems of microorganisms and are degraded by other much slower processes that can take hundreds or even thousands of years.
Plastic bottles are mainly made of PET (polyethylene terephthalate), a petroleum-derived plastic that is not biodegradable. The degradation of PET in nature occurs mainly through photodegradation. The action of UV rays from the Sun breaks the polymer bonds and over time a piece of plastic is transformed into a multitude of smaller pieces. It is such a slow process A plastic bottle takes an average of 450 years to decompose..
In addition to being such a slow process, the bottles and other plastic objects that are wasted in the fields are easily buried and are not reached by sunlight. A buried plastic bottle can last thousands of years without degrading.
Nevertheless, photodegradation is rapid in the oceans. A study by Nihon University (Japan) concluded that a plastic bottle can decompose in the ocean in little more than 1 year.
Although a priori it may seem like a good figure, the photodegradation of plastic in the seas produces very toxic compounds, such as bisphenol A or polystyrene, which end up being ingested by aquatic animals and contaminate the water, reaching humans again. It is these invisible derivatives of plastic that are the main danger of plastic pollution.
actually yes there are bacteria that can degrade PET, but they are so rare that it is very rare for a plastic bottle to come across them naturally. However, the discovery of these bacteria opens the door to the design of treatment systems for PET and other plastics that do not generate toxic waste as photodegradation does.
For now, the best thing to do with plastic bottles and containers is to recycle them properly so that they can be reused and do not end up polluting the environment.