Plastic Biodegradation

Plastic is generally a durable material. Its durability has made the culprit of the problem since it is considered resistant to natural biodegradation processes, i.e. the microbes that break down other substances do not recognize plastic as food. Yet plastic can be fragmented with the effects of UV, being broken down by light in smaller and smaller debris over time.

Biodegradation, the breaking down of organic substances by natural means, happens all the time in nature. All plant-based, animal-based, or natural mineral-based substances will over time biodegrade. In its natural state raw crude oil will biodegrade, but man-made petrochemical compounds made from oil, such as plastic, will not. Why not? Because plastic is a combination of elements extracted from crude oil then re-mixed up by men in white coats. Because these combinations are man made they are unknown to nature. Consequently, it has been thought that there is no natural system to break them down. The enzymes and the micro organisms responsible for breaking down organic materials that occur naturally such as plants, dead animals, rocks and minerals, don’t recognize them. This means that plastic products are said indestructible, in a biodegradable sense at least.

Indian beach
Indian Beach, Manori. Photo Source: Malad Bolivari.
In sum, as time passes, we know that plastic will eventually photo-degrade, i.e. break down into smaller and smaller fragments by exposure to the sun. The photo-degradation process continues down to the molecular level, yet photo-degraded plastic remains a polymer. No matter how small the pieces, they are still and always will be plastic, i.e. they are not absorbed into or changed by natural processes. At sea, the plastic fragmentation process occurs as well, due to wave, sand action, and oxidation. Estimates for plastic degradation at sea has been ranged from 450 to 1,000 years.

Of particular concern are the floating small plastic fragments often referred in the media to as mermaids’ tears, which are tiny nurdles of raw plastic resin that form the building material of every manufactured plastic product, or are granules of domestic waste that have fragmented over the years. Dr Richard Thompson of the University of Plymouth, UK has identified plastic particles thinner than the diameter of a human hair. But while they cannot be seen, those pieces are still there and are still plastic. Not absorbed into the natural system, they just float around within it. He estimates that there are 100,000 particles of plastic per sq km of seabed and 300,000 items of plastic per sq km of sea surface.

Either way, mermaid tears, or fragmented plastic debris, reaching microscopic size over time, remain everywhere and are almost impossible to clean up. They are light enough to float in the wind, landing in the earth’s oceans. Mermaid’s tears are often found in filter feeders like mussels, barnacle, lugworm and amphipods.

Thus, the photo degradation of plastic debris makes the matter worse. Plastic becomes microscopic, invisible, yet ever polluting waters, beaches, coasts, seafloor, being eaten by even tinier marine organisms, therefore entering the food chain insidiously and ineluctably.

Information source: http://coastalcare.org