Introduction



Figure 1 : Common uses of plastics

Plastics are ubiquitous in the modern society. From cutlery to industrial equipments, petroleum-derived polymers are found in virtually all facets of our society. Due to their low cost and versatility, conventional plastics have enjoyed widespread adoption in the past century. Unfortunately, most modern plastics comprise hydrocarbon-based polymers, which results in low rates of degradation. Degradation of polymers is a thermodynamically favourable process. It involves the breakdown of a large polymer into smaller fragments, therefore it is entropy driven. However, the degradation is extremely slow since is it a kinetically unfavourable process. Hence, the degradation of polymers is under kinetic control.

In the recent decade or so, the concern for environmental protection has become an important issue. In 1960s, it was suggested that "**so much plastic had been manufactured that the planet could be wrapped in it**". To reduce the amount of plastics reaching the landfill, recycling efforts have been increased while in some cases have seen total replacements readily biodegraded materials such as paper. However, petroleum-based polymers still continue to be manufactured and widely used. To alleviate this problem, the so-called “biodegradable plastics” have been explored as an alternative to petroleum-based conventional plastics. No standard definition of biodegradation is agreed upon. However, biodegradation is believed to either be the degradation of polymers by the action of enzymes and/or the chemical decomposition of polymers that takes place due to the action of living organisms, such as bacteria and fungi. Biodegradable polymers are mainly composed of polymers that show increased rates of degradation by microorganisms. Various types of materials, ranging from sugar-linked polymers to poly(ester amides), have been developed and tested for their suitability for use as plastics. This project aims to discuss the rationale, historical development, production, degradation, uses and environmental impact of biodegradable polymers.



Figure 2 : The life cycle of a biodegradable polymer, specifically PLA or polylactic acid. These polymers are produced from carbohydrates and sugars by the fermentation process. After, their biodegradation, they return to the environment in an environmentally benign fashion.