Microplastic Pollution of Biodegradable Polymers

In October 2020,the British Standards Institute introduced PAS 9017, a new standard which specifies the requirements for the biodegradability of plastics in open-air land environments. This document resulted from the UK government’s call for experts in 2019 towards developing standards for bioplastics and biodegradable plastics. Laboratory testing services following standards like PAS 9017 help manufacturers validate biodegradability claims and ensure materials won’t create microplastic pollution.

With the confusion existing over the meaning of biodegradability, the growth in the number of plastics and products advertised as biodegradable has created a rising concern on possible greenwashing practices by manufacturers to mislead public. In this regard, defining the duration of biodegradation is critical for classification of plastics. A polymer can be biodegradable in an environment, as proved by conversion of organic C to CO₂, but if the degradation rate is very slow, it can accumulate and persist in the environment for a long time. Another issue is break-down of a biodegradable plastic into microplastics, due to weathering and service conditions, before converting to safe organic compounds. Accumulation and migration of these fragments still impose threats to the environment and human health.

Amid this confusion over terminology, PAS 9017 provides a level of consensus on how to measure the biodegradability of a family of thermoplastics called polyolefins that includes polyethylene and polypropylene, two widely used plastic types. To be classified as biodegradable, the standard specifies that 90% of the organic carbon contained in plastic must be converted into carbon dioxide within 730 days. PAS 9017 also involves testing plastic to prove it can break down into a harmless wax in an open-air environment. The benchmark for this testing is a chemical developed by a British company called Polymateria that enables the transformation of plastic items into a sludge at a certain time in the product’s life.

Polymateria’s bio-transformation process relies on an additive incorporated into plastic parts during manufacturing. Upon activation of the degradation process by air, moisture, light and microbe, the polymer experiences a rapid loss of physical properties and transforms into a wax-like material that is neither a plastic nor harmful to the environment. This degradation process therefore does not create any microplastics that could potentially disperse into the environment and contaminate air, water and soil.

The urgency and market opportunities for biodegradable or compostable products might lead to the adoption of new plastics which might be introduced as environmentally friendly without being holistically assessed for their impact. PAS 9017 is contributing to the development of this holistic methodology for assessing the biodegradation of plastics to ensure their efficacy in alleviating pollution and environmental harm. An effort that needs to be expanded to other plastic types and environmental conditions. In addition, life cycle assessment (LCA) ensures that biodegradable plastics deliver genuine environmental benefits across their full lifecycle, not just at end-of-life.