Most so-called compostable plastics require specific conditions to degrade that are only obtainable in industrial settings, warns a study published in the journal PLoS One. Polylactic acid - a polymer obtained from natural renewable sources that is used as an alternative to petroleum-based plastics - takes more than a year to degrade in a marine environment, compared to 35 days for natural cellulose fibres, according to the analysis, which combines observations in waters off the coast of California (US) with laboratory measurements.
Researcher of excellence in the area of Ecology at the University Institute of Marine Research of the University of Cadiz
The study has been developed in a very clear and concise way. In recent years, there has been a rapid increase in the use of supposedly biodegradable and/or bio-based plastics. But this terminology is misleading and can lead to misunderstandings on the part of the consumer, as this study demonstrates. These materials degrade under very specific conditions that are not common in the environment. Certainly, when looking for an alternative to plastics, we must consider the whole cycle of the material, from its origin to the end of its life.
In addition, we know that there are some 13,000 chemical compounds associated with plastics to give them colour, flexibility and particular characteristics. Many of these additives and associated substances are known to be highly toxic—such as plasticisers, flame retardants, bisphenols or PFAs, among others. So-called biodegradable plastics contain very similar types and quantities of chemicals as those used in fossil-based plastics. All of these issues are relevant to the Plastics Treaty negotiations that continue in Paris next week.