Everything will decompose eventually – it just takes hundreds of years for fossil-based plastics to disappear. Of course, they don’t really disappear, they just break down into smaller microplastics and nanophysics. This begs the question, what exactly do we mean by decompose? Things get even more complicated with an increasing range of biodegradable polymers available – what are the end-of-life prospects for PLA, PBAT and cellulose-derived materials?
To try and answer this standards and certificates have been developed to provide a framework for declaring whether or not a product can biodegrade in an environment and under what conditions. A group of experts from an impressive group of associations including the Nova Institute (Germany), Normec OWS (Belgium), Hydra Marine Science (Italy/Germany), IKT Stuttgart (Germany), Wageningen University & Research (The Netherlands), DIN CERTCO (Germany) and TÜV AUSTRIA (Austria/Belgium) have evaluated the latest scientific research to address this question.
The Nova Institute has produced a handy reference chart summarising the results of decomposing tests performed in soil (including home composting), freshwater, marine and anaerobic conditions. Details of the tests and standards applied for each process are given in the chart.
While the chart clearly indicates which materials will decompose under specified conditions some important caveats are highlighted including: “The biodegradability of plastics can only be guaranteed if all additives and (organic) fillers are biodegradable, too…generalised claims about biodegradability can only serve as approximations and need to be confirmed by standardised testing under lab conditions. In-situ behaviour can vary, depending on the mentioned conditions, size of the plastic, grade of the polymer and other factors.”
Of course, finding materials that contain organic fillers and are free from chemical additives is a challenge and one that often cannot yet be met. However, this chart provides a handy reference to brief designers on the conditions under which the increasing range of polymers advertised as biodegradable will actually decompose.