In the name of climate #2: biodegradable does not (always) mean sustainable

In recent years an increasing number of policies have been adopted aimed at reducing the use of plastic packaging in favour of environmentally sustainable alternatives in order to reduce pollution. However, what we mean by “biodegradable” often does not correspond to what we are led to believe: we tend to think that if something is biodegradable then it decomposes naturally without any negative environmental impacts, but in fact this is not entirely true.

Materials that are classed as biodegradable do not necessarily have a low environmental impact: certain types of packaging bearing this classification often have to be treated by industrial processes that produce polluting emissions, and don't break down quickly without impacting the environment.

“Biodegradable” and “compostable” are not synonyms: a compostable material is biodegradable, but a biodegradable material is not necessarily compostable or environmentally sustainable. Compared to biodegradable materials, compostable materials break down completely in a short period of time (in the course of a few weeks, even), and once processed can be recycled to be used as natural fertiliser or transformed into biomethane.

The difference between “biodegradable” and “compostable” is “tremendously confusing, not just to the consumer, but even to many scientists”, explains Jason Locklin, the director of the New Materials Institute of the University of Georgia in the United States. Moreover, according to an article in the New York Times, those same designers who develop the biodegradable materials have often not fully mapped the consequences of the entire product life cycle.

Paper, for example, is recyclable in itself, yet in food packaging it is often bonded with layers of plastic, foil or other materials that form protective barriers (such as in certain crisp packets, for example), which make the product almost impossible to recycle.

Similarly, packaging made from polylactic acid (PLA) is defined as biodegradable as it is made by processing corn or other plants, and is widely used because it can potentially break down in just a few weeks. The problem is that to properly degrade, this type of packaging requires industrial processing at very high temperatures and specific humidity levels; if left to decompose naturally, without the right conditions it could take months or even years for the product to degrade completely.

As such, only materials classified as compostable offer the certainty that, once the product has definitively degraded, no artificial substances will end up in the environment and, therefore, that the product is truly environmentally sustainable.