"Biodegradable" you've probably seen it in bright green on the side of some packaging...but what does it mean? Nowadays, the term is still under discussion between experts and decision-makers, so don't worry, you are not the only one scratching your head. To help explain, let's start with the definition. Biodegradable is defined as capable of being decomposed rapidly by natural biological processes. This means  breakdown occurs with the help of micro-organisms such as bacteria or fungi, with no ecological harm to the planet. Biodegradability was first defined in terms of use in the soil; however, further studies have proved its use in water.

According to the United Nation's (UN) environment program, polymers, which biodegrade under favourable conditions on land, are much slower to break up in the ocean. This is why keeping waste out of the sea is a such a growing concern!  

As you can imagine conducting experiments in the ocean can be pretty tricky, the influence of weathering on various materials represents a complex issue. The degradation of the material depends on some different parameters, such as the temperature, mechanical factors, sunlight and depth.

Researchers looking at the decomposition behaviour of single-use tableware in the ocean, over a one-year period, monitored the biodegradability of selected tableware items. Not surprisingly, the experiment found that PLA and CPLA as well as plastic items (in this case PS),  are not degradable in one year. What was promising for the planet's health is that products made from palm leaves, bagasse, wood and paper (like ours!) in most conditions are degradable within a year, some totally degrade even sooner.  

Examples of degraded items

The experiment's findings show that temperature plays a vital role in accelerating the degradation of bagasse and paper products. This means that bagasse and paper products depending on conditions will almost always degrade within a year. As we suspected, the experiment demonstrated the possibility that plant-based (PLA) plastic products have similar effects as fossil-based plastic packaging in the aquatic environment. 

When we look at how long other plastic products take to break down in the ocean, it is clear why reducing plastic consumption is key to saving our oceans.  See below graphic showing WWF's life cycle of plastics.

REFERENCES:

Chaabane, A.; Robbe, E.;  Schernewski, G.; Schubert, H. Decomposition Behavior of Biodegradable and Single-Use Tableware Items in the Warnow Estuary (Baltic Sea). Sustainability. 2022. Available online.
UNEP. Biodegradable Plastics and Marine Litter. Misconceptions, Concerns and Impacts on Marine Environments. United Nations Environment Programme (UNEP), Nairobi. 2015. Available online.
Ter Halle, A.; Ladirat, L.; Martignac, M.; Mingotaud, A.F.; Boyron, O.; Perez, E. To what extent are microplastics from the open ocean weathered? J. Environ. Pollut. 2017, 227, 167–174. [Google Scholar] [CrossRef]
WWF, The Life Of Plastics, 2021. Available online.