By Rachel Swiatek, Community Champion
Your plastic bag is labelled “biodegradable” and that cup is apparently a “bioplastic”. But what does sticking “bio” in front of a word actually mean? And are they better for the environment?
To unravel this labelling, let’s go back to a few basic definitions. A “plastic” is a synthetic polymer. Chemically, polymers are large molecules made up of repeating carbon-based units. They can be natural, such as silk and DNA, or synthetic (known as plastics), such as nylon and Teflon. Plastics have become a staple material in modern life as they are versatile, light and long-lasting… which is also their problem. The carbon-carbon bonds in plastics are so strong that they can’t be broken down easily in the environment and they are not the bonds microorganisms are used to breaking down.
This is where the idea of a biodegradable plastic comes in, a plastic which can be broken down by microorganisms. If the degradation is occurring specifically in soil and will deliver nutrients to it, then this can be referred to as compostable. However, the environmental conditions required for biodegradation can vary widely. These conditions, such as temperature, may only be met in an industrial composter, meaning the plastic still won’t break down on a domestic compost heap or elsewhere in the environment. So biodegradable plastics are not the magic solution to the plastic problem.
At the other end of the plastic life-cycle is another problem. Plastics are traditionally manufactured from fossil fuels; non-renewable resources which we are rapidly running out of. This led to alternatively making plastics from renewable organic matter. This could be organic waste or crops like maize and sugar cane. These are bio-based plastics but may not be the answer either. Just like conventional plastics can be either biodegradable or non-biodegradable, so can bio-based plastics. Some bio-based plastics can persist in the environment for a long time. “Bio-based” and “biodegradable” are labels referring to two ends of a plastic’s life-cycle; the source the plastic is derived from and how the plastic breaks down. You can have plastics which are bio-based or biodegradable or both or neither!
So where does the term “bioplastic” come into all of this? In fact, the definition of “bioplastic” is quite loose and could be referring to a bio-based and/or biodegradable plastic. It’s not a very helpful label and only adds to the public confusion surrounding bio-based and biodegradable plastics.
Ultimately, bio-based and/or biodegradable plastics should not be perceived as the technological fix to the plastic issue. Sadly, that biodegradable plastic bag and bioplastic cup aren’t necessarily environmentally-friendly.
UNEP (2015) Biodegradable Plastics and Marine Litter. Misconceptions, concerns and impacts on marine environments. United Nations Environment Programme (UNEP), Nairobi.
Why doesn’t plastic biodegrade? Natalie Wolchover (2011).