Are "biodegradable" plastics just greenwashing?

Chris Smith put this question to Anna Ploszajski...

Anna - One thing that we have to be really careful about when we talk about materials, but also things that are good and bad for the environment is this word being "better" - this kind of value judgement of how good a material is. It can either be polluting or it can be something that gets into the bellies of sea turtles, but calling it better or good and bad I think is a little bit tricky to get our head around. With biodegrading, it's important to think about what is it that we want these materials to do, because I think when we talk about things being better for the environment, ideally what we want is for the stuff that we make and produce and use and then dispose of to have, ideally, zero impact on our natural environment. The holy grail really for materials is that they exist in what we call a circular material economy in the same way that, in the natural world, all the materials that are produced by plants and animals come from other plants and animals and eventually end up going back to plants and animals. And so if we were to think about our ideal situation for what we do with our materials, it would be a very good idea to look at the natural world and how the natural world creates this extremely circular material economy. Our man made material economy is pretty linear. We dig stuff out of the ground, we use it, we throw it away. So to look at the natural world, how does it actually recycle its materials? A lot of the time it degrades, which means that little bugs and worms and bacteria and fungi come along and they use those substances, those materials, as food quite often. Or a place to live. Our materials that we are making, our synthetic materials that are able to biodegrade, what we are hoping for are bacteria and worms, that will be able to find the stuff that we make a useful nutrient source.

Chris - And is it possible to do that, Anna?

Anna - It is. In 2016, scientists found that there are types of bacteria that consume the sorts of polymers that we make in a synthetic way. The problem though is that the situation, the environment that you need, the conditions that you need for that to happen, are often very specific. So when we talk about biodegradable materials, what we're hoping is that the end products are going to be friendly, and are going to not harm any animals in the environment. Unfortunately, a lot of biodegradable materials either don't fully biodegrade, so they break down into microplastics, which then wreak even more havoc to the environment, or they degrade into substances that are basically like liquid polymers or liquid plastics, which can even more easily get into our ecosystems and start causing havoc there. So we need to be careful about if we are just creating biodegradable materials, we need to make sure that the actual products that they are degrading into are going to be okay for the environment still.