By Michelle Dookwah, University of Georgia, USA
“Where should I put my recycling?” – a common phrase I’ll hear a house guest ask if they can’t spot the recycling bin in my kitchen. But unfortunately, this question is posing a larger problem when put in the context of a global scale. Recent changes in China’s policies for accepting plastic waste for recycling is leaving the UK facing the challenge of what to do with half a million tonnes of plastic waste. And this isn’t an issue only faced in Europe; these new restrictions leave the US with massive quantities of plastic waste to deal with as well. The UK and US rely on China for the exportation of specific types of recyclable waste products because they lack the infrastructure to handle such quantities themselves. Without access to other plastic markets, such as China, the current solution for the plastic waste problem is moving it to a landfill, incinerating it, or possibly burying it. And none of these are long-term or sustainable solutions.
Plastics packed with problems
A major contributor to much of this build up is waste plastic from the packaging industry. In the UK, it’s believed to make up about 60% of the total plastic waste each year. Packaging waste includes bottles, plastic wrapping, those hard-to-open encasings for small electronics (awful in their own right). And while there’s been a recent big push to switch plastic packaging to recyclable plastics, this solution does little good if we don’t have access to the infrastructure needed to actually recycle these products. Another avenue that’s being explored is the reduction of packaging waste, and many manufacturers are taking on the challenge. However, more action will be needed to combat the global plastic waste crisis sufficiently.
Better, stronger, more edible? Biodegradable Plastics
If reducing, reusing and recycling isn’t enough to get us to a more sustainable future with plastics, are biodegradable plastics the answer? Currently, one of the most popular types of biodegradable plastic comes in the form of Polylactic Acid or PLA. PLA mimics some of the characteristics of several common non-biodegradable plastics such as polypropylene, polyethylene, and polystyrene, but is made from corn starch or sugar cane rather than being petroleum based. PLA can be used to create a variety of products – it can be stretched into plastic films or molded into bottles for example. It’s also considered food-safe, which addresses a major contributor to plastic packaging waste!
However, use of PLA commercially does come with its challenges. Initially, the cost of production was very high, but that’s decreased over time with better technology and mass production. PLA’s melting point of 150-160°C is one of the characteristics that allows it to be easily melted and molded into various shapes and products. However, its relatively low glass transition temperature of 44-63°C limits its applications – nothing that would require exposure to high heat, and even storage and transportation can pose a problem. The biodegradability aspect of PLA also comes with some caveats. While these corn-based plastics tout themselves as decomposable, this doesn’t necessarily mean you can just toss that bottle into your backyard compost bin and watch it disappear. PLA requires a high temperature industrial composting facility to degrade efficiently. Unfortunately, access to these facilities, while growing, is still limited – making the practicality of these products less than ideal. Researchers around the world are working towards finding better biodegradable materials for the packaging industry.
A growing area of research for biodegradable plastics is to move away from corn-based polymers, like PLA, and ideally use non-food crops for bioplastics. Reducing the competition with food crops offers a more sustainable solution for plastic waste. An example of this would be the use of algae to make biodegradable plastics. Algae contain particular polysaccharides, or chains of complex carbohydrates, which make it an ideal biopolymer to make plastic products from. As mentioned, growing algae wouldn’t compete with land used for growing food crops, and algae can be grown and harvested sustainably.
Bioplastics derived from algae have numerous options for degradation too! Some companies are making plastic products that simply dissolve in water. There are also already enzymes in soil that can break down the polysaccharides, making algae bioplastic more easily compostable. There are even groups that are promoting eating the algae-based plastics! While there’s still more research to be done on the ways to integrate algae or other non-food crop derived bioplastics into mainstream packaging processes, it’s quite possible that the solution to the plastic waste problem may end up being – if you can’t beat them, eat them!
I am a graduate student at the University of Georgia’s Complex Carbohydrate Research Center, based in the Tiemeyer Lab. I’m pretty passionate about science and science communication. However, I also enjoy numerous activities in my free time, including reading, listening to podcasts/audiobooks, hiking, baking, and obsessing over my labradoodle named Goose!
This post is the third in our biomaterials series. The first post, Plant-based biomaterials: engineering the future by Emily May Armstrong, and the second, Your scales look awfully fishy by Paulo Szwarc, were published earlier this month. If you are interested in reading more on this topic, you can also check out the February issue of The Biochemist magazine on the theme of biomaterials.