Corn Starch Dental Floss

This dental floss is made from corn-derived PLA (polylactic acid) with candelilla wax and spearmint oil. PLA is produced by fermenting the starches found in crops like corn, cassava, sugarcane or potatoes to produce lactic acid, which is then polymerised. This bioplastic can then be processed in the same way as traditional petrol-based polymers.

This floss is marketed as ‘eco-friendly’ and compostable. Compostable materials are a subset of biodegradable plastics that break down safely into water, biomass, and gases under composting conditions. With something like dental floss, where a reusable alternative to this single-use product is not feasible for hygiene reasons, replacing the usual petrol-based plastic with a bio-based and compostable alternative seems like a good move. However, as our UCL Plastics Waste Hub team have explored in their recent research project, biodegradable plastics are not without their issues.

Both biobased and biodegradable plastics are growing in popularity because they are seen as the solution to the problem of single use plastic waste. The Plastics Waste Hub’s citizen science survey found that 84% of UK households reported that they are more likely to choose products that are marked as “biodegradable” or “compostable”. The global market for biodegradable plastics was 1.2 million tonnes in 2018 and is set to grow by 60% by 2023 (European Bioplastics, 2018) with each brand claiming to provide a sustainable solution to the plastic waste problem. These claims are largely unsubstantiated and have led to widespread confusion among consumers about: how they should dispose of these products; what frequently used terms such as “bioplastic,” “biodegradable,” and “compostable” actually mean; and whether these new products are safe for the environment.

Many biodegradable and compostable plastics need high temperature industrial composting facilities to break down, and very few cities have the infrastructure needed to deal with them. In the UK there is currently no system for collection, sorting or processing of compostable plastics. Some of these plastics can be composted at home, but there is confusion as to which ones can be put into domestic compost and whether they will indeed compost. Because there is poor instruction and labelling to indicate what citizens should do with them; most biodegradable plastics are burnt, or put in landfill, defeating their purpose. These plastics often end up in landfills where, deprived of oxygen, they degrade to release methane, a greenhouse gas twenty three times more potent than carbon dioxide. When bioplastics are not discarded properly, they can also contaminate batches of recycled plastic and harm recycling infrastructure. There are currently no automated sorting technologies available for separating biodegradable and non-biodegradable plastics, so if bioplastic contaminates recycled PET (polyethylene terephthalate, the most common plastic, used for water and soda bottles), the entire lot could be rejected and end up in a landfill.

The biomass origin of this dental floss does mean it probably has a much lower global warming potential (GWP) than a conventional petrol-based plastic floss. This is not without its issues however, as a higher mass of PLA is sometimes required to supply the same functionality as conventional polythene (you need more of it to do the same job). As with biofuels, the land required for bioplastics can compete with food production because the crops that produce bioplastics can also be used to feed people.