Perjantai 14.10.2022 klo 15:16 - Nikk Nikinmaa
One of the biggest problems with recycling plastic waste has been that a mixture of different plastics cannot be used as a feedstock for generating new plastic products. This means that either the consumers have to be quite careful and knowledgeable in sorting plastics or recycling stations need to carry out expensive sorting of plastics for further use. In a recent article in Science (October 13, 2022; DOI: 10.1126/science.abo4626) Sullivan et al. present a method that can be used for a mixture of plastics to generate starting material for commercial use. The method is comprised of two steps: first oxidizing the plastic mixture with metal-based catalysis (Co and Mn) to intermediates that can be digested by engineered bacteria to produce a feedstock for new commercial products. By varying the way that the bacteria are engineered, different starting products can be generated.
To my eyes, this method is quite safe and practical. It avoids the inherent problem with plastic-eating bacteria. I remember the book Mutant 59 by Kid Pedler and Gerry Davis (from 1971) where the plastic waste was planned to be eaten by bacterial mutation, which was very effective in consuming plastics, favoring them over any other foodstuff. The mutant naturally got accidentally free and started devouring everything made of plastics. Planes started crashing down, because all the plastics covering electric leads were eaten up and motors short-circuited. Most things in our houses became non-functional or half-disappeared etc., naturally, if you look around: most things are at least partly made of plastics. Since in the method described by Sullivan et al. the engineered bacteria eat only the oxidized end product of catalysis, they can only live in the recycling plant. By combining this method with effective collection of plastic waste, much of the plastics problem can be removed.
However, even if we get smokers to put their cigarette butts to waste bins, there will be one significant source of small plastic particles. Almost half of the microplastics in the environment is tire wear particles. They are impossible to collect. Thus, even if the recycling of all other plastics were more than 90% successful, this source would remain. It can only be reduced by drastically reducing road traffic. In this regard, electric cars are not a solution, the only solution could be using rail traffic and public transport more generally.