There’s a lot of effort put into recycling plastics, glass, and other materials all around the US. Despite efforts towards recycling, less than nine percent of plastic currently gets recycled in the country, with most ending up in landfills or polluting the environment. Researchers believe that biodegradable plastic bags and containers could help ease pollution, but they can contaminate recyclable plastics if not correctly sorted.
Researchers note that most biodegradable plastics also take months to break down, and when they do break down, they form microplastics. Microplastics are particularly damaging because they can end up in the oceans and inside the bodies of animals and humans alike. Researchers at the Department of Energy Lawrence Berkeley National Laboratory and UC Berkeley have designed an enzyme-activated compostable plastic that could diminish microplastics pollution and holds promise for plastics upcycling.
The new material can be broken down into its building blocks, which are small individual molecules called monomers, and reformed into a new compostable plastic product. Typical biodegradable plastics used today are made from polylactic acid or PLA, which is vegetable-based and blended with cornstarch. Another type of plastic is PCL, a polyester used for biomedical applications, including tissue engineering.
Researchers at the lab took a different approach to biodegradable plastics by nanoconfining enzymes directly into them. The challenge was to carve out safe places in the plastic for the enzymes to lie dormant until they’re needed. Researchers embedded trace amounts of commercial enzymes BC-lipase and proteinase K within PLA and PCL plastic materials for their experiment. The team used an enzyme protectant called four-monomer random heteropolymer or RHP to disperse the enzymes a few nanometers apart.
Scientists discovered that ordinary household tap water or standard soil composts converted the enzyme-embedded plastic material into its monomers and eliminated microplastics in just a few days or weeks. The team says that industrial enzymes can cost around $10 per kilogram, but the new approach would add only a few cents to the production cost of a kilogram of resin because of the amount of enzyme required is so low. The material also has a shelf life of more than seven months.