A pinch of polymer-munching enzymes may make biodegradable plastic packaging and forks really compostable.
“Biodegradability doesn’t equal compostability,” says Xu, a polymer scientist on the College of California, Berkeley and Lawrence Berkeley Nationwide Laboratory. She typically finds bits of biodegradable plastic within the compost she picks up for her dad and mom’ backyard. Most biodegradable plastics go to landfills, the place the situations aren’t proper for them to interrupt down, in order that they degrade no quicker than regular plastics.
Embedding polymer-chomping enzymes in biodegradable plastic ought to speed up decomposition. However that course of typically inadvertently varieties probably dangerous microplastics, that are displaying up in ecosystems throughout the globe (SN: 11/20/20). The enzymes clump collectively and randomly snip plastics’ molecular chains, resulting in an incomplete breakdown. “It’s worse than in case you don’t degrade them within the first place,” Xu says.
Her workforce added particular person enzymes into two biodegradable plastics, together with polylactic acid, generally utilized in meals packaging. They inserted the enzymes together with one other ingredient, a degradable additive Xu beforehand developed, which ensured the enzymes didn’t clump collectively and didn’t crumble. The solitary enzymes grabbed the ends of the plastics’ molecular chains and ate as if they have been slurping spaghetti, severing each chain hyperlink and stopping microplastic formation.
Including enzymes often makes plastic costly and compromises its properties. Nonetheless, Xu’s enzymes make up as little as 0.02 p.c of the plastic’s weight, and her plastics are as sturdy and versatile as one sometimes utilized in grocery luggage.
The know-how doesn’t work on all plastics as a result of their molecular constructions range, a limitation Xu’s workforce is working to beat. She’s filed a patent software for the know-how, and a coauthor based a startup to commercialize it. “We wish this to be in each grocery retailer,” she says.