359 million tons of plastics are produced annually worldwide, and 150–200 million tons accumulate in landfill or in the natural environment. One of the most common types of plastic is PET (polyethylene terephthalate), which is produced at a rate of 70 million tons per year. 20 millions are used to make packages and 50 millions for textiles. The current way to recycle PET is called thermomechanical recycling, which is not an efficient solution because it causes a loss of mechanical properties of the material, making it less suitable for reuse. Therefore, PET is generally produced de novo.
Tournier and colleagues optimized a new strategy to recycle plastic in an efficient way. The idea is to use an enzyme to break down polyester. PET plastic is made by two units (called monomers) that are linked by a bond. The enzyme works as molecular scissors that break the bond and release the two monomers. Such enzyme existed already, but it was not very efficient. We can say that Tournier and colleagues sharpened its blades, to make it work better.
This improvement sets a milestone in the plastic manufacture: fossil-based sources could be replaced by PET waste to produce virgin plastic (with the same properties of the de novo one), in a 100% efficient recycling strategy. A bottle was already created in this way, to confirm that the idea is feasible.
Tournier, V., Topham, C.M., Gilles, A. et al. An engineered PET depolymerase to break down and recycle plastic bottles. Nature 580, 216–219 (2020). https://doi.org/10.1038/s41586-020-2149-4