A French company is using enzymes to recycle one of the most common single-use plastics

Plastics, which are mostly made from petroleum, could account for 20 percent of world's annual oil consumption by 2050. Emissions could be greatly reduced by reducing our dependence on plastics and finding ways to recycle plastics that are already in use around the globe.
Only 15% of plastics are currently being recycled each year worldwide. Since the 1990s, researchers have tried to develop new methods to break down plastics with the goal of increasing their recycling. Researchers and companies have been working together to create enzymatic, chemical, and other processes. Only recently, however, have commercializations of enzymatic or chemical processes been possible.

Carbios' new reactor is 20 cubic meters in size, which is about the same size as a cargo van. It can store two metric tons of plastic at once, which is equivalent to about 100,000 bottles. The reactor then breaks it down into the building blocks PETethylene glycol or terephthalic acids in between 10 and 16 hours.

The company will use the lessons learned from the demonstration plant to construct its first industrial plant. It will contain a reactor 20 times larger than that of the demonstration reactor. The full-scale plant, which will be located near a European or American plastic manufacturer, should be operational by 2025 according to Alain Marty (Carbios' chief science officer).

Since 2011, Carbios has been working on enzymatic recycling. The enzymes used to break down the long chains of plastic polymers are what make it possible. The monomers can then easily be purified and re-used to create new plastics. Carbios researchers started with a natural enzyme that bacteria uses to break down leaves. They then modified it to be more efficient in breaking down PET.

Carbios's demonstration plant in Clermont-Ferrand France. Image courtesy SkotchProd.

Carbios estimates that their enzymatic recycling process reduces greenhouse gases emissions by around 30% when compared to virgin PET. Marty said that he anticipates that this number will rise as they iron out the kinks.

Recent research has shown that PET made from enzymatic recycled PET could lower greenhouse gas emissions by between 17% to 43%, as compared with virgin PET. Gregg Beckham, a coauthor of the report and a researcher at US National Renewable Energy Laboratory, said that although the report was not specifically focused on Carbios, it is likely to be a good estimate for the process.

Beckham, who heads a consortium that studies new methods of plastic recycling, said that while the development of new enzymes is a key focus of current research and commercial efforts in this area, other aspects of the process will also determine the cost effectiveness and efficiency of the technology.

Beckham said that it is all the more mundane stuff. For example, getting the plastic into a form that enzymes can efficiently degrade or separate what they spit out can take a lot time and energy. This can increase emissions and cost.