While the technology for recycling PET already exists, the systems currently out there have a number of limitations. For example, there is no way to create plastic bottles made entirely of recycled PET – at least some of the raw materials must be new. “That means purchasing them from refineries, which convert oil into ethylene glycol and terephthalic acid, the two compounds needed to make PET,” says Samantha Anderson, founder & CEO of DePoly and a PhD student at the Laboratory of Molecular Simulation (LSMO) at EPFL’s Valais-Wallis campus. In addition, many PET containers can’t be recycled because they contain chemical and food contaminants, additives or dyes – most of these containers end up being incinerated.
Recycling through depolymerization
DePoly has developed an innovative method that can recycle just about any PET container using a chemical process that breaks down the plastic into its base compounds. “It doesn’t matter if the container held water, peanut butter or soap, or if it’s crystal clear or pitch black,” says Anderson. With the new method, PET containers don’t have to be sorted by color, meaning they can all be processed in one batch. The method also works with fabrics like polyester, breaking down old t-shirts, for example, into cotton and PET fibers.
The chemical process involves depolymerizing the PET – hence the name DePoly. “We combine the plastic with various compounds in a reactor and then apply light to the mixture to trigger a series of chemical reactions. These reactions break the bonds between the ethylene glycol and terephthalic acid, freeing up the compounds for further use,” says Anderson. The process results in ethylene glycol in clear liquid form and terephthalic acid as a white powder, which are then easily separable. The process also generates a small amount of dyes, additives and other waste. Anderson will not reveal any more details, since a patent for the technology is pending.
An award-winning innovation
This year DePoly competed in the 2019 >>venture>> competition, in the Hardware category, and took home the grand prize. >>venture>> is a Swiss entrepreneurship competition held every year by EPFL, ETH Zurich, McKinsey & Company, Knecht Holding and Innosuisse. Winners receive 150,000 francs and a package of business consulting services. They also join the >>venture>> network to make contacts and boost their visibility.
To develop the method, Anderson teamed up with two LSMO colleagues: postdoc Christopher Ireland and PhD student Bardiya Valizadeh. “DePoly had already received funding from the Swiss National Science Foundation and an Innogrant before winning >>venture>>,” says Professor Berend Smit, head of LSMO, the lab that supported the research. “I’m very proud of the team’s success.”
Tests on an industrial scale
The next step for DePoly will be to scale up its technology from the lab to industry. “In November, we will begin building a pilot unit with more capacity than the lab,” says Anderson. The unit, located at the Central Valais Waste Treatment Plant in Uvrier, will allow the startup to test and refine its method so that it performs well under industrial conditions. “The testing phase will probably last a year,” says Anderson. “I’m sure chemical recycling methods for PET will eventually hit the market – if not our method, then someone else’s. We aren’t the only ones working on this approach.”
For now Anderson is dividing her time between managing DePoly and writing her thesis. But after she graduates in November, she will devote herself fully to her project, which promises to help clean up the plastic polluting our environment.