Scientists Are Transforming Styrofoam Into Something Useful

Each year, more than 20 million tons of polystyrene, or Styrofoam, accumulate on earth. It's being used as a take-out container, food packaging, and shipping packing that cushions any online purchase. Once it’s thrown away, it persists for centuries.

Unlike some plastics, polystyrene is recalcitrant and doesn’t usually find its way into recycling. But a recent report shows a light of hope: instead of letting it clog landfills and waterways, scientists are discovering how to break it down and remake it into brand-new materials.

The process, called biological upcycling, doesn’t merely shatter foam into pieces and re-form them into lower-quality products. It actually recycles the waste into the exact same high-value building blocks that produce brand-new plastics, fibers, and coatings. It’s sort of giving trash a second life—without oil.

Polystyrene is made up of very long chains of styrene molecules. They are hard to disassemble. Saarland University professor of biotechnology Christoph Wittmann put together a team that met the challenge with the help of bacteria and enzymes. After years of laboratory tinkering, they trained a bacterium, Pseudomonas putida, to "digest" fragments of polystyrene and transform them into valuable chemical compounds.

"The real break-through," Wittmann said, "is that our research collaborators at INM led by Professor Aránzazu del Campo were able to demonstrate that the materials made with our process possess the same properties as the materials made from virgin petroleum-based feedstocks." That is to say, the recycled materials are just as strong and as dependable as plastics made directly from oil.

The team didn’t do it alone. They partnered with polymer chemists from Markus Gallei’s research group, scientists from the Leibniz Institute for New Materials, and collaborators in Dortmund and Vienna. The project received support from the European Union’s Repurpose program, which focuses on creative ways to cut plastic waste.

One of the most surprising products is chemicals used to make nylon. By inducing bacteria to make muconic acid, researchers could then chemically convert it into adipic acid and hexamethylenediamine. Each has six-carbon chains, one ending in acid groups and the other capped with amine groups. Blend them together, and you have nylon—a substance that shows up in stockings, carpets, car seats, zip ties, and millions of other items.

The team also showed that it is possible to make other significant chemicals, like hexanediol, from waste polystyrene. These kinds of chemicals are normally made from petroleum. Now that they have some microbial help, they can be made from waste foam cups and trays.

Proof-of-concept experiments like these are never perfect. The yields — the amount of product extracted from waste — are still low relative to industrial chemical plants. Certain enzymes lose their activity after being used many times, and separating pure products out of reaction residue remains expensive and technically difficult.

Though, the presence of microbes that can be convinced to recycle trash into nylon products is a giant step. The scientists assert their products are chemically no different from conventional options, which would enable industries to adopt them without altering manufacturing processes.