We see it mainly in disposable Styrofoam coffee cups, but where does polystyrene go after we toss it in the bin? It ends up in landfills where it takes thousands of years to break down. UCD researchers have discovered a method of converting polystyrene into re-usable, biodegradable plastic.
Dr Kevin O’Connor and his research team from the UCD School of Biomolecular & Biomedical Science, and the Centre for Synthesis and Chemical Biology have transformed non-environmentally friendly polystyrene foam into something quite the opposite. A paper published in the American chemical society journal “Environmental Science and Technology” describes how a combination of chemistry and microbes can transform polystyrene foam. Put at its simplest, it involves the following process - the chemists melt the plastic; the bugs eat it and convert it into another plastic that is biodegradable.
Dr O’Connor teamed up with Professor Walter Kaminsky of the University of Hamburg, an expert in a technique called pyrolysis, which converts the polystyrene into styrene oil. This oil can be used as cheap fuel, or as Dr O’Connor discovered, it can be used to make something even more valuable, once his special bugs are allowed to feast on it.
So what exactly is going on? Dr O’Connor uses a bacterium that is able to eat styrene. After feeding on the styrene, this bacterium breaks it down into even smaller molecules and stores it in the form of a plastic called PHA. The exceptional thing about PHA is that it is a flexible heat resistant plastic that, unlike polystyrene, is biodegradable.
“The plastic can be easily retrieved from the bacterium by using a mild detergent to break open the cells. It can then be used to make plastic bottles or be used in medicine as special biodegradable plastic in the body”, says Dr O’Connor.
According to the US Environmental Protection Agency, more than 14 million metric tons of polystyrene are produced worldwide annually and only 1 per cent of polystyrene waste is currently recycled. However this ratio may shift dramatically if Dr O’Connor’s proposed technology gains widespread recognition and is put into practice.
It’s the first study to investigate the possibility of converting a petroleum-based plastic waste into a reusable biodegradable form. “The diversion of polystyrene from landfill and its subsequent conversion to a biodegradable plastic is doubly beneficial as it reduces the burden of polystyrene on the environment and produces a plastic that can be added to compost, thus assisting the carbon recycling into the environment”, concludes Dr. O’Connor.
