The idea of upcycling plastic waste into even more valuable products is a meritorious one, but some forms of the material lend themselves to this process better than others. Polystyrene lays at the more problematic end of the spectrum, but a team of Virginia Tech researchers is hoping to change this with a novel method that turns it into a product of relatively high value.
Polystyrene is the main component of Styrofoam and is light, buoyant, water-resistant and rigid. This makes it a popular material for everything from packaging, to bean bag fillings, to interiors for fishing platforms, but its non-biodegradable nature means that like other plastics, disposing of it responsibly is a real challenge.
While it is possible to recycle polystyrene, the products that are left over are of such little value that it makes the process economically impractical on any kind of meaningful scale. Could this process be refined so that it not just helps recycling centers break even, but produces something that is worth even more than what they started with?
Led by associate professor of chemistry at Virginia Tech Guoliang Liu, the Virginia Tech team developed a new, more fruitful method of polystyrene recycling. The technique starts by subjecting the material to UV light and then exposing it to aluminum chloride, which acts as a low-cost catalyst. This process creates what's known as diphenylmethane, or DPM, an organic compound used in drug development, cosmetics and plastics manufacturing.
DPM has a market price that is 10 times higher than the products that can be currently made from recycled polystyrene. The chemists teamed up with business experts to run the numbers on how this could impact a future recycling center, and concluded that the high value of DPM could indeed make the collection and processing of polystyrene a viable undertaking.
"The low-value-input and high-value-output approach is thus substantially more sustainable and economically viable than conventional thermal processes, which operate at high-temperature, high-pressure conditions and use precious-metal catalysts, but produce low-value oligomers, monomers, and common aromatics," the scientists write in their paper.
The research was published in the journal Proceedings of the National Academy of Sciences.
Source: Virginia Tech