Currently, the main method for recycling polystyrene yields a product that is often too low-quality to make the process economically viable. In other words, if a recycling plant tries to recycle polystyrene on a large scale, it will either need a financial boost, such as a government subsidy, or the operation risks running out of money and shutting down.
One solution to this problem is to improve the recycling process so that it becomes economically viable, or even better, economically attractive. With his experience in polymer chemistry and as an affiliate of the Macromolecules Innovation Institute, this is exactly what Liu was able to guide his team to do.
In a paper recently published in the Proceedings of the National Academy of Sciences, the team presents a new method for recycling – or perhaps more accurately, "upcycling"– polystyrene. By exposing the material to ultraviolet light and adding a chemical catalyst, this method creates a product called diphenylmethane (DPM) that is immensely useful. DPM is used as a precursor in drug development, polymer manufacturing, and even as a fragrance in consumer products. Importantly, DPM has a market price that is 10 times higher than other materials that can currently be made from recycled polystyrene.
The researchers took their investigation one step further: They wanted to confirm that this new method would achieve the economic viability they were striving for. The chemists from Virginia Tech teamed up with business experts from Santa Clara University and the Dongbei University of Finance and Economics, who ran an analysis to determine how profitable the recycling method would be overall. Their results showed that because DPM has such a high economic value, the costs of collecting and processing the polystyrene would be fully justified. This new recycling method would create an incentive for polystyrene to be collected and recycled instead of going into landfills or becoming plastic pollution.
"I think it's important for people to realize that big global challenges like plastic waste can have — and most likely demand — multiple solutions," said Liu. "We at Virginia Tech can contribute a small piece to the big puzzle and offer solutions to positively impact the world."