In waters spanning the west coast of North America all the way to Japan swirls the Great Pacific Garbage Patch, an 80,000-ton glob comprising more than 1.8 million pieces of plastic. The patch reflects not just humans’ voracious appetite for plastic packaging but also a failure to recycle. Only about 9% of plastic packaging is recycled; 12% is incinerated in facilities that create electricity or heat from garbage, and the remaining 79% ends up in landfills and the environment. A team led by Chao Wang, an associate professor of chemical and biomolecular engineering, has devised a way to transform the bulk of this worthless and harmful trash into something of value: p-xylene, a colorless chemical liquid used in manufacturing.
1. Can you walk us through the plastic treatment process?
In the lab, our group simulated the mixture that typically ends up in landfills by accumulating plastic and trash from home. We treat it with chlorine and then place it into a hydrocracking reactor. Then comes a two-stage process for hydrocracking depolymerization, a fancy name for plastic refining, akin to turning crude oil into gasoline. In step 1, the plastics react with a hydrogen catalyst to convert hydrocarbons to unrefined xylene. In step 2, pure p-xylene is separated from the less valuable isomers of xylene. P-xylene, worth $1 per kilogram, is a key building block in manufacturing things like rubber and leather products, and to refine other industrial chemicals.
2. How could this chemical process benefit the environment?
It provides an economic motivation to keep these plastics out of the water and land, with an added benefit of cleaning up the environment. The fact that companies want and need this product is what we hope will drive its commercialization. It could become a valuable commodity.
3. What next steps must happen in order to commercialize the process?
Within a year or two, we hope to demonstrate its effectiveness at a solid waste management facility in Maryland. If successful and implemented nationwide, the number of plastics recycled in the country could shoot up from 9% to 50%, or even higher. The sooner, the better.