Kevin Schug, the Shimadzu Distinguished Professor of Analytical Chemistry at The University of Texas at Arlington, is developing novel techniques for separating and recycling mixed plastics to increase recycling rates. He worked with a group of UTA graduate and undergraduate researchers on a novel, peer-reviewed study released in the Journal of Chromatography A in April.
Kevin Schug, the Shimadzu Distinguished Professor of Analytical Chemistry. Image Credit: The University of Texas at Arlington
Despite consumer attempts to sort and segregate recyclables, most plastic bottles end up in landfill. Standard recycling procedures for sorting, shredding, and remaking plastics are restricted to type-1 and type-2 plastics, which are mostly soda bottles, water bottles, and milk jugs.
Global plastic manufacturing has risen from 2 million tons in 1950 to 360 million tons in 2018, with almost half of that plastic becoming waste after a single usage. By 2050, it is estimated that 12 billion tons of plastic waste will be in the environment and landfills.
A prominent means of chemical recycling is called pyrolysis, during pyrolysis, plastics are heated in an oxygen-free environment until they decompose into pyrolysis oils. These oils have much of the same characteristics as crude oil, with a few exceptions. Importantly, they can be further refined into fuels and, even better, turned into chemical feedstocks to make new plastics.
Kevin Schug, Shimadzu Distinguished Professor, Department of Analytical Chemistry, University of Texas at Arlington
Unlike traditional plastic recycling, which requires sorting and shredding before the material can be recycled, pyrolysis is not confined to any particular form of plastic. It can accommodate everything.
However, the pyrolysis of mixed plastic waste yields several complicated mixtures that manufacturers must properly investigate. Contaminants like sulfur and nitrogen can produce chemical compounds that harm downstream processing methods.
Schug added, “Pyrolysis has become quite a big deal. Many companies are ramping up large chemical recycling operations, still, the characterization of the pyrolysis oils requires the development of new analytical methods, such as the one we describe in our new peer-reviewed research.”
Schug and his UTA colleagues—graduate students Alexander Kaplitz and Niray Bhakta, as well as undergraduate researchers Shane Marshall and Sadid Morshed—developed a new supercritical fluid chromatography method to separate the pyrolysis oils with the help of Jean-Francois Borny of Lummus Technologies LLC, a Houston-based chemical company. The researchers discovered that polyethylene and polypropylene feedstocks produced distinct oils.
Schug concluded, “This is just the beginning, but we are very excited at the potential of this technique to differentiate oils produced from many different plastics and mixtures, finding a way to better recycle these plastics will help us reduce our reliance on new fossil fuels and, hopefully, do our part to stop contributing to climate change.”
Journal Reference:
Kaplitz, A. S., et al. (2024) Discrimination of plastic waste pyrolysis oil feedstocks using supercritical fluid chromatography. Journal of Chromatography A. doi.org/10.1016/j.chroma.2024.464804.