Advances in chemical recycling of plastics

The world is still in a situation where recycling efforts are struggling to keep up with the pace of plastic production, the result of which is a continuing rise in plastic waste.

To accelerate the refinement of plastic waste, recyclers are using chemical methods to make the most of end-of-life plastics. One such technology is pyrolysis in which mixed plastic waste including hard to recycle plastics, can be subjected to heat without the presence of oxygen, a process that breaks down the material into liquid or wax that can further be refined into chemicals. When compared to incineration where only heat and electricity are generated, pyrolysis can produce different hydrocarbons that can be used as feedstock for new plastic products, thus contributing to a circular economy.

In the news recently, chemist Kevin Schug from the University of Texas at Arlington (UTA) has discovered a faster way to separate then recycle mixed plastics to accelerate recycling rates using pyrolysis. A  Shimadzu Distinguished Professor of Analytical Chemistry at UTA, Schug and his team of student researchers worked on a peer-reviewed study that came out in the April issue of Journal of Chromatography A.

Schug explains, “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.”

The main advantage of pyrolysis over mechanical or traditional plastic recycling is that the materials don’t have to be sorted and shredded prior to recycling. But while mixed plastic waste can undergo pyrolysis, the result can yield complex mixtures that contain contaminants such as sulfur and nitrogen. These can create chemical compounds that can hurt downstream processing strategies.

“Pyrolysis has become quite a big deal. Many companies are ramping up large chemical recycling operations,” Schug said. “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.”

The method discovered is a supercritical fluid chromatography method that can separate the pyrolysis oils. The researchers found they could clearly differentiate oils created from polyethylene versus polypropylene feedstock, which was created by Schug and his colleagues at UTA—graduate students Alexander Kaplitz and Niray Bhakta and undergraduate researchers Shane Marshall and Sadid Morshed. They were supported by Jean-Francois Borny from Lummus Technologies LLC, a Houston-based chemical company.

“This is just the beginning, but we’re very excited at the potential of this technique to differentiate oils produced from many different plastics and mixtures,” Schug was quoted in the news released by UTA. “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.”

Feedstock production

Many companies are increasing chemical recycling operations, as Schug has mentioned. Among them are Renewi and Freepoint Eco-Systems, two leading companies that plan to build a waste plastic sorting and treatment infrastructure under a long-term cooperation, to produce feedstock for the advanced recycling of waste plastics.

This collaboration aims to divert end-of-life plastics from incineration by developing the sorting and treatment infrastructure. The goal is to supply 80,000 tonnes of feedstock for Freepoint Eco-Systems' first European advanced recycling facility to be located at the Kluizendok site in Ghent, Belgium. By joining forces, they are addressing the demand for sustainable solutions for end-of-life plastics and the use of pyrolysis oil to create recycled products.

Freepoint Eco-Systems' advanced recycling facility will make it possible to recycle complex, mixed plastics that are difficult to process in any other way, making this facility a perfect complement to mechanical recycling.

By diverting end-of-life plastics that would otherwise be incinerated, this advanced recycling project is expected to enable a significant reduction in CO2 emissions, as well as a reduced need for fossil resources to produce new products. It will bring value to the local and global circular economies, from upstream waste material extraction to downstream end products.

Renewi will leverage its accumulated expertise with its state-of-the-art residual waste sorting line to produce high-quality feedstock for advanced recycling. The sorting line will utilize various innovative sorting techniques, including the utilization of residual heat from the advanced recycling plant. This process will transform different end-of-life plastic sources into a consistent and high-quality feedstock, reintegrating them into the circular economy.

Rendering of Encina's circular manufacturing facility (Source: Encina)

Also recently, Encina Development Group, LLC, a manufacturer of ISCC PLUS certified circular chemicals, and BASF announced their long-term supply agreement for chemically recycled circular benzene derived from post-consumer end-of-life plastics.

BASF will use the chemically recycled benzene as raw material for its broad Ccycled® product portfolio designed for customers in packaging, textile and automative.

Encina’s circular chemicals are key ingredients used in the production of everyday and novel plastics. Its proprietary catalytic technology produces drop-in quality and high yield circular feedstocks.