The ‘Sledgehammer’ Approach to Recycling Medical Plastics

Thermochemical recycling can be used to process mixed plastics from healthcare waste safely and efficiently, according to researchers at Chalmers University of Technology in Sweden, where the technology was developed. Based on a steam cracking process, the technique can recycle medical waste that is currently being incinerated or ending up in landfill and convert it into new plastic products that meet the highest purity and quality requirements.

In circular economy policies, medical waste is often overlooked, notes the university in a press release. “Disposable healthcare items usually consist of several types of plastic that cannot be recycled with today's technology. In addition, the items must be considered contaminated after use, and so, they must be handled so that risks of spreading potential infections are avoided. When it comes to the production of single-use healthcare items, it is also not possible to use recycled plastic, since the requirements for purity and quality are so high for materials intended for medical use,” said the release.

Taking a thermal sledgehammer to molecules

The solution, according to Chalmers University, is thermochemical recycling. The technology mixes the waste plastic with sand at temperatures reaching 800°C. The plastic molecules are then broken apart and converted into a gas, which contains the building blocks for new plastic. Martin Seemann, associate professor at Chalmers' Division of Energy Technology, compares the process to a thermal sledgehammer that smashes up the molecules while simultaneously destroying bacteria and micro-organisms. "What is left are different types of carbon and hydrocarbon compounds. These can then be separated and used in the petrochemical industry, to replace fossil materials that are currently used in production," explains Seemann. An additional advantage of thermochemical recycling is the recovery of carbon atoms, aligning it with the principles of a circular economy, according to the researchers.

Tests show technology works . . .

The technique has been tested via two projects, one using specific types of medical products such as face masks and gloves, the other involving a mixture representing the average composition of waste from regional hospitals, including 10 different types of plastic as well as cellulose. Both tests showed the technology worked as intended and, in the view of researchers, resulted in materials that meet the strict requirements for purity and quality in medical products.

Gloves, surgical gowns, tubing, and marker pens were among the medical waste ground up into a material mix for the test. Image courtesy of Chalmers University of Technology.

. . . but new business models are needed

Regulations regarding recycling medical waste and other mixed plastic waste via steam cracking would need to be reconsidered in order for the technology to be implemented in various countries, the researchers acknowledge. Compatible business models also would need to be developed. Single-use healthcare products would not create a sufficient flow of materials given the investment needed, for example. "To build a plant of the size required for profitable thermochemical recycling, you would have to ensure a material flow of around 100,000 tonnes per year before start up,” notes Judith González-Arias, who led one of the test projects. In 2019, only around 4,000 metric tons of such plastic were put on the market.

"Thermochemical recycling would become more beneficial with new political frameworks that create a recycling solution for our plastic-rich waste," said Seemann. “Certain political decisions would increase the value of plastic waste as a raw material for industry, and increase the chances of creating functioning circular business models around this type of recycling. For example, a requirement for carbon dioxide capture, when incinerating plastic, would create incentives to instead invest in more energy-efficient alternative technologies such as ours.”

The research has been published in Resources, Conservation and Recycling. The paper is titled, “Steam gasification as a viable solution for converting single-use medical items into chemical building blocks with high yields for the plastic industry.”

The video embedded below describes thermochemical recycling in greater detail.