Turning mixed plastic waste into clean hydrogen fuel

TECHNOLOGY

A discarded bottle, shopping bag or a car part can remain in landfill or elsewhere in the environment long after its useful life comes to an end. Recycling it remains a challenge because most systems require different types to be separated first, which is both expensive and labour-intensive. As a result, plastic recycling rates remain low. However, that could all be about to change.

Researchers co-led by the University of California Los Angeles’ Samueli School of Engineering and Ewha Womans University in South Korea have demonstrated a chemical process that converts a mixture of three widely used plastics into high-purity hydrogen fuel. And the process operates at substantially lower temperatures than conventional gasification and stores the carbon as calcium carbonate — a solid mineral — instead of it being released to the atmosphere as pollution.

The findings, published in Proceedings of the National Academy of Sciences, outline an alkaline thermal treatment in which heated sodium hydroxide reacts with organic material to produce hydrogen. In a single reactor, the process treats mixed polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) without requiring the plastics to be pre-sorted. The resulting hydrogen is better than 90% purity.

Next up is to prove it works commercially, which, say researchers, will require further improving its performance.

“By reducing the sorting costs and process complexity that have been major barriers to commercialisation, this technology has the potential to become a next-generation core technology that supports both the hydrogen economy and the circular economy,” says study co-corresponding author Woo-Jae Kim, a professor of chemical engineering and materials science at Ewha.

ABOVE An illustration of a treatment process that transforms mixed plastic waste into a biomass-like hydrogen source, enabling hydrogen production without atmospheric pollution

PHOTO Younghee Lee/CUBE3D Graphic

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