New low-temp process converts mixed plastic trash into pure hydrogen while locking carbon

Scientists have demonstrated a method that turns unsorted PET, PE and PP waste into over 90% pure hydrogen and captures most of the carbon as solid minerals.

A joint team from UCLA's Samueli School of Engineering and Ewha Womans University has refined an alkaline thermal treatment that converts a blend of PET, polyethylene and polypropylene into clean hydrogen without the need for sorting. Operating 300-400 °C lower than conventional gasification, the process first subjects the plastics to a mild oxidative heat step, creating reactive sites on the polymer chains. In the main reactor, sodium hydroxide reacts with the activated plastics, releasing hydrogen that is over 90% pure while binding the carbon into solid sodium carbonate.

Subsequent conversion can produce calcium carbonate, permanently sequestering the carbon. Laboratory tests showed that more than 75% of the plastic’s carbon is retained in solid or liquid products, with less than 13% entering the gas phase and virtually no direct CO₂ release. The researchers stress that further work is needed to assess economic viability at scale. Funding came from the National Research Foundation of Korea, and the findings were published in the Proceedings of the National Academy of Sciences.