Lab process turns mixed plastic waste directly into hydrogen

Researchers report converting three common plastics into 90%-plus purity hydrogen without a sorting step, at lab scale only.

Researchers described a method that converts three common plastics directly into hydrogen without any sorting step. Called alkaline thermal treatment, it uses sodium hydroxide and heat to drive hydrogen production. The work was co-led by Ah-Hyung Park, a chemical and biomolecular engineer at UCLA, with researchers in South Korea, and published in PNAS.

The process handled PET, PE, and PP, producing hydrogen at purities above 90 percent from mixed waste. It ran roughly 300 to 400 °C cooler than alternative approaches and captured about 75 percent of carbon byproducts as a solid instead of releasing CO2. PE and PP were pre-treated by heating and oxidizing to make them more reactive. The same team previously developed the approach to convert seaweed into hydrogen.

The abundance angle touches two needs at once. Only about 9 percent of plastics currently get recycled, partly because sorting is expensive, and most hydrogen today comes from natural gas in a CO2-emitting process. A method that skips sorting and locks up most of its carbon could, if it scales, turn a waste stream into fuel while cutting emissions from both plastic handling and hydrogen production.

The caveats are firm. Only very small lab-scale samples were tested, and the process is not commercial. The researchers say more work is needed to optimize yields, minimize emissions, and keep temperatures low before scaling. Co-author Woo-Jae Kim of Ewha Womans University calls it a potential next-generation technology, not a proven one.

Source: ScienceAlert