Researchers from the UCLA Samueli School of Engineering and South Korea’s Ewha Womans University have developed a new method that converts mixed plastic waste into high-purity hydrogen fuel without requiring plastics to be sorted first.
The process handles some of the world’s most commonly used plastics in a single reactor while capturing carbon in solid form instead of releasing it into the atmosphere. The approach offers a new way to address two major global challenges at once: plastic pollution and clean energy production.
Plastic waste remains one of the most difficult environmental problems worldwide. Although plastic products are used daily in packaging, consumer goods, vehicles, and electronics, recycling rates remain low. Current estimates show that only about 9% of discarded plastic is recycled, while most ends up in landfills or is burned, generating greenhouse gas emissions.
Addressing Two Global Challenges
The new research was published in the journal Proceedings of the National Academy of Sciences.
Scientists demonstrated that a process known as alkaline thermal treatment(ATT), can convert mixed plastic waste directly into hydrogen fuel. The method works with polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP), which together make up a large share of global plastic waste.
Unlike conventional recycling systems, the process does not require plastics to be separated by type before treatment. Sorting plastic is often one of the most expensive and time-consuming stages of recycling. Eliminating that step may simplify operations and reduce processing costs.
Ah-Hyung “Alissa” Park, Ronald and Valerie Sugar Dean of UCLA Samueli and a professor of chemical and biomolecular engineering, said the technology addresses two pressing issues simultaneously. She noted that plastic waste continues to accumulate worldwide while demand for clean hydrogen is growing. According to Park, the new process offers a practical way to tackle both challenges through a single system.
How The Process Works
The ATT method uses sodium hydroxide and heat to trigger chemical reactions that generate hydrogen gas. Researchers adapted the process from an earlier system designed to produce hydrogen from biomass materials such as seaweed. In laboratory testing, the modified approach successfully converted mixed plastic waste into hydrogen with purity levels exceeding 90%.
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The system operates at temperatures significantly lower than traditional gasification methods. Researchers reported that the process runs at temperatures roughly 300 to 400 degrees Celsius lower than conventional steam gasification. Lower operating temperatures can help reduce energy requirements and improve overall efficiency.
Among the plastics tested, PET generated the highest hydrogen output. Scientists found that polyethylene and polypropylene initially produced less hydrogen because of their chemical structure. These materials consist mainly of carbon and hydrogen, making them less reactive under alkaline treatment.
To overcome this limitation, the research team introduced an additional preparation step. The plastics undergo a brief thermal oxidation treatment in air before entering the main reactor. This step adds oxygen-containing groups to the material, making it easier for the alkaline treatment process to break down the plastic.
Capturing Carbon During Conversion
Once activated, all three plastic types decomposed efficiently during the reaction. The process produced hydrogen while preventing carbon from escaping as carbon dioxide gas. Instead, sodium hydroxide captured the carbon, converting it into solid sodium carbonate.
This feature distinguishes the method from many conventional waste-to-energy technologies. Traditional high-temperature gasification can process mixed plastics but often releases large amounts of carbon dioxide. The new approach keeps most of the carbon locked in solid materials throughout the reaction.
Researchers found that more than 75% of the original carbon contained in the plastics remained in stable carbonate compounds or liquid organic residues. Less than 13% appeared in gaseous form. Direct atmospheric carbon emissions during the reaction were reported as negligible.
The resulting sodium carbonate can also undergo additional processing. Scientists said it can be converted into calcium carbonate through a simple recovery process. Calcium carbonate is widely used in industries such as construction, paper production, and manufacturing, creating another potential value stream from waste materials.
Potential for Large-Scale Use
The study addresses limitations found in previous low-temperature hydrogen production methods. Technologies such as photoreforming and electrochemical conversion generally work only with oxygen-containing plastics like PET. As a result, they cannot effectively process large volumes of polyethylene and polypropylene commonly found in household waste.
The new ATT approach handles all three major plastic types within a single process. This expands the range of waste materials that can be converted into useful products. It also reduces reliance on extensive sorting systems, which often limit recycling efficiency.
Woo-Jae Kim, professor of chemical engineering and materials science at Ewha Womans University, said reducing sorting requirements may help lower barriers to commercial adoption.
He explained that simplifying the process could support both the growing hydrogen economy and efforts to build a circular economy. A circular economy focuses on reusing materials and minimizing waste rather than discarding resources after use.
The researchers emphasized that additional work remains before commercial deployment becomes possible. Future studies will focus on improving efficiency, optimizing operating conditions, and evaluating economic performance at larger scales. If those efforts prove successful, the technology may offer a new pathway for turning difficult-to-recycle plastic waste into clean hydrogen fuel while permanently storing much of its carbon content.
