Mixed plastic packaging waste gains second life as high-purity hydrogen

A recent study has converted mixed plastic packaging waste into high-purity hydrogen in a low-temperature process that locks carbon in solid carbonate compounds. 

Researchers from the University of California, Los Angeles, Samueli School of Engineering, US, and Ewha Womans University, South Korea, find that alkaline thermal treatment (ATT) can treat PET, PE, and PP waste in a single reactor, yielding hydrogen gas with purities above 90%. 

ATT is a process in which sodium hydroxide reacts with organic material under heat to spur hydrogen production. Hydrogen is an industrial feedstock and energy carrier used in fertilizers, fuel refining and chemical manufacturing, with potential to decarbonize many sectors. 

“Our technology is designed for packaging waste that is difficult to recycle using conventional methods. Mixed plastic packaging, food-contaminated containers, films, trays, caps, and other heterogeneous packaging wastes are ideal candidates,” Woo-Jae Kim, co-corresponding author and a professor of chemical engineering and materials science at Ewha Womans University, tells Packaging Insights.

“These materials are often incinerated because separating each polymer is technically challenging and economically unattractive. In this way, the technology can both increase overall resource recovery and make a meaningful contribution toward achieving carbon neutrality.” 

Kim continues that, rather than competing with mechanical recycling, he envisions the process to target residual plastic packaging that has “little recycling value” and reduce plastic incineration.

No mechanical separation 

The study, published in Proceedings of the National Academy of Sciences, established ATT as a “promising and sustainable” solution for plastic waste management and clean energy production.

One challenge to mechanical recycling is the separation of multilayer packs, labels, and other packaging components. But Kim asserts that the ATT method bypasses this problem. 

“In principle, multilayer packaging, labels, adhesives, and printing inks can all be processed together, significantly simplifying waste treatment.” 

He notes that some basic pretreatment, such as removing metals or large contaminants and reducing particle size, “would still be desirable.” 

“However, unlike conventional recycling, the process does not require complete separation of individual plastic types before treatment. This makes it particularly attractive for complex packaging waste that is currently difficult or impossible to recycle economically.” 

Capturing carbon 

Kim stresses that the technology should “complement, not replace” existing recycling systems. Instead, he positions the technology for the “unrecyclable fraction” of plastic waste by converting it into clean energy and diverting it from incineration. 

“This is particularly important from a climate perspective,” he outlines. “Conventional incineration converts nearly all of the carbon in plastic directly into carbon dioxide. In contrast, the ATT process captures a substantial portion of the carbon as stable sodium carbonate while simultaneously producing high-purity hydrogen.” 

The result is a method in which CO2 emissions are “significantly suppressed” compared with incineration and packaging waste that becomes a resource “rather than a source of GHG emissions.”

Hydrogen is an industrial raw material and energy carrier. It is used to make products such as ammonia for fertilizers, refine fuels, and support chemical manufacturing. It could also help decarbonize sectors that are difficult to electrify directly, steelmaking, and some heavy transport.

However, he asserts that “high-quality, single-polymer packaging should continue to be mechanically recycled whenever possible.”

Scaling up

The study notes that, while the process shows promise, further work must optimize temperature, recycle sodium hydroxide, use unwanted hydrocarbon gases as process fuel, and assess the economic-environmental trade-offs at a commercial scale. 

Kim adds: “The next steps include optimizing alkali recovery and reuse, improving reactor efficiency, and demonstrating continuous operation with real mixed packaging waste. Establishing reliable collection systems and integrating hydrogen purification and distribution infrastructure will also be important.”

Despite this, he argues that for the industry, the potential benefits of the process are “substantial.” Packaging companies are increasingly under pressure to reduce carbon emissions, landfill, and incineration. 

“Ultimately, we see this technology not simply as a waste-treatment process, but as a new platform that simultaneously addresses waste management, clean hydrogen production, and carbon neutrality,” concludes Kim.