A July 2026 study in PNAS tested alkaline thermal treatment (ATT) as a way to convert mixed plastic waste into hydrogen without first sorting the plastics. The process uses sodium hydroxide and steam at temperatures between 200 and 600 degrees Celsius, well below the 800 to 1000 degrees Celsius typical of gasification. Under the best lab conditions, the plastics produced hydrogen yields comparable to steam gasification while retaining most of the carbon in solid sodium carbonate and tarry or waxy liquids, with less than 13 percent escaping as gas. The authors report lifecycle emissions per kilogram of hydrogen that range from 4.8 kg CO2e for polyethylene to 10.9 kg for PET under ATT, compared with about 20.7 kg for steam gasification of PET and the 8 to 10 kg range of steam methane reforming. But the work is still at laboratory scale, using only 0.05 g of polymer per run. The 50-hour pre-oxidation step, mass loss from oxidation, and the need to recycle sodium hydroxide will determine whether the process can scale to real waste streams and compete on cost. For anyone tracking clean hydrogen or plastic waste management, this is a useful proof of concept, not a commercial breakthrough. The next stage needs to show how the process handles tonnage quantities, what the sodium hydroxide recovery actually costs, and whether the tar and wax fractions can be used or must be treated as waste.
