Carbon negative pyrolysis of PLA waste for clean hydrogen production: Techno-economic analysis and life cycle assessment

Global demand for polylactic acid (PLA) is rising, yet current PLA waste (PLAW) management imposes environmental burdens and recovers limited value. This study proposes a hydrogen production pathway integrating CO 2 -assisted PLAW pyrolysis with natural gas steam methane reforming (SMR). Pyrolysis-derived syngas is fed to the water–gas shift reactor, increasing H 2 production by 60.1%. The optimized SMR + PLAW opt configuration utilizes PSA off-gas, pyrolysis oil combustion, and flue-gas waste heat, thereby reducing total energy consumption by 19.3% compared with conventional SMR. CO 2 emissions from the process are captured and stored via CCS. Techno-economic and life-cycle analyses show that SMR + PLAW opt reduces the levelized cost of hydrogen by 49.6% to 3.51 USD/kg H 2 and lowers global warming potential by 44.5% to 4.98 kg CO 2 /kg H 2 , enabling net-negative CO 2 emissions. By valorizing PLAW into syngas and coupling the system with CCS, resource recovery is enhanced and deep decarbonization goals for hydrogen supply are supported.