A review on hydrogen from plastic and tire waste: Thermochemical pathways, carbon management, and scale-up barriers

The increasing volume of plastic and tire wastes creates environmental and energy challenges, and their utilization as feedstock for hydrogen production is being promoted under a circular economy. This systematic review critically summarizes and compares developments in waste-to-hydrogen conversion pathways using Process Systems Engineering concepts that combine thermochemical modeling with techno-economic analysis and LCA. The literature was obtained through a comprehensive search of the Web of Science, Scopus, and ScienceDirect databases and selected according to PRISMA criteria. The results show that the reported energy efficiencies (first-law) range between 7.3% and 48.67% (LHV basis), the exergy efficiencies range between 5.2% and 45.0%, and the sustainability indices range between 1.055 and 2.76, demonstrating high sensitivity of the results to process configuration, heat integration, and feedstock composition. Among the technologies reviewed, plasma gasification reported the highest simulated hydrogen production rate (up to 1.2 kg/s at a 5 kg/s plastic-waste throughput) with a levelized cost of hydrogen (LCOH) of USD 3.3 per kg H₂ in Aspen Plus studies, comparable to steam methane reforming; microwave-assisted pyrolysis reported hydrogen concentrations up to 45.2 vol% in the product gas under optimized catalyst loading. Life cycle assessments have estimated a 38–80% reduction in CO₂ emissions, with the hybrid solar-biomass system achieving a carbon avoidance of up to 55,777 t of CO₂/year. The techno-economic calculations suggest that industrial-scale (20,000 kg h⁻¹) (equivalent to approximately 160,000 tons of plastic waste per year at 8000 operating hours) plants would have reported annual revenue from hydrogen sales in the range USD 271–358 million. Overall, as highlighted in the review, a combination of thermochemical conversion, carbon capture, and digital simulation tools can facilitate efficient, low-emission, and cost-effective hydrogen production. The results make waste-to-hydrogen systems an important direction to a sustainable, circular, and low-carbon hydrogen economy.