Hydrogen and methanol production via CO2-assisted pyrolysis of nonwoven polymer waste: Techno-economic analysis and life cycle assessment

초록

Nonwoven polymer waste (NPW) from spent HEPA filters is expected to increase as indoor PM2.5 exposure control becomes more prevalent, yet end-of-life management still relies largely on incineration with associated air-pollutant emissions. We evaluated CO2-assisted pyrolysis of spent HEPA media as a chemical-recycling route that upgrades NPW to syngas while enabling CO2 utilization. Compared with N2-assisted pyrolysis, CO2-assisted pyrolysis achieved a 6.5-fold higher CO yield, motivating three integrated process designs: waste-to‑hydrogen (WtH), waste-to-methanol with a multi-pressure pressure-swing adsorption (PSA) train (WtMMPSA), and waste-to-methanol with a pre-reformer and a single PSA unit (WtMSPSA). In all routes, pyrolysis syngas is conditioned and converted to H2 or methanol; WtH supplements syngas via natural-gas steam methane reforming and produces H2 through water–gas shift and PSA purification. For methanol, WtMMPSA uses staged compression and two PSA blocks operated at different adsorption pressures to meet synthesis specifications, whereas WtMSPSA mitigates CH4 and C2H2 via pre-reforming and applies selective CO2 removal in a single PSA, validated by dynamic adsorption simulation. Techno-economic analysis and life-cycle assessment were performed under grid and renewable electricity (wind, solar, hydropower) using levelized cost of energy (LCOE) and global warming potential (GWP) metrics. Sensitivity analyses quantified how electricity carbon intensity and avoided-burden credits influence net emissions and economics. Across electricity scenarios, WtMSPSA achieved the lowest LCOE (0.327–0.504 USD/kWh) and, with renewable electricity and avoided-burden credits, the lowest GWP (−4.77 to −5.33 kg CO2-eq.), indicating pathways to scale NPW valorization with competitive cost and climate performance. © 2026 Elsevier B.V.

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