Zero direct carbon emission renewable natural gas production from municipal solid waste via chemical looping

Municipal solid waste (MSW) can be rapidly converted to synthetic natural gas (SNG) by thermochemical routes, capturing feed energy while yielding a versatile fuel for city gas and industry. Adding renewable power-to-X (PtX) further raises carbon use and embeds intermittent electricity in a storable product. A chemical-looping hydrogen production (CLHP) MSW-to-SNG system is proposed with full process CO 2 management at the plant gate and a day-switch dual-tank hydrogen buffer that steadies variable renewable input while keeping reactor operation near steady. With a realistic tipping fee, a no-PtX baseline running on MSW attains a levelized cost of SNG (LCOSNG) of 0.78–0.97 USD/kg-SNG, competitive with fossil natural gas in municipal public–private partnership settings. Two PtX integrations sharing one backbone are then assessed: Option 1 uses electrolytic hydrogen to convert residual CO 2 to additional SNG, and Option 2 co-produces methanol from the same CO 2 and hydrogen. Across 30,000 Monte Carlo draws, median LCOSNG is 1.92 and 2.19 USD/kg-SNG for Option 1 and Option 2, respectively. With landfill-diversion crediting, cradle-to-gate carbon intensity is strongly negative for both routes (medians −7.39 and −9.71 t-CO 2 e/t-SNG); without credit, medians are 0.130 and 0.168 t-CO 2 e/t-SNG. Feed composition, summarized by oxygen-to-carbon and hydrogen-to-carbon ratios (O/C, H/C), shapes outcomes: higher O/C lowers SNG yield and raises LCOSNG while increasing credited carbon per unit product, whereas higher H/C has the opposite effect and reduces the credited benefit. Overall, the advantages of MSW chemical looping and the potential of PtX coupling were supported.