Microwave-Assisted Catalytic Pyrolysis of Mixed and MSW-Relevant Wastes: Reaction Engineering, Selective Chemical Upcycling, Process Intensification and Scale-Up

Municipal solid waste (MSW) is a heterogeneous mixture of plastics, biomass-derived materials, moisture, inorganics and contaminants. Microwave-assisted catalytic pyrolysis (MACP) combines volumetric dielectric heating with catalytic upgrading and is increasingly proposed for such residual streams. This critical narrative review examines what has actually been demonstrated for MSW and what is extrapolated from single-polymer, biomass and mixed-model studies. A structured literature search (418 records screened to 77 core sources, 2015–2026) was combined with an explicit three-tier classification of evidence by feedstock realism. Only a handful of studies used real or model MSW, so most mechanistic and performance conclusions rest on extrapolated evidence. The main findings are: (i) dielectric heterogeneity is a first-order design variable, with calculated penetration depths at 2.45 GHz ranging from a few millimeters to centimeters for wet organics, char and susceptors to tens of meters for dry polyolefins; (ii) susceptor–catalyst arrangement and contaminant management (Cl, N, ash) govern selectivity and catalyst lifetime more than microwave power alone; (iii) hydrogen yields of about 9–12 wt% of feed have been reported for clean polyolefins but remain unproven for real MSW; (iv) published techno-economic analysis (TEA), life cycle assessment (LCA) and machine learning results cannot be compared directly because boundaries, functional units, electricity assumptions and datasets differ; and (v) no study reporting weeks-to-months continuous operation on MSW-type feed was identified. A prioritized roadmap is proposed, comprising standardized feed and reporting protocols, contamination-tolerant catalysts, coupled electromagnetic–thermal–reaction design and a long-duration pilot campaign.