Solid waste-derived membranes for CO2 capture: Material design, separation mechanism, and techno-environmental evaluation

Solid waste-derived membranes (SWDMs) represent an emerging class of sustainable materials that integrate carbon capture functionality with circular utilization of industrial and agricultural residues. This review systematically summarizes the transformation of solid wastes including fly ash, steel slag, plastics, and biomass into functional membranes for CO2 separation, and highlights their potential in reducing landfill burden and offsetting carbon-intensive materials. Various fabrication strategies such as dip-coating, phase inversion, and electrospinning are discussed, along with structure-function mechanisms that govern gas separation performance. Special attention is paid to interface engineering, porosity control, and chemical compatibility, which underpin selective CO2 transport. Furthermore, those reported techno-economic and life-cycle data were analyzed and indicated that under favorable, proxy-based assumptions SWDM-based systems could in principle approach capture costs below 30 US$ per ton CO2 and offer reduced embodied emissions and material consumption relative to conventional membranes. Next, the current limitations, data gaps, especially regarding long-term stability under industrial conditions, and research bottlenecks of SWDMs were critically analyzed. Finally, a development roadmap is proposed to align membrane innovation with net-zero goals, offering a prospective pathway toward low-carbon manufacturing and sustainable industrial decarbonization.