Synergistic CO₂ co-utilization with biomass, organic solid waste and wastewater: mechanisms, technologies, and...

Carbon dioxide (CO₂) utilization contributes to carbon mitigation and sustainable production, but its practical application is constrained by the high thermodynamic stability of CO₂, sluggish activation kinetics, limited C-C coupling efficiency, as well as the high demand for electrons and reducing power. Coupling CO₂ conversion with waste-derived resources provides an effective way to address these limitations. Strategically, biomass, organic solid waste, and wastewater can supply reduced carbon, hydrogen, nutrients, electron donors, sacrificial oxidation substrates, and microbial growth media, thereby enabling more efficient carbon and electron redistribution. As such, this review holistically summarizes CO₂ co-utilization with biomass, organic solid waste, and wastewater from the perspectives of mechanisms, technologies, and prospects. Therefore, this review specifically emphasizes the coupled redistribution of electrons and carbon between CO₂ and these waste-derived resources. The mechanistic basis is first discussed in terms of electron flow, carbon flow, and metabolic coupling. Afterwards, representative CO₂ valorization routes are reviewed, including thermochemical conversion, electrochemical and photochemical co-conversion, microalgal and algal-bacterial wastewater treatment, bioelectrochemical transformation, and coupled catalytic-microbial relay upgrading. Finally, performance metrics, key bottlenecks, and future directions are discussed. Overall, the co-utilization of CO₂ and waste shall be not regarded only as a simple combination of CO₂ conversion and waste treatment, but also as an integrated carbon-electron management strategy.