The potential of syngas as a central mediator for a carbon-agnostic circular economy

Carbon is the foundation of life and industrial production, but the current use of fossil-based carbon in a linear economy leads to climate breakdown with global ecological consequences. To mitigate the effects of the climate catastrophe, transitioning from a fossil-based linear economy to a circular carbon economy requires scalable strategies that do not compete with arable land resources. Accordingly, processes for the utilization of waste streams from various sources including CO₂ must be established to enable circularity. Here, we propose synthesis gas (syngas; CO, H₂ and CO₂) as a universal, homogenized hub feedstock that decouples upstream waste heterogeneity from downstream chemical and biotechnological manufacturing. We review established and emerging routes for syngas production from biogenic and fossil-derived wastes and discuss their integration with thermocatalytic upgrading and biological gas fermentation. Advances in aerobic and anaerobic microbial assimilation and hybrid abiotic-biotic systems enable the selective conversion of syngas and syngas-derived intermediates such as methanol, acetate and ethanol into a broad spectrum of fuels, chemicals and materials. We argue that syngas-based value chains provide a flexible, carbon-agnostic platform for closing carbon loops across sectors and geographies. Realizing this vision will require (i) further quantitative exploration to identify optimal waste-to-product strategies; (ii) continued innovation in catalyst and bioprocess engineering, continuous operation concepts; and (iii) supportive policy frameworks that incentivize chemical recycling and gas-based carbon utilization as core pillars of the circular economy.