Decarbonisation Technology February 2026 Issue

carbide) promotes C₅ ⁺ formation (Yohannes & Gates, 2026) . Relative to methanol or alcohol-mediated routes, direct CO₂-to-hydrocarbon conversion offers drop-in compatibility with existing refinery infrastructure. Recent simulations show that integrated RWGS-FT systems with renewable heat can reach 45-55% CO₂-to-liquid efficiency (Chen, et al., 2024) . Early demonstration efforts – including Norsk e-fuel (Norway) and Sunfire’s PowerFuel pilot (Germany) – highlight the technical feasibility of e-SAF production, though commercial-scale plants remain at the design stage. CO₂-to-ethanol and higher alcohols Catalytic hydrogenation of CO₂ to higher alcohols offers a promising but complex route to synthetic fuels. Target products such as ethanol, propanol, and butanol provide high energy density and compatibility with existing fuel infrastructure. Production generally follows a bifunctional pathway in which RWGS converts CO₂ to CO, followed by chain growth and hydrogenation reactions to form higher alcohols (Tan, et al., 2024). Advances in catalyst design – particularly multifunctional systems combining RWGS and chain-growth sites, such as Cu-Zn-Zr or Co-Mo on metal-oxide supports – have enabled ethanol selectivities above 30% (Chen, et al., 2024 ). Remaining barriers include catalyst deactivation, methane side reactions, limited space-time yields, and the need for elevated pressures and ~300°C operation (He, et al., 2022) . Even so, the pathway is attractive for integration with alcohol-to-jet or alcohol- to-olefin processes and can be paired with renewable H₂ and modular CO₂ capture for decentralised e-fuel production (Tan, et al., 2024) . With improved catalyst stability and intensified processing, CO₂-to-alcohol systems could serve as an intermediate step between “ Electrochemical and photocatalytic CO₂ reduction provide potential routes for converting CO₂ and water into fuels using renewable electricity or sunlight ”

early methanol routes and more advanced hydrocarbon synthesis.

Electrochemical and photocatalytic CO₂ reduction Electrochemical and photocatalytic CO₂ reduction provide potential routes for converting CO₂ and water into fuels using renewable electricity or sunlight. Electrochemical CO₂ reduction (CO₂RR) relies on metal catalysts (such as Cu, Ag, Sn) to produce CO, formate, methanol, or hydrocarbons, with recent surface-engineered electrocatalysts achieving >60% Faradaic efficiencies for C₂ ⁺ products at >200 mA cm ⁻ ². Remaining barriers, including electrode degradation, product separation challenges, and energy inefficiency, limit industrial adoption (Han, et al., 2024) . Photocatalytic CO₂ reduction employs semiconductor materials such as TiO₂, g-C₃N₄, and metal-organic frameworks (MOFs) to convert CO₂ under solar irradiation. However, quantum efficiencies typically remain below 1% and catalyst stability is insufficient for long-term operation (Tan, et al., 2024) . Consequently, both approaches remain at low technology readiness (TRL <4). Together, the three pathways explored above compose a layered synthetic e-fuel portfolio: higher alcohols offer nearer-term compatibility, direct CO₂-to-hydrocarbon routes target heavy transport, and electrochemical/photocatalytic systems represent longer-term, fully renewable options. E-ammonia production pathways Conventional ammonia is produced from nitrogen extracted from air and hydrogen typically derived from natural gas under high- temperature and high-pressure HB conditions. With global output near 183 MT, the ammonia sector emits about 1% of global CO₂ (≈0.5 Gt) and primarily serves fertiliser demand. Ammonia is increasingly viewed as a carbon-free fuel for heavy transport – especially shipping – and as a hydrogen carrier with >50% higher volumetric energy density than liquid H₂ and relatively simple storage and transport (IEA, 2023) . Green or e-ammonia replaces fossil H₂ with renewable hydrogen from electrolysis and nitrogen from air separation, integrating