A large-scale solar-driven direct air capture and utilisation process to produce sustainable aviation fuel

Renewable energy-powered direct air capture (DAC) combined with CO2 utilisation offers a sustainable decarbonisation strategy for a circular economy. However, current liquid-based DAC (L-DAC) technology relies on natural gas combustion for high-temperature calcination. This paper proposes a process design for a solar-driven L-DAC system capable of capturing 1MtCO2/year. The proposed system uses a hydrogen fluidised solar calciner and is integrated with onsite CO2 conversion to sustainable aviation fuel (SAF) via a one-step direct CO2-Fischer-Tropsch synthesis (FTS). This work employs a combination of methodologies, including process modelling, simulation, scale-up and comprehensive techno-economic assessment. Key findings from this work include: (a) L-DAC with solar calciner harnesses thermal energy from sunlight, saving 63% electricity consumption and reducing onsite CO2 emissions by 59%; (b) The minimum selling price of SAF produced by solar-driven L-DAC with direct CO2-FTS is US$4.62 kg-1 which is cost-effective when compared to the stepwise process; (c) Sensitivity analysis based on geographical locations indicates that the most favourable deployment locations are low-risk countries with high solar irradiance and low hydrogen cost; (d) A detailed roadmap outlining the transition from first-of-a-kind (FOAK) plants to Nth-of-a-kind (NOAK) plants, demonstrates the potential for commercialisation of the technology to policymakers and industry investors. Thus, this study provides valuable insights into the development and operation of next-generation large-scale L-DAC with CO2 utilisation powered entirely by renewable energy.