Managing intermittency of renewable power in sustainable production of methanol, coupled with direct air capture

Coupling direct air capture (DAC) with methanol production is a technically attainable opportunity for CO2 capture and utilisation (CCU). The process, known as power-to-methanol (PtM), consumes large amounts of renewable electricity for water electrolysis and DAC. However, the time-variability of renewable power remains a major challenge. Here, we consider erecting a wind farm as part of a PtM facility and propose using four parallel reactors to adjust the methanol production according to daily wind power generation, which we model for 90 onshore and offshore locations with real-world data. Batteries and reserve storage of compressed H2 and CO2 allow methanol production during near-zero availability of wind power. We investigate different operation strategies, aiming to either minimise the reserve storage or maximise production, ultimately finding minimised storage as more cost-effective. The resulting selling price of methanol from a plant powered by an onshore wind farm is $1400 per tonne, rising to $2200 for offshore wind power because of higher farm installation costs. However, with a well-located wind farm, coupled with improvements to DAC, electrolysis, and catalysts, the selling price falls as low as $300 per tonne of methanol, reaching parity with fossil fuel-derived methanol. Purchasing stable grid power for PtM avoids issues of intermittency, and results in a lower methanol selling price of $960 per tonne, falling to $340 with process improvements. However, life cycle assessment (LCA) shows the global warming potential (GWP) of the grid-based cases is no better than producing methanol from natural gas; whereas, wind-powered DAC-PtM delivers net-negative GWP between -760 and -1240 kgCO2eq. per tMeOH, demonstrating successful CCU. This study leverages worldwide wind data, process modelling, and life cycle assessment to reveal the potential of dynamic methanol production for atmospheric CO2 drawdown, while handling power intermittency and minimising reliance on reserve storage.