Understanding the dynamic interplay of CH4/CO2 ratio in electrified reforming of biogas to renewable methanol production: A pilot plant story

This study demonstrates syngas production from direct biogas reforming for methanol production using electrified steam methane reforming (eSMR). Sourcing biogas directly from an anaerobic digester introduces complexity due to its fluctuating nature, which changes the CH₄/CO₂ ratio over time. These fluctuations affect syngas quality, a critical parameter for downstream methanol synthesis. To address this, a feed-forward control system was implemented to maintain stable oxygen-to‑carbon (O/C) and hydrogen-to‑carbon (H/C) ratios prior to the eSMR unit by dynamically adjusted the steam and H₂ flow rates based on the CH₄/CO₂ ratio. The control system demonstrated stable syngas production, as expected from thermodynamics, even with 10 % fluctuations in CH₄ concentration. It achieved a syngas module (MeOH module) of 1.99 ± 0.01, suitable for steady-state methanol synthesis. In comparison, without the control system, the MeOH module would have been 1.9 ± 0.2. The control system consistently performed well in maintaining the targeted MeOH module under conditions of 900–1050 °C, 6–10 barg, and normalized steam-to-hydrocarbon ratios of 1.3–2.3. This work demonstrates that the feed-forward control system combined with the thermodynamic selection of H/C and O/C is a robust and flexible control strategy in accurate prediction and stable syngas production. Electrified steam biogas reforming and electrolyzed H₂ enable methanol production using only biogenic carbon, water, and power. If the power is renewable, this approach supports biogas valorization, high carbon utilization and near-zero carbon emissions in the production of renewable methanol. • Electrified steam biogas reforming for syngas manufacturing demonstrated for methanol synthesis (eSMR-MeOH) • Predictable syngas production achieved via O/C and H/C operation • Feed-forward control dynamically adjusted steam and H₂ to counter biogas fluctuations. • Stable syngas production at up to 1050 °C and steam-to-hydrocarbon ratios down to1.3. • eSMR-MeOH enables renewable methanol production with high carbon utilization and near-zero emissions