Scaling up biological methanation in trickle bed reactor: performance and techno-economic feasibility analysis

Biological methanation in trickle bed reactors (TBRs) offers a sustainable pathway for converting carbon dioxide (CO₂) and hydrogen (H₂) into low-carbon methane (CH₄). This study bridges the gap between lab- and industrial-scale deployments by scaling a microbial consortium-optimized TBR system 100-fold (from 1 L to 100 L). Operating under thermophilic conditions (55^οC) for 364 days of continuous pilot-scale operation, the pilot system achieved a CH₄ purity of greater than 95% at gas retention times (GRTs) as low as 1 h, with peak methane concentration (99.7% CH₄) at a 3-hour GRT. Key challenges included metabolic water dilution and low H₂ conversion, mitigated by adjusting hydraulic loading rates and nutrient replenishment. Trace metal analysis confirmed the sufficiency of Fe/Ni/Co, although dilution effects emerged at high water production rates. Techno-economic evaluation of the assessed PtM system revealed a baseline production cost of 2.47 €/kg LNG, with performance strongly governed by electricity price and electrolyser efficiency. Under low-cost renewable electricity, bio-LNG cost could fall to ∼ 1.7 €/kg, underscoring the competitiveness of biological methanation.