Build and Optimization of Trickle Bed Reactor for the use in Ex-situ Biomethanation Using Biochar as a Novel Carrier

The urgent global transition toward renewable energy systems requires scalable and efficient technologies for carbon-neutral fuel production and energy storage. Biological methanation, particularly in trickle bed reactors (TBRs), has emerged as a viable method for converting hydrogen (H2) and carbon dioxide (CO2) into methane (CH4), a grid-compatible renewable fuel. This Ph.D. research focused on the design, optimization, and evaluation of a lab-scale TBR system employing novel biochar and conventional K1 media as packing materials for ex-situ biomethanation under mesophilic conditions. The study comprehensively addressed mass transfer limitations, carrier material surface area, gas retention time (GRT), and intermittent liquid recirculation (ILLR) to enhance methane production and process stability.
Results from abiotic testing revealed that biochar had superior mass transfer performance, exhibiting a high surface area of 2437 m²/m³ and kLa of 658 h⁻¹, compared to K1 media with 950 m²/m³ and a slightly lower kLa of 618 h⁻¹. However, under biotic conditions, K1 media outperformed biochar in terms of methane production and hydrogen conversion, likely due to its higher liquid-film mass transfer coefficient (kL > 0.6 h⁻¹ per m²/m³) versus biochar (~0.25 h⁻¹ per m²/m³). These findings underscore the importance of distinguishing between abiotic and biotic mass transfer mechanisms and point toward the need for further research into liquidfilm dynamics in biological systems. The study contributes foundational data for engineering high-efficiency TBR systems for renewable gas storage and CO2
recycling.