Spiral-Pipe Gas Anaerobic Digester

The reduction of carbon dioxide to methane using hydrogen is an important process in biogas production. However, designing gas anaerobic digesters (GADs) based on this reaction presents several challenges. In this study, we developed an innovative spiral-pipe gas anaerobic digester (SGAD) to increase the displacement distance between the bubbles, thus prolonging the gas retention time and facilitating the reduction of CO₂ to CH₄ via H₂. The process was successfully demonstrated by using a CO₂/H₂ ratio of 1:3 and a gas-feeding rate of 3.9 L L_r ^-1 d^-1. During the experiment, more than 98% of the CO₂ and 96% of the H₂ were consumed, resulting in biogas containing ca. 86-96% CH₄. Additionally, we applied our proposed evaluation methodology for assessing GAD performance to evaluate the performance of the SGAD. This methodology serves as a reference for evaluating and designing GAD systems. The innovative design of the SGAD and the corresponding evaluation methodology offer new insights into the design of reactors.