Work

Physicochemical properties of carbon-based materials enhance in situ biomethanation performances under organic overload

Year: 2025

Type: article

Abstract: Carbon-based materials gained attention for their potential to improve anaerobic digestion (AD) performance. Meanwhile, in situ biomethanation, where external H 2 is injected into the AD process to enhance the CH 4 content in biogas, is more subjected to process inhibition than AD while facing sudden changes in operational parameters. This study explored the effects of carbon-based materials on a semi-continuous in situ biomethanation process performance and stability. Two biochars and one granular activated carbon were tested at a concentration of 10 g·L -1 . The experiment was conducted in three phases: a one-week start-up phase in AD conditions, an 8-week phase of in situ biomethanation, reaching a steady state, and a 2-week overload phase performed to create instability during the in situ biomethanation process. All additives significantly mitigated process failure under overload conditions, with CH 4 production reaching 117 ± 16 vs 160 ± 16 NmL CH 4 ·d -1 on the first week of organic overload (control vs average of all supplemented conditions). Specifically, the use of GAC-BC, with the highest surface area, pore volume, and diameter, led to a tenfold increase in CH 4 production compared to the control in the overload phase. This improvement was associated with higher archaeal diversity and dominance of the Bacteroidales class. Conversely, the biochars, with lower surface properties, did not enhance microbial growth or improve final VFA consumption, resulting in final VFA concentrations similar to the control (11 g COD·L -1 ). These findings highlight the importance of surface properties in additives for mitigating VFA accumulation under stressed conditions during in situ biomethanation.

Source: Waste Management

DOI: 10.1016/j.wasman.2025.114869