Surface-modified activated carbon for anaerobic digestion to optimize the microbe-material interaction

The anaerobic digestion of organic materials produces biogas; however, optimizing methane (CH₄) content within biogas plants by capturing carbon dioxide (CO₂) is one of the challenges for sustainable biomethane production. CH₄ is separated from biogas, which is called biogas upgrading for biomethane production. In this regard, in-situ CO₂ capture and utilization could be an alternative approach that can be achieved using conductive particles, where the conductive particles support the direct intraspecific electron transfer (DIET) to promote CH₄ production. In this investigation, a carbon nanotube (CNT) was grown over conductive activated carbon (AC). Then an iron (Fe) nanoparticle was anchored (AC/CNT/Fe), which ultimately supported microbes to build the biofilm matrix, thereby enhancing the DIET for CH₄ formation. The biogas production and CH₄ content increased by 17.57 % and 15.91 %, respectively, when AC/CNT/Fe was utilized. Additionally, 18S rRNA gene sequencing reveals that Methanosarcinaceae and Methanobacteriaceae families were the most dominant microbes in the reactor when conductive particles (AC/CNT/Fe) were applied. The proposed study supports the stable operation of biogas plants to utilize CO₂ for CH₄ production by using surface-modified material.