Enhanced methane production by granular activated carbon: A review

Biomethane production by anaerobic digestion is an efficient technology to treat organic waste and produce clean energy. A growing number of studies has attempted to use carbon-based materials to enhance methane production performance. Granular activated carbon (GAC) is commonly used due to its low price and high efficiency. Moreover, the high conductivity of GAC favors direct interspecies electron transfer (DIET) coupled with CO₂ reduction to accelerate electromethanogenesis. GAC has also other properties such as porosity, which may influence microbial methanogenesis. But the comprehensive contributions to microbiome function were hardly summarized. Herein, we review the effects of GAC on anaerobic carbon mineralization, with focus on conductivity, adhesion, adsorption, pH buffering, and redox mediation. The findings are also applicable to natural ecosystems, such as soils and sediments. We also discuss modification of GAC by nanomaterials to enhance anaerobic performance. We suggest practical GAC applications in anaerobic digestion and energy conservation.