Dimension-dependent effects of bio-based carbon materials on alleviating acid inhibition and enhancing biomethane production in anaerobic digestion

Anaerobic digestion (AD) is a promising technology for treating straw-based waste and resource recovery, yet acid inhibition from rapid hydrolysis remains a challenge. This study is the first to systematically compare the effects of different dimensional carbon materials on anaerobic digestion under acid-inhibited conditions. Results indicated that these additives enhanced the enrichment of mutualistic microorganisms, acid producers, and hydrogenotrophic methanogens, thereby intensifying direct interspecies electron transfer and boosting biomethane production (with a 3.3%-14.3% increase compared to the control). Graphene oxide, owing to its abundant oxygen-containing functional groups, significantly shortens the digester startup time by 44.6%, while increasing the maximum biomethane yield to 177.1 mL/g VS (a 14.3% improvement) and the peak biomethane production rate to 9.0 mL/g VS/d (a 9.1% improvement), compared to the control. These enhancements were primarily attributed to the markedly accelerated conversion of volatile fatty acids induced by graphene oxide addition, which effectively alleviated acid inhibition and improved the system's buffering capacity and operational stability. This study provides a theoretical basis for mitigating acid inhibition using various carbon materials and underscores their vital role in AD.