Carbon bioaccessibility-driven nitrogen release compensates for extremely high C/N ratio in lignocellulose anaerobic digestion
Year: 2026
Type: article
Abstract: High C/N ratios induced by alkali pretreatment in lignocellulosic biomass are widely considered detrimental to anaerobic digestion (AD). Paradoxically, this pretreatment has been observed to enhance methane production from such feedstocks without any exogenous organic nitrogen supplementation. However, a systematic understanding of this counterintuitive phenomenon remains elusive, particularly from the integrated perspective of C/N ratio, substrate bioaccessibility, and microbial metabolic activity. To address this gap, we conducted mesophilic AD experiments on hybrid Pennisetum (HP) and corn stover (CS) using alkali delignification to regulate bioaccessibility, and tracked functional microorganisms and metabolic pathways. Despite the extreme high C/N ratios (1708.40∼2151.00), both pretreated substrates achieved substantially higher methane yields (394∼434 mL/g VS) than untreated controls. This enhancement stemmed from increased bioavailable carbon, which supported microbial growth and hydrolytic enzyme synthesis, thereby boosting substrate conversion. Consistently, nitrogen-degrading populations proteolytic Proteiniphilum and nucleolytic Izemoplasmatales were enriched by 3.75∼5.36 folds and 14.80∼21.60 folds, respectively, accompanied by corresponding annotated hydrolase increases of 27.84%∼31.42% and 8.76%∼9.36%. These findings suggest that enhanced substrate bioaccessibility may facilitate the degradation of nitrogen-containing organic matter in the inoculum, potentially contributing to nitrogen recycling within the AD systems. However, the release and subsequent reutilization of necromass-derived nitrogen remain to be directly verified. Our findings reveal that inoculum-derived nitrogenous compounds can improve mono-AD performance of high-C/N feedstocks, offering a strategy to simplify operation and regulation of lignocellulosic AD systems.
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,400
OpenAlex ID: W7225614094