Biochar accelerates methane production efficiency from Baijiu wastewater: Some viewpoints considering direct interspecies electron transfer

•Biochar could significantly improve AD performance of Maotai flavor Baijiu wastewater.•Joint modification could significantly enhance the electron donating capacity.•Enrichment of electroactive microorganisms was a prerequisite for enhancing the DIET.•Syntrophomonas had a tenfold increase in relative abundance by biochar.•The assistance of biochar changed the pathway of methane production. The low pH of Maotai-flavor Baijiu wastewater (MFBW) adversely affects its anaerobic digestion (AD) performance, resulting in low AD efficiency. Here, coconut shell was used to produce biochar. The characteristics of biochar were regulated through acid, alkali, and magnetic modification, respectively. Biochar and modified biochars were applied to assist the AD of MFBW. The results showed that biochar could significantly increase methane yield by 220.8 %–241.7 % with the corresponding soluble chemical oxygen demand (sCOD) degradation increasing by 52.3 %–57.5 % (p