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Potato pulp waste is a potential biomass material and easily acidified substrate for anaerobic digestion. The present study evaluated the methane yield and microbial community resulted from biochar amendment for the co-digestion of potato pulp waste and dairy manure at different feed-to-inoculum ratios (2:1, 1:1, 1:2, and 1:3) and potato pulp waste to dairy manure ratios (4:0, 3:1 and 1:1). The results indicated that the digesters with a high feed-to-inoculum ratio (2:1, 1:1) and without biochar lead to volatile fatty acid accumulation and process failure, whereas the addition of biochar and/or co-digestion can increase the buffer capacity and improve the digestion efficiency. The biogas and methane yields of the digesters with biochar were 1.1–2.8 and 1.4–5.3 times higher, respectively, than those without biochar. The maximum biogas and methane yields of 476 and 200 mL/g TS, respectively, were achieved with a feed-to-inoculum ratio of 1:2, potato pulp waste to dairy manure ratio of 4:0, and biochar addition. Biochar and co-digestion can also enhance the relative abundance of the bacterial community. Methanomicrobiales and Methanosaetaceae were the main methanogens present in the anaerobic digestion of PPW. This paper provides a theoretical basis of easily acidified substrates used for biogas production. • Potato pulp waste is a potential feedstock for biogas production but easily acidifies. • Effects of biochar and co-digestion on anaerobic digestion were evaluated. • Different ratios of feedstocks and feed to inoculum were considered. • Diversity of the microbial community was analyzed. • Biochar and co-digestion increase the buffer capacity and digestion efficiency. [ABSTRACT FROM AUTHOR]