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. (C) 2020 Elsevier Ltd. All rights reserved.