Biohydrogen production from co-digestion of cow manure and waste milk under thermophilic temperature

► We studied biohydrogen production from co-digestion of cow manure and waste milk. ► Heat pretreatment alone could not successfully inhibit methanogenesis. ► Increasing waste milk concentration increased butyrate accumulation and H2 yield. ► Optimal M:WM and OL were of 30:70 (VS/VS) and 40 g VS L−1 respectively. ► H2-producing conditions enabled reduction of >90% of antibiotic resistant bacteria.