Biogas productivity by co-digesting Taihu blue algae with corn straw as an external carbon source

► Taihu blue algae are good feedstocks for biogas production. ► Co-digestion could be an option for efficient methane production and waste treatment. ► The increased methane production from co-digestion is attributed to synergistic effects. ► Increasing cellulase activity from corn straw could promote the methane production. A batch anaerobic test was conducted to evaluate the effects of adding high carbon content of corn straw to the digestion of Taihu blue algae to attain an optimal C/N ratio for higher methane yield. The addition of corn straw in algae at a C/N ratio of 20/1 increased methane yield by 61.69% at 325mLg−1VS−1 (compared with 201mLg−1VS−1 of algae digestion alone), followed by C/N ratios of 16/1 and 25/1, all operated at 20gVSL−1 and 35°C. The results suggest the optimal C/N ratio for co-digestion of algae with corn straw is 20/1. The findings could offer options for efficient methane production and waste treatment.