Mesophilic anaerobic bacteria rely on a relay degradation process to convert chitin-containing waste into methane. This study investigated the effects of biochar on the anaerobic digestion (AD) of shell waste (SW) and explored the impact on methane yield in the anaerobic co-digestion of food waste with SW. The biochar (BC) added for AD of SW increased the methane yield by 18.45 %. Compared to the inoculum, the relative abundance of Pseudomonas decreased by 72.69 % in the SW group and 91.18 % in the SW + BC group. The second experiment with the same total volatile solids (VS) content showed that the group with an VS of 20 % SW had the highest methane yield, significantly surpassing the yields of the 0 % SW group by 25.24 %. The results presented in this study demonstrated that SW synergistically promotes methane yield in the AD of food waste by reducing lag time and facilitating methanogenic archaeal community colonization.