Metagenomic approach reveals the mechanism of calcium oxide improving kitchen waste dry anaerobic digestion

[Display omitted] •CaO effectively promoted kitchen waste dry anaerobic digestion, and the maximum biogas was 656.84 mL/g.•CaO facilitated the production of dissolved organic matter and the transformation of VFA, thereby avoiding its negative impact on biogas production.•Metagenomics revealed the microbial mechanism underlying the CaO enhanced kitchen waste dry anaerobic digestion. In light of the characteristics of excessive acidification and low biogas yield during kitchen waste (KW) dry digestion, the impact of the calcium oxide (CaO) on KW mesophilic dry digestion was investigated, and the enhanced mechanism was revealed through metagenomic approach. The results showed that CaO increased the biogas production, when the CaO dosage was 0.07 g/g (based on total solid), the biogas production reached 656.84 mL/g suspended solids (VS), approximately 8.38 times of that in the control. CaO promoted the leaching and hydrolysis of key organic matter in KW. CaO effectively promoted the conversion of volatile fatty acid (VFA) and mitigated over-acidification. Macrogenome analysis revealed that CaO increased the microbial diversity in KW dry digestion and upregulated the abundance of genes related to amino acid and carbohydrates metabolism. This study provides an effective strategy with potential economic benefits to improve the bioconversion efficiency of organic matter in KW.