Multivariate insights into enhanced biogas production in thermophilic dry anaerobic co-digestion of food waste with kitchen waste or garden waste: Process properties, microbial communities and metagenomic analyses

•Co-digestion promoted biogas production and the maximum OLR tolerance.•Co-digestion reduced ammonia nitrogen inhibition and VFAs accumulation.•Co-digestion enriched key hydrolytic bacteria at high OLRs.•FW and KW co-digestion strengthened the methane metabolic pathway.•FW and GW co-digestion increased ABC transporters abundance.