In-situ urea treatment facilitates wheat straw deconstruction and enhances syntrophy to boost methane production in high solids anaerobic digestion

16S rRNA amplicon sequencing coupled with functional inference, revealed selective enrichment of hydrolytic/fermentative taxa (e.g., Firmicutes, Bacteroidetes) and hydrogenotrophic methanogens (Methanobacterium, Methanoculleus), alongside upregulated up-regulated genes encoding carbohydrate-active enzymes, energy conserving pathways and methanogenesis.