Comprehensive insights into hydrothermal pretreatment of rice straw from physicochemical structure, organic matter transformation and hydrolysate reuse

•Effect of various combination hydrothermal pretreatment on rice straw was explored.•Alkaline-thermal pretreatment retained more cellulose and hemicellulose in solid phase.•Re-aggregation and precipitation of lignin affected the pore structure.•Hydrolysate had the potential to be developed into foliar fertilizers and reused.