**5. Conclusions**

Hydro-fractionation enhanced lignin removal and provided a higher yield of sugar-based chemical platform production from biomass. The three green processes including subcritical water extraction, supercritical water extraction, and steam explosion are practical for biomass treatment. With the adjustable water properties, subcritical and supercritical water extractions are attractive tunable techniques for various bio-based compound extractions while the rapid volume expansion of water in steam explosion can destroy the high crystallinity of biopolymers. In addition, some technical feasibility in terms of energy consumption and reactor system as well as economic feasibility should be taken into consideration for future advancement.
