Process Water Recirculation during Hydrothermal Carbonization of Waste Biomass: Current Knowledge and Challenges

Hydrothermal carbonization (HTC) is considered as an efficient and constantly expanding eco-friendly methodology for thermochemical processing of high moisture waste biomass into solid biofuels valuable carbonaceous materials. However, during HTC, a considerable amount organics, initially present in the feedstock, are found process water (PW). PW recirculation attracting increasing interest hydrothermal field it offers potential to increase carbon recovery yield while hydrochar energy density. can be viable method valorization reuse HTC aqueous phase, both by reducing additional used maximizing from liquid residual fraction. In this work, effects recirculation, different starting biomasses, on properties hydrochars phase products reviewed. The mechanism production evolution steps discussed, highlighting possible pathways which could enhance recovery. Challenges presented research opportunities proposed, showing how economic viability contributing mitigating environmental impacts.