**6. Hydrothermal processing**

Biomass materials are typically wet and have a moisture content range of up to 95 wt.%. Biomass with more than 30 wt.% moisture content is not suitable for

#### *Advances in Bioenergy Production Using Fast Pyrolysis and Hydrothermal Processing DOI: http://dx.doi.org/10.5772/intechopen.105185*

pyrolysis. It needs to be dried before being suitable for pyrolysis, which requires a large amount of energy. It becomes a net energy consumption for biomass with high moisture content because the heat available from the biomass is less than the heat of moisture evaporation. Hydrothermal processing involves applying heat and pressure in the presence of water (subcritical or supercritical). Biomass typically with 70 wt.% or more water can be converted into carbonaceous end products without atmospheric oxygen. Water plays an active role as a solvent and reactant in hydrothermal processing. It is a promising technique for converting wet biomass into carbonaceous solids at relatively high yields without energy-intensive drying before or during the process. Depending on the operating conditions (temperature, pressure, and residence time), hydrothermal processes are classified as hydrothermal carbonization (HTC), hydrothermal liquefaction (HTL), and hydrothermal gasification (HTG) [2, 4].
