**2.4 Liquefaction**

Other than torrefaction, pyrolysis, gasification, an alternative thermochemical process for converting biomass to biofuel is liquefaction [17]. In order to form bio-crude oil, biomass must be hydrogenated and thermally disintegrated at high

**Figure 3.** *Illustration of torrefaction process.*

*Production of Biochar from Oilseed Residue (Deoiled Cakes): State-of-the-Art DOI: http://dx.doi.org/10.5772/intechopen.114228*

pressures. In the process of hydrothermal liquefaction, solid waste contains lots of moisture and it is transformed into bio-crude oil in the presence of some catalysts [18]. The temperature and pressure ranges for liquefaction generally fall within the ranges of 240–380°C and 5–30 MPa, respectively [11]. In **Figure 5**, a view of liquefaction process is reported.

**Figure 5.** *Simple flow diagram of liquefaction.*
