Depolymerization of lignin in sub — and supercritical water (pc > 22.1 MPa; Tc > 374 °C) lead to extensive lower molar mass fragments, dealkylation and deme — thoxylation, but a part of these fragments tend to cross-link in larger fragments. The economic viability of this process is severely controlled by the extent to which the heat is recovered from the effluents. The yield of monomers is positively correlated with base concen­tration added with maximum yield of one-third of the initial lignin. Low molecular weight fraction yields increased with longer reaction times in supercritical water without catalysts at 350—400 °C and 25—40 MPa. The water-soluble fraction consists of catechol (28%), phenol (7.5%), and cresols (11%), suggesting the cleav­age of both ether and carbon—carbon (Wahyudiono et al., 2008). Addition of phenolics (e. g. phenol and p-cresol Okuda et al., 2004a, b, 2008; Fang et al., 2008) gives a complete depolymerization of lignin into dimers without char formation. Phenol and p-cresol depressed

cross-linking reactions due to entrapment of reactive fragments, like formaldehyde, and capping of active sites like Ca in the lignin structure.