Diesel-soluble lignin oils and methods of their production

A process for production of liquid lignin fuel comprising the steps of:

• (i) providing lignin-rich solid residual from lignocellulosic biomass feedstock that has been hydrothermally pre-treated and subsequently subjected to cellulase enzyme hydrolysis,
• (ii) subjecting the lignin-rich solid residual to solvolysis in supercritical ethanol in the absence of an effective amount of added substance other than primary solvent which either acts as a hydrogen-donor reactant in hydrogenation of lignin residual during solvolysis, or which catalyses hydrogen-donor activity of the primary solvent, and in the absence of an effective amount of added hydrogen donor co-solvent, and in the absence of an effective amount of one or more supported or unsupported reduced metal or transition metal oxides, and in the absence of an effective of amount of added hydrogen gas (H2);
• and
• (iii) recovering product oil from the liquid product of the alcohol reaction mixture as the separated heavy fraction having boiling point greater than 120° C. remaining after distillation of one or more light fractions having boiling point beneath 120° C.,
• wherein the water content, w/w ratio of solid to solvent, temperature and reaction period for solvolysis are selected so as to produce a product oil having O:C ratio of 0.20 or less.