Assessing the opportunities for applying deep eutectic solvents for fractionation of beech wood and wheat straw

Deep eutectic solvents are alternative solvent systems for biomass processing. Eutectic mixtures of lactic acid:alanine (in a molar ratio of 9:1), lactic acid:betaine (2:1), lactic acid:glycine (9:1) choline chloride:glycolic acid (1:3) and choline chloride:ethylene glycol (1:2) were tested. The characteristic properties (density, viscosity and conductivity) of these lactic acid or choline chloride mixtures were investigated. The 5 eutectic mixtures were then applied as delignifying agents to samples of wheat straw and beech wood sawdust to investigate their behavior and efficiency. The findings demonstrated that, in the case of wheat straw, the eutectic mixture of lactic acid and alanine was the most effective delignification agent as it removed 23.7% of the lignin from the sample. The most efficient eutectic solvents for the delignification of beech wood were found to be the mixtures of lactic acid:alanine, with an efficiency of delignification of 14.4%, and choline chloride:glycolic acid (15.4%).