In industrial paper-making processes, organosolv is a pulping technique that uses an organic solvent to solubilise lignin and hemicellulose.
It has been considered in the context of both pulp and paper manufacture and biorefining for subsequent conversion of cellulose to fuel ethanol.
Organosolv solvents are easily recovered by distillation, leading to less water pollution and elimination of the odour usually associated with kraft pulping.
Organosolv pulping involves contacting a lignocellulosic feedstock such as chipped wood with an aqueous organic solvent at temperatures ranging from 140 to 220 °C.
[4] Organic solvents are almost always used as a mixture with water for process considerations such as reducing the vapour pressure and lowering the pH in order to also solubilise hemicellulose.
The effect of temperature (120–180 °C), residence time (30–90 min), and ethanol concentration (45–75% v/v) on the hydrogen yield, residual biomass, and lignin recovery was investigated using RSM.
[10] The recovery of lignin from ethylene glycol organosolv pulping can be effected by 3 times dilution with acidified water.
[13] The Alcohol Pulping and Recovery (APR) process treats wood in 3 stages, each using increasingly cleaner solvent.
It is said that the technology can be used to exploit small regions of hardwood resource that could not support a modern sized kraft mill.
Organic acids are collected by concentration of the cooking liquor and then lignin is precipitated by adding water and high pressure filtration.
The so-called "formico" technology incorporates full biosolvent recovery by evaporation and distillation in order to have a closed-loop process with minimal water need and effluent discharge.
Part of the hemicelluloses react to furfural and acetic acid, which are recovered in the distillation process to high-grade commercial products.
With a 2 ton/day production facility located in Wausau, Wisconsin, AST can also make high quality pulp, glucose, fructose and lignin.