TNO 1/6 PRE-TREATMENT OF LIGNO-CELLULOSE WITH BIOLOGICAL ACID RECYCLING (THE BIOSULFUROL PROCESS)

A biomass pretreatment process is being developed based on contacting ligno-cellulosic biomass with 70 % sulphuric acid and subsequent hydrolysis by adding water. In this process, the hydrolysate can be fermented yielding ethanol, while the sulphuric acid is partly recovered by anion-selective membranes before the fermentation process, and partly via biological sulphate reduction in the anaerobic wastewater treatment plant. The produced sulphide is recovered as H2S gas and chemically converted (burned) into SO2 and SO3 (by which heat is recovered as well) and subsequently into sulphuric acid. In this unique approach, the sulphuric acid is recycled to a large extent. This process, the Biosulfurol process, is able to handle a wide variety of ligno-cellulosic biomass and does not need the addition of enzymes. In the project switchgrass and willow wood are tested as model substrates. 1. Bioethanol from ligno-cellulosic biomass The production of suitable commodities from biomass, ready to use in organic chemistry and energy supply, is a prerequisite for sustainable development. Carbohydrates such as hexoses and pentoses are attractive to be used as ra