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 SO 2 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, willow wood and bagasse are tested as model substrates. The utilization of bagasse can be of interest for the sugar industry and the production of monosaccharides can be regarded as an alternative way to produce sugars from sugarcane residues.