THERCHEM · Thermochemical pre-treatment technology for residues from breweries and other biomass to enhance anaerobic digestion

The aim of the project is the development of a thermochemical pre-treatment technology to increase the gas yield of brewers spent grains during an anaerobic digestion process. Thermochemical pre-treatment will be realised in a pressure vessel by addition of sulphuric acid. Pre-treatment of organic biomass will lead to a break down of the complex lignocellulose structure and release oligomeric/monomeric carbohydrate units which will then be better available for degradation by anaerobic digestion. This leads to improved utilization of the substrate and to a higher gas yield per tonne substrate inserted.After the pre-treatment the hydrolysate is digested in multi-stage biogas system. During anaerobic digestion H2S is formed out of sulphur containing compounds of the substrate by the anaerobic and facultative anaerobic bacteria. H2S is volatile and will be found in the biogas. Because of the fact that sulphuric acid is used in the pretreatment step, the H2S concentrations in the biogas will be increased. A clean up of the biogas is in all cases inevitable before feed in into e.g. a gas engine. The gas cleaning will be realised by using a trickle bed system. Here H2S will be converted into H2SO4 by microbiological desulphurisation process. The H2SO4 solution can be recovered for the thermochemical pre-treatment process.After lab scale investigation, a demonstration plant will be constructed and the process will be evaluated at two different breweries.For further application TherChem process will be tested on 5 different substrates in lab scale.