Biogas from brewery waste In light of the EU's 2020 goals, there is an urgent need for new sources of renewable energy. Brewer's spent grain (BSG) is an appealing waste product for conversion to biogas, but a complex pre-treatment process is required to ensure its economic viability. Energy © Thinkstock The brewing industry can reduce its environmental impact and become more sustainable by properly converting the organic residues it generates into biogas. The project THERCHEM (Thermochemical pre-treatment technology for residues from breweries and other biomass to enhance anaerobic digestion) addressed this challenge. Consortium members developed a thermochemical pre- and post-treatment process for the anaerobic digestion of BSG. This process increased the yield of biogas and reduced the size needed for an anaerobic digestion plant. Although BSG has a high biogas potential, it is composed of lignocellulose that is difficult to degrade, thereby preventing exploitation of the feedstock's full potential. By thermochemically pre-treating the substrate at high temperatures and under the influence of an acidic catalyst, the complex structure of the substrate can be broken down. Project partners optimised the conditions (temperature, pressure and duration) for the pre-treatment of BSG with sulphuric acid (H2SO4). A post-treatment trickle bed was also designed to remove unwanted hydrogen sulphide gas by converting it into H2SO4. The laboratory prototype of the THERCHEM pre-treatment system increased yields from BSG by 30 % compared to anaerobic digestion alone. Researchers also built an industrial-scale pilot plant to be tested in two different breweries. In addition, scientists searched for other waste streams to which the technology could be applied. They also investigated ways to recycle H2SO4 back into sulphuric acid for reuse in the pre-treatment process. THERCHEM's process can be easily applied to existing plants and will help to make Europe's brewing industry more competitive by reducing costs and energy demands. The technology can also be offered to companies building biogas plants. Keywords Biogas, brewery, Brewer's spent grain, thermochemical, anaerobic digestion, sulphuric acid
