Gaining energy from spent grains

摘要

Brewers spent grains can be used to recover biogas by anaerobic decomposition. In a pilot scale plant spent grains were treated physically, chemically and biochemically. In order to make the process economically more attractive, the trials were executed to reduce the duration of the process and optimise the performance. Parameters to control the process efficiency are temperature, mixing, pH, residence time, filling levels, redox potential and the selection of microbiological cultures. A pilot scale plant was designed and used to accomplish the necessary steps for the generation of biogas and degradation of spent grains. The mechanical breaking up was performed with a ball mill. In the next step of hydrolyses organic high-molecular particles, mainly the carbohydrates are metabolised into short chain intermediate products. A number of variations of this process were tried to speed-up the following steps of methane generating and acidification. The material it then transferred to a methane reactor, where organic sludge is added as starter culture for the methanogenic process. The paper describes the process and technical means of enhancing the mechanical and chemical preparation leading to shorter process times. The results show that the process can be used as an environmentally friendly way to dispose spent grains economically, if other use is not feasible.