Innovative operational strategies for biogas plant including temperature and stirring management

Finding the optimum operational conditions (mainly temperature and stirring) inside the fermenters is crucial in the field of anaerobic digestion. This study was conducted to contribute to the research area of anaerobic digestion process optimization and is an example for other biogas plants to improve efficiency. The research aimed at finding the optimum operational conditions in a large-scale biogas plant located in Lower Saxony, Germany, which started operation in 2011. The optimization activities were performed by operating the fermenters under different operational conditions: the temperature inside the fermenters ranged between 40°C and 43°C, while applying several stirring scenarios. These changes led to an increase in specific electricity yield of 11.7% and a decrease in internal energy consumption of 10.4%. The total internal energy consumption of the biogas plant was in the range of 6.3-7.2% (the average monthly internal energy consumption was 6.7% in 2013 and 6.0% in 2014) from their own production, and 28% of this energy consumption was used by the stirrers before optimization. Therefore, finding the optimum operational conditions leads to high energy harvesting and lower internal energy consumption.