Towards scale-down of anaerobic digestion – aspects of scaling, process reproducibility, stability, and productivity

Anaerobic digestion is a process in which microorganisms work in symbiosis to produce biogas, a mixture of methane and carbon dioxide. Methane production is relevant, as methane can be used as a fuel for vehicles and for electricity and heat generation. The anaerobic digestion process is not yet fully understood, although it has been studied for more than a century. Due to the complexity and risks of performing industrial-scale experiments, many studies have been conducted in laboratory-scale digesters so far. This work aimed to determine which parameters affect process stability and productivity and to identify scale-dependent parameters. The results show that the influence of a specific substance on the process can be studied on the laboratory scale. However, physico-chemical parameters also have to be considered, as they affect the reaction rates and gas equilibria and thus determine when potential process inhibition will start. This work can be used as a basis for process scaling and understanding differences in anaerobic digestion on different scales.