Conducting a Transient-State Anaerobic Digestion Process at Start-up Phase of a Biogas Plant

In a biological start-up phase, caused by the opening of digesters for technical revisions, the biological process collapsed. The digesters from an on-farm biogas plant were incorectly fed during the start-up phase with high-organic contents feedstock, including high carbohydrate substrate (silage, milled cereals). As a result of this type of operation, the values of the essential parameters that indicating the equilibrium state of the microbiological and biochemical process have deteriorated. Samples were taken and analyzed in the laboratory. During a two-months period of monitoring and conducting the anaerobic digestion process, a steady state of the biotechnological was reached. Subsequently, mixture recipe for feeding the digesters after reaching the neutral pH and the maximum FOS/TAC value of 0.4, have been established according to the materials available on the farm. Cow manure will constitute the main substrate with important microorganic input, this orgnic material being available in large quantities in biogas operator’s own farm. Maize silage is available as the main substrate with high energy input. To increase economics of the process, it is recommended to feed the digester with residual raw materials, available in the area of the biogas plant operator.