Determining Conditions of Intermittently Fed Digesters from Biogas Production Rate Data

As the contribution from renewable energy to the power grid increases, biogas plants could profit from on-demand production. Flexible feeding can supplement gas storage for further benefits. Changing to flexible feeding introduces transient events to the feeding, and by monitoring the system response to the feeding transients it is possible to gain information about the system stability. Testing was performed at the laboratory and pilot scale to investigate the response characteristics. A statistical analysis was carried out to assess the response to feeding events and make an estimate of the system stability. This analysis was then used as the input to a proportional integral derivative controller for controlling the feeding rate for an anaerobic digestion model No. 1 simulation.