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Biogas plants have the potential to provide demand-oriented electricity to compensate the occurring divergence between energy demand and supply by uncontrollable sources like wind and solar power. The general flexibility of the biological process is proofed in particular under full-scale conditions for a biogas production according to the grid demand. A model predictive control was developed to calculate feeding strategies in order to fulfill a demand-oriented gas utilization timetable. Full-scale experiments showed a high intraday flexibility in a wide range of the average gas production and high process stability in reaction to pulse feeding. The gas storage demand could be reduced significantly compared to the common constant feeding operation.

For future energy supply systems with high proportions from renewable energy sources, biogas plants are a promising option to supply demand-driven electricity to compensate the divergence between energy demand and energy supply by uncontrolled sources like wind and solar. Apart expanding gas storage capacity a demand-oriented feeding with the aim of flexible gas production can be an effective alternative. The presented study demonstrated a high degree of intraday flexibility (up to 50% compared to the average) and a potential for an electricity shutdown of up to 3 days (decreasing gas production by more than 60%) by flexible feeding in full-scale. Furthermore, the long-term process stability was not affected negatively due to the flexible feeding. The flexible feeding resulted in a variable rate of gas production and a dynamic progression of individual acids and the respective pH-value. In consequence, a demand-driven biogas production may enable significant savings in terms of the required gas storage volume (up to 65%) and permit far greater plant flexibility compared to constant gas production.

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