Demand-driven biogas production by flexible feeding in full-scale - Process stability and flexibility potentials

•Flexible biogas production demonstrated in full-scale by demand-oriented feeding.•Savings in necessary gas storage volume of up to 65% by flexible feeding.•Intraday dynamic in biogas production rate of up to ±50% based on average.•Intraday alteration of methane, carbon dioxide, acid concentrations and pH- values corresponding to the flexible feeding.•Comparison with laboratory-scale results based on CSTR and hydrolysis/fixed bed configuration.

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.