Bio4gas : evaluation and analysis of wastewater treatment facilities in the scope of biogas production maximization and energy production optimization

The present work presents some of the results of five reports developed in the scope of optimization feasibility studies carried out at 6 small- and medium-sized wastewater treatment plants (WWTP) in Portugal. These 6 WWTP are operated by five companies that belong to the Águas de Portugal holding. The objective of the studies was twofold: to assess to which extent the production of biogas could be increased by means of operational modifications and/or by the implementation of co-digestion regimes; and also to simulate different scenarios for feed-in tariff of electricity taking in account energy prices calculated based upon the DL n.º 225/2007 of 11th May. In this way, several co-digestion scenarios were defined based upon standard available organic residues. The results obtained showed that the implementation of co-digestion regimes represent a considerable potential to increase the production of biogas, in some cases, over 600%. Even though, it was concluded that in some cases the costs of introducing new regimes of energy management were not supported by the increase of energy production, so a scale factor is associated to the revenues. This study contributed to the establishment of specific needs in terms of information management (digester operation, energy production/consumption, strategy for optimisation)