Digester gas produced at sewage plants is usually used in combined heat and power plants (CHPP) or boilers and only a minor portion is wasted in gas torches. In combination with an optimised power consumption of the sewage plant and the implementation of a co-digestion even an energy self-sufficiency of sewage plants is possible (Kolisch et al., 2009). Selling of the digester gas to external consumers or an upgrade to natural gas quality with subsequent injection into the natural gas grid might be alternatives to the conventional use. The mentioned options were investigated in consideration of the current energy consumption of sewage plants. The results show that the internal power production by a CHPP is currently most economic. However, the implementation of a local energy network in order to to deliver an energy surplus to external users can be feasible.

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