The aim of this thesis is to investigate the effectiveness and economic feasibility of installing a biogas treatment plant and power-to-gas (PtG) technology at a wastewater treatment plant (WWTP) in Berlin. After extensive literary research, suitable technologies for the biogas treatment as well as the PtG technology were selected. The next step was to develop an energy tool to determine the best technological solution for the available biogas at the WWTP in question. Several scenarios were selected to be tested by the energy tool. In addition, the selected scenarios were analysed and evaluated from both economic and ecological standpoints. The results show that the use of a combined heat and power (CHP) plant along with a wind turbine or a biogas treatment plant is the best option for the selected WWTP. A biogas upgrading plant does not currently offer any environmental and economic benefits. However, the results of economic analysis also reveal that a biogas treatment plant is very cost-effective for digester gas. Compared to the current situation regarding the reference WWTP, the gas treatment technology requires approximately 75% less investment and approximately 85% lower operating costs. In addition, a biogas treatment can compete with a CHP plant if the 2017 CHP Act is considered and CHP subsidy is no longer granted. The results show that PtG technology is not an economically viable investment, since this technology is associated with very high investment costs and has no support scheme.