The constantly increasing political and social demands for an environmentally friendly use of raw materials and resources leads to technical improvements and the development of new systems at a municipal wastewater treatment plant. The wastewater association Hall in Tirol - Fritzens has already improved its ecological performance by establishing the collection and utilisation of used cooking oil. The focus of this master thesis is on the further optimisation of the used cooking oil utilisation line at the site. In doing so, the process boundary is not only limited to the current utilisation method, but new utilisation options are also considered. A closer look at the used cooking oil utilisation line reveals several possible solutions for the utilisation of used cooking oil, such as combustion in a CHP plant, processing into biodiesel or as a fuel additive, biological methanisation and utilisation in the CHP plant, and the production of soaps. By comparing the utilisation options in view of the conditions on-site, biological methanisation was determined to be the most promising process. In the utilisation process of biological methanisation of used cooking oil, several ideas are implemented, such as increasing the spatial load, decoupling the municipal wastewater treatment and a utilisation method at the site. In order to be able to examine the process of biological methanisation of used cooking oil more closely, several experiments were carried out with used cooking oil and co-substrate in a custom-built reactor. The aim is to control a highly loaded biological process for the utilisation of used cooking oil.