Sustainable wastewater treatment and energy supply is becoming increasingly relevant, especially in cities. This is also the case in Nuremberg. The Franconian metropolis has set itself big goals: By 2035, the city's municipal government is to become climate-neutral. Stadtentwässerung und Umweltanalytik Nürnberg (SUN) has a key role to play here: With its two large-scale wastewater treatment plants, it is the largest single consumer and the largest producer of electricity. Therefore, the topic of resource efficiency is an important component for achieving greater sustainability. A key role here is played by Wastewater Treatment Plant 1, which elaborately cleans the majority of the wastewater from more than 500,000 inhabitants of the metropolis mechanically, biologically and chemically before the treated water is discharged into the Pegnitz River. Matthias Germeroth has a great view from the roof of one of the five 35-meter-high digestion towers. But that's not why he comes here often. As energy manager at Stadtentwässerung und Umweltanalytik Nürnberg (SUN), Matthias Germeroth's tasks include optimizing the energy consumption of the facilities in the area of urban drainage and environmental analysis – and the wastewater plant's digestion towers are an important component in this.