Wastewater heat has a hitherto untapped but large environmentally friendly potential. In the future, the wastewater infrastructure could be integrated into the regional energy supply and be another building block of the energy transition.

In the search for renewable energy sources, wastewater has increasingly come into focus as a possible resource in recent years. The existence of a relevant potential is also underlined by the fact that at the end of 2018, the European Commission explicitly recognized wastewater as such in the recast of the Directive on the Promotion of the Use of Energy from Renewable Sources.
The question thus arises as to what role wastewater can play as a building block of a future energy or heat supply. The following aspects are of central importance: What types of energy can be provided from wastewater? In which dimensions are these available? Which current and future utilization options are conceivable? What opportunities does this offer apart from climate protection? These questions were explored by the presenters and panelists on Tuesday, January 18, 2022, at the BOKU Energy Cluster event "Wastewater Energy as a Building Block of a Future Heat Supply".
Thomas Ertl, director of the Institute of Sanitary Engineering, Industrial Water Management and Water Protection (BOKU) emphasized that the wastewater industry in Austria has been striving for many years to optimize its plants in terms of energy efficiency and the use of renewable energy sources. "The integration of wastewater engineering infrastructure into local and regional energy supply can succeed, while ensuring the fulfillment of excellent water protection as a priority task of wastewater management," Ertl said.
This requires a transdisciplinary approach. "Solution approaches from the perspective of a single discipline generally no longer meet the challenges of our time," Florian Kretschmer, senior scientist at the same institute, said in his presentation. "The world has become more complex, and the answer can only be holistic, cross-sector concepts. The use of wastewater energy is a good example of this."
Georg Neugebauer of BOKU's Institute for Spatial Planning, Environmental Planning and Land Use Planning (IRUB) emphasized that "by tapping previously unused thermal potential, the use of wastewater for energy contributes to increasing energy efficiency in spatial structures." The use of thermal energy contained in wastewater supports the energy transition and contributes to climate protection, he said. "This is especially true if the heat pumps required for this purpose are powered by green electricity."
Spatial planning plays an important role in switching to renewable energies, he said, including the use of wastewater to generate heat. "Spatial planning can make significant contributions to being able to shape the energy transition. The topic of wastewater energy clearly shows how spatial aspects can influence a sustainable energy supply in a holistic view," was the summary of Gernot Stöglehner from IRUB.
In her contribution to the discussion, Ulrike Rabmer-Koller from WKO reminded the audience that in the residential sector alone, 73% of the energy demand is required for heating and cooling, including hot water preparation. "Technologies for using energy from wastewater are innovative and efficient solutions - and absolutely on the cutting edge," Rabmer-Koller said. Currently, mainly CO2-critical energy sources are used for this purpose, she said. "So renewable alternatives are urgently needed here. With wastewater heat, we have a huge environmentally friendly energy potential at our disposal, which can be used for both heating and cooling by means of state-of-the-art heat exchanger and heat pump technology."
"The current energy market situation and the associated geopolitical upheavals are a very stark reminder of the need for energy sources whose availability is guaranteed and whose price is calculable," stressed Christoph Wolfsegger of the Climate and Energy Fund. Energy generation from wastewater has low operating costs - so costs can be planned - and is available in large quantities throughout Austria, he said. "On top of that, the extraction is also an investment in climate protection. The Climate and Energy Fund has therefore developed a new funding program," Wolfsegger concluded.
BOKU Energycluster
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Information on the BOKU Energycluster: www.boku.ac.at/boku-energiecluster