Blueprint for sector coupling - A sewage treatment plant becomes an innovation driver of the energy transition with green hydrogen

Lower Saxony's oldest sewage treatment plant will soon not only supply Hannover with clean water, but also public transport with green hydrogen. In the large-scale modernisation concept, Stadtentwässerung Hannover wants, among other things, to drastically reduce its own energy consumption of the sewage treatment plant in Herrenhausen and produce green hydrogen itself. The Lower Saxony Ministry for the Environment, Energy, Building and Climate Protection is funding the investment and research project with 6.37 million euros.  

"It is with great pleasure that I support this lighthouse project in the Hannover Region. Hydrogen is the fuel of the energy transition. It shows in an exemplary way how the transformation of Lower Saxony's economy towards climate neutrality brings forth new cooperations and opportunities. In the future, we will not only need hydrogen production on a large, industrial scale, but also within the framework of such decentralised projects if we want to meet the demand for the decarbonisation of our economy and thus make the location and the jobs here future-proof. The project also has enormous charisma for municipal operations throughout Germany," said Lower Saxony's Environment Minister Olaf Lies, who handed over the funding today at the "Future Forum of the Water Industry" in Hanover.

For the City of Hannover, this project is an important milestone. "As the state capital of Hannover, we focus on sustainability and resource conservation in the accomplishment of our tasks and make this objective the basis of our actions. This includes investing in forward-looking technologies. We are very proud of this creative and innovative project in Hannover. It shows how municipal partnerships bring us a whole step closer to our goal of climate neutrality in Hannover by 2035," said Belit Onay, Lord Mayor of the City of Hannover.

What is particularly forward-looking about this lighthouse project is the sector coupling. For example, the municipal wastewater treatment plant wants to primarily use the oxygen for wastewater treatment that is produced as a by-product during the production of hydrogen. At present, this is extracted from the ambient air in most sewage treatment plants with turbo compressors - a process for which a large part of the energy consumption of the sewage treatment plant is necessary. In addition to the aeration basins, the project focuses on filtrate water and ozone in a fourth purification stage. The hydrogen produced is to be used, among other things, to power buses operated by ÜSTRA and regiobus Hannover GmbH from 2023 in order to reduce emissions in Hannover's public transport system. "We are relying on hydrogen technology to enable sustainable and future-proof local public transport in Hannover. With Stadtentwässerung Hannover we have the ideal partner to source green hydrogen locally," said Elke Maria van Zadel, CEO of ÜSTRA and regiobus Managing Director. The waste heat generated during the electrolysis process is fed into the district heating network. Part of the project is also the development of an intelligent plant control system for electrolysis systems by the partners Aspens GmbH and Leibniz Universität Hannover.

Only electricity from renewable energies is used as the energy source for electrolysis, so that the entire value chain is_CO2-neutral. Furthermore, Stadtentwässerung uses process water instead of valuable drinking water for hydrogen production, thus making an additional contribution to sustainability. "As a municipal company, we bear responsibility and invest in the sustainable future of the state capital of Hannover. Our goal is quite clear: we want to ensure a clean water cycle while conserving resources and using the most modern methods, thus ensuring water quality for around 750,000 people in Hannover and the surrounding area," said Operations Manager Matthias Görn.