Enercity Commences Operations at Sewage Sludge Treatment Plant

The heating transition is making great strides: enercity today commissioned a sewage sludge recovery plant in Hannover. It is the first newly built replacement facility for the first unit of the coal-fired power plant in the Stöcken district, which is set to be taken offline by the end of 2024. Enercity is expected to phase out coal entirely by the end of 2026. With the district heating extraction from the waste-to-energy plant in the Lahe district, which was completed three years ago, up to 30 percent of Hannover’s district heating demand can now be met in a climate-neutral manner. 

District heating for up to 15,000 customers

The new facility can thermally treat approximately 130,000 tons of dewatered sewage sludge per year. This generates up to 56 million kilowatt-hours of district heating, covering the annual heating needs of up to 15,000 customers in the Enercity service area. It is the first single-combustion plant to feed into a municipal heating network. The project’s investment volume totals approximately 70 million euros.

The project also strengthens the regional circular economy

“With this new facility, Enercity is leading the way in advancing the heating transition in Hannover. We are getting a little closer to the goal of climate-neutral district heating,” says Belit Onay, Mayor of the state capital of Hannover. “And not only that: Hannover’s sewage sludge will be put to good and sustainable use locally in the future. We are harvesting heat and are well-prepared to recover the valuable raw material phosphorus from the ash in the future as well.”

Enercity is transforming its entire energy production toward climate neutrality 

“We are maintaining a rapid pace in our phase-out of coal so that one-third of Hannover’s residents can heat their homes with climate-neutral district heating by 2027,” says Enercity CEO Dr. Susanna Zapreva. “This plant is the next step in the transformation of our entire energy production toward climate neutrality. In just over three years, 75 percent of our district heating will already be green, and by 2030, more than 90 percent of our total electricity generation will be green.”

The plant removes pollutants and enables the recovery of phosphorus 

Through thermal recovery at the facility, which runs exclusively on sewage sludge, this waste product provides real added value for the people of the Region Hannover. Previous disposal methods, such as spreading on agricultural fields, are becoming increasingly restricted. The plant enables the recovery of phosphorus from sewage sludge ash, which will be required by law starting in 2029. Phosphorus is a finite resource and is needed, for example, in fertilizers. In addition, Enercity uses the plant to remove other pollutants contained in the sewage sludge, thereby protecting soil and groundwater.

State-of-the-art environmental protection technology

The facility is equipped with a highly efficient flue gas cleaning system. As a result, emission levels—such as dust and nitrogen oxides—are well below the legal limits. In the receiving hall, the delivery of sewage sludge is carried out in a closed area. Wastewater generated during the process, as well as condensed water vapor produced during the drying of the sewage sludge, is thoroughly treated before being discharged into the wastewater system. 

(Published: July 6, 2023)