E.ON turns sewage into a valuable resource with GEA heat pump technology


Reducing greenhouse gas emissions from the heating supplied to Malmö in Sweden required a sea change in thinking by a major power company, using GEA’s energy-efficient heat pumps. After testing the water, a sewage plant was considered the best source for heating homes in an innovative approach for turning waste into usable energy.

Carbon footprint goal

Under the banner of ‘Clean 2025’, energy company E.ON Sweden has been working towards ambitious climate protection targets first set in 2017. It intends to provide to its customers 100% recycled or renewable energy by 2025 and has developed appropriate measures to achieve this goal.

The company decided that GEA’s ammonia heat pumps were ideal for district heating in southern Sweden, along with biomass and other renewable technologies to mitigate greenhouse gas emissions from heating. With a heating capacity of 10MW each, four GEA heat pumps were installed next to a sewage treatment plant and waste incinerator in the harbour area of the city of Malmö, where they are now providing 8% of the total energy to approximately 100,000 homes, the yearly equivalent usage of 10,000 households, contributing to around 50,000 metric tons of CO2 savings per year.

Power from waste

Whether drawing energy from effluent or a waste incinerator plant, heat pumps are quickly becoming the technology of choice for renewable district and residential heating, in order to meet ever-stricter environmental rules and reduce CO2 emissions as well as operational costs.

The heat pumps operating in Malmö take advantage of the waste heat from the sewage and waste incinerator plants. E.ON decided to use recycled sewage water for the system due to the higher temperatures emitted by the sewage plant (14°C / 57.2°F) – making the water warmer than the seawater near the city which was too cold for efficient use.

Withdrawing 30MW / 40,230HP of heat from the sewage water, the energy harvested is upgraded to useful heat for the district heating network, with the integrated heat pumps working in conjunction with the nearby waste incinerator plant. The heat pump is designed for delivering up to 80°C / 176°F but will rarely be required to deliver temperatures above 71 °C / 159.8°F.

GEA ammonia heat pump plant in E.ON, Malmö

GEA ammonia heat pump plant in E.ON, Malmö

Ammonia key to a sustainable a future

As fluorinated gases are phased out to meet with European F-Gas regulation, also designed to reduce greenhouse gas emissions, natural refrigerants are becoming more popular– especially ammonia, a climate-friendly refrigerant which is readily available, inexpensive and has no impact on global warming or ozone depletion.

While this is not the first time that heat pumps have been used in Sweden, the Malmö project is the first in the country to specify ammonia. E.ON opted for ammonia rather than chemical-based refrigerants due to the EU F-Gas regulation, which aims to phase down HFCs by 79% by 2030, and the company’s understanding of and commitment to its environmentally conscious customers.

3D model of the GEA ammonia heat pump for this Malmö project

3D model of the GEA ammonia heat pump for this Malmö project

Mats Egard, Project Manager at E.ON Värme Sverige AB, said: “It would have been cheaper to install an R134a heat pump, but we didn’t believe in that refrigerant for the future, because we are going to become 100% renewable. We’re going to supply district heating energy that is either recycled or renewable by 2025.”

Kenneth Hoffman, GEA’s Product Manager Heat Pumps, added: “Whereas older systems were running off F-Gas refrigerant, the F-Gas regulation has made these systems with large refrigerant charges unsustainable. Ammonia is the way forward.” 

Warming to the task

Kenneth summed up the science behind the cost-effective heat pump technology that is transforming district and residential heating and is delivering the recycled energy that will keep the good citizens of Malmö warm well into the future.

He said: “The four heat pumps work in parallel to deliver the promised temperatures. Each has a coefficient of performance (COP) above 3.5, so for each 1kWh of electricity used by the heat pump, 3.5 kWh of heat is produced for the city.”

A heat pump system requires comprehensiveanalysis of the requested temperatures and assessment of the right process parameters.Every degree counts with a heat pump and the more accurate the initial design, the more energy can be saved. Instead of focusing on small pipes with large temperature difference to keep the initial cost down, a heat pump investment is based on continuous savings every day. 

GEA ammonia heat pump in E.ON, Malmö

GEA ammonia heat pump in E.ON, Malmö

Driving increased sustainability

Heat pump technology delivers energy-saving advantages regardless of the industry in which it is used or the extent to which it is utilized. It can do basic jobs, like heating and cooling a small suburban home, right up to taking a central role in a super smart, zero-emissions strategy for district heating.

In countries where emission requirements are less stringent or where cap and trade policies allow, some manufacturers are choosing to maintain the status quo given that fossil fuels still tend to be cheaper than cleaner energy solutions. However, to meet sustainability goals the IEA says that the share of clean energy technologies, such as heat pumps and solar thermal heating, needs to triple to more than one quarter of new heating equipment sales by 2030. So, let’s take action now and engineer for a better world together!

GEA logo

GEA Scope of Supply:

  • GEA solution: Customized heat pump system (4 heat pumps)
  • Heating capacity: 40 MW
  • Heat source: Sewage water (8 to 14°C / 46.4°F to 57.2°F)
  • Heat sink: District heating water (55 to 65°C / 131°F to 149°F)
  • COP: >3.5 (yearly average)
  • Compressor type: GEA Grasso Screw compressors
  • Natural refrigerant: Ammonia
Decarbonizing district heating with heat pump technology


Join GEA’s Cooling Club webinar on District Heating entitled “Decarbonizing district heating with heat pump technology”. Svend Vinther Pedersen, Senior Consultant from The Danish Technological Institute and GEA district heating expert Kenneth Hoffmann will provide their insights on how to decarbonize district heating and decrease energy bills with heat pumps.
Receive news from GEA

Stay in touch with GEA innovations and stories by signing up for news from GEA.

Contact us

We are here to help! With just a few details we will be able to respond to your inquiry.