The AmbiHeat heat pump plant, utilizing world-leading heat pump technology, converts the waste heat from municipal wastewater in Lahti, Finland into up to 90°C heat for the district heating network.
The 5 MW AmbiHeat heat pump plant is built by Calefa Oy for a local energy company Lahti Energia Oy, situated in Lahti, Finland. The modular heat pump plant consists of three modules, assembled on-site into a unified facility. The implementation includes seven heat pumps, systems for wastewater treatment and heat recovery, and an electrical automation center.
“It was crucial for us to receive a complete plant with design and implementation clearly managed by a single party.”– Sandor Luukkanen, Project Manager, Lahti Energia
Untapped Potential in Wastewater Heat
Wastewater heat is a valuable energy reserve for heating across the world. Many local energy companies for example in Finland already use municipal wastewater heat as a source for district heating via heat pumps.
However, there is still significant untapped potential across Europe. For example, in Finland municipal wastewater heat still accounts for over 10% of the country’s unutilized waste heat potential.
In Finland every municipality and city has a wastewater treatment plant, offering an excellent opportunity for heat recovery. Depending on the volume of wastewater and the size of the district heating network, wastewater heat can cover up to 15% of the required district heating for the whole town.
A heat pump plant located at a wastewater treatment facility can efficiently convert even low-temperature heat recovered from wastewater into 90°C district heating.
Comprehensive Delivery for Wastewater Heat Utilization
The AmbiHeat heat pump plant by Calefa is built next to the Ali-Juhakkala wastewater treatment facility in the city of Lahti. The AmbiHeat plant recovers heat from an average of 10°C treated wastewater using heat pumps and produces 90°C heat for the district heating network.
The plant was commissioned in 2022. It is connected to Lahti Energia’s main control room and operates fully autonomously. If needed, it can also be remotely monitored and optimized by Calefa.
The plant was entirely designed and built in Finland. The modules, manufactured and tested in controlled factory conditions, were transported to Ali-Juhakkala and installed in a single day. On-site work was mostly limited to electrical and automation tasks before commissioning.
“Modular delivery simplifies quality control, scheduling, and coordination. Less on-site work is needed, and weather conditions don’t delay construction” – Petri Vuori, CEO of Calefa
1,700 Tons Less CO₂ Emissions Annually with Wastewater Heat Recovery
The AmbiHeat heat pump plant in Lahti, which uses world-leading heat pump technology, has been operating flawlessly for 1.5 years. Annual maintenance and servicing are handled by Calefa through the CalefaCare service.
The plant supports Lahti Energia’s strategic goals, such as reducing natural gas use. It cuts CO₂ emissions by 1,700 tons annually—equivalent to the emissions from driving 11 million kilometers in an average car.
As the 2021 European Green Capital, Lahti continues to lead by example in circular economy practices.
“Calefa’s AmbiHeat system supports our journey toward sustainable energy production,”
– Sandor Luukkanen, Project Manager, Lahti Energia
How to Harness Municipal Wastewater Heat to Use
- Wastewater is treated and purified at a wastewater treatment plant.
- The heat from the treated wastewater is recovered using heat pumps.
- The heat pump plant can be built on-site, for example, in a separate building.
- The recovered heat is transferred to district heating water.
- The system can produce up to 90°C heat for the district heating network.
- Wastewater heat enables completely CO₂-free heat production.
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