Caverion will implement a wastewater heat recovery system for the city of Seinäjoki, Finland, aiming to supply the district heating network with thermal energy equivalent to the annual consumption of approximately 2,000 detached houses. The project, commissioned by Seinäjoen Voima, will be among the first in Finland to use ammonia (NH₃) as a refrigerant for this application.
The heat recovery system will be integrated into the local wastewater treatment plant. A 1,000 m³ (35,314 ft³) basin will store purified wastewater, from which heat will be extracted using ammonia-based heat pumps. The system will deliver up to 4.9 MW of thermal energy in the form of 90°C (194°F) water to the district heating network.
Ammonia is a natural refrigerant with high energy efficiency and zero global warming potential. The solution supports Seinäjoki’s environmental targets and demonstrates the circular economy in practice.
“About one third of household wastewater is domestic hot water, meaning energy is lost into sewers,” said Pasi Salo, CEO of Seinäjoen Voima. “By using purified wastewater, we can safely and sustainably recover thermal energy for district heating. Ammonia-based solutions have proven effective in Europe over the past decade, and we’re pleased to bring this approach to Seinäjoki with Caverion.”
Caverion emphasized the use of proven Finnish industrial refrigeration technology in the project. The system reflects growing interest in low-emission heating solutions across Nordic municipalities.
“We bring the best technology on the market and Finnish industrial refrigeration expertise to this project, which strongly supports the achievement of local environmental goals,” said Sami Hatakka, Head of Sales, Energy Solutions and Industrial Refrigeration at Caverion Finland. “Seinäjoki is setting an example for other cities in Finland.”
Seinäjoen Voima handles all district heat production in the Seinäjoki region. The company operates a combined heat and power plant on the shore of Lake Kyrkösjärvi, along with additional facilities in Kapernaum, Hanneksenrinne, and Puhdistamokatu.