Metsä Fibre and Rauman Energia Prepare to Utilise Pulp Mill Waste Heat in District Heating Network

Metsä Fibre, part of Metsä Group, and Rauman Energia are preparing to begin supplying recovered waste heat from the Rauma pulp mill to the city’s district heating network, with commercial heat production targeted for the end of December 2026.

A new district heating station required for the project has arrived at the pulp mill site. The next phase involves connecting the station to the mill’s systems, followed by testing and commissioning. System testing is scheduled to begin in early December.

The project will recover excess heat generated by the pulp mill’s processes and transfer it to Rauma’s district heating network. Preparations began in 2025, when the necessary connection points were installed in the mill’s steam and condensate systems during the annual maintenance shutdown.

Construction of district heating pipelines at the mill site started in January 2026, with installation work completed during the spring. Metsä Fibre and Rauman Energia experts have jointly overseen the planning and implementation, with safety maintained as a priority throughout the work.

Waste heat recovery to cover up to 20% of heat demand

The recovered heat originates from the mill’s recovery boiler, which is part of the pulp production chemical recovery cycle. Black liquor is burned in the boiler to generate steam, which is primarily used for electricity generation and the mill’s production processes.

The Rauma pulp mill generates more energy than it requires for its own operations. Previously, some surplus steam was cooled in a condenser, with the resulting heat dissipated through cooling towers.

The new district heating station will allow this excess heat to be recovered and supplied to the local network. The project is estimated to cover approximately 10–20% of Rauman Energia’s total heat demand.

Jaakko Rautala, Production Manager at Metsä Fibre’s Rauma pulp mill, said the project would improve the mill’s energy efficiency by reducing the need to cool surplus heat and enabling more efficient energy utilisation.

Jouni Kartano, Director of District Heating at Rauman Energia, said the additional heat source would diversify the company’s production capacity, improve security of supply and cost efficiency, and potentially reduce reliance on oil-fired backup and peak-load heating plants during disruptions and periods of exceptional demand.

The system is targeted to enter production use by the end of December 2026.