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The heat produced from biogas corresponds to the annual demand of


detached houses

The sludge treatment process

In the first phase, sewage sludge is dewatered using mechanical drum thickeners. The thickened sludge is led to methane tanks to digest.

During the digestion process, the organic matter in the wastewater sludge is broken down under anaerobic conditions. Biogas, or methane, is generated during this process. Biogas is used to produce heat by burning it in gas boilers at the wastewater treatment plants in Lahti. The heat generated is used to heat the treatment plant buildings and business premises, and any surplus heat is sold to Lahti Energia’s district heating network.

After the digestion process, the sludge is further treated with centrifuges, which mechanically separate water from the sludge. The centrifuged sludge is transported to our subsidiary Labio’s composting plant for further processing. The composting of dried sludge and organic waste produces compost, which is used in building green spaces.

Wastewater sludge refers to the settleable solids generated in the wastewater treatment process.

Approximately 14,000 tonnes of dried sludge is produced every year, which corresponds to about


700,000 sacks of compost


(20 kg/sack)