The Kakolanmäki wastewater treatment plant in Turku features a heat pumping station. Turku Energy Ltd. uses the station to extract some of the thermal energy from the wastewater to produce heat for district heating purposes (160 GWh / year) of 15.000 households. The water that is cooled down by the pumping station is also used for district cooling (30 GWh / year, or almost all of the need in Turku city). The heat recovery system has been made particularly efficient by several investements in research and development: one unit of electrical energy used at the station produces three units of district heating and two units of district cooling. It is estimated that carbon emissions in the Turku region are 80.000 tons lower per year because of the use of the heat pump station. Moreover, the Kakolanmäki wastewater treatment plant transport sludge to the Topinoja waste treatment center in Turku where the sludge is processed using anaerobic digestion. The plant processes 50.000 tons of sludge from Kakolanmäki per year, producing 30 GWh / year used in various regional transport needs. One third of the nutrients from the digestate are used as fertilizers in agriculture and two thirds in landscaping. Nitrogen products produced from the sludge and sold to chemical industries. The sludge treatment process, it is considered CO2 negative and energy positive.