AS Tallinna Vesi signed a contract with Filter Solutions OÜ on December 30, 2022 for the construction of a combined heat and power plant (CHP)onthe Wastewater Treatment Plant at Paljassaare, which will help to reduce the cost of heat and electricity by using biogas generated in the wastewater treatment process. The cost for the construction of the new CHP complex is approximately EUR 2.4 million and the plant is expected to be launched at the end of 2023. The contract with the Solutions OÜ also includes maintenance during the warranty period.

Biogas, which is generated in the Wastewater Treatment Plant during the stabilisation of sewage sludge, can be used to produce electricity in addition to the production of heat once the combined heat and power plant is launched. The combined heat and power plant consists of biogas purification and two Jenbacher gas engines. The biogas consumption capacity of the complex is up to 4.6 MW.

At this biogas consumption capacity, the electricity generation capacity is 1.9 MW and the heat generation capacity is up to 2.1 MW. Both electricity and heat are fully used for the own use of the Wastewater Treatment Plant at Paljassaare. The construction of the combined heat and power plant is part of a larger project which also includes the reconstruction of digesters at the Wastewater Treatment Plant in Paljassaare which will ensure that the energy potential of sewage sludge is maximised.

After the reconstruction of digesters, approximately 3.2 MWh of biogas can be produced from sewage sludge every hour. The Wastewater Treatment Plant is equipped with a buffer reservoir where 20 MWh of biogas can be stored to be used as an energy storage facility. Thus, the buffer reservoir can be compared to an electric battery with the fastest charge and discharge cycle of approximately 1 day.

The buffer reservoir allows to generate electricity as needed and according to the electricity prices.