Disposal of sludge from wastewater treatment plants is an environmental problem, however there are solutions. In Copenhagen, a new sludge incineration plant has been put into operation in 2011 at the plant Lynetten owned by BIOFOS, jointly owned by 8 municipalities in the central part of the Copenhagen region.

As part of the new project, a fluid-bed incinerator has been installed together with a modern flue gas cleaning system. Furthermore, a flue gas condensation step has been added. Thereby, with this project the process of disposal of sludge has been turned from an energy consuming to an energy producing process. There is much more surplus heat available to the district heating system and there is a lot of biogas available. The main part of the high temperature heat from the boiler is first used for pre-drying of sludge and the rest of it, plus the energy from the condensation, is used for district heating. The additional surplus heat capacity is used in the local low temperature district heating network.

Detailed analysis showed that the best for the whole society would be to clean the surplus biogas and use it directly to produce city gas, which today is produced by mixing natural gas with air.

Over the recent 10 years, we have been involved in a number of other sludge incineration projects of which can be mentioned Skt. Petersburg South; Skt. Petersburg North; Hong Kong (in progress).

Key data for the new plant are:

• Capacity: 2.35 tons of Dry Solids per hour
• Sludge from 1,000,000 Person Equivalents
• Boiler production: 3.8 MW
• Heat from boiler is used for drying the sludge and for district heating
• Flue gas condensation: 2.8 MW
• Heat from flue gas condensation is used for district heating
• It is connected to the district heating of CTR and Copenhagen Energy
• Biogas production on digesters: 900 Nm³/h
• Biogas is used for city gas production to Copenhagen Energy
• The main part of the residues (fly ash) can be used for building material
• Located with respect to the city infrastructure

With this remarkable environmentally friendly project Copenhagen has one more sustainable energy solution to show visitors. The most well known other solutions are:

• 98% district heating
• integrated regional district heating system
• 95% share of CHP in the district heating
• new district cooling system
• 20% of district heating from waste to energy
• huge share of bikes in local transport
• off shore wind farms
• a new metro system
• a swim in the harbor thanks to good waste water treatment

For further details, please contact Martin Hostrup, Ramboll, by email: [email protected] or phone +45 5161 8391.