Great to see an engaged community here!
For the sake of brevity I did not clarify the distinction between district heating separate from cogeneration (in 2011, 79% of all district heating in OECD countries was produced by co‐generation plants – so usually but not always DH and co-gen are hand-in-hand).
Edward – definitely agree with you on why abandon infrastructure when we can improve it. Another great demonstrator project from CELCIUS delivers waste heat from an incinerator in the Port of Rotterdam 26 kilometers to the city where it connects to the existing district heating network. A heat hub, operational since late 2013 and located in the middle of the distribution network, acts as a distribution station and has a well-insulated buffering tank. The capacity of the buffer is 185MWh and the discharge capacity is 30MWth.This allows for an increase in total heat delivery of the heat network without any additional investments in a new transport infrastructure or by means of additional heat sources.
WRT natural gas fired co-gen, there are major concerns about the vulnerability of the Baltic States to disruptions in natural gas supply from Russia. In Europe, on average 44% of district heating runs on gas with a share of up to 80% in the countries where district heating is well-established such as Latvia, Lithuania, Slovakia, Bulgaria and Hungary. In the Baltics and Finland, gas consumption in district heating and in combined heat and power plants typically represents around 50% of total gas consumption. So energy efficiency measures and enabling fuel switching (preferably to renewables such as biomass / biogas) for DH are high on the agenda.
Of course I’m not suggesting this is a one-size-fits-all solution but I reckon it is an underexploited low carbon solution suitable for many applications.