I. Fossil fuel-fired CHP
Cogeneration units can run on a variety of fuels, all of which offer unique environmental benefits compared to the conventional technology alternatives. Based on 2012 Eurostat data, natural gas is the most widely used fuel in CHPs with a share of 49.5% in Europe.
Natural gas-fuelled applications:
Natural gas offers numerous benefits, such as its high heating value, its attractive fuel cost and its availability in many locations. In addition, it is a clean fuel with a low carbon content. It produces 40 to 50% less CO2, than coal-fired CHP. These characteristics make natural gas the fuel of choice in many cogeneration systems.
Heating oil has a high energy content per volume and is very easy to transport and store.
II. Renewable fuels
In Europe, 16.3% of the electricity produced by CHPs comes from renewable fuels. Cogeneration fuelled by renewable energy combines the advantages of environmental sustainability with maximum energy efficiency.
Biomass for heat production
Combustion of solid biomass (deriving from wood) for heat production is the main CHP bioenergy route in the world, with a constant drive for improved efficiency and reduced pollutant emissions. Several systems can be considered, depending on the size. Small-scale heating systems for households typically use firewood or pellets. Medium-scale users typically burn wood chips in grate boilers while large-scale boilers are able to burn a larger variety of fuels, including those deriving from waste wood and refuse. Heat can also be produced on a medium or large scale through cogeneration, which provides heat for industrial processes in the form of steam and can supply district heat networks.
Pulled by EU legislation, biogas production (either via conversion of bioenergy or capture and upgrade or “waste”) is growing. Many small- to medium-sized CHPs now operate on biogas.
Biogas produces no net carbon emissions.
Today biodiesel fuel is made from biomass such as vegetable oils (rapeseed oil in several parts of Europe). It seems that biodiesel will be price-competitive in the future.
Geothermal: A growing area of interest is focusing on the use of heat from geothermal sources coupled to a CHP unit. Geothermal is recognised as being a pivotal contributor to Europe’s energy mix now and in the future.