Production of Heat and/or Electricity
Heat and electricity can be produced separately or together in a combined process. The fuel can be any combustible material, such as natural gas, coal, oil, wood, biogas, straw, and waste in conventional plants or it can be uranium in nuclear power plants. The emissions from heat and power production is determined by the fuel type, the combustion technology, use environmental protection equipment as well as 
operational practices. Coal and oil are major fuels in today's heat and power supply and the exchange diagram below refers to these two fuels.

Coal power plant                                               Power plant seen from the sky
Transport of electricity through power lines
Typical exchanges associated with heat and electricity production based on coal and oil