-Capturing them at their source (through choice of fuel or in the combustion chamber,) -By de polluting combustion gases by treating flue gas before it is released into the air, and, -By choosing clean combustion technologies. For EDF SA in France, CO2, SO2 and NOx content per kWh fluctuates from one year to the next depending chiefly on weather conditions, which determine how much the fossil-fired units are used.