Steel manufacturing produces residual gases with high levels of carbon monoxide, carbon dioxide and methane, which, because of their toxicity and contribution to increasing the greenhouse effect, should be burned before their release into the atmosphere. The high flow rates from steel manufacturing, together with their variability, mean that these energy sources cannot be stored and are fluid in nature and, therefore, if they are not burned in a thermal power station, the gases would have to be burned by fire in the atmosphere, which would mean energy wastage. Thus, burning these waste gases in the combustion boiler of a thermoelectric plant is an excellent use of a contaminated industrial by-product. In addition to the generation of electricity and / or heat from the use of these steel gases, the industrial symbiosis between EDP and Arcelor also leads to considerable environmental benefits, by avoiding the annual emission of approximately 1.2 million tonnes of CO2 into the atmosphere.