Around 25 to 30% of the weight of the coal charged to coke ovens is driven off as effluent gases rich in volatile matter and moisture. After drying this raw gas and separating tar, light oil and sulphur fractions (which have values themselves), coke oven gas (COG) is obtained.  This gas has a heating value between 17 – 20 MJ/Nm³ and is generally used for coke oven heating, heating of other furnaces and for power generation, both internally and externally.  Although COG recovery is performed in most plants, it still offers a considerable potential. 

According to a 2007 study by International Energy Agency (IEA, 2007, p. 111), approximately 70% of the COG was used in iron and steel making processes, 15% for coke oven heating, and 15% for electricity production.  It was stated that by using more of the COG for power generation (preferably combined with more efficient combined cycle power generation techniques that can provide efficiencies of around 42% techniques as opposed to those based on steam cycles - with an average efficiency of around 30%) improvements in energy efficiencies can be realised.  

   Although COG recovery is performed in most plants, this technology is regarded to have high expansion potential in China, India and the United States.