Coal is one of the sources of sulphur. It has been used as fuel for the centuries, but also contained sulphur is recovered from it. Quality of coal has been improved through the removal of high quality sulphur along with the other materials. Due to the concern of atmospheric pollution, several extensive researches are on going to remove sulphur completely from coal. Many of them have been successful in different aspects as easiness of recovery process or technically feasible. Although are found unable to justify their uses as per the value of sulphur recovered.
They are usually used where there's no alternative solutions to pollution problem, even if the value of sulphur recovered is very small. Combustion plants fired by fossil fuel are the biggest source of SO2.