Sulphur is present in all oil and gas deposits, usually as hydrogen sulphide or as alkyl sulphides. Combustion of fossil fuels will therefore produce sulphur dioxide, which will dissolve in atmospheric water vapour to produce acidic precipitation. The presence of sulphur compounds in oil and gas can also cause problems when these are used as chemical feedstock, as catalysts are often "poisoned" by sulphur.

The change of feedstock for sulphuric acid from mined elemental sulphur to recovered sulphur from fuels reflects concern about the impact of sulphur dioxide on health and the environment. Industry now accounts for less than 10% of all sulphur dioxide emissions, natural and human, and the largest contribution is now from transport.

Some problems associated with sulphur dioxide include:

  • Sulphur dioxide is a choking irritant at high levels, but even at low levels can result in respiratory problems
  • Sulphur dioxide reacts with water and oxygen in the air, making dilute sulphuric acid which may fall as precipitation ("acid rain"), with effects on the pH (acidity) of water and soil
  • Acid soil and water conditions may have a detrimental effect on plant and animal habitat, and may attack buildings made from limestone.









Sulphuric Acid Recycling
Sulphuric acid is used as a reagent in many processes, often as a catalyst. Disposal of spent sulphuric acid as waste is increasingly being seen as economically and environmentally undesirable, and much effort has gone into developing efficient methods for recovery and recycling of the acid. In some cases the used acid is "cleaned", but where this is not feasible, it may be broken down to provide feedstock for the manufacture of fresh acid. For more details on these developments see the acid recycling section.



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