Sulphur emissions can cause respiratory diseases and create acid rain that destroys vegetation.

The cost of ethanol rose 70 per cent last year as the market reacted to the regulatory pressure to reduce carbon and sulphur emissions.

It did not cut carbon emissions, but it was free of sulphur emissions.

Since then, sulphur emissions have been reduced by over 90 percent.

Investment continued in the late 1980s, principally to reduce smoke and sulphur emissions.