They have shown that emissions of nitrous oxides (NOX) and sulphur oxides (SOX) combine with gases already in the atmosphere to create very fine particles that are especially dangerous to human health.

ECONOMIST: Planes and pollution

In the week of the Asilomar meeting Science published evidence that more pollutants than previously appreciated, including oxides of sulphur, are getting into the lower stratosphere.

ECONOMIST: Geoengineering

That means shipowners who wish to ply these waters will have to stop using bunker fuel (the cheap stuff left over once petrol, diesel and aviation fuel have been distilled from crude oil) to power their vessels because burning it produces too much sulphur dioxide, nitrogen oxides and soot.

ECONOMIST: Marine technology: A voyage of discovery | The

The bacteria convert the sulphides to oxides, and the metal flows out with the acid, leaving only the sulphur behind.

ECONOMIST: A cleaner and cheaper way of refining ore is to use bacteria