The price that companies pay for generating carbon dioxide pollution has seen the biggest fall in nearly two years this week as growing expectations of a recession reduce the demand for carbon credits , writes David Oakley.

The cost to emit one tonne of carbon dioxide fell from €24 at the start of the week to €18.50 at one point yesterday in Europe - where the main over-the-counter market for the buying and selling of CO2 is located - although prices recovered a little later in the day.