20 OCTOBER 2007, Page 21

Simple chemistry

Sir: Elliot Wilson writes in his biofuels article: 'A single ton of refined palm oil generates 33 tons of carbon dioxide emissions — 10 times more than petroleum' (Business, 6 October).

A ton of palm oil, or indeed petroleum, coal or any other fuel, can only contain at a maximum one ton of carbon, and generally a bit less, depending on the proportion of hydrogen, nitrogen and other elements. Burning one ton of carbon from any source can only produce a maximum of 3.28 tons of CO2 — that is simple chemistry.

So is Mr Elliott talking about the CO2 cost of the other components of the production chain, such as forest or peatswamp destruction, fertiliser, processing or transport? If so, he should say so clearly and cite his authority for the number. Depending on the origin of a particular crop, where it is grown, what it displaces, processing and transport, the figure for other costs will vary enormously. Why 33 tons? Why not 10, 20, 30 or 40?

There are many, many concerns about the destruction of forests to produce palm oil; Mr Elliott would add clarity to the discussion by indicating the range of uncertainty of these other costs.

David Hutton-Squire Northallerton, North Yorkshire