Why wood stoves can be carbon-neutral for some of us

Sir: Quentin Craven argues that Donnachadh McCarthy "is the victim of a common misunderstanding" in considering wood-burning stoves to be carbon neutral (letter, 28 December). In fact, it is Mr Craven who is the greater victim: such stoves may indeed reasonably be classified as carbon neutral.

It is a matter of timescales. When we burn wood, we merely release back into the atmosphere carbon that was taken up by the growing tree. If each tree that is felled and burnt is replaced with a new tree (and this is admittedly a big if), then this process contributes no net increase to atmospheric carbon dioxide levels when averaged over decades.

For similar reasons, breathing is not regarded as contributing to our carbon footprint even though six billion humans breathe out enormous volumes of carbon dioxide because that carbon has its origins in the plants we eat, which are re-grown within a year.

In contrast, when we burn fossil fuels, we release back into the atmosphere carbon that was taken out over hundreds of millions of years. There is no replacement mechanism for this process on the timescales of human interest.

Dr Paul Williams

Department of Meteorology, University of Reading