What makes burning wood good for the environment?

Wood burners use what is called "woody biomass" as fuel. Biomass (also often called biofuel) encompasses two principal categories: woody biomass (which is exactly what it sounds like) and non-woody biomass which is everything else including various sorts of biodegradable waste material and crops intentionally grown as biofuel, for example sugar and maize.

Woody biomass fuel suitable for use in a wood burning stove is typically wood pellets, wood chips and wood logs. Many modern wood burning stoves are described as "dual-fire" meaning that they are capable of being run by any of these fuels (wood biomass pellets are similar in size and appearance to the sort of thing people feed pet rabbits but made from highly compressed sawdust).

Dual-fire burners are not to be confused with "multi-fuel" stoves which are capable of burning both wood products and smokeless fossil fuels. While it might be convenient to use smokeless fossil fuel - not least because unlike wood which should be burned "fast" it can be slowly burned - smokeless fossil fuel is extremely environmentally hostile. Smokeless fossil fuel is, hands down, far and away the worst fuel as regards CO2 pollution, beating both oil and gas by a considerable margin. Although the Climate Change Levy (a tax on energy designed to encourage energy efficiency and reduce carbon dioxide emissions) does not at present apply to domestic energy users, it is still worth noting that while wood fuel is exempt, smokeless fossil fuel is most certainly not.

The main difference between the two is that wood, unlike fossil fuels, is renewable and in the course of growing new wood (i.e. trees) carbon is extracted from the atmosphere and locked back up inside the wood. The carbon in a tree is eventually released back into the atmosphere regardless, so burning it releases no more carbon than leaving it to rot. It is a more or less balanced carbon cycle.

It is for this very reason that many architects and builders now incorporate energy saving wood burners in their designs for new buildings - it enables them to simultaneously provide an economical and aesthetically pleasing domestic space heating, hot water and optional cooking solution and much more easily comply with ever tougher regulations targeting low carbon emissions.