Wood fuel that comes from forestry operations where the total area of forest is maintained is genuinely low carbon if it meets certain criteria. A tree will grow and absorb carbon before being cut down and used for fuel, over the next thirty years a tree will grow in its place and absorb the equivalent amount of carbon that was emitted when it was burnt. This is a thirty-year carbon cycle, and effectively the total atmospheric CO2 remains constant.
Fuel from waste wood can be seen in the same way, except that it has been utilised for other purposes until the end of its service life. There are several factors that can affect the sustainability of wood fuel.
- Forestry operations which clear cut established forest ecosystems are detrimental to the environment.
- Monoculture forests can impact biodiversity and generate additional carbon emissions if they are expanded into unsuitable environments.
- Processing and transporting the wood results in carbon emissions, although it is important to consider that shipping emissions are orders of magnitude lower per mile than road transport. A fifty-mile lorry journey could emit more CO2 per tonne of woodchip than shipping the wood from overseas, however it is always best to source fuel as locally as possible.
Although all wood fuel used in boilers must meet sustainability criteria as a condition of RHI payments, the criteria should be seen as the minimum standard. We encourage dialogue with fuel suppliers to understand the sources of their wood, so that enhanced sustainability can be considered as part of the fuel supply contract decision.