@Eceni but there will always be parts of the tree you cannot easily process; and the fossil fuel cost of moving timber from where it fell, to where it can be processed, and onwards to where the products can be used, needs to be part of the equation.So burning waste wood locally for domestic heating, even if it isn't perfectly efficient, may not be a bad thing. It means the minerals from the timber, as wood ash, go right back into the soil locally to feed the next generation of trees.>>>