The amount of ash produced during combustion relative to the amount of fuel fed into the wood pellet stove. Ash content is one indicator of quality for wood pellet fuel. Ash content for wood pellets should be between one and three percent. 

bio fuel is produced by animal wastes
Wood IS used as a domestic fuel. Often it is the only fuel available.
Burning fossil fuels and burning wood produce similar pollutants because wood and fossil fuels are both consist of hydrogen and carbon. Carbon dioxide is produced when burning wood and fossil fuel.
Wood is used for fuel through burning it in air (or Oxygen).
Wood is an excellent fuel because it has low kindling temperatue.
Wood is a fuel as it can provide energy by burning. But, it is not formed by fossils and hence not called a fossil fuel.
wood
It Depends what wood it is! >B^)
Yes, I said so.
Wood is not a fossil, it is biomass
carbon monoxide is produced by the burning of many different types of fuels.