[FrankR]

"The fire you see is actually the gasses burning, not the wood."

So...if the wood doesn't actually burn, then what is that pile of ash that's left...gas ashes? Also, why is it the wood is no longer there?

[mnehring]

The remaining carbon after the gasses burn off or broken down and ‘went up in smoke’.
http://www.arboristsite.com/firewood-heating-wood-burning-equipment/160520.htm