My step dad and I are still in the process of creating a self sustaining wood heater. Using saw dust and heated copper lines coiled inside of a barrel. Basically you fill the barrel, get it up to temp with propane, shut the propane off, and have an insane amount of heat for North of 48 hours. It recirculates the emitted chemicals to keep going, he says we can make it last almost a week. Im not sure on that. We almost have it nailed for his 2500 sq.ft. house though. But anyway sorry for getting off topic, Wood heating is sooooooo much cheaper.