Modern woodburning stoves that are airtight and have automatic draft controls are more efficient. Tests show a well-constructed fireplace, using all the modern innovations, such as double wall recirculating systems and glass doors, produces 10 to 20 percent efficiency from the wood consumed. A well designed, airtight woodstove, or woodstove fireplace insert, can easily achieve an efficiency of 50 percent or better, while also consuming more of the pollutants normally going into the air. The ability of an airtight stove to control the amount of air used for combustion is the key to this higher output. Some fuels are pollution and health hazards, but wood is much lower in irritating pollutants than most fuels.
Wood has a low ash content.
It burns cleanly, leaving only a minimum amount of waste ash. Also, in using wood, you are utilizing a renewable fuel resource. Coal, oil, and gas are limited resources. Once used, they cannot be replaced. But new trees are constantly growing.