The design of a wood stove determines how efficient it is, with modern models much better at converting energy than older ones. Despite the major differences between stoves, there are steps you can take to make wood burn longer. It's important to take into consideration, however, that if a log burns too slowly, it stops producing as much heat, which results in wasted wood.
Hardwood produces more heat than softwood and burns slower and longer. Using hardwood is the simplest way to increase burn time or make the wood last longer in a stove. The slowest-burning, longest-lasting hardwoods include hickory, red or white oak, sugar maple, yellow birch, apple, ironwood and American beech. Softwoods that burn quickly and should be avoided if a long burn is desired are aspen, pine, spruce, hemlock and cottonwood.
Size and Amount
Larger logs burn at a slower rate in relation to their volume than smaller logs. Once a coal base is established, add larger logs to increase the burn time. Large, unsplit logs burn the longest. Adding too much wood to the stove at one time, however, can increase the burn speed. A small, hot fire will burn longer than a large, roaring one. Add large logs only one at a time to prevent them from burning too fast.
A fire needs oxygen to burn, and the more oxygen that is available, the faster and hotter it will burn. On the other hand, lack of oxygen creates a lot of smoke and little heat, resulting in an inefficient fire that burns the wood slowly but wastes fuel due to the lack of heat. Increase the time a log burns without wasting energy by adjusting the damper and vents to a setting that results in hot steady flames that aren't large or roaring but are still producing heat.
Removing grime from the wood stove will improve air flow and improve the length of the burn. Remove soot and creosote from the flue, doors and vents. Sweep or vacuum away most of the ash, but leave a thin layer, about one inch thick, on the bottom of the stove. This layer protects the bottom of the stove and also absorbs and reflects heat.
Green wood does take longer to burn than properly seasoned wood; however, it burns inefficiently, does not produce as much heat and creates a lot of polluting smoke. Wood that has been seasoned properly, or contains about 20 percent moisture, burns a little faster than green wood, but produces far more heat, resulting in less waste. It typically takes a minimum of six to nine months for freshly cut wood to become properly dried and seasoned.