The capture and control of fire is right up near the top when one considers technology and human evolution. Whether simply warming the hearth, defending a home place from wild animals or cooking food, fire is a most essential ingredient. Estimates are that an ancestral species Homo erectus learned to control fire ½ a million years ago, and some scholars believe as early as 1.7 million years ago.
Wood fueled the production of the various metal ages up to and including the iron age. Wood was still the dominant fuel used in blast furnaces in early 19th century England. In fact it was the shortage of wood for the furnaces that stimulated the development of the use of coal. Forests were gradually cleared farther and farther from the furnaces until transportation costs made hauling the wood impractical.
Wood, straw, dung, etc are still major fuels in the underdeveloped world. Worldwide wood is the fourth largest source of fuel after the fossil fuels – coal, oil, and natural gas. Wood and derived products like charcoal are about one third of all fuel use in Africa and over half in Oceania.
Industrial fuel wood use in the United States is limited. Certain industries that produce significant amounts waste wood can burn it to produce steam for process heat or to drive turbines.
The amount of heat derived from burning wood varies as the density of the wood with hardwoods such as oak and hickory having the highest fuel values. At the other end of the scale are softwoods such as pine. This is only true where the wood is measured by volume such as a cord (a stack of wood 4 feet by 4 feet by 8 feet- 128 cubic feet.)
When measured by mass all wood has about the same fuel value which is the same as the fuel value of carbohydrates like sugar or potatoes. A toothpick and a piece of spaghetti of the same weight will produce the same amount of heat when burned.
In rural areas where available, wood is used for space heat. It may be hard to think about it now in August, but come January or so, there will be nothing like a hot wood stove to back up to on a cold morning. An air tight wood stove can be a useful source of heat, but an open fireplace, regardless of how attractive, will actually remove heat from a room.
Wood can be a renewable energy source but just how “green” is it? Not all that much. There is much waste when wood is harvested for fuel, it’s call the “roots and shoots” issue. The roots below ground and the unused branches and leaves mean that a lot of biomass is wasted.
The biggest drawback about use of wood as fuel is the burning. Any time something burns varying amounts of noxious products are produced. Fine particulates damage respiratory systems and cause asthma, especially in children. Polycyclic Aromatic Hydrocarbons produced by combustion are carcinogenic. Carbon Monoxide production can be deadly. It interferes with oxygen absorption in the blood and result in acute respiratory failure or chronic obstructive pulmonary disease.
It is estimated that over 4 million premature deaths a year can be blamed on cooking and heating with biomass, essentially all in the underdeveloped parts of the world.