Man’s use of charcoal extends back as far as human history itself.
It was first used more than 30,000 years ago to make some of the earliest cave paintings. Much later, charcoal played an important role in what might be considered mankind’s first technology, the smelting and working of metals. In more recent times, charcoal has remained a technologically important material, primarily as a result of its adsorptive properties. The use of activated charcoal in gas masks during World War I saved many thousands of lives, and today charcoal is used on an enormous scale for the purification of air and water. From a scientific perspective, charcoal is also of great interest since we are beginning to achieve a detailed picture of its atomic structure for the first time. In this article I want to look at charcoal from the point of view of art, technology and science.
Historically, production of wood charcoal in districts where there is an abundance of wood dates back to a very ancient period, and generally consists of piling billets of wood on their ends so as to form a conical pile, openings being left at the bottom to admit air, with a central shaft to serve as a flue. The whole pile is covered with turf or moistened clay. The firing is begun at the bottom of the flue, and gradually spreads outwards and upwards. The success of the operation depends upon the rate of the combustion. Under average conditions, 100 parts of wood yield about 60 parts byvolume, or 25 parts by weight, of charcoal; small-scale production on the spot often yields only about 50%, large-scale was efficient to about 90% even by the seventeenth century. The operation is so delicate that it was generally left to colliers (professional charcoal burners).
The massive production of charcoal (at its height employing hundreds of thousands, mainly in Alpine and neighbouring forests) was a major cause of deforestation, especially in Central Europe. In England, many woods were managed as coppices, which were cut and regrew cyclically, so that a steady supply of charcoal would be available (in principle) forever; complaints (as early as theStuart period) about shortages may relate to the results of temporary over-exploitation or the impossibility of increasing production to match growing demand. The increasing scarcity of easily harvested wood was a major factor for the switch to the fossil fuel equivalents, mainly coal andbrown coal for industrial use.
The use of charcoal as a smelting fuel has been experiencing a resurgence in South America following Brazilian law changes in 2010 to reduce carbon emissions as part of President Lula da Silva’s commitment to make a “green steel”.
The modern process of carbonizing wood, either in small pieces or as sawdust in cast iron retorts, is extensively practiced where wood is scarce, and also for the recovery of valuable byproducts (wood spirit, pyroligneous acid, wood tar), which the process permits. The question of thetemperature of the carbonization is important; according to J. Percy, wood becomes brown at 220 °C (428 °F), a deep brown-black after some time at 280 °C (536 °F), and an easily powdered mass at 310 °C (590 °F). Charcoal made at 300°C (572 °F) is brown, soft and friable, and readily inflames at 380 °C (716 °F); made at higher temperatures it is hard and brittle, and does not fire until heated to about 700 °C (1,292 °F).
In Finland and Scandinavia, the charcoal was considered the by-product of wood tar production. The best tar came from pine, thus pinewoods were cut down for tar pyrolysis. The residual charcoal was widely used as substitute for metallurgical coke in blast furnacesfor smelting. Tar production led to rapid deforestation: it has been estimated all Finnish forests are younger than 300 years. The end of tar production at the end of the 19th century resulted in rapid re-forestation.
The charcoal briquette was first invented and patented by Ellsworth B. A. Zwoyer of Pennsylvania in 1897 and was produced by the Zwoyer Fuel Company. The process was further popularized by Henry Ford, who used wood and sawdust byproducts from automobile fabrication as a feedstock. Ford Charcoal went on to become the Kingsford Company.
“We want ours to burn good and slow,” said Young Billy. “If he burns fast he leaves nowt but ash. The slower the fire the better the charcoal”.
Susan was watching carefully.
“Why doesn’t it go out?” she asked.
“Got too good a hold,” said Young Billy. “Once he’s got a good hold you can cover a fire up and the better you cover him the hotter he is and the slower he burns. But if you let him have plenty of air there’s no holding him.”
Arthur Ransome, “Swallows & Amazons”, 1930.
Source : wikipedia & Interdisciplinary Science Reviews 1999, Vol.24, No.4, pp.301-306
Charcoal making in Present Day
By the early part of the eighteenth century experimentation in the conversion of coal resulted in 1735 in the creation of coke. This new fuel became quickly preferred and the importance of charcoal declined. Within a century most of the furnaces had converted and over 4000 years of charcoal use as an industrial fuel came gradually to a close.
During the first half of the twentieth century the main use for charcoal was for the production of carbon disulphide – a chemical used by the artificial silk industry. However a number of other specialised uses developed. In its activated form charcoal has exceptional properties for the absorption of gasses and in purifying liquids. It has been used in gas masks and has been used to refine chemical solutions. It has also found use in animal feed and with the horticultural and pharmaceutical industries. By 1980 production in the UK was down to a few thousand tonnes per annum and at a low point.
Most recently charcoal has enjoyed a renaissance as a domestic BBQ fuel. Concerns as to the adverse environmental impact of some imported charcoal, and the desire to return local woodland to coppice management have rekindled the local English charcoal industry.