Charcoal

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Charcoal

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Charcoal burning
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Wood pile before covering with turf or soil, and firing it (c. 1890) Charcoal pile 05.jpg
Wood pile before covering with turf or soil, and firing it (c.1890)

Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, called charcoal burning, often by forming a charcoal kiln, the heat is supplied by burning part of the starting material itself, with a limited supply of oxygen. The material can also be heated in a closed retort. Modern "charcoal" briquettes used for outdoor cooking may contain many other additives, e.g. coal.

Contents

This process happens naturally when combustion is incomplete, and is sometimes used in radiocarbon dating. It also happens inadvertently while burning wood, as in a fireplace or wood stove. The visible flame in these is due to combustion of the volatile gases exuded as the wood turns into charcoal. The soot and smoke commonly given off by wood fires result from incomplete combustion of those volatiles. Charcoal burns at a higher temperature than wood, with hardly a visible flame, and releases almost nothing except heat, water, and carbon dioxide.

History

The production of wood charcoal in locations where there is an abundance of wood dates back to ancient times. It generally begins with piling billets of wood on their ends to form a conical pile. Openings are left at the bottom to admit air, with a central shaft serving 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 outward and upward. The success of the operation depends upon the rate of the combustion. Under average conditions wood yields about 60% charcoal by volume, or 25% by weight; [1] small-scale production methods often yield only about 50% by volume, while large-scale methods enabled higher yields of about 90% by the 17th century.

The operation is so delicate that it was generally left to colliers (professional charcoal burners). They often lived alone in small huts to tend their wood piles. For example, in the Harz Mountains of Germany, charcoal burners lived in conical huts called Köten which are extant today.[ when? ]

An abandoned charcoal kiln near Walker, Arizona, US Charcoal Kiln.JPG
An abandoned charcoal kiln near Walker, Arizona, US

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. [2] [ when? ] In England, many woods were managed as coppices, which were cut and regrown cyclically, so that a steady supply of charcoal was available. Complaints (as early as the Stuart 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 behind the switch to fossil fuel equivalents, mainly coal and brown coal for industrial use.

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 the temperature of the carbonization is important; according to J. Percy, wood becomes brown at 220 °C (430 °F), a deep brown-black after some time at 280 °C (540 °F), and an easily powdered mass at 310 °C (590 °F). Charcoal made at 300 °C (570 °F) is brown, soft and friable, and readily inflames at 380 °C (720 °F); made at higher temperatures it is hard and brittle, and does not fire until heated to about 700 °C (1,300 °F). [1] [3]

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 furnaces for smelting. Tar production led to rapid local deforestation. The end of tar production at the end of the 19th century resulted in rapid re-forestation of affected areas.

The American form of the charcoal briquette was first invented and patented by Ellsworth B. A. Zwoyer of Pennsylvania in 1897 [4] 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.

Production methods

Charcoal under a microscope Drevesnyi ugol'.jpg
Charcoal under a microscope

Charcoal has been made by various methods. The traditional method in Britain used a clamp. [5] This is essentially a pile of wooden logs (e.g. seasoned oak) leaning in a circle against a chimney. The chimney consists of 4 wooden stakes held up by some rope. The logs are completely covered with soil and straw allowing no air to enter. It must be lit by introducing some burning fuel into the chimney; the logs burn slowly and transform into charcoal over a period of 5 days. If the soil covering gets torn or cracked by the fire, additional soil is placed on the cracks. Once the burn is complete, the chimney is plugged to prevent air from entering. The true art of this production method is in managing the sufficient generation of heat, by combusting part of the wood material, and its transfer to wood parts in the process of being carbonized. A strong disadvantage of this production method is the huge amount of emissions that are harmful to human health and the environment (emissions of unburnt methane). [6] As a result of the partial combustion of wood material, the efficiency of the traditional method is low.

Modern methods employ retorting technology, in which process heat is recovered from, and solely provided by, the combustion of gas released during carbonization. [7] Yields of retorting are considerably higher than those of kilning, and may reach 35%-40%.

The properties of the charcoal produced depend on the material charred. The charring temperature is also important. Charcoal contains varying amounts of hydrogen and oxygen as well as ash and other impurities that, together with the structure, determine the properties. The approximate composition of charcoal for gunpowders is sometimes empirically described as C7H4O.[ citation needed ] To obtain a coal with high purity, source material should be free of non-volatile compounds.

Wood charcoal is obtained as the residue by destructive distillation of wood such that the products are:

Types

Binchotan, Japanese high grade charcoal made from ubame oak Japanese Binchotan (Japanese high-grade charcoal produced from ubame oak).jpg
Binchōtan , Japanese high grade charcoal made from ubame oak
Ogatan, charcoal briquettes made from sawdust Ogatan(JapaneseBriquetteCharcoal).jpg
Ogatan , charcoal briquettes made from sawdust
Burning ogatan

Uses

Grill charcoal made from coconut shell Japanese RoundStove Charcoal.JPG
Grill charcoal made from coconut shell

Charcoal has been used since earliest times for a large range of purposes including art and medicine, but by far its most important use has been as a metallurgical fuel. Charcoal is the traditional fuel of a blacksmith's forge and other applications where an intense heat is required. Charcoal was also used historically as a source of black pigment by grinding it up. In this form charcoal was important to early chemists and was a constituent of formulas for mixtures such as black powder. Due to its high surface area charcoal can be used as a filter, and as a catalyst or as an adsorbent.

Metallurgical fuel

Charcoal burns at temperatures exceeding 1,100 degrees Celsius (2,010 degrees Fahrenheit). [9] By comparison, the melting point of iron is approximately 1,200 to 1,550 °C (2,190 to 2,820 °F). Due to its porosity, it is sensitive to the flow of air and the heat generated can be moderated by controlling the air flow to the fire. For this reason charcoal is still widely used by blacksmiths. Charcoal has been used for the production of iron since Roman times and steel in modern times where it also provided the necessary carbon. Charcoal briquettes can burn up to approximately 1,260 °C (2,300 °F) with a forced air blower forge. [10]

In the 16th century, England had to pass laws to prevent the country from becoming completely denuded of trees due to production of iron.[ citation needed ] In the 19th century charcoal was largely replaced by coke in steel production due to cost, even though coke usually adds sulphur and sometimes other deleterious contaminants to the pig iron. Wooded metallurgical regions devoid of coal like Sweden, the Urals, or Siberia transitioned from charcoal in the early 20th century.

Industrial fuel

Historically, charcoal was used in great quantities for smelting iron in bloomeries and later blast furnaces and finery forges. This use was replaced by coal in the 19th Century as part of the Industrial Revolution.

Cooking and heating fuel

Prior to the Industrial Revolution, charcoal was occasionally used as a cooking fuel. It is counted as a smokeless fuel; that is, the carbon is sufficiently pure that burning it causes substantially less air pollution than burning the original uncarbonized organic material would. In the 20th century, clean-air legislation mandated smokeless fuels (mostly coke or charcoal) in many areas of Europe. In the 21st century, charcoal has been advocated as a way to improve the health of people burning raw biomass for cooking and/or heating. Modern "charcoal" briquettes, widely used for outdoor cooking, are made with charcoal but may also include coal as an energy source as well as accelerants, binders and filler.

To contain the charcoal and use it for cooking purposes, a barbecue grill may be used. A small Japanese charcoal grill is known as a shichirin . A brazier is a container used to burn charcoal or other solid fuel.

To start the charcoal burning is harder than starting a wood fire and charcoal lighter fluid may be employed. A chimney starter or electric charcoal starter are tools to help with starting to light charcoal.

Approximately 75% of fuel burned in Haiti is charcoal. [11]

Reducing agent

Certain types of charcoal, such as wood charcoal, are used for reducing heated metallic oxides to their respective metals:[ citation needed ]

Charcoal can also be used to reduce super heated steam to hydrogen (along with the formation of carbon monoxide):[ citation needed ]

Syngas production, automotive fuel

Like many other sources of carbon, charcoal can be used for the production of various syngas compositions; i.e., various CO + H2 + CO2 + N2 mixtures. The syngas is typically used as fuel, including automotive propulsion, or as a chemical feedstock.

In times of scarce petroleum, automobiles and even buses have been converted to burn wood gas: a gas mixture consisting primarily of diluting atmospheric nitrogen, but also containing combustible gasses (mostly carbon monoxide) released by burning charcoal or wood in a wood gas generator. In 1931, Tang Zhongming developed an automobile powered by charcoal, and these cars were popular in China until the 1950s, and in occupied France during World War II, where they were called gazogènes .

Pyrotechnics

Charcoal is used in the production of black powder, which is used extensively in the production of fireworks. It is usually ground into a fine powder, with air float grade being the finest particle size available commercially. When used in black powder compositions, it is often ball-milled with other ingredients so that they are intimately mixed together. Certain charcoals perform better when used to make black powder; these include spruce, willow, paulownia and grapevine among others.[ citation needed ] Charcoal produces fine dark orange/golden sparks. Usually, powder with a mesh size from 10 to 325 is used to obtain showers of golden sparks in pyrotechnic compositions. [12]

Cosmetic use of bamboo charcoal

Charcoal is also incorporated in multiple cosmetic products. [13] It can be produced from regular bamboo cut into small pieces and boiled in water to remove soluble compounds. [13] Raw bamboo charcoal is obtained after drying and carbonization in an oven at elevated temperature. [13] The role of charcoal in cosmetics is based on its highly effective absorbing properties at a microscopic scale. [13]

Carbon source

Charcoal may be used as a source of carbon in chemical reactions. One example of this is the production of carbon disulphide through the reaction of sulfur vapors with hot charcoal. In that case, the wood should be charred at high temperature to reduce the residual amounts of hydrogen and oxygen that lead to side reactions.

Purification and filtration

Activated carbon Activated Carbon.jpg
Activated carbon
Charcoal for dehumidification and air purification in bathroom -114wiki.jpg
Charcoal for dehumidification and air purification in bathroom

Charcoal may be activated to increase its effectiveness as a filter. Activated charcoal readily adsorbs a wide range of organic compounds dissolved or suspended in gases and liquids. In certain industrial processes, such as the purification of sucrose from cane sugar, impurities cause an undesirable color, which can be removed with activated charcoal. It is also used to absorb odors and toxins in gaseous solutions, as in home air purifiers and some types of gas mask. The medical use of activated charcoal is mainly the absorption of poisons. [14] Activated charcoal is available without a prescription, so it is used for a variety of health-related applications. For example, it is often used to reduce discomfort and embarrassment due to excessive gas (flatulence) in the digestive tract. [15]

Animal charcoal or bone black is the carbonaceous residue obtained by the dry distillation of bones. It contains only about 10% carbon, the remaining being calcium and magnesium phosphates (80%) and other inorganic material originally present in the bones. It is generally manufactured from the residues obtained in the glue and gelatin industries. Its bleaching power was applied in 1812 by Derosne for clarifying sugar syrup, but its use in this direction has now greatly diminished. Today it is seldom used for this purpose due to the introduction of more active and easily managed reagents, but it is still employed to some extent in laboratory practice. The bleaching action of the charcoal in solution diminishes as it adsorbs colored contaminants and it must be reactivated periodically by separate washing and reheating. [1] While wood charcoal effectively removes some pigments and contaminants from solutions, bone charcoal is generally more effective as an adsorption filter due to its increased porosity and surface area.[ citation needed ]

Art

Four sticks of vine charcoal and four sticks of compressed charcoal Charcoal sticks 051907.jpg
Four sticks of vine charcoal and four sticks of compressed charcoal
Two charcoal pencils in paper sheaths that are unwrapped as the pencil is used, and two charcoal pencils in wooden sheaths Charcoal pencils 051907.jpg
Two charcoal pencils in paper sheaths that are unwrapped as the pencil is used, and two charcoal pencils in wooden sheaths

Charcoal is used for drawing, making rough sketches in painting, and is one of the possible media used for making a parsemage. It usually must be preserved by the application of a fixative. Artists generally utilize charcoal in four forms:

Horticulture

One additional use of charcoal was rediscovered recently for horticulture. Although American gardeners have used charcoal for a short time, research on Terra preta soils in Amazonia has discovered the widespread use of biochar by pre-Columbian natives to ameliorate unproductive soil into soil rich in carbon. The technique may find modern application, both to improve soils and as a means of carbon sequestration. [17]

Animal husbandry

Charcoal is mixed with feed, added to litter, or used in the treatment of manure. [18] Poultry benefits from using charcoal in this manner. [19] [20]

A concern that activated charcoal might be used unscrupulously to allow livestock to tolerate low quality feed contaminated with aflatoxins resulted in the Association of American Feed Control Officials banning it in 2012 from use in commercial livestock feeds. [21]

Medicine

Charcoal pile Meule charbon bois.jpg
Charcoal pile

Charcoal in the form of charcoal biscuits was consumed in the past for gastric problems. Now it can be consumed in tablet, capsule, or powder form for digestive effects. [22] Research regarding its effectiveness is controversial. [23]

Charcoal has been used in combination with saccharin in research to measure mucociliary transport time. [24]

Charcoal has also been incorporated into toothpaste formulas; however, there is no evidence to determine its safety and effectiveness. [25]

Red colobus monkeys in Africa have been observed eating charcoal for self-medication. Because their leafy diets contain high levels of cyanide, which may lead to indigestion, they learned to consume charcoal, which absorbs the cyanide and relieves discomfort. This knowledge is transmitted from mother to infant. [26]

Environmental sustainability

Production and utilization of charcoal, like any use of woody biomass as fuel, typically results in emissions and can contribute to deforestation.

The use of charcoal as a smelting fuel has been experiencing a resurgence in South America resulting in severe environmental, social and medical problems. [27] [28] Charcoal production at a sub-industrial level is one of the causes of deforestation. Charcoal production is now usually illegal and nearly always unregulated, as in Brazil, where charcoal production is a large illegal industry for making pig iron. [29] [30] [31]

Massive forest destruction has been documented in areas such as Virunga National Park in the Democratic Republic of Congo, where it is considered a primary threat to the survival of the mountain gorillas. [32] Similar threats are found in Zambia. [33] In Malawi, illegal charcoal trade employs 92,800 workers and is the main source of heat and cooking fuel for 90 percent of the nation's population. [34] Some experts, such as Duncan MacQueen, Principal Researcher–Forest Team, International Institute for Environment and Development (IIED), argue that while illegal charcoal production causes deforestation, a regulated charcoal industry that required replanting and sustainable use of the forests "would give their people clean efficient energy – and their energy industries a strong competitive advantage". [34]

Recent assessments of charcoal imported to Europe have shown that many charcoal products are produced from tropical wood, often of undeclared origin. In an analysis of barbecue charcoal marketed in Germany, the World Wildlife Fund found that most products contain tropical wood. As a notable exception, reference is made to barbecue charcoal imports from Namibia, where charcoal is typically produced from surplus biomass resulting from bush encroachment. [35] [36] Charcoal trafficking in Somalia is an economic and environmental issue with significant regional-security implications. [37]

The last section of the film Le Quattro Volte (2010) gives a good and long, if poetic, documentation of the traditional method of making charcoal. [38] The Arthur Ransome children's series Swallows and Amazons (particularly the second book, Swallowdale ) features carefully drawn vignettes of the lives and the techniques of charcoal burners at the start of the 20th century, in the Lake District of the UK. Antonín Dvořák's opera King and Charcoal Burner is based on a Czech legend about a king who gets lost in a forest and is rescued by a charcoal burner.

See also

Related Research Articles

<span class="mw-page-title-main">Coke (fuel)</span> Hard fuel containing mostly carbon

Coke is a grey, hard, and porous coal-based fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air—a destructive distillation process. It is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges when air pollution is a concern.

<span class="mw-page-title-main">Wood gas</span> Syngas fuel created by gasification of biomass

Wood gas is a fuel gas that can be used for furnaces, stoves, and vehicles. During the production process, biomass or related carbon-containing materials are gasified within the oxygen-limited environment of a wood gas generator to produce a combustible mixture. In some gasifiers this process is preceded by pyrolysis, where the biomass or coal is first converted to char, releasing methane and tar rich in polycyclic aromatic hydrocarbons.

<span class="mw-page-title-main">Pyrolysis</span> Thermal decomposition of materials at elevated temperatures in an inert atmosphere

The pyrolysis process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere.

<span class="mw-page-title-main">Barbecue grill</span> Device for barbecueing or grilling

A barbecue grill or barbeque grill is a device that cooks food by applying heat from below. There are several varieties of grills, with most falling into one of three categories: gas-fueled, charcoal, or electric. There is debate over which method yields superior results.

<span class="mw-page-title-main">Solid fuel</span> Solid material that can be burnt to release energy

Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fuels include wood, charcoal, peat, coal, hexamine fuel tablets, dry dung, wood pellets, corn, wheat, rice, rye, and other grains. Solid fuels are extensively used in rocketry as solid propellants. Solid fuels have been used throughout human history to create fire and solid fuel is still in widespread use throughout the world in the present day.

<span class="mw-page-title-main">Dry distillation</span> Heating of solids to produce gases

Dry distillation is the heating of solid materials to produce gaseous products. The method may involve pyrolysis or thermolysis, or it may not.

White coal is a form of fuel produced by drying chopped wood over a fire. It differs from charcoal which is carbonised wood. White coal was used in England to melt lead ore from the mid-sixteenth to the late seventeenth centuries. It produces more heat than green wood but less than charcoal and thus prevents the lead evaporating. White coal could be used mixed with charcoal for other industrial uses than lead smelting. White coal was produced in distinctive circular pits with a channel, known as Q-pits. They are frequently found in the woods of South Yorkshire.

<span class="mw-page-title-main">Briquette</span> Compressed block of biomass used for fueling a fire

A briquette is a compressed block of coal dust or other combustible biomass material used for fuel and kindling to start a fire. The term derives from the French word brique, meaning brick.

Carbonization is the conversion of organic matters like plants and dead animal remains into carbon through destructive distillation.

<span class="mw-page-title-main">Karrick process</span>

The Karrick process is a low-temperature carbonization (LTC) and pyrolysis process of carbonaceous materials. Although primarily meant for coal carbonization, it also could be used for processing of oil shale, lignite or any carbonaceous materials. These are heated at 450 °C (800 °F) to 700 °C (1,300 °F) in the absence of air to distill out synthetic fuels–unconventional oil and syngas. It could be used for a coal liquefaction as also for a semi-coke production. The process was the work of oil shale technologist Lewis Cass Karrick at the United States Bureau of Mines in the 1920s.

<span class="mw-page-title-main">Smouldering</span> Slow, flameless combustion

Smouldering or smoldering is the slow, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. Many solid materials can sustain a smouldering reaction, including coal, cellulose, wood, cotton, tobacco, cannabis, peat, plant litter, humus, synthetic foams, charring polymers including polyurethane foam and some types of dust. Common examples of smouldering phenomena are the initiation of residential fires on upholstered furniture by weak heat sources, and the persistent combustion of biomass behind the flaming front of wildfires.

Pyrolysis oil, sometimes also known as bio-crude or bio-oil, is a synthetic fuel with limited industrial application and under investigation as substitute for petroleum. It is obtained by heating dried biomass without oxygen in a reactor at a temperature of about 500 °C (900 °F) with subsequent cooling, separation from the aqueous phase and other processes. Pyrolysis oil is a kind of tar and normally contains levels of oxygen too high to be considered a pure hydrocarbon. This high oxygen content results in non-volatility, corrosiveness, partial miscibility with fossil fuels, thermal instability, and a tendency to polymerize when exposed to air. As such, it is distinctly different from petroleum products. Removing oxygen from bio-oil or nitrogen from algal bio-oil is known as upgrading.

<span class="mw-page-title-main">Biochar</span> Lightweight black residue, made of carbon and ashes, after pyrolysis of biomass

Biochar is the lightweight black residue, made of carbon and ashes, remaining after the pyrolysis of biomass, and is a form of charcoal. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment". Biochar is a stable solid that is rich in pyrogenic carbon and can endure in soil for thousands of years.

<span class="mw-page-title-main">Kingsford (charcoal)</span> Brand of charcoal briquette

Kingsford is a brand of charcoal briquette used for grilling, along with related products. Established in 1920, the brand is owned by The Clorox Company. Currently, the Kingsford Products Company remains the leading manufacturer of charcoal in the United States, with 80% market share. More than 1 million tons of wood scraps are converted into charcoal briquettes annually.

<span class="mw-page-title-main">Smokeless fuel</span>

Smokeless fuel is a type of solid fuel which either does not emit visible smoke or emits minimal amounts during combustion. These types of fuel find use where the use of fuels which produce smoke, such as coal and unseasoned or wet wood, is prohibited.

<span class="mw-page-title-main">Slash-and-char</span> Farming method for clearing vegetation

Slash-and-char is an alternative to slash-and-burn that has a lesser effect on the environment. It is the practice of charring the biomass resulting from the slashing, instead of burning it. Due to incomplete combustion (pyrolysis) the resulting residue matter charcoal can be utilized as biochar to improve the soil fertility.

Combustion Resources, Inc. was a consulting company based in Provo, Utah, United States. It provided consulting services in the fields of fuel and combustion, such as testing of flow and mixing systems, reactor design, gas and particle sampling, gasification modeling, and shale oil extraction design and testing. The company was incorporated in 1995 as a spin-off from the Center for Advanced Combustion Engineering Research, joint collaboration between Brigham Young University and the University of Utah.

<span class="mw-page-title-main">Biomass briquettes</span> Fuel source made from green waste

Biomass briquettes are a biofuel substitute made of biodegradable green waste with lower emissions of greenhouses gases and carbon dioxide then traditional fuel sources. This fuel source is used as an alternative for harmful biofuels. Briquettes are used for heating, cooking fuel, and electricity generation usually in developing countries that do not have access to more modern fuel sources. Biomass briquettes have become popular in developed countries due to the accessibility, and eco-friendly impact. The briquettes can be used in the developed countries for producing electricity from steam power by heating water in boilers.

<span class="mw-page-title-main">Fuel</span> Material used to create heat and energy

A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy, such as nuclear energy.

<span class="mw-page-title-main">Disposable grill</span> Barbecue grill type

A disposable grill is a specific barbecue grill type which is used in a single application, with the grill being recycled or disposed of after use.

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