Charcoal

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Charcoal burning Charbon de bois rouge.jpg
Charcoal burning
Mangrove charcoal burning video
Wood pile before covering it with turf or soil, and firing it (circa 1890) Charcoal pile 05.jpg
Wood pile before covering it with turf or soil, and firing it (circa 1890)

Charcoal is a lightweight black carbon residue produced by removing water and other volatile constituents from animal and plant materials. Charcoal is usually produced by slow pyrolysis—the heating of wood or other organic materials in the absence of oxygen. This process is called charcoal burning. The finished charcoal consists largely of carbon.

Contents

The advantage of burning charcoal compared to burning wood is the absence of water and other components. This allows charcoal to burn at higher temperatures, and give off very little smoke; wood can release a significant amount of steam, organic volatiles, and unburnt carbon particles—soot—in its smoke, when it is not burned completely.

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 outwards and upwards. 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; 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, USA. Charcoal Kiln.JPG
An abandoned charcoal kiln near Walker, Arizona, USA.

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.[ 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 (428 °F), a deep brown-black after some time at 280 °C (536 °F), and an easily powdered mass at 310 °C (590 °F). [1] 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 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 charcoal briquette was first invented and patented by Ellsworth B. A. Zwoyer of Pennsylvania in 1897 [2] 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 has been made by various methods. The traditional method in Britain used a clamp. [3] 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 very slowly and transform into charcoal in a period of 5 days' burning. 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 carbonised. 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). [4] 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 carbonisation. [5] 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). [8] 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. [9]

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.

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 coke in the 19th Century as part of the Industrial Revolution.

Cooking fuel

Prior to the Industrial Revolution, charcoal was occasionally used as a cooking fuel. 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.

Reducing agent

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

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

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 (called gazogènes).[ citation needed ]

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 airfloat 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. 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. [10]

Cosmetic use of bamboo charcoal

Charcoal is also incorporated in multiple cosmetic products. [11] It can be produced a.o. from regular bamboo cut into small pieces and boiled in water to remove soluble compounds. [11] Raw bamboo charcoal is obtained after drying and carbonization in an oven at elevated temperature. [11] The role of charcoal in cosmetics is based on its highly effective absorbing properties at a microscopic-scale. [11]

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 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 gases, such as air. Charcoal filters are also used in some types of gas masks. The medical use of activated charcoal is mainly the absorption of poisons. [12] 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. [13]

Animal charcoal or bone black is the carbonaceous residue obtained by the dry distillation of bones. It contains only about 10% carbon, the remainder 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 decolorizing power was applied in 1812 by Derosne to the clarification of the syrups obtained in sugar refining; but its use in this direction has now greatly diminished, owing to the introduction of more active and easily managed reagents. It is still used to some extent in laboratory practice. The decolorizing power is not permanent, becoming lost after using for some time; it may be revived, however, by washing and reheating. Wood charcoal also to some extent removes coloring material from solutions, but animal charcoal is generally more effective.[ 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 in art for drawing, making rough sketches in painting and is one of the possible media for making a parsemage. It must usually be preserved by the application of a fixative. Artists generally utilize charcoal in three forms:

Horticulture

One additional use of charcoal was rediscovered recently in horticulture. Although American gardeners have been using charcoal for a short while, research on Terra preta soils in the Amazon has found the widespread use of biochar by pre-Columbian natives to turn unproductive soil into carbon rich soil. The technique may find modern application, both to improve soils and as a means of carbon sequestration. [15]

Animal husbandry

Charcoal is mixed with feed, added to litter, or used in the treatment of the manure. [16] Poultry benefits from using charcoal in this manner. [17] [18]

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. [19]

Medicine

Charcoal pile Meule charbon bois.jpg
Charcoal pile

Charcoal was consumed in the past as dietary supplement for gastric problems in the form of charcoal biscuits. Now it can be consumed in tablet, capsule or powder form, for digestive effects. [20] Research regarding its effectiveness is controversial. [21] To measure the mucociliary transport time the use was introduced by Passali in combination with saccharin. [22]

Red colobus monkeys in Africa have been observed eating charcoal for the purposes of self-medication. Their leafy diets contain high levels of cyanide, which may lead to indigestion. So they learned to consume charcoal, which absorbs the cyanide and relieves indigestion. This knowledge about supplementing their diet is transmitted from mother to infant. [23]

Charcoal has also been incorporated in toothpaste formulas; however, there is no evidence to determine its safety and effectiveness. [24]

Environmental sustainability

Production and utilisation 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. [25] [26] 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. [27] [28] [29]

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. [30] Similar threats are found in Zambia. [31] 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. [32] 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". [32]

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 finds 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. [33] [34]

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. [35] 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

Coke (fuel) A grey, hard and porous fuel with high carbon content and few impurities.

Coke is a grey, hard, and porous 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.

Wood gas

Wood gas is a syngas fuel which can be used as a fuel for furnaces, stoves and vehicles in place of gasoline, diesel or other fuels. During the production process biomass or other carbon-containing materials are gasified within the oxygen-limited environment of a wood gas generator to produce hydrogen and carbon monoxide. These gases can then be burnt as a fuel within an oxygen rich environment to produce carbon dioxide, water and heat. 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.

Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements pyro "fire" and lysis "separating".

Barbecue grill device that cooks food by applying heat from below

A barbecue 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.

Solid fuel 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, wood pellets, corn, wheat, 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.

Wood fuel type of energy

Wood fuel is a fuel such as firewood, charcoal, chips, sheets, pellets, and sawdust. The particular form used depends upon factors such as source, quantity, quality and application. In many areas, wood is the most easily available form of fuel, requiring no tools in the case of picking up dead wood, or few tools, although as in any industry, specialized tools, such as skidders and hydraulic wood splitters, have been developed to mechanize production. Sawmill waste and construction industry by-products also include various forms of lumber tailings. The discovery of how to make fire for the purpose of burning wood is regarded as one of humanity's most important advances. The use of wood as a fuel source for heating is much older than civilization and is assumed to have been used by Neanderthals. Today, burning of wood is the largest use of energy derived from a solid fuel biomass. Wood fuel can be used for cooking and heating, and occasionally for fueling steam engines and steam turbines that generate electricity. Wood may be used indoors in a furnace, stove, or fireplace, or outdoors in furnace, campfire, or bonfire.

Dry distillation heating of solid materials to produce gaseous products (which may condense into liquids or solids)

Dry distillation is the heating of solid materials to produce gaseous products. The method may involve pyrolysis or thermolysis, or it may not. If there are no chemical changes, just phase changes, it resembles classical distillation, although it will generally need higher temperatures. Dry distillation in which chemical changes occur is a type of destructive distillation or cracking.

Briquette 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.

Smouldering

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 biocrude or bio-oil, is a synthetic fuel 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 with subsequent cooling. Pyrolytic oil is a kind of tar and normally contains levels of oxygen too high to be considered a hydrocarbon. This high oxygen content results in non-volatility, corrosiveness, immiscibity 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 called upgrading.

Brown powder or prismatic powder, sometimes referred as "cocoa powder" due to its color, was a propellant used in large artillery and ship's guns from about the 1870s. While similar to black powder, it was chemically formulated and formed hydraulically into a specific grain shape to provide a slower burn rates with neutral or progressive burning, as opposed to the faster and regressive burn typical of randomly shaped grains of black powder produced by crushing and screening powder formed into sheets in a press box, as was typical for cannon powder previously.

Biochar Lightweight black residue, made of carbon and ashes, after pyrolysis of biomass

Biochar is charcoal used as a soil amendment for both carbon sequestration and soil health benefits. Biochar is a stable solid, rich in carbon, and can endure in soil for thousands of years. Like most charcoal, biochar is made from biomass via pyrolysis. Biochar is under investigation as a viable approach for carbon sequestration, as it has the potential to help mitigate global warming and climate change. It results from processes related to pyrogenic carbon capture and storage (PyCCS).

Bamboo charcoal

Bamboo charcoal comes from pieces of bamboo plants, harvested after at least five years, and burned in ovens at temperatures ranging from 800 to 1200 °C. It benefits environmental protection by reducing pollutant residue. It is an environmentally functional material featuring excellent absorption properties.

Kingsford (charcoal) cooking fuel

Kingsford is a brand of charcoal briquette used for grilling, along with related products. 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.

Smokeless fuel

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 are becoming increasingly popular in areas which ban the use of coal and other fuels such as unseasoned or wet wood which produce much smoke. Open fires are still popular with many domestic consumers, especially for those living in older houses where open fireplaces have not been removed or replaced by stoves for example. All houses older than about 1970 are fitted with open fireplaces when coal was in widespread use for domestic heating. However, modern houses are rarely equipped with fireplaces and central heating with natural gas or electricity is the usual choice. As a result of many places banning smoke and pollution, some studies have shown that overall air quality has improved along with fewer annual deaths related to smoke. Many consider smokeless fuel to be the near future replacement of all other solid fuels which cause toxic smoke emissions. The term in general is used to refer to solid fuels, such as: anthracite, coke, charcoal and hexamine fuel tablets. Smoke free carbonaceous fuels are usually supplied in the form of standard pillow-shaped briquettes made from powdered coal or charcoal. Fuel tablets are used by campers and walkers for temporary cooking using a small folding metal stove.

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. The resulting residue matter charcoal can be utilized as biochar to improve the soil fertility.

Biomass briquettes

Biomass briquettes are a biofuel substitute to coal and charcoal. Briquettes are mostly used in the developing world, where cooking fuels are not as easily available. There has been a move to the use of briquettes in the developed world, where they are used to heat industrial boilers in order to produce electricity from steam. The briquettes are cofired with coal in order to create the heat supplied to the boiler.

Fuel Material that stores energy later extracted by use of oxidizer, catalyst, or tool, but which is not conserved

A fuel is any material that can be made to react with other substances so that it releases energy as heat 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.

Hydrothermal carbonization

Hydrothermal carbonization (HTC) is a chemical process for the conversion of organic compounds to structured carbons. It can be used to make a wide variety of nanostructured carbons, simple production of brown coal substitute, synthesis gas, liquid petroleum precursors and humus from biomass with release of energy. Technically the process imitates, within a few hours, the brown coal formation process which takes place in nature over enormously longer geological time periods of 50,000 to 50 million years. It was investigated by Friedrich Bergius and first described in 1913.

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