Wood fuel

Wood fuel

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Wood fuel is wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 used as fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

. The burning
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 of wood is currently the largest use of energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 derived from a solid fuel
Solid fuel
Solid fuel refers to various types of solid material that are used as fuel to produce energy and provide heating, usually released through combustion....

 biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

. Wood fuel can be used for cooking
Cooking
Cooking is the process of preparing food by use of heat. Cooking techniques and ingredients vary widely across the world, reflecting unique environmental, economic, and cultural traditions. Cooks themselves also vary widely in skill and training...

 and heating, and occasionally for fueling steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s and steam turbines that generate electricity
Electricity generation
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...

. Wood fuel may be available as firewood (e.g. logs, bolts, blocks), charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

, chips, sheets, pellets
Wood pellets
Wood pellets are a type of wood fuel, generally made from compacted sawdust or other wastes from sawmilling and other wood products manufacture, but also sometimes from sources such as whole-tree removal or tree tops and branches leftover after logging and which otherwise help replenish soil...

 and sawdust
Sawdust
Sawdust is a by-product of cutting lumber with a saw, composed of fine particles of wood. It can present a hazard in manufacturing industries, especially in terms of its flammability....

. The particular form used depends upon factors such as source, quantity, quality and application. Sawmill
Sawmill
A sawmill is a facility where logs are cut into boards.-Sawmill process:A sawmill's basic operation is much like those of hundreds of years ago; a log enters on one end and dimensional lumber exits on the other end....

 waste and construction industry by-product
By-product
A by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....

s also include various forms of lumber tailings. Some consider wood fuel bad for the environment, however this is not the case if proper techniques are used. One might increase carbon emissions using gas powered saws and splitters in the production of firewood, but when wood heat replaces carbon-producing fuels such as propane, heating oil or electricity from a coal-burning plant, then wood burning has a positive impact on the carbon footprint.

Wood may be used indoors in a furnace, stove
Wood-burning stove
For a list of stove types see Stove .A wood-burning stove is a heating appliance capable of burning wood fuel and wood-derived biomass fuel. Generally the appliance consists of a solid metal closed fire chamber, a grate and an adjustable air control...

, or fireplace
Fireplace
A fireplace is an architectural structure to contain a fire for heating and, especially historically, for cooking. A fire is contained in a firebox or firepit; a chimney or other flue allows gas and particulate exhaust to escape...

. Wood also may be burned outdoors in a campfire
Campfire
A campfire is a fire lit at a campsite, to serve the following functions: light, warmth, a beacon, a bug and/or apex predator deterrent, to cook, and for a psychological sense of security. In established campgrounds they are usually in a fire ring for safety. Campfires are a popular feature of...

, or bonfire
Bonfire
A bonfire is a controlled outdoor fire used for informal disposal of burnable waste material or as part of a celebration. Celebratory bonfires are typically designed to burn quickly and may be very large...

. Wood is the most easily available form of fuel, requiring no tool
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...

s in the case of picking up dead wood, or little tools, although as in any industry, specialized tools, such as skidder
Skidder
A skidder is any type of heavy vehicle used in a logging operation for pulling cut trees out of a forest in a process called "skidding", in which the logs are transported from the cutting site to a landing. Here they are loaded onto trucks , and sent to the mill...

s and hydraulic wood splitters, have evolved to mechanize production.

The discovery of how to make fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

 for the purpose of burning wood is regarded as one of humanity's most important advances.

Historical development


The use of wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 as a fuel source for heating is much older than civilization and was used by neanderthals. Historically, it was limited in use only by the distribution of technology required to make a spark. Wood heat is still common throughout much of the world.

Early examples include the use of wood heat in tents. Fires were constructed on the ground, and a smoke hole in the top of the tent allowed the smoke to escape by convection.

In permanent structures and in caves, hearth
Hearth
In common historic and modern usage, a hearth is a brick- or stone-lined fireplace or oven often used for cooking and/or heating. For centuries, the hearth was considered an integral part of a home, often its central or most important feature...

s were constructed or established—surfaces of stone or another noncombustible material upon which a fire could be built. Smoke escaped through a smoke hole in the roof.

Wood has been used as fuel for millennia. The Greeks, Romans, Celts, Britons, and Gauls all had access to forests suitable for using as fuel. Over the centuries there was a partial deforestation of climax forests and the evolution of the remainder to coppice with standards woodland as the primary source of wood fuel. These woodlands involved a continuous cycle of new stems harvested from old stumps, on rotations between seven and thirty years. One of the earliest printed books in English was John Evelyn
John Evelyn
John Evelyn was an English writer, gardener and diarist.Evelyn's diaries or Memoirs are largely contemporaneous with those of the other noted diarist of the time, Samuel Pepys, and cast considerable light on the art, culture and politics of the time John Evelyn (31 October 1620 – 27 February...

 "Sylva, or a discourse on forest trees" (1664) advising landowners on the proper management of forest estates. H.L.Edlin, in "Woodland Crafts in Britain", 1949 outlines the extraordinary techniques employed, and range of wood products that have been produced from these managed forests since pre-roman times. And throughout this time the preferred form of wood fuel was the branches of cut coppice stems bundled into faggots. Larger, bent or deformed stems that were of no other use to the woodland craftsmen were converted to charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

.

As with most of Europe, these managed woodlands continued to supply their markets right up to the end of World War two. Since then much of these woodlands have been converted to broadscale agriculture. Total demand for fuel increased considerably with the industrial revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

 but most of this increased demand was met by the new fuel source, Coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

, which was more compact and more suited to the larger scale of the new industries.

The development of the chimney
Chimney
A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the...

 and the fireplace
Fireplace
A fireplace is an architectural structure to contain a fire for heating and, especially historically, for cooking. A fire is contained in a firebox or firepit; a chimney or other flue allows gas and particulate exhaust to escape...

 allowed for more effective exhaustion of the smoke. Masonry heater
Masonry heater
A masonry heater is a device for warming a home that captures the heat from periodic burning of fuels , and then radiates that heat over a long period at a fairly constant temperature. The technology exists in many forms from the Roman hypocaust to the Austrian/German kachelofen...

s or stoves went a step further by capturing much of the heat of the fire and exhaust in a large thermal mass, becoming much more efficient than a fireplace alone.

The metal stove
Stove
A stove is an enclosed heated space. The term is commonly taken to mean an enclosed space in which fuel is burned to provide heating, either to heat the space in which the stove is situated or to heat the stove itself, and items placed on it...

 was a technological development concurrent with the industrial revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

. Stoves were manufactured or constructed pieces of equipment that contained the fire on all sides and provided a means for controlling the draft—the amount of air allowed to reach the fire. Stoves have been made of a variety of materials. Cast iron is among the more common. Soapstone (talc
Talc
Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg34 or Mg3Si4O102. In loose form, it is the widely-used substance known as talcum powder. It occurs as foliated to fibrous masses, its crystals being so rare as to be almost unknown...

), tile
Tile
A tile is a manufactured piece of hard-wearing material such as ceramic, stone, metal, or even glass. Tiles are generally used for covering roofs, floors, walls, showers, or other objects such as tabletops...

, and steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 have all been used. Metal stoves are often lined with refractory materials such as firebrick, since the hottest part of a woodburning fire will burn away steel over the course of several years' use.

The Franklin stove
Franklin stove
The Franklin stove is a metal-lined fireplace named after its inventor, Benjamin Franklin. It was invented in 1741.L.W. Labaree, W. Bell, W.B. Willcox, et al., eds., The Papers of Benjamin Franklin , vol. 2, page 419...

 was developed in the United States by Benjamin Franklin
Benjamin Franklin
Dr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...

. More a manufactured fireplace than a stove, it had an open front and a heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

 in the back that was designed to draw air from the cellar
Basement
__FORCETOC__A basement is one or more floors of a building that are either completely or partially below the ground floor. Basements are typically used as a utility space for a building where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system...

 and heat it before releasing it out the sides. The heat exchanger was never a popular feature and was omitted in later versions. So-called "Franklin" stoves today are made in a great variety of styles, though none resembles the original design.

The 1800s became the high point of the cast iron stove. Each local foundry would make their own design, and stoves were built for myriads of purposes—parlour stoves, box stoves, camp stoves, railroad stoves, portable stoves, cooking stoves and so on. Elaborate nickel and
chrome edged models took designs to the edge, with cast ornaments, feet and doors. Wood or coal could be burnt in the stoves and
thus they were popular for over one hundred years. The action of the fire, combined with the causticity of the ash, ensured that the stove would eventually disintegrate or crack over time. Thus a steady supply of stoves was needed. The maintenance of stoves, needing to be blacked, their smokiness, and the need to split wood meant that oil or electric heat found favour.

The airtight stove, originally made of steel, allowed greater control of combustion, being more tightly fitted than other stoves of the day. Airtight stoves became common in the 19th century.

Use of wood heat declined in popularity with the growing availability of other, less labor-intensive fuels. Wood heat was gradually replaced by coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 and later by fuel oil
Fuel oil
Fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. Broadly speaking, fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power, except oils having a flash...

, natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

 and propane
Propane
Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...

 heating except in rural areas with available forests.

After the 1967 Oil Embargo
1967 Oil Embargo
The 1967 Oil Embargo began on June 6, 1967, one day after the beginning of the Six-Day War, with a joint Arab decision to deter any countries from supporting Israel militarily. Several Middle Eastern countries eventually limited their oil shipments, some embargoing only the United States and the...

, many in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 used wood for the first time. The EPA provided information on clean stoves, which burned much more efficiently.

Firewood



Some firewood is harvested in "woodlot
Woodlot
A woodlot is a term used in North America to refer to a segment of a woodland or forest capable of small-scale production of forest products such as wood fuel, sap for maple syrup, sawlogs, as well as recreational uses like bird watching, bushwalking, and wildflower appreciation...

s" managed for that purpose, but in heavily wooded areas it is more usually harvested as a byproduct of natural forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

s. Deadfall that has not started to rot is preferred, since it is already partly seasoned. Standing dead timber is considered better still, as it is both seasoned, and has less rot. Harvesting this form of timber reduces the speed and intensity of bushfires. Harvesting timber for firewood is normally carried out by hand with chainsaw
Chainsaw
A chainsaw is a portable mechanical saw, powered by electricity, compressed air, hydraulic power, or most commonly a two-stroke engine...

s. Thus, longer pieces - requiring less manual labour, and less chainsaw fuel - are less expensive and only limited by the size of their firebox. Prices also vary considerably with the distance from wood lots, and quality of the wood.
Firewood usually relates to timber or trees unsuitable for building or construction
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...

. Firewood is a renewable resource
Renewable resource
A renewable resource is a natural resource with the ability of being replaced through biological or other natural processes and replenished with the passage of time...

 provided the consumption rate is controlled to sustainable levels. The shortage of suitable firewood in some places has seen local populations damaging huge tracts of bush thus leading to further desertification
Desertification
Desertification is the degradation of land in drylands. Caused by a variety of factors, such as climate change and human activities, desertification is one of the most significant global environmental problems.-Definitions:...

.

Energy content


A common hardwood, red oak, has an energy content of 14.89 megajoules per kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

 (6,388 BTU per pound), and 10.423 megajoules recoverable if burned at 70% efficiency.

The Sustainable Energy Development Office (SEDO), part of the Government of Western Australia states that the energy content of wood is 16.2 megajoules per kilogram (4.5 kWh/kg).

According to The Bioenergy Knowledge Centre, the energy content of wood is much more dependent on the moisture content than the species. The energy content (number of joules of heat produced) improves towards the total number of joules stored in the wood as it dries. There is some variation between species of wood as to the heat output, but it is small. Species also have different green moisture contents.

Measurement of firewood


In the metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...

, firewood is normally sold by the cubic metre or stere
Stère
The stere or stère is a unit of volume in the original metric system equal to one cubic metre. The name was coined from the Greek στερεός stereos 'solid' in 1793 France as a metric equivalent to the cord. The stère is typically used for measuring large quantities of firewood or other cut wood,...

 (1 m³ = ~0.276 cords).

In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, firewood is usually sold by the cord
Cord (unit of volume)
The cord is a unit of measure of dry volume used in Canada and the United States to measure firewood and pulpwood. A cord is the amount of wood that, when "ranked and well stowed" , occupies a volume of...

, 128 ft³ (3.62 m³), corresponding to a woodpile 8 ft wide × 4 ft high of 4 ft-long logs. The cord is legally defined by statute in most states. A "thrown cord" is firewood that has not been stacked and is defined as 4 ft wide x 4 ft tall x 10 ft long. The additional volume is to make it equivalent to a standard stacked cord, where there is less void space. It is also common to see wood sold by the "face cord", which is usually not legally defined, and varies from one area to another. For example, in one state a pile of wood 8 feet wide × 4 feet high of 16"-long logs will often be sold as a "face cord", though its volume is only one-third of a cord. In another state, or even another area of the same state, the volume of a face cord may be considerably different. Hence, it is risky to buy wood sold in this manner, as the transaction is not based on a legally enforceable unit of measure.

In Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, it is normally sold by the tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

.

Combustion by-products


As with any fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

, burning wood fuel creates numerous by-products, some of which may be useful (heat and steam), and others that are undesirable, irritating or dangerous.

One by-product of wood burning is wood ash
Wood ash
Wood ash is the residue powder left after the combustion of wood. Main producers of wood ash are wood industries and power plants.-Composition:...

, which in moderate amounts is a fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

 (mainly potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

), contributing minerals, but is strongly alkaline as it contains potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

(lye). Wood ash can also be used to manufacture soap
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...

.

Smoke
Smoke
Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...

, containing water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...

, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 and other chemicals and aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...

 particulates, can be an irritating (and potentially dangerous) by-product of partially burnt wood fuel. A major component of wood smoke is fine particles that may account for a large portion of particulate air pollution in some regions. During cooler months, wood heating accounts for as much as 60% of fine particles in Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.

Slow combustion stoves increase efficiency of wood heaters burning logs, but also increase particulate production. Low pollution/slow combustion stoves are a current area of research. An alternative approach is to use pyrolysis
Pyrolysis
Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...

 to produce several useful biochemical byproducts, and clean burning charcoal, or to burn fuel extremely quickly inside a large thermal mass, such as a masonry heater. This has the effect of allowing the fuel to burn completely without producing particulates while maintaining the efficiency of the system.

In some of the most efficient burners, the temperature of the smoke is raised to a much higher temperature where the smoke will itself burn (e.g. 609°C for igniting carbon monoxide gas). This may result in significant reduction of smoke hazards while also providing additional heat from the process. By using a catalytic converter
Catalytic converter
A catalytic converter is a device used to convert toxic exhaust emissions from an internal combustion engine into non-toxic substances. Inside a catalytic converter, a catalyst stimulates a chemical reaction in which noxious byproducts of combustion are converted to less toxic substances by dint...

, the temperature for obtaining cleaner smoke can be reduced. Some U.S. jurisdictions prohibit sale or installation of stoves that do not incorporate catalytic converters.

Combustion by-product effects on human health


Depending on population density, topography, climatic conditions and combustion equipment used, wood heating may substantially contribute to air pollution
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

, particularly particulates. The conditions in which wood is burnt will greatly influence the content of the emission. Particulate air pollution can contribute to human health problems and increased hospital admissions for asthma & heart diseases.

The technique of compressing wood pulp into pellets or artificial logs can reduce emissions. The combustion is cleaner, and the increased wood density and reduced water content can eliminate 3 to 7% of the transport bulk. Thus the fossil energy consumed in transport is reduced (and in fact represents a tiny fraction of the fossil fuel consumed in producing and distributing heating oil or gas).

Wood combustion products can include toxic and carcinogenic substances. Generally, the heartwood of a tree contains the highest amounts of toxic substances, but precautions should be taken if one is burning wood of an unknown nature, since some trees' woodsmoke can be highly toxic.

Harvesting operations


Much wood fuel comes from native
Indigenous (ecology)
In biogeography, a species is defined as native to a given region or ecosystem if its presence in that region is the result of only natural processes, with no human intervention. Every natural organism has its own natural range of distribution in which it is regarded as native...

 forests around the world. Plantation
Plantation
A plantation is a long artificially established forest, farm or estate, where crops are grown for sale, often in distant markets rather than for local on-site consumption...

 wood is rarely used for firewood, as it is more valuable as timber
Timber
Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...

 or wood pulp
Wood pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...

, however, some wood fuel is gathered from trees planted amongst crops, also known as agroforestry
Agroforestry
Agroforestry is an integrated approach of using the interactive benefits from combining trees and shrubs with crops and/or livestock.It combines agricultural and forestry technologies to create more diverse, productive, profitable, healthy and sustainable land-use systems.-Definitions:According to...

. The collection or harvesting of this wood can have serious environmental implications for the collection area. The concerns are often specific to the particular area, but can include all the problems that regular logging
Logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...

 create. The heavy removal of wood from forests can cause habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...

 and soil erosion.
However, in many countries, for example in Europe and Canada, the forest residues are being collected and turned into useful wood fuels with minimal impact on the environment. Consideration is given to soil nutrition as well as erosion.
The environmental impact of using wood as a fuel depends on how it is burnt, but even if a fire gives off lots of smoke and particulates at least it is using a sustainable fuel, compared with fossil fuels. When wood that is sourced from a sustainable plantation, it can be regarded as being carbon-neutral. That is, a tree absorbs as much carbon (or carbon dioxide) as it releases when burnt.

Greenhouse gases


Wood burning does not release any more carbon dioxide than the eventual biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...

 of the wood if it was not burned. However, the carbon dioxide released through incineration occurs at a much faster rate than decomposition because burning wood takes a few seconds and decomposition takes years. Therefore, by burning wood one is releasing carbon dioxide into the atmosphere at a more concentrated rate than if one was to allow the wood fuel to decompose in soil. Wood harvesting and transport operations do produce varying degrees of greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

 pollution. Inefficient and incomplete combustion of wood can result in elevated levels of greenhouse gases other than CO2, which may result in positive emissions where the byproducts have greater Carbon dioxide equivalent
Carbon dioxide equivalent
Carbon dioxide equivalent and Equivalent carbon dioxide are two related but distinct measures for describing how much global warming a given type and amount of greenhouse gas may cause, using the functionally equivalent amount or concentration of carbon dioxide as the reference.- Global warming...

 values.

The intentional and controlled charring of wood and its incorporation into the soil is an effective method for carbon sequestration as well as an important technique to improve soil conditions for agriculture, particularly in heavily forested regions. It forms the basis of the rich soils known as Terra preta
Terra preta
Terra preta is a type of very dark, fertile anthropogenic soil found in the Amazon Basin. Terra preta owes its name to its very high charcoal content, and was indeed made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil, and stays there for...

.

Wood fuels around the world



Europe


Some countries produce a significant fraction of their electricity needs from wood or wood wastes. In Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, there is a growing interest in using wood waste as fuel for home and industrial heating, in the form of compacted pellets
Wood pellets
Wood pellets are a type of wood fuel, generally made from compacted sawdust or other wastes from sawmilling and other wood products manufacture, but also sometimes from sources such as whole-tree removal or tree tops and branches leftover after logging and which otherwise help replenish soil...

.

In Scandinavian countries the costs of manual labour to process firewood is very high. Therefore it is common to import firewood from countries with cheap labour and natural resources. The main exporters to Scandinavia are the Baltic countries (Estonia, Lithuania, and Latvia).

Historic Japanese use


Wood, during the Edo period
Edo period
The , or , is a division of Japanese history which was ruled by the shoguns of the Tokugawa family, running from 1603 to 1868. The political entity of this period was the Tokugawa shogunate....

, was used for many purposes, and the consumption of wood led Japan to develop a forest management
Forest management
200px|thumb|right|[[Sustainable development|Sustainable]] forest management carried out by [[Complejo Forestal y Maderero Panguipulli|Complejo Panguipulli]] has contributed to the preservation of the forested landscape around [[Neltume]], a sawmill town in Chile...

 policy during that era. Demand for timber resources was on the rise not only for fuel, but also for construction of ships and buildings, and consequently deforestation was widespread. As a result, forest fires occurred, along with floods and soil erosion. Around 1666, the shogun made it a policy to reduce logging and increase the planting of trees. This policy decreed that only the shogun, and/or a daimyo
Daimyo
is a generic term referring to the powerful territorial lords in pre-modern Japan who ruled most of the country from their vast, hereditary land holdings...

, could authorize the use of wood. By the 18th century, Japan had developed detailed scientific knowledge about silviculture
Silviculture
Silviculture is the practice of controlling the establishment, growth, composition, health, and quality of forests to meet diverse needs and values. The name comes from the Latin silvi- + culture...

 and plantation forestry
Forestry
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...

.

Australia


About 1.5 million households in Australia use firewood as the main form of domestic heating. As of 1995, approximately 1.85 million cubic metres of firewood (1m³ equals approximately one car trailer
Trailer (vehicle)
A trailer is generally an unpowered vehicle pulled by a powered vehicle. Commonly, the term trailer refers to such vehicles used for transport of goods and materials....

 load) was used in Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....

 annually, with half being consumed in Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...

. This amount is comparable to the wood consumed by all of Victoria’s sawlog and pulplog forestry operations (1.9 million m³).
Species used as sources of firewood include:
  • Red Gum, from forest
    Forest
    A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

    s along the Murray River
    Murray River
    The Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...

     (the Mid-Murray Forest Management Area, including the Barmah and Gunbower forests, provides about 80% of Victoria’s red gum timber).
  • Box and Messmate Stringybark
    Eucalyptus obliqua
    Eucalyptus obliqua, commonly known as Australian Oak, Brown Top, Brown Top Stringbark, Messmate, Messmate Stringybark, Stringybark and Tasmanian Oak, is a hardwood tree native to south-eastern Australia....

    , in southern Australia.
  • Sugar gum
    Eucalyptus cladocalyx
    The Sugar Gum is a eucalypt from South Australia. It is found naturally in three distinct populations - in the Flinders Ranges, Eyre Peninsula and on Kangaroo Island. Sugar Gums from the Flinders Ranges reach up to 35m in height and have the classic "gum" habit - with a straight trunk and steep...

    , a wood with high thermal efficiency
    Thermal efficiency
    In thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...

     that usually comes from small plantations.


Environmental concerns

The environmental impact of burning wood fossil fuel is debatable. Several cities have moved towards setting standards of use and/or bans of wood burning fireplaces. For example, the city of Montréal, Québec passed a resolution to ban wood fireplace installation in new construction.

The environmental impact is debatable, however, as many wood burning advocates claim that properly harvested wood in carbon-neutral, therefore off-setting the negative impact of by-product particles given off during the burning process.

Efficiency and sustainability


With appropriately certified and operated modern wood heaters, the use of good quality wood fuel is one of the most efficient and cheapest forms of heating in Australia. The replacement of existing national domestic heating needs supplied by wood with gas and electricity would result in a significant net increase in carbon dioxide emissions, while the application and enforcement of national standards for wood heaters and wood fuel would substantially reduce particulate emissions. The peak industry body, the Australian Home Heating Association Inc is a major financial supporter of Landcare Australia
Landcare
Landcare may refer to:*Landcare , a group formed to seek land protection*Landcare Australia, an umbrella organisation seeking land protection in Australia*Landcare Research New Zealand Limited*Landcare...

, sponsoring the planting of over 40,000 trees per year. Landcare groups have planted millions of trees in revegetation programs to replace the estimated 20 billion trees removed since European settlement, laid thousands of kilometres of protective fencing, introduced sustainable farming techniques, removed hundreds of thousands of tonnes of weeds, and volunteered countless hours to the land care ethic.

Firewood plantations also provide alternative financial opportunities for farmers and local government, with fuel being one of the multi-uses of tree plantations.


1973 energy crisis


A brief resurgence in popularity occurred during and after the 1973 energy crisis, when some believed that fossil fuel
Fossil fuel
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...

s would become so expensive as to preclude their use. A period of innovation followed, with many small manufacturers producing stoves based on designs old and new. Notable innovations from that era include the Ashley heater, a thermostatically controlled stove with an optional perforated steel enclosure that prevented accidental contact with hot surfaces.

A number of dual-fuel furnaces and boilers were made, which utilized ductwork and piping to deliver heat throughout a house or other building.

The growth in popularity of wood heat also led to the development and marketing of a greater variety of equipment for cutting and splitting wood. Consumer grade hydraulic log splitter
Log splitter
A log splitter is a piece of machinery or equipment used for splitting firewood from softwood or hardwood logs that have been pre-cut into sections , usually by chainsaw or on a saw bench. Many log splitters consist of a hydraulic or electrical rod and piston assembly and these are often rated by...

s were developed to be powered by electricity, gasoline, or PTO
Power take-off
A power take-off or power takeoff is a splined driveshaft, usually on a tractor or truck, that can be used to provide power to an attachment or separate machine. It is designed to be easily connected and disconnected...

 of farm tractors.

The magazine "Wood Burning Quarterly" was published for several years before changing its name to "Home Energy Digest" and, subsequently, disappearing.

Today


A pellet stove
Pellet stove
A pellet stove is a stove that burns compressed wood or biomass pellets to create a source of heat for residential and sometimes industrial spaces...

 is an appliance that burns compressed wood or biomass pellets
Wood pellets
Wood pellets are a type of wood fuel, generally made from compacted sawdust or other wastes from sawmilling and other wood products manufacture, but also sometimes from sources such as whole-tree removal or tree tops and branches leftover after logging and which otherwise help replenish soil...

.
Wood heat continues to be used in areas where firewood is abundant. For serious attempts at heating, rather than mere ambience (open fireplaces), stoves, fireplace inserts, and furnaces are most commonly used today. In rural, forested parts of the U.S., freestanding boiler
Boiler
A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...

s are increasingly common. They are installed outdoors, some distance from the house, and connected to a heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

 in the house using underground piping. The mess of wood, bark, smoke, and ashes is kept outside and the risk of fire is reduced. The boilers are large enough to hold a fire all night, and can burn larger pieces of wood, so that less cutting and splitting is required. There is no need to retrofit a chimney in the house. However, outdoor wood boilers emit more wood smoke and associated pollutants than other wood-burning appliances. This is due to design characteristics such as the water-filled jacket surrounding the firebox, which acts to cool the fire and leads to incomplete combustion. Outdoor wood boilers also typically have short stack heights in comparison to other wood-burning appliances, contributing to ambient levels of particulates at ground level. An alternative that is increasing in popularity are wood gasification boilers, which burn wood at very high efficiencies (85-91%) and can be placed indoors or in an outbuilding.

Wood is still used today for cooking in many places, either in a stove or an open fire. It is also used as a fuel in many industrial processes, including smoking meat and making maple syrup
Maple syrup
Maple syrup is a syrup usually made from the xylem sap of sugar maple, red maple, or black maple trees, although it can also be made from other maple species such as the bigleaf maple. In cold climates, these trees store starch in their trunks and roots before the winter; the starch is then...

.

As a sustainable energy source, wood fuel also remains viable for generating electricity in areas with easy access to forest products and by-products.

Potential use in renewable energy technologies

  • Efficient stove for developing nations
  • Pellet stove
    Pellet stove
    A pellet stove is a stove that burns compressed wood or biomass pellets to create a source of heat for residential and sometimes industrial spaces...

  • Sawdust can be pelletized
  • Wood pellets
    Wood pellets
    Wood pellets are a type of wood fuel, generally made from compacted sawdust or other wastes from sawmilling and other wood products manufacture, but also sometimes from sources such as whole-tree removal or tree tops and branches leftover after logging and which otherwise help replenish soil...


See also

  • Biofuel
    Biofuel
    Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...

  • Biomass
    Biomass
    Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

  • Forestry
    Forestry
    Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...

  • Renewable heat
    Renewable heat
    Renewable heat is an application of renewable energy and it refers to the renewable generation of heat, rather than electrical power ....

  • Urban lumberjacking
    Urban lumberjacking
    Urban lumberjacking is a particular type of skipping or dumpster diving where the focus is to salvage wood either for home construction projects or for home heating.- Deliberate encouragement by businesses :...

  • Wood gas
    Wood gas
    Wood gas is a syngas fuel which can be used as a fuel for furnaces, stoves and vehicles in place of petrol, diesel or other fuels. During the production process biomass or other carbon-containing materials is gasified within the oxygen-limited environment of a wood gas generator to produce hydrogen...

  • Wood-fired oven
    Wood-fired oven
    Wood-fired ovens, also known as wood ovens , are ovens that use wood fuel for cooking. There are two types of wood-fired ovens: "black ovens" and "white ovens"...

  • Woodchips
    Woodchips
    Woodchips are a medium-sized solid material made by cutting, or chipping, larger pieces of wood. Woodchips may be used as a biomass solid fuel. They may also be used as an organic mulch in gardening, landscaping, restoration ecology and mushroom cultivation...


External links