What is charcoal?
DefinitionCharcoal is a processed biomass that can be burned for heat energy. Charcoal means the black solid remaining after carbonisation or pyrolysis of organic matter. Various resources are used to produce charcoal such as wood, agricultural and forest residues, Municipal Solid Waste and fossil type matter; like peat.
During the carbonisation process, part of organic matter or solid biomass is burnt to provide the necessary heat. During this process where solid biomass is heated in the absence of air, the greater part of the volatiles are removed.
Resources other than wood used for charcoal production require pre-treatment like briquetting or drying and moulding before or after being charred. This kind of non forest wood charcoal is generally produced in order to substitute it. It is noted that briquettes converted to charcoal have seen real successes in Thailand, Sudan and Malaysia (reference please??). Despite efforts to introduce and promote char briquettes (from non-wood biomass) as an alternative to the production of wood charcoal from ligneous formation, this remains more important.
Charcoal characteristicsThe table below presents the characteristics of various charcoals and raw wood. Calorific value, density, Volatile matter content other than water, fixed carbon, ash content, and burning time represents the key elements used to appreciate the different type of charcoals.
|''||Calorific value (Kcal/Kg)||Density||Volatile matter (%)||Fixed carbon (%)||Ash content (%)||Burning time (%)||Reference (%)|
|Charcoal from wood||7400 - 8000||0.23 – 0.73||17.7 – 19.1||77.6 – 79.5||2.7 – 3.6||30 - 45||3, 5, 6, 7, 8|
|Charcoal from fossil wood||7300||0.6||18.8||76.5||4.65|
|Charcoal briquette from bagasse||8691||0.8||32.46|
|16||60 - 75||1|
|Charcoal briquette from crop residues||7500 - 7800||1.4||7|
|5 - 7||60 - 90||2, 3|
|Raw Wood||4000 - 5000||0.31 – 0.88||75 – 80||18 – 24||1.6 – 4.6|
|5, 6, 7, 8|
Wood charcoal seems more interesting owing to its lightest weight, to its lower ash content and the fact that it has higher energy content per unit weight and the greatest percentage of fixed carbon.
Char briquette with their highest calorific value and burning time can be a good alternative fuel to substitute wood charcoal.
Char peat may show comparable effect with standard raw wood. The fact that chars peat is more smokeless than wood, means that it will be a valuable alternative fuel to firewood.
Concerning green houses gas emission, in the range of household fuels used, charcoal releases more than LPG, biogas, kerosene, woodfuel and crop residues.
Table 2: Emissions in g/MJ delivered energy for seven fuels
|Fuel||Overall Stove Efficiency (%)||CO2||CO||Methane||TNMOC||N2O|
The uses of charcoalPatterns of wood charcoal consumption are site-specific, i.e. they vary from country to country, and from area to area within countries. They are dependant on the type of area (e.g. rural or urban), availability of local resources and alternative fuels (LPG, kerosene), climate, and they can vary by season. Still, some general observations can be made.
In countries which have a long tradition of using wood charcoal as fuel:
- Household sector is the greatest consumer. Restaurant and the handcraft sector come in second position with low percent. The use of charcoal in industrial sector is not significant.
- Cooking is the main purpose for consuming wood charcoal. Ironing, water heating and conditioning is satisfied exclusively by charcoal.
- Most of charcoal produced from ligneous formation are consumed by urban household
- Charcoal production and distribution contribute significantly to the Nation’s economy and employment.
Advantages and Disadvantages
|The advantages of wood charcoal||The disadvantages of wood charcoal|
|Charcoal meets a number of requirements concerning safety. This aspect is one of the reasons why charcoal is favoured more than LPG||Charcoal is not a clean fuel|
|Charcoal burns with a small flame and with less smoke||Charcoal transport and storage can be affected by the loss of weight|
|Charcoal is easier to handle than wood||Its delay to start burning is longer than other household fuel such as LPG, Kerosene and gelfuel|
|It generates more ash than LPG, Kerosene and gelfuel|
Type of carbonization technologyThe earth mounds kiln represents the technique of carbonization widely used in many countries. The production of one tonne of wood charcoal required between 7 to 10 tonnes of raw wood. In Senegal where urban household rely mainly to charcoal to meet their need of cooking, the improved earth mounds kiln is well-known the Casamance Kiln.
The different types of earth mounds kiln
The different steps of production wood charcoal
- harvesting wood
- felling and bucking to required length
- drying of firewood
The different steps of carbonization with casamance improved kilng align=
- Traditional charcoal kiln?
Making Charcoal Briquettes
Photo of thai bucket charcoal burning stove
External links and referenceshttp://en.wikipedia.org/wiki/Charcoal
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