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.
|''||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|
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.
|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|
The different types of earth mounds kiln
- harvesting wood
- felling and bucking to required length
- drying of firewood
Photo of thai bucket charcoal burning stove