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Extruded charcoal is charcoal that is made by compressing sawdust into some shape via the process of extruding the sawdust through a die. The heat and pressure of the extrusion process serves to bind the sawdust into a log that can then be carbonized, i.e., made into charcoal.
Two forms of raw material are known to us to be used in this process, sawdust collected from sawmills, and ground coconut shells. The raw material is dried and then compressed by a screw extruder or forming machine. The material is then extruded under a pressure of approximately 40 tons through a hot (300 to 350 degrees C) mold. The heat and pressure cause the lignin in the raw material to bind the material together into a solid log which is denser than the original material.
Once the logs are formed, they can be carbonized in a kiln. The carbonized logs are then either cooled in the kiln or in a cooling chamber or box before being graded and packed. Once source on the web indicates the following grading system is used:
- Grade "A" -- void of cracks, hard with metallic sound when rolled and lengthy (not more than 4 pcs in a length of 390mm).
- Grade "B" -- with minimum cracks, hard and not less than 75mm in length.
- Grade "C" -- same as "B" except the length is not less than 50mm in length.
Here are some of the claims made by manufacturers of extruded charcoal:
- Smokeless - the product burns without any smoke or fumes during the initial ignition and during the subsequent burning.
- Low Ash Content - low residual ash, typically less than 5% of the original weight of the charcoal.
- Higher fixed carbon - a high charring temperature ensures a high fixed carbon content.
- Odorless - well charred charcoal will have minimum volatile substances within the charcoal, thus eliminating the possibility of odor.
- Longer burning time - the charcoal burns longer compared to hardwood charcoal.
- Higher calorific value - the minimum heating value of the charcoal should be 7,500KCal/Kg or better.
- Low volatile content - the volatile content is low, allowing a burn without flame, smoke and fumes.
- Chemical/binder free - the charcoal is produced with untreated (chemically) waste and void of binder.
- Higher burning temperature - the charcoal is charred at high temperature so it will only burn at higher temperatures.
- Sparkless - the charcoal does not produce sparks during burning.
As you will see in the reviews of extruded charcoals that we tested, some of these goals are not always met.
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