Factors Influencing Charcoal Quality

What Factors Influence Charcoal Quality?
Tom Miles, Biomass Cooking Stoves June 18, 2006

Temperature

100C -> Wood drying 19 MJ/kg

220C -> Wood becomes brown
250-270C-> Torrefaction 28% fixed carbon, 72% volatile 23.9 MJ/kg
280C -> Wood becomes deep brown-black

300C -> 68% char 32% volatile 40% yield soft, brown, friable

400C FAO ->the process stops and the temperature reaches a maximum of about 400°C. This charcoal, however, will still contain appreciable amounts of tarry residue, together with the ash of the original wood. The ash content of the charcoal is about 3-5%; the tarry residue may amount to about 30% by weight and the balance is fixed carbon about 65-70%.

400-450C -> 80% char 20% volatile

500C- > 86% char 13% volatile, 33% yield 32 MJ/kg

700C -> 93% char 7% volatile 30% yield hard and brittle

or
FAO: Low carbonization temperatures give a higher yield of charcoal but this charcoal is low grade, is corrosive due to its content of acidic tars, and does not burn with a clean smoke-free flame. Good commercial charcoal should have a fixed carbon content of about 75% and this calls for a final carbonising temperature of around 500°C.

References:
FAO Simple technologies for Charcoal Making #41 Rome 1987 M-37 ISBN 92-5-101328-1
FAO Chapter 4 Carbonization Processes
FAP Chapter 10 Using Charcoal Efficiently
10.1 The Quality of Charcoal
10.1.5 Typical Charcoal Analyses
10.2 Burning Charcoal Efficiently
Tropical Charcoal
Wikipedia Charcoal
Kamado Corporation
Introduction to Bamboo Charcoal China
Bamboo Charcoal StandardAnnex 1
Hibajene, S. H. 1994. Assessment of Earth Kiln Charcoal Production Technology Zambia, SEI EE&D 39 p. ISBN: 91-88714-01-2.
Evaluation of Woody Biomass Torrefaction Jingge Li and John Gifford Forest Research, Rotorua, New Zealand September 2001
Testing of Barbecue Coal and Barbeque Coal Briquettes Force Technology, Denmark.
A Social and Technical Analysis of Charcoal Production in the Narok District of Kenya RAEL
Industrial Charcoal Production" Appendix B Sustainable Steelmaking Using Renewable Forest Energy NSW Sustainable Energy Research and Development Fund (SERDF)
Effect of Final Pyrolysis Temperature on Charcoal Yield Table 2. Cookstove.net

>From the Phyllis database

Reed and Guar (ID 1954): 34390 kJ/kg at 1% ash and 9.4% volatiles.

Gliricida, Nigeria (ID 2118): 33100 kJ/kg at 2.2% ash and 48% volatiles

Oak Wood, Antal, flash carbonization: 31600 kJ/kg 20% volatile, 0.5% ash

Pine, Di Blasi, (ID1725): 31107 kJ/kg 0.3% ash

Eucalyptus, Reed and Guar (ID1956): 27600 kJ/kg,
10.4% ash. 19.2% volatiles

Casuarina, Reed and Guar (ID 1953): 27120 kJ/kg 13.2% ash and 15.2%
volatile.

Willow char ECN (ID 2716): 26700 kJ/kg 4.1% ash, 34.4% volatile.

Charcoal, EPA India (600R00052AppF), LHV (NCV) 25715 at 7.4% ash
Char Briquette , EPA India (600R00052AppF), LHV (NCV) 15298 at 40% ash

Oak, Reed and Guar (ID 1958): 24800 kJ/kg 14.9% ash and 25.8% volatile

Oak, Reed and Guar (ID 1957) 23050 kJ/kg 17.3% ash and 27.1% volatiles.

Char, ECN measured (ID 2111): 20120 kJ/kg with 20.9% ash and 32.3%
volatiles.

SNV Nepal S. Nienhuy Beehive Briquette Stove; Charcoal mixed with clay = 18 MJ/kg.

Tom Reed Nov 29 2001:
"Cooking charcoal typically retains 20% of the volatiles and is more like 24
kJ/g. (Other species along the pyrolysis
trail are: torrefied wood (240-280C) ~23 kJ/g; Sea Sweep, our oil
absorbent. . .at 350C, higher; then cooking charcoal ~25
kJ/g; metallurgical charcoal, ~ 600 C; activated charcoal, ~800 C with
steam, CO2 or chemicals."