Main knowledge bank page | Recent additions | Recent changes | What links here | Categories | Category cloud
How-to guides | Organisation profiles | Project profiles
 

edit this page

Wood as Fuel - a guide to burning wood efficiently by M E Crowther

Boiling Point
Front cover of Boiling Point issue 28
Issue 28 (1992) Biomass Combustion, Chimneys & Hoods
ArticleWood as fuel - a guide to burning wood efficiently by Geoff Keighley
AuthorGeoff Keighley?

[top] [end]Use dry wood

1 cubic metre of fresh felled timber weighs about 1 tonne, or 1000 kilogrammes and contains up to 600 kg of water.

Heat Energy comes from the dry wood; some is used up converting the water into steam.

[top] [end]Burn wood efficiently

Under efficient, controlled conditions of burning, wood breaks down with air into ash, carbon dioxide and steam. Control of the air supply is critical. Burning occurs in three stages:

Pre-heating to 200ºC to oven dry wood and steam.
  1. With primary air, wood burns at 200-500ºC to hydrocarbon gases and charcoal.
  2. With hot secondary air, gases burn at 600-700ºC into carbon dioxide and steam.
  3. With primary air, charcoal burns at 300-500ºC into carbon dioxide and ash.


For efficient combustion remember the 3 Ts-Temperature to allow the reactions to occur, Turbulence to ensure there is good mixing, Time for the gases to remain in the combustion zone.

Figure1
Figure1


[top] [end]Comparative 'Effective Energy' for Various Stoves & Fuels

where effective energy = calorific value x percentage heat utilized (PHU)
Stove Fuel Calorific Value MJ/kg x PHU % = Effective Energy MJ/kg
Open fire Wood 18 10 - 15 1.8 - 2.7


Improved woodstove 		Wood 18 25 - 55 4.5 - 9.9


Traditional metal stove 		Charcoal 29 15 - 20 4.4 - 5.8


Improved ceramic Stove 		Charcoal 29 25 - 35 7.3 - 10.2


Gas stove, simple 		LPG 46 55 - 65 25.3 - 29.9


Kerosene stove (wick type)		 Kerosene 44 50 - 65 22.0 - 28.6



[top] [end]Contents: Boiling Point 28: Biomass Combustion, Chimneys & Hoods

.
.
Wood as Fuel - a guide to burning wood efficiently - Chimneys and Hoods for Smoke Removal - Biomass Combustion and the Environment - Charcoal and the Environment - Pros and Cons - Smoke Measurement - Stove emission monitoring - Successful Mud Brick Chimneys - Alternative Approach to Wood Combustion - Triple Cone Stove Burning Ricehulls and Woodsmoke - Energy Assistance Revisited - A Discussion Paper - Clays for Stoves - ITDG and The Maendeleo Review



edit this page

Page created: 17 July 2008; Last edited: 08 September 2008; Version: 0
Knowledge Bank text is available under the terms of the GNU Free Documentation License.

Pagename: WoodAsFuel-AGuideToBurningWoodEfficiently @HEDON: QKMA