[Stoves] Suggested calculations

[Otto Formo]

Dear Frank,
According to lab tests done by FAO in Nairobi in 1986?, they got 250 kg of char out of one tonne of very dry wood, 25%.How much C (carbon) is it in charcoal - 95%?  and 5% ash?
Estimates done from traditional kilns, gives charcoal yields around 150 kg, out of one tonne of wood, moisture content unknown, but normaly and most likely sundried.One out of five kilns goes "wrong" and gives no char (burn out) or char of poor or low quality. 
This issues has to be taken into consideration as well when you compare woodchips and charcoal in rural Africa.
Thanks for higlighting this for us.
Otto

From: frank at compostlab.com
To: stoves at lists.bioenergylists.org
Date: Wed, 24 Apr 2013 13:08:55 -0700
Subject: [Stoves] Suggested calculations

Dear Stovers,   When looking at the total picture of trees (fuel) per end use I suggest two different possible approaches. ONEThe tree chips have 40% carbon and we use a total of 100 kg of chips in a TLUD stove. We start with 40 kg of carbon. We boil water then steam rice and have left 30 kg of carbon in the char left so using 10 kg of carbon ( 25 kg of tree) in the process.The 30 kg carbon left is char chips and we use that for heating food as a street vender. At the end of the day we take home 10 kg carbon to add to our soil. So 20 kg carbon (50 kg tree) used for heating and 10 kg carbon (25 kg tree) for the soil. We start with 100 kg tree.25 kg tree used for boiling water50 kg tree for heating street food25 kg tree for garden.  = 100 % total treeWe do not follow energy but follow the fuel (in this case the tree).   TWOSame problem:To boil the water it took 100 kg of treeTo get the 20 kg of char for the street vender we would need to have 50 kg tree to make the char to do that job. To get the 10 kg char to add to the soil we would need 25 kg of tree to make the char for that garden. That’s a sum of (100+50+25)= 175 kg of tree. But we only used 100 by combining the processes so we have saved 75 kg of tree (or 43% of the forest) by combining uses.  I think I like the second method better to illustrate the savings when piggy backing the uses of fuel but still thinking about it.  Thanks Frank Thanks  Frank Shields BioChar DivisionControl Laboratories, Inc. 42 Hangar WayWatsonville, CE  95076 (831) 724-5422 tel(81) 724-3188 faxfrank at biocharlab.comwww.controllabs.com    
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