[Stoves] MUST CHARCOAL BE A CAUSE FOR CONCERN?

[rogerio carneiro de miranda]

Dear Crispin and others who has responded.

Making a simple calculation (see table below), I found the following
numbers based on 1 kg of Eucalyptus grandis, with 4650 kcal/kg as
fuelwood, or 7600 kcal/kg as charcoal.

Considering the worst case scenarios, with woodstoves efficiency of 10
to 15% one would get 450 to 698 kcal of energy into the pot, and to
have the same amount of energy from charcoal into the pot, one would
need to have either a relative medium charcoaling efficiency of 20%
but with a charcoal stove with 30% efficiency, or charcoal stoves of
normal efficiency around 20% but with higher charcoaling efficiencies
of  30 or 40-%.

Based on that, shouldn't be logical to assume that under "primitive"
existing  general conditions as seeing in the field today, that
cooking with wood is more energy efficient than cooking with charcoal?

Assuming that woodstoves can easily achieve 20% efficiency which
delivers 900 kcal into the pot, and to do the same job with charcol
one would need a 30% energy efficiency charcoal stove using charcoal
produced at 40% charcoaling process,  what is nearly impossible to
achieve.

Unless charcoal stoves of 40% are possible, so to use with charcoaling
kilns of high 30% efficiency?

Rogerio



			                     cooking with charcoal
 	         efficiency(%)             10%-20%-30%
                                 (kcal)
charcoaling	10%	(760)	        (76)	(152)	(22)
                        20%	(1520)	(152)	(304)	(456)
	                30%	(2280) 	(228)	(456)	(684)
                	40%	(3040) 	(304)	(608)	(912)
					
			cooking with fuelwood	
 	efficiency(%)		10%	15%    20%  30%
	(Kcal)		        (450)	 (698)  (900)  (1350)




2010/10/12 Crispin Pemberton-Pigott <crispinpigott at gmail.com>:
> Dear Rogerio
>
> We discussed this a while back and I forwarded some example of the energy
> balance.
>
> Yes, the fact is there is nearly no difference between the amount of food
> cooked with wood or that same wood turned into charcoal. The caveats are
> that I depends on the wood stove, the charcoaling method and the charcoal
> stove.
>
> Those are three huge variables, but for 'medium quality' on all three
> counts, the answers are about the same.
>
> The overall difference that one might be inclined to ponder is the amount of
> energy that is used to being the fuel to the cook. In the case of charcoal,
> say in Mozambique, the distance that one can profitably transport charcoal
> is far greater than that for wood because it is so much more energy dense.
> It is even better than coal because coal usually has a lot of ash in it.
>
> So, when considering what to criticise, replace and promote, one has to look
> at the three main variables, what one could do to change them, and what the
> transport implications are. It is pretty tempting to think of charcoal
> making vehicles using wood gas for locomotion, delivering charcoal to the
> cities. They would start off heavily loaded and get lighter as they got
> closer to town!
>
> I recall Cecil Cook and I having fun with this equation some time ago.
>
> What is always good (as Richard Stanley recently point out) is to make sure
> that all the chips and dust from the charcoal business end up in briquettes
> of some form. Usually the review of charcoal is made by a hostile agent and
> the 'waste' involved is emphasized, not the methods by which it can easily
> be made very efficient, all things considered.
>
> There is still a lot of this story to be told by someone with a talent for
> integrating technologies and stove ideas.
>
> Regards
> Crispin
>
>
> +++++++++++++++
>
>>I found the following quote on a FAO publication
> (http://www.fao.org/docrep/005/y4450e/y4450e10.htm), and I wonder if this is
> a correct statement responding to the question :
>
> "Must charcoal be a cause for concern?
>
> The shift from fuelwood to charcoal, even if it lasts only a few decades,
> could have major ecological consequences if it is not kept under control.
> However, since charcoal stoves are more efficient than wood stoves, the
> ratio of primary energy to usable energy is almost the same as with
> fuelwood. Thus with adequate supervision, management and support, the shift
> does not need to disrupt present levels of resource use."
>
> What do you think?  Can at the end, with actual stoves and charcoaling
> efficiencies, be the wood consumption the same?
>
> Rogerio
>
>
>
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