[Stoves] MUST CHARCOAL BE A CAUSE FOR CONCERN?

Wed Oct 13 09:33:52 CDT 2010

Dear Rogerio

I think that the wrong question is being asked. One can also ask the 
question: "Must wood be a cause for concern?"

1: If the ultimate concern is simply availability of fuel, then both 
primitive wood stoves and primitive charcoal systems are indeed a concern.

2: If health, as a result of products of combustion considerations is the 
ultimate concern, then both primitive cooking systems are a concern.

3: The good thing about 3 stone wood fires is that they emit gross irritants 
that minimize the potential for users to be killed during the cooking 
session from CO poisoning. Good gharcoal stoves can be very efficient and 
not emit apparent poisons, but if used in a confined space, the much more 
efficient charcoal stove can kill the Family before the meal is finished.

4: Charcoal gives a quality of cooking that cannot be duplicated by a wood 
fire.

Obviously, a dreadfully inefficient "3 Stone Fire" can be much safer than an 
"Improved Cooking Stove" that has much higher efficiency. There is so much 
smoke and poisons coming off the 3 Stone Fire that people move upwind. An 
"Improved Cooking Stove" might be improved just enough that people move it 
inside a living space, and then they start dying from all sorts of 
disorders. Charcoal stoves could end up being superior, in that there might 
still be enough "residual irritants" emitted such that the Cook uses it in a 
well ventilated space.

The "problem", whatever it is, must be clearly defined before one can arrive 
at a meaningful answer to the "problem." A better question might be along 
the lines of: "What is the best way for people to accomplish their desired 
cooking task, with a given quantity of wood fuel, while improving the health 
of the people using a particular "cooking system?"

Perhaps someone else can formulate a better question that is more relevant 
to whatever issue is of concern. There is no point in promoting an "improved 
stove system" that cuts wood usage in half, but doesn't cook the food the 
way the people want it, and then kills them afterward.

Best wishes,

Kevin

----- Original Message ----- 
From: "rogerio carneiro de miranda" <carneirodemiranda at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Wednesday, October 13, 2010 9:01 AM
Subject: Re: [Stoves] MUST CHARCOAL BE A CAUSE FOR CONCERN?

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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