Dear Abelnour Samer, dear Kevin Chisholm, dear all,
There is probably no general answer on the
question of dominating causes of deforestation, because it depends on the local
conditions, but it should be considered that an urban household causes every
year the logging of 8 tons or more of mature trees, when the family is cooking
with charcoal. By multiplying this by the number of families of the city, the
total annual consumption can be calculated. Deforestation can be done at a
distance of several hundred kilometers from the town because charcoal can be
transported easily. The greenhouse gas emissions of this family, caused by
deforestation, is equivalent to that of a car journey around the globe
each year. If the cooking is done with fuel wood, thin branches can be used,
without logging of the tree.
The dated FAO study refers on fuel wood. For charcoal, there are special
studies (e.g. CHAPOSA Studies), these prove in detail the
relationship between charcoal use and deforestation. For fuel wood use, however
bushes can be planted to enable harvesting of thin sticks every year, so that a
sustainable supply is possible ("energy plantations").
On the issue of thermos-technique: The theoretically required energy for
heating and holding hot an egg is below 20 kWs resp. 20 kJ (assuming a
weight of 60 g and the specific heat of water, which surely is higher
than that of eggs), this means that using a 1 kW-heater, theoretically
20 seconds are needed. Also this example shows that the potential for
savings is enormous. The advantages of the thermos-technology ("cooking
with retained heat", "fireless cooking", etc.) are described in detail
in the Internet (e.g. from Practical Action). The production of a hay
basket in the manner described is so simple that I want to recommend
practical experience for everyone. Thermos-technology should be part of
primary education worldwide. It is critical that for simple solutions
the insulation can be easily dried after use (advantage of a basket with
pillow-insulation), that there is enough hot content in the pot, and
that the insulation does not allow heat convection (pillows should be
hold together with a cloth).
I remember a report (from Aprovecho ?) with
the test of cooking meals both with and without thermos-technology. With
thermos-technology the difference of consumed fuel wood between of the
different stoves was small and the consumption at all was very low. I learned
in Africa that cooking of beans is
often abandoned, because after four hours cooking on a charcoal brazier the
cook has got a headache and because the charcoal consumption is too expensive.
These
four hours of cooking can be reduced to about half an hour, consuming appox.
330 g of
thin sticks for boiling 6 kg of pot content.
With kind regards
Dieter
Am 13.01.2014 19:44, schrieb Kevin:
Dear Dr. Seifert
How much energy does it take to cook various foods?
For example, take a single egg... if I took a single egg and placed it in a
"Retained Heat Cooker" that had a very large thermal mass, how much heat energy
would be drawn from the thermal mass to warm the egg to cooking temperature, and to
supply the heat necessary to complete the cooking reaction?
If you don't know the energy to cook an egg, perhaps there is some other "standard
food", such as 1.00 kg of potatoes, rice, carrots, beans, etc. Perhaps there is a
Table showing the energy required to preheat foods to cooking temperature and complete
the cooking reaction. Such a Reference would be very helpful.
Thanks!
Kevin Chisholm
----- Original Message -----
From: Dr.-Ing. Dieter Seifert
To: stoves@lists.bioenergylists.org
Sent: Friday, January 10, 2014 3:04 AM
Subject: Re: [Stoves] ETHOS Discussion about decentalized stove efforts
Dear all,
My name is Dieter Seifert and I am active in the area of renewable energy
(e.g. parabolic solar cookers), together with my family, for about 30 years.
Maybe some quantitative considerations in the debate on the question of decentralized cooking
power supply are helpful. Using the combination of efficient stoves and the "thermos
technology" (cooking with retained heat), only small amounts of fuel wood are consumed, so
that a sustainable supply is possible. Refering to data from Table 2 in the article of R. Bailis
"Wood in Household Energy Use" in the Encyclopedia of Energy, Vol. 6, Elsevier (2004) , p
. 518 (for Nairobi as example for urban households):
a) consumption of firewood with open fire: 1626 to 3250 kg firewood per
household per year at 10 to 20 percent efficiency;
b ) consumption of charcoal with improved or regular stove 531 to 1238 kg
charcoal per household per year at 15 to 35 percent efficiency .
If we assume that the charcoal is produced with the conventional conversion
factor of 6 tons of wood per ton of charcoal, then this corresponds to a
consumption of 3186 to 7428 kg of wood (mature trees!) per household per year.
The consumption of wood or charcoal may be much higher in countries with higher
forest cover still present.
If we consider a household that uses an improved stove with more than 30 %
efficiency and the thermos technology, then the consumption per household per
year can be reduced to approx. 600 kg of wood (thin sticks, not trees). This
can be achieved by a stove with grate and with shielding of the pot and, for
example, 1 or 2 hay-baskets with a straw pillow under the pot and cotton
pillows around the pot and on the lid of the pot - and enough hot pot contents.
The firewood consumption is thus reduced to a small percentage (less than 10 %
compared to charcoal-use).
The hay baskets are a typical appropriate technology and it is inconceivable
that the wonderful opportunities of thermos-technology are still very limited,
concerning to the avoidable damage to the health and prosperity of families and
to the environment.
The supply of urban households with the thin sticks is an opportunity for
income generation. The support of this change should be recognized as a public
task. In contrast to the established charcoal supply for urban households these
incomes are sustainable, as it is only a matter of time when the incomes from
charcoal will cease (with growth rates of the urban population of over 3
percent, i.e. doubling of urban population every 20 years) as the sources dry
up and the country is deforested.
The necessary measures can be accomplished in a decentralized manner; but
the necessary information and practical advice could be disseminated through
the global education system, as we know that for the acceptance of the required
change, it is necessary to involve the parties affected, to recognize and
realize the challenges and opportunities.
With kind regards,
Dieter
Dr.-Ing. Dieter Seifert
Neuoetting/Germany
bdiv.seif...@t-online.de
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