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Half the worldÕs population of
nearly six billion people prepare
their food and heat their homes
with coal and the traditional biomass
fuels of dung, crop residues, wood and
charcoal. The procurement and con-
sumption of these fuels deÞne the char-
acter of everyday life in many develop-
ing countries.
In rural areas, women and children
may spend several hours a day collect-
ing wood for cooking or making char-
coal, tasks that contribute to deforesta-
tion and soil erosion. Worse, the chok-
ing smoke from indoor wood Þres
causes respiratory diseaseÑmainly
pneumoniaÑwhich is the leading health
hazard in developing nations and an-
nually kills four to Þve million children
worldwide.
Living in the city provides no refuge.
The urban poor frequently spend a sig-
niÞcant fraction of their income on the
purchase of charcoal and wood. Com-
bustion of biofuels contributes to the
hazy pall that hangs over the cities of
the developing world. Carbon dioxide,
methane and other greenhouse gases
from cooking Þres may also foster
global warming.
Since the energy crisis of the 1970s,
international aid organizations have
targeted the improvement of tradition-
al cooking practices as a simple and af-
fordable way to address the environ-
mental, economic and energy issues
posed by the home Þre. Several hundred
projects spread throughout dozens of
countries have promoted the Òim-
provedÓ cookstoveÑa more eÛcient
adaptation of the metal or clay imple-
ments on which many of the worldÕs
families cook their daily meals. These
eÝorts range from national initiatives
that have introduced more than 120
million stoves into homes in rural Chi-
na to village training programs in East
Africa in which small groups of women
learn to build and maintain their own
stoves.
Cookstove programs follow closely
the model for technology development
and adoption established by the late
British economist E. F. Schumacher in
his 1973 classic Small Is Beautiful. Schu-
macher made a compelling case for
Òappropriate technologiesÓ that were
aÝordable and could be produced and
maintained locally. Unfortunately, the
enthusiasm of many of SchumacherÕs
early followers concealed a meager
technical know-how or simple na•vetŽ.
Virtually every developing country can
point to examples of dilapidated wind
pumps or photovoltaic power systems
that either did not work or could not
be repaired with local materials.
Modernized woodstoves were often
too bulky or saved fuel only when used
under ideal conditions seldom found
in the Þeld. Cookstove training courses
were sometimes oÝered only to men,
even though women perform more than
90 percent of the cooking duties in
most developing countries.
Over the past decade government
programs, development assistance
groups and community-based organiz-
ers have undertaken a thorough review
of the requirements for successful dis-
semination of cookstove technology. A
new generation of stove programs is
now implementing these hard-won
lessons. This eÝort encompasses ev-
erything from an examination of stove
thermodynamics and materials science
to market research and grass-roots ed-
ucational campaigns.
Cookstoves in Kenya
Acase history that traces the prog-
ress of stove development from
early misstep to ultimate acceptance
can be found in East Africa. Almost one
million households now cook with the
72 SCIENTIFIC AMERICAN July 1995
Cookstoves for the
Developing World
Traditional wood, charcoal and coal stoves are used in hundreds
of millions of homes. Their redesign can have a dramatic e›ect
on energy usage, the environment and community health
by Daniel M. Kammen
OPEN FIRE (left ) used for cooking in
millions of rural homes transfers heat
to a pot poorly. As little as 10 percent
of the heat goes to the cooking utensil;
the rest is released to the environment.
DIMITRY SCHIDLOVSKY
Copyright 1995 Scientific American, Inc.
Kenya ceramic Jiko. The JikoÑthe word
means ÒstoveÓ in SwahiliÑconsists of a
metal casing with a ceramic lining that
helps to direct 25 to 40 percent of the
heat from a Þre to a cooking pot. The
traditional metal stove that the ceramic
Jiko replaces delivers only 10 to 20 per-
cent of the heat generated to a pot,
whereas an open cooking Þre may yield
eÛciencies of as little as 10 percent.
The Þrst improved stoves began to
appear in the early 1980s and were de-
signed by aid groups such as UNICEF
and CARE-Kenya. The response from
stove users was mixed at best. The de-
signers, mainly natives of the U.S. and
Europe, two havens of consumerism,
had forgotten the Þrst thing about mar-
keting. Field testing was all too brief,
sometimes with pathetic results. In one
of the Þrst models, the stoveÕs opening
did not match the size of most pots.
Even more fundamental problems
plagued some of the early prototypes.
Designers acted as if it would be an ele-
mentary exercise to improve the eÛ-
ciency of the common metal stove, a
deceptively simple canlike enclosure
into which charcoal or wood is fed and
ignited. In fact, after much trial and er-
ror, it turned out that an extensive in-
vestigation of stove physics and engi-
neering design was needed. This analy-
sis revealed that the largest loss of heat
from the Þre, about 50 to 70 percent,
occurs from radiation and conduction
through the metal walls. Makers of
some of the Þrst stoves took measures
to deliver more of the ÞreÕs energy di-
rectly to the pot. They sometimes ac-
complished their job a little too well.
The design for one early improved
Jiko model emerged after an aid group
named the Kenya Renewable Energy
Development Program sponsored a re-
search trip to Thailand to inspect an
improved stoveÑthe Thai bucket. The
resulting Jiko design had inward-slop-
ing metal walls, like the Thai stove, as
well as an insulating liner made of ce-
ramic and a mica called vermiculite.
The liner was cemented from the top
to the bottom of the inner surface
walls. It caused excessive amounts of
heat to be retained inside the ta-
pered vessel. Metal fatigue re-
sulted from exposure to the
trapped hot gases, which caused
structural segments to crack.
An initial round of Þeld tests
did not provide enough feedback
to stop this Þrst-generation im-
proved Jiko from reaching the
SCIENTIFIC AMERICAN July 1995 73
METAL STOVE (left ), a traditional cook-
ing implement, directs only 10 to 20
percent of the heat to a pot. From 50 to
70 percent of the heat is lost through
the stoveÕs metal sides, and another 10
to 30 percent escapes as carbon diox-
ide, carbon monoxide, methane and
other ßue gases.
KENYA CERAMIC JIKO (left ) in-
creases stove eÛciency by addi-
tion of a ceramic insulating liner
(the brown element), which en-
ables 25 to 40 percent of the heat
to be delivered to the pot. From
20 to 40 percent of the heat is ab-
sorbed by the stove walls or else
escapes to the environment. In
addition, 10 to 30 percent gets
lost as ßue gases, such as carbon
dioxide.
COOKSTOVE SMOKE is ubiquitous in Kenya, where wood, char-
coal and other biomass fuels are used for cooking and heat- ing. Particulates in smoke are a major contributor to respirato-
ry disease, the leading cause of illness in developing nations.
GEORGE MULALA
Copyright 1995 Scientific American, Inc.
market, where it received an equivocal
response from purchasers. Various
governmental and international aid
groups, however, continued to work
with a loose consortium of craftspeo-
ple, called Jua Kali, or ÒHot Sun,Ó to try
to rectify the problems.
Better stove designs gradually came
about during the mid-1980s. At that
time, a number of academics began to
publish serious analyses of optimal
stove combustion temperatures and of
the insulating properties of the ceramic
liner materials. One of the most no-
table contributions to enhanced design
came through the responses of several
womenÕs organizations that had formed
around such issues as community
health and protection of the environ-
ment. These groups were part of a fem-
inist movement spreading throughout
the developing world. In Kenya, it was
women who suggested recasting the
metal bucket design, with its unstable
narrow base, into an hourglass shape.
That alteration prevented the new
stove from tipping over, a constant dan-
ger when food was vigorously stirred
in the Thai-inßuenced, bucketlike im-
plement. It also meant that the insulat-
ing liner need extend only from the up-
per lip to its narrowest circumference
at the stoveÕs middleÑand the tapered
shape let the liner rest stably cemented
to the upper metal walls without falling
into the stoveÕs bottom cavity. Because
the liner covered only half the stoveÕs
interior, it did not cause the overheat-
ing and consequent cracking that had
plagued the early versions.
These design changes, along with ex-
tensive training programs established
by aid groups and womenÕs organiza-
tions, caused dramatic gains in accep-
tance for the more eÛcient stoves.
Schools, churches and businesses were
among the Þrst owners and helped to
spark the interest of individual buyers.
Today hundreds of Jua Kali manufac-
turers provide stoves to some 20,000
purchasers every month.
Benefits of the Jiko
The ceramic Jiko has had a consider-
able impact on household Þnances.
Typical savings of 1,300 pounds of fuel
a year frees up about $65 per house-
holdÑup to a Þfth of the annual in-
come for urban dwellers. Women have
beneÞted in that they control a dispro-
portionately small share of family in-
come yet are the primary purchasers of
fuel. The Kenya ceramic Jiko has im-
proved their lot in impor-
tant ways. Many have in-
vested the savings from re-
duced fuel purchases in
small businesses or school
fees for their children.
Currently more than half
of all urban households in
Kenya own the ceramic
Jiko, and purchasers range
from the poor to the af-
ßuent. The concentration
of demand in urban areas
points up another diÛculty
with the early stove pro-
grams, which commonly
targeted users in the coun-
tryside. Programs outside
the cities, where more than
70 percent of the Kenyan
population lives, seemed
justiÞed because they met
the needs of the poorest
segment of society. But the
$2 to $5 stove price proved
too high for many house-
holds that had the option
of collecting their own Þre-
wood and cooking over
open Þres. For city dwell-
ers, who sought ways to
cut their unavoidable fuel
costs, more eÛcient stoves
held a greater allure.
Establishing an infra-
structure for stove produc-
tion has begun to beneÞt the masses
who live outside the city. Village resi-
dents have little ability to pay for a ce-
ramic Jiko that may cost up to $5. But
they may be willing to spend something
less than that amount, some observers
reasoned. After all, there are undeni-
able beneÞts for an implement that will
diminish the drudgery of collecting
wood for hours on end and that will re-
duce the acrid smoke in cooking huts.
The smoke can cause exposure to par-
ticulates at 20 times the level that the
World Health Organization considers a
serious health risk.
Success of the ceramic Jiko in Nairobi
and Mombasa did not go unnoticed by
many of the womenÕs groups that had
organized in rural areas. An alliance de-
veloped between leading government
and aid organizations in Nairobi and
womenÕs groups, most notably Maen-
deleo ya Wanawake (literally ÒWomenÕs
DevelopmentÓ). From these eÝorts has
come a simpliÞed and aÝordable vari-
ant of the ceramic Jiko.
The Maendeleo stove borrows the in-
sulating element from the ceramic Jiko
without the metal outer covering. The
ceramic liner is set down in the middle
of the open Þreplace; it is then rein-
forced with mud and stones. A pot
placed atop the stove heats almost as
quickly as one on a Kenya ceramic Jiko.
Indoor smoke is reduced considerably
through more eÛcient combustion.
Further, a Maendeleo stove is usually
placed near a wall of the hut so that
smoke can climb along the wall and
exit more easily.
The Maendeleo stove costs as little as
80 cents; more than 100,000 of them
have been disseminated so far. This ru-
ral success story helped to spawn a
third-generation cookstove, the Kuni
Mbili (Ò two-stickÓ) stove, which has a
larger Þrebox to accommodate wood
instead of the charcoal typically used
in urban settings.
The Kenyan program has been emu-
lated in a number of other African
countries, where the improved stoves
continue to gain popularity. Variants of
the Kenya ceramic Jiko have made their
way to Tanzania, which has more than
54,000 stoves; Sudan, which has
28,000; Uganda, which has 25,000; and
Zambia and Burundi, each having from
5,000 to 10,000.
Chinese and Indian Programs
Higher eÛciency cookstoves have
been adopted throughout the de-
veloping world. China has by far the
worldÕs most extensive program, with
more than 120 million stoves in placeÑ
seven out of 10 rural households own
METAL COOKSTOVE: Traditional cookstove, pro-
duced by local artisans, has a metal skin that lets heat
escape easily. Efficiency: 10 to 20 percent. Cost: $0.25
to $10. Number disseminated: hundreds of millions.
KENYA CERAMIC
JIKO:
This metal stove with a
ceramic liner has achieved great popularity both with-
in Kenya and in neighboring countries. Efficiency: 25
to 40 percent. Cost: $2 to $5. Number disseminated:
nearly one million.
MAENDELEO:
This ceramic insulating liner can
serve as an inexpensive stove when placed in an
open fireplace and reinforced with mud and stones.
Efficiency: 15 to 35 percent. Cost: $0.80 to $1.20.
Number disseminated: more than 100,000.
KUNI MBILI:
A variation on the ceramic
Jiko,
this
stove has a large firebox to hold wood sticks instead
of charcoal, making it more suited for rural cooking.
Efficiency: 25 to 40 percent. Cost: $2 to $5. Number
disseminated: more than 20,000.
CHINESE IMPROVED COOKSTOVE: Brick and
mortar stoves with chimneys are used to burn wood,
straw, rice husks and coal. Efficiency: 20 to 40 per-
cent. Cost: $8 to $9. Number disseminated: more
than 120 million.
INDIAN
CHULA:
Efficient clay fireplaces, called
Chulas,
have been installed in rural homes in India.
Efficiency: 10 to 40 percent. Cost: $8 to $10. Number
disseminated: more than eight million.
74 SCIENTIFIC AMERICAN July 1995
DIMITRY SCHIDLOVSKY
Copyright 1995 Scientific American, Inc.
these units. The longtime isolation
of that huge country has, until re-
cently, made it less inßuential than
Kenya as a model for other devel-
oping countries.
The Chinese stoves, which burn
wood, crop residues and coal, con-
sist of a brick and mortar construc-
tion with a chimney that Þts in the
central living area of a home. An
insulating material, such as ash
and mortar, is packed around the
circular cast-iron opening, which
holds a wok.
Even the centralized Chinese gov-
ernment recognized that a suc-
cessful stove program could not
be mandated from Beijing and
must meet local peopleÕs needs.
Besides conducting stove research,
the government conÞned itself to
clearing away bureaucratic hur-
dles, giving local energy oÛces the
responsibility for technical training
and setting standards for manu-
facturing production. Most impor-
tant, people made their own deci-
sions to buy the stoves: no direct
subsidies were supplied to pur-
chasers by the government.
In contrast, a program in India, in
which the government subsidized 50
percent of the cost of the eight million
stoves distributed, resulted in half the
stoves lying unused. The government
ignored important regional diÝerences
in cooking habits. Respondents to fol-
low-up inquiries often complained that
the stove did not really save energy or
get rid of smoke. Fortunately, reforms
by the government and the launching
of new research programs during the
past Þve years have begun to correct
these problems.
The lessons of improved stove pro-
grams can serve as the basis for a more
radical shift away from traditional
cooking technologiesÑfuel use can be
eliminated by harnessing the energy of
the sun. The solar oven, an idea report-
ed a century ago in ScientiÞc American,
is essentially a greenhouse for cooking
food. It consists of an insulated box
made of wood, metal, plastic or card-
board whose open top is covered with
one or two plates of glass.
Trapping Sunlight
Solar oven designs are as varied as
cookstoves, but a Òbox cooker,Ó as
it is known, typically incorporates walls
with a reßective coating, such as alu-
minum sheet or foil, and a metal ßoor
plate to absorb sunlight. The energy is
then reradiated within the box as in-
frared heat, which does not escape be-
cause it is blocked by the glass. Pots on
the bottom metal plate can heat several
liters of water or food to more than 300
degrees in under an hour.
The ovens are mostly used for crock-
pot-style cooking. They allow for slow
simmering, baking and roasting in cov-
ered pots. On a sunny day, rice, stews,
chicken or bean dishes will be fully
cooked in two to Þve hours.
Solar-box ovens will never com-
pete with the microwave oven in
speed of preparation, and they
must be supplemented with a
wood cookstove for a rainy day.
But they require no fuel except the
sunÕs raysÑand they emit no
health-damaging smoke. By using
the technology, some households
in Africa, Latin America and else-
where have reduced their cooking-
fuel expenditures by 50 percent.
As with the early stove pro-
grams, acceptance rates are still
modest: only 20 to 40 percent of
the Kenyan families who adopted
some 2,500 solar ovens early on
continue to use them. The cost of
the stovesÑ$20 to $40 apieceÑre-
mains too high for many house-
holds. Yet the Jua Kali artisans
who have mastered mass produc-
tion of the ceramic Jiko might also
be able to make large numbers of
solar ovens, which could halve the
price. The cost of the ceramic Jiko
dropped markedly, from $12 to as
little as $2, once the stoves were
mass-produced. In many places,
a manufacturing base has begun to
emerge that could bring costs down.
WomenÕs groups, artisans and several
large-scale commercial industries in
more than 100 countries are making
solar ovens in a diverse range of styles.
(Besides Kenya, China and India each
have more than 100,000 in use.)
Cookstove projects boast a record of
accomplishment that may serve as a
model for the development of an array
of renewable-energy projects, such as
wind-energy systems and photovoltaic
electrical generators. The halting Þrst
steps of the appropriate technology
movement are now being translated
into solid research and a more prag-
matic execution. These programs may
become a realization of SchumacherÕs
vision: for one out of every two people
worldwide, modiÞcations in their means
of cooking oÝer enormous promise for
improvements in health and economic
well-being.
SCIENTIFIC AMERICAN July 1995 75
The Author
DANIEL M. KAMMEN is assistant professor and co-chairperson of the Science,
Technology & Public Policy Program of the Woodrow Wilson School of Public and
International AÝairs at Princeton University. His research focuses on energy re-
source management, technology policy, and gender and environmental issues.
Kammen received his bachelorÕs degree from Cornell University and his Ph.D.
from Harvard University, both in physics. Before moving to Princeton, he did post-
doctoral work at the California Institute of Technology in neurobiology and re-
newable-energy engineering and at Harvard in global change studies. Kammen di-
rects a Þeld training program on renewable energy and development in partner-
ship with the African Academy of Sciences and the University of Nairobi.
SOLAR OVEN, shown in Kenya, cooks food in a
glass-covered box where pots are placed.
Further Reading
BOILING POINT. The journal of the Intermediate Tech-
nology Development Group (in Rugby, England) and
the German Association for Technical Cooperation.
BIOMASS STOVES: ENGINEERING DESIGN, DEVELOPMENT
AND DISSEMINATION. Samuel F. Baldwin. Volunteers
in Technical Assistance, 1987.
WHAT MAKES PEOPLE COOK WITH IMPROVED BIOMASS
STOVES? Douglas F. Barnes, Keith Openshaw, Kirk R.
Smith and Robert van der Plas. World Bank Techni-
cal Paper No. 242, Energy Series, 1994.
DANIEL M. KAMMEN
Copyright 1995 Scientific American, Inc.
