12 to support large pots used for shea processing
and to heat bathing water for large families.
We also investigated the effects of cooking
systems on fuel usage. We wanted to gather
data on factors from the entire cooking environment rather than only the cookstove. We
looked at 17 factors ranging from mass of the
water and ingredients being heated and the
size of the cooking vessel to the species and
water content of the wood being burned.
data on these factors were recorded in the 155
cooking tests completed across all meal types and
stove types8. The tests were strictly observational.
No wood or food ingredients were provided and
no instructions given to respondents. This allowed
respondents to cook as if it were a typical day.
Multiple regression analysis with forward selection was used to analyze the data. Six factors
proved to be statistically significant in estimating
energy use: the type of cookstove application,
family size, total mass of wet and dry ingredients,
mass of dry ingredients, the use of burning embers as an igniter, and the number of fires used
during a cooking event. The smallest families, for
example, used almost twice as much energy, per
person, as families of 20 people.
It has been proposed that reducing grain
flour size would reduce energy use in this
village, the thinking being that smaller grains
would cook faster. We didn’t find any evidence
to support that. The diameters of the various
grains used in breakfast porridges, for example,
Most interestingly, little evidence was found
to suggest that improved cookstoves signifi-
cantly influenced cooking energy use after ac-
counting for other factors. Only one stove had a
statistically significant effect on energy use.
Though the specific numbers in our find-
ings may not apply directly to other settings,
they may suggest a general lesson: The impacts of cookstove improvements can depend
more on factors in local cooking systems than
on improvements in thermal efficiency. The
actual fuel savings demonstrated by improved
cookstoves in this case study were far smaller
than savings measured in laboratory tests.
actual savings can be calculated using the
rated fuelwood savings in the laboratory, the
adoption rate for the cookstove, how often
each cooking task is performed, and the rate
the cookstove is used for each task. Fuelwood
savings for a consumer group can be calculated using the following equation:
(rated fuelwood savings) × (cookstove adoption
rate) × (rate of each cooking task) × (rate the
cookstove is used for each cooking task) = actual
Taking the data on cookstove use and a rated
fuelwood savings of 50%, the actual fuelwood
savings for the low-thermal-capacity cookstove
for this group of consumers equates to
(50%) × (100%) × ( 1.13% × 50%) × (100%) =
• Wood and charcoal are the only viable fuels in
the short term. Petroleum fuel expenditures
for cooking would be 7 to 11 times greater than
current domestic energy expenditures. Biogas can
only supply a limited amount of domestic cooking
needs. Solar cookers would require substantial
changes in meal times, eating practices, and work
schedules due to agrarian living.
• A single improved cooking device will likely
be insufficient to address the wide range of
• Cookstove portability is important. Women
prefer to cook meals inside the kitchen and heat
water outside the kitchen. Further, approximately
10% of the village travels to hamlets during the
farming season and would be unable to transport
stationary cookstoves installed into kitchens.
• Stationary cookstoves may be lost when the
wattle-and-daub kitchens collapse from heavy
rains in the monsoon season.
• A delivered cookstove cost of US$10 seems to
prevent purchase for many families that have
access to an improved locally-made stove but do
not own the stove despite stated aspirations.
• A solar water heater could displace a portion of
domestic wood use. The outgoing water temperature
from the solar heater should provide water that can
be mixed to create bathing water of 39 to 48°C.
• Women can be away from the fire for up to 15
minutes. A cookstove that can maintain a stable
fire over this interval without being tended could
lead to faster cooking and reductions in incomplete
combustion by avoiding a smoldering fire.
Meal Percentage of all meals prepared (%)c Percentage of meals prepared on cookstove (%)a,b TSF GK LTC HCM MM
Breakfast porridge (thin) 17.86 7.78 92.22 0.00 0.00 0.00
Breakfast porridge (thick) 15.48 8.97 91.03 0.00 0.00 0.00
Lunch or dinner porridge (thin)
with sauce 37.11 7.34 92.66 0.00 0.00 0.00
Lunch or dinner porridge (thick)
with sauce 21.54 9.04 90.96 0.00 0.00 0.00
Rice 1.59 50.00 50.00 0.00 0.00 0.00
Couscous 5. 29 0.00 100.00 0.00 0.00 0.00
Porridged 1. 13 0.00 100.00 0.00 0.00 0.00
Sauced 0.00 0.00 100.00 0.00 0.00
TABLE 5: Cookstove use for cooking meals
TECHNICAL DESIGN GUIDELINES FOR COOKING TECHNOLOGY IN THE STUDY AREA