HUAMANZAÑA, PERU: Phase II Assessment and Plan for Future Projects
Shannon M. Brink, EWB–PRINCETON UNIVERSITY, Princeton, NJ March 2007
Trip: 27 December 2006 –10 January 2007
I am member of a student chapter of Engineers Without Borders. We have built two Inkawasi stoves with somewhat disappointing results. (We are still not achieving complete combustion, the sunken pot chambers are problematic for accommodating a variety of cooking utensils, and the smoke escapes from the gap around the pot skirts.) The engineers on the team are discouraged and have given up on the rocket elbow stove design. Though I'm not an engineer, I am skeptical that the stoves were built according to specifications (one was tiny, the other huge); outside engineers who have experience with similar stoves have suggested that our combustion chamber (which was short‹only a little more than 12") was too short.
Our design objectives are threefold:
1) Reduce the amount of smoke
2) Reduce the amount of fuel wood necessary
3) Reduce the amount of time needed for cooking
We work in Peru, and the townspeople also use tusa (dried corn cobs) as a fuel during certain seasons and to ignite the fire. It produces a thick, acrid smoke.
Sources outside the University have recommended that we look into other rocket elbow stoves, such as the Onil stove. I am interested in the following data on the Onil stoves:
1) Materials list and costs
2) Results data (smoke reduction, percent complete combustion, fuel
3) Plans (if available to the public)
4) Estimation of its effectiveness using the corn cob fuel
5) Any experience you have working with Helps International (I'm planning to contact them directly as well)
The engineers in our group are currently working on chimneys instead of stoves as a smoke-reduction technology. Because this won't address the combustion and efficiency issues, I am concerned about the viability of simply installing chimneys over their existing stoves, which are two bricks with rebar across the top. Do you know something similar to a chimney has been effective in other regions?
If you need further information about our project and testing it the Inkawasi, I'm happy to share it. I'm not familiar with how listserves work, so tell me whether I can email that privately or what's the best way to get it to you.
Thank you in advance, and best wishes.
See document: BioListservinfo.pdf" attached.
Excerpts from the project report " Assessment 2006-2007.pdf" (3.5 MB):
In December 2006 and January 2007, EWB–Princeton returned to Huamanzaña, La Libertad,
Peru to conduct an assessment trip with four sets of objectives:
1. Evaluating the solar energy system at the primary school
2. Constructing and testing an efficient wood-burning stove
3. Conducting water quality testing and performing an overall site assessment
4. Fostering increased community involvement in the projects
This report discusse the findings in each of these areas, as well as gives a thorough account of the preparation, execution, and follow-up for the trip. Additionally, this document describes the logistics of travel to Huamanzaña and includes a final budget. Finally, it concludes with recommendations for how EWB–Princeton should move forward with its work in Huamanzaña, Peru.
3.2 Wood-Burning Stove Objectives
Background: Currently, cooking in Huamanzaña is done on open fires in enclosed homes. This leads to considerable pollution inside the homes, resulting in smoke-related illnesses. We are performing a complete assessment of the use of wood-fueled
cooking in Huamanzaña, to enable the design of alternative stoves, which use a sustainable fuel source and remove pollutants from homes.
Objective 1: Wood Fuel Assessment. Determine the annual demand for fuel wood by the
community and compare this to the available sources of wood. Determine the current depletion levels of local trees. Survey the land availability to support a sustainable fuel source from wood. Estimate the cost and labor involved with managing an arboretum.
Objective 2: Alternative Fuel Assessment. Assess the availability of alternative fuels from nearby towns. Determine the annual cost for a family to cook with an alternative fuel such as LPG or Propane: materials, fuel and transport
Objective 3: Material Availability Survey. Identify the locations to purchase necessary materials for wood burning stoves: bricks, mortar, rebar, ceramic. Estimate the cost of implementing a wood burning stove: materials, fuel wood, and transport.
Objective 4: Materials Testing. Test bricks for heat/flame compatibility. Test suitability of ceramic for insulation. Assess fire hazards and heat sensitive materials in buildings.
Objective 5: Establishment of Baseline. Observe current food preparation habits: duration, quantity of food, boiling vs. simmering, etc. Survey current fire management methods: size of wood, size of fire, frequency of replenishment, etc. PerformWater Boiling Tests on current stoves. Test current emissions levels. Talk to
community members about their cooking habits, fuel use, use of fire as a heat
source, and any other comments.
Objective 6: Model Stove. Build a model stove to show our current design to the local
community. Engage community members in discussion about the stove and allow them to make comments. Give community members time to try out the stove with their own fuel burning and cooking methods.
7. Efficient Wood-Burning Stoves
7.1 Summary (Project Choice)
The aim of redesigning stoves in Huamanzaña is to reduce the environmental and health
problems resulting from current cooking methods. Currently, near-open fires are used to cook inside homes in Huamanzaña, resulting in significant indoor air pollution and inefficient fuel use.
Additionally, the main fuel currently used in Huamanzaña is wood, which is not only scarce, but also leads to local deforestation.
The associated health problems described to EWB-Princeton University during the summer 2006 trip included respiratory problems such as bronchitis, pneumonia and increased frequency and severity of colds. In addition, villagers complained of black smoke particles in their saliva and eye problems due to smoke exposure. The primary groups affected were women and children.
As a result there are three technological aims to redesigning stoves in Huamanzaña. First, the indoor air pollution needs to be reduced by improving completion of fuel combustion and minimizing the amount of exhaust gas entering the homes. Second, maximizing heat transfer to cooking pots, will increase stove efficiency resulting in a reduced demand for fuel. Third, the stoves should reduce the amount of time women must spend cooking each day.
In order to ensure sustainability of the new stoves, a number of constraints must be met. The stoves must be applicable to the fuels available in Huamanzaña. The stoves must cook the foodin a way that is convenient, acceptable and sensitive to the demands of the community. The stoves must be durable over a reasonable lifetime and must be able to be constructed using locally available materials, tools and labor. Consequently, they must incorporate the mental and physical input of the local community in design and construction.
We are trying to approach the problems associated with cooking in a holistic manner,
considering practical, technical, and economic limitations. As a result, the solution is not straightforward, but will hopefully be a compromise between functionality, efficiency, and cost.
7.2 Preparation and Designs
The combustion of wood to produce energy is already very efficient in open fires. Therefore, the main advantage of improving combustion efficiency is to reduce smoke and harmful emissions.
Improvement of heat transfer from the fire to the pots presents the largest opportunity for reduced fuel use. The design principles for both aims are summarized briefly below.
For complete combustion, excess air is required; however, this air should be preheated to
facilitate oxidation reactions. Insulating the area around the fire helps it burn at a higher
temperature, reducing smoke production and facilitating more complete combustion. A chimney
above the fire increases draft through the fire. It also gives exhaust gases a place to further react,
thus reducing harmful emissions.
7.2.2 Fuel Efficiency
Increasing temperature and speed of gases in contact with pots will increase fuel efficiency. This can be done by insulating the hot gas pathway, except where it contacts the pots. Maximizing contact area between pots and hot gases will also improve efficiency.
In order to propose an example of an efficient, clean-burning stove to the community of Huamanzaña in January, EWB-Princeton built a stove based upon the “rocket-elbow” or “Inkawasi” design. The Inkawasi design was chosen because it has proven to be a successful implementation of the design principles outlined above. Nonetheless, after constructing the stove in the community, we realized that there are drawbacks to this model. The final design must improve efficiency and reduce emissions in a way that complements villagers’ needs, rather than solely driving the stove design from a technocratic point of view.
7.3 Current Stoves
Current stoves have no chimneys for exhaust gases. However, they are nearly open fires, which can often be more efficient than a more complex stove if the latter is poorly insulated with massive materials close to the fire. Therefore, removal of exhaust gases through redesigned stoves must not compromise the efficiency of heat transfer or fuel use. In fact, a good design will improve on all of these aspects.
7.4 New Stove Design
The following three schematics depict the proposed stoves, which are based on an elbow shaped combustion chamber that preheats the air. The exhaust passage passes by the pots, transferring this heat to them. The cross-sectional area of the gas pathway is kept constant to ensure continuous flow through to the chimney. The stove is hottest closest to the combustion chamber.
Water boils fastest for this pot; however there will be sufficient heat to the other pots for reheating and simmering pots of food.
7.5.1 Campus Testing
In November 2006, EWB–Princeton team members built a prototype stove in the Engineering Quadrangle, approximating local materials with American versions available at Home Depot. Construction took several days and was overseen by Chris Pritchard and Dobromir Parushev. Stove testing consisted of the Water Boiling test and was conducted in a single evening, though in retrospect, this was not enough time to truly evaluate the stove’s efficiency.
7.5.2 Efficiency Testing
The success of the stoves to deliver heat to the cooking pots was to be measured by a
standardized test procedure (1995 VITA International Standard Water Boiling Test) consisting of three parts:
• High Power Test (Cold Start). This test measures the time and fuel required to boil a pot of water on a freshly ignited stove.
• High Power Test (Hot Start). This test measures the time and fuel required to boil a pot of water on a hot stove.
• Low Power Test. This test measures the fuel required to maintain water at simmering
The majority of cooking occurs at simmering temperatures. Therefore the most fuel savings can be obtained by ensuring the stoves do not produce excessive amounts of steam during this phase. Our plan was for villagers to be invited to prepare common meals on the stoves so we couldevaluate their efficacy for daily cooking purposes, but because of time constraints relating to Peter Templer’s evacuation, there was not enough time for this during the visit. We plan to follow up by phone to see how the stove is working.
7.5.3 Exhaust Testing
Testing of the exhaust gases should include measuring the exhaust gas temperature. This can ensure the stove is transferring sufficient energy to the pots whilst ensuring the exhaust gases have significant energy to react completely. Also, an analysis of exhaust gas components was collected by taking samples using pump filters that trap particles and trace elements. These were analyzed upon return to Princeton.
EWB–Princeton conducted two sets of tests, one set in the home of Doña Rosa Navaez while she used tusa as fuel, and another in the home of Doña Asunciona Rojas while she used algorrobo. The tusa test was particularly difficult on the parts of Chris and Ted who had to use a hand pump for 3 minutes to collect the particulates from the smoke; the fumes were acrid and burned their eyes, leading them to cough and pull their shirts over their mouths for protection against the smoke. This test was not truly indicative of the general conditions under which women cook because some leave the room while the tusa ignites the other fuels, and moreover, Doña Rosa
added tusa to ensure that the smoke continued for the full three minutes. Although one of the two tests conducted during this set failed because the filter was inserted incorrectly, from both filters, it is obvious that the tusa produces a thick, brown cloud of particulates that the cook ingests.
Shannon conducted the second test in the home of Doña Asunciona with the help of her granddaughter and fellow cook Lejdi Diana Ibañez Polonio. This test with algorrobo, a
common type of firewood,5 and the particulates captured were much cleaner. Shannon also reported that it was significantly easier to breathe during the algorrobo test.
Definite quantitative conclusions are difficult to reach with the data from the hand pump, but EWB–Princeton did weigh the filters to provide a rough comparison of the mass of particulates per pump. If we extrapolate that one pump might be roughly
equivalent to one breath, the data suggests that the effects of tusa are 16 times those of algorrobo.
See Appendix 15.2 for more information about species of woods used. Right: Chris displays the filter from the tusa exhaust testing. Below: Filters from exhaust testing. #1 and #2: Tusa at Rosa Navaez’s home. (On test #2, the filter was
inserted incorrectly, but it is clear that a comparable amount of particulate matter accumulated.) #3 and #4: Algorrobo at Asunciona Roja’s homes. A blank filter has been included for comparison.
Test Fuel Minutes Pumps Particulate Mass Mass/Pump
7.6 Fuel Assessment
The main fuels available in Huamanzaña are leña (wood) and tusa (corncobs). The amount of time families spend collecting fuel wood varies depending on the availability of firewood on their chacras (plots). They collect branches that have fallen to the ground, and they often climb into the trees and cut branches down with machetes. The corn is grown locally, and once the kernels are stripped from the cobs, the cobs are collected and used as fuel. The major disadvantages of corncobs are that they burn very quickly, do not produce as much heat as wood, and produce tremendous amounts of smoke. However, due to the scarcity of trees in the area, they constitute a major source of fuel for the community, particularly after the
harvest, when wood is scarce, or during the rainy season when wood is constantly damp.
Alternative fuels, such as propane or kerosene were available, but considered too expensive for usual cooking. A small canister of kerosene cost around $10 USD. Only a few houses in the community had kerosene canisters, in case they ran out of wood or corncobs. The cost of liquid or gas fuels was clearly prohibitive and not a viable option compared to perhaps more labor intensive, less efficient but cheaper solid biomass fuels.
7.7 Materials and Their Availability
The materials used were:
• Steel pipe for chimney
• Rebar for supporting pots and to provide a grate for fuel wood.
• Ceramic tiles (called ladrillos pasteleros)
All of the necessary materials were found within three hours of Huamanzaña, either in Chao or Trujillo. It was possible to have heavy items, such as brick and mortar delivered to the village, though this takes several days and can be expensive.
The second test failed because the filter was inserted incorrectly. However, we can observe that the amount of tusa particulate matter seems comparable to the amount collected during the first test, suggesting that the first test was no anomaly.
For further discussion of fuel uses as reported by women during the interviews, please seesection 9.6.1.
7.8 Prototype Site Selection
The prototype stove was built in the school’s new comedor (dining hall), currently still under construction. We designed the stove to accommodate the large 35-centimeter pots used for cooking for the school children’s lunchtime meals.
7.9 Stove Construction
The stove was constructed on a tendal, or table, which is customary in the area. Locals did all of the construction. Don Norberto was appointed as the project leader to direct the construction. We worked with him to explain the concepts behind the design and the necessary dimensions. Following that, he directed a group of men to construct the stove. This facilitated not only community involvement, but also community leadership and responsibility.
The community decided on the site for the prototype stove during the second meeting. See section 9.4 for a complete discussion of what went on during that meeting.
Many families have tendales made from iron or other metals; the metal serves as a counter over a table supported by concrete. (Some families have space underneath their tendales while others have solid block tendales. The tendal built for the new comedor was made from adobe bricks.
7.10 Community Feedback
We received significant feedback from the community on the prototype stove. The major
• Cost: The stove cost around $70 dollars to construct, which was far too expensive. The community asked us to look into ways of using fewer bricks and a cheaper option for the chimney.
• Use of corncobs: The stove was unsuitable for corncobs due to the small access to the combustion chamber. Corncobs would clog the combustion chamber and inhibit the flow of air into the stove. However, because corncobs are such a significant source of fuel, the design needs to accommodate this fuel source.
• Variable pot sizes: The current stove design requires that each household choose three pot sizes to which the stove be fitted. However, this does not provide sufficient flexibility for cooking. A modification needs to be created to allow people to vary which pots they use in each opening.
• Boiling more than one pot simultaneously: The current design only produces enough heat for boiling in the first opening. However, often women in Huamanzaña boil different foods in more than one pot at the same time.
• Using fewer than three pots simultaneously: The current design only works if all three openings are filled. Therefore, without covers, it is not possibly to use fewer than three pots simultaneously.
7.11 Design Revisions and Future Plans
After the assessment trip we have met for a number of brainstorming sessions to try and resolve the issues with the stove design we built in Huamanzaña. This enabled us to step back and reassess our goals for the project: a) to improve health standards in Huamanzaña; b) to lessen pressures on fuel supply; and c) to reduce the amount of time women need to spend cooking each day, thus freeing them to participate in other productive activities.
Currently, we are rethinking the approach in two ways:
• Reassessing the viability of solar cooking. The capacity for solar cooking in
Huamanzaña needs to be assessed. This could determine to what extent solar cooking
could be a substitute for conventional cooking, such as pasteurizing water, or heating food to a certain temperature and then finishing off the cooking on an efficient woodburning stove.
• Redesigning the efficient stoves to allow more flexibility and the use of corncobs.
9.6.1 Talking with Women About Their Stoves and Cooking Techniques
Stove interviews were structured around investigating thirteen primary questions in order to
collect comparable data from each household. Questions were as follows:
1. What type of combustible do you use in your current stove (firewood, tusa, kerosene, gas,
2. What type of firewood do you use (algorrobo, sapote, espino, etc.)?
3. At what times of the day do you generally cook?
4. How much time do you spend cooking each meal?
5. What meals do you cook frequently?
6. Do you boil your water before drinking it?
7. What effects does the smoke from the stove have upon you and your family?
8. How much firewood do you use?
9. How much time does it take you to collect firewood?
10. How many pots do you need to cook and of what size?
11. How many buckets or barrels of water do you fill each day?
12. Do you use chlorine or bleach to treat the water?
13. Of the priorities that the townspeople have generated for future EWB–Princeton projects, which are most important to you and your family? Why?
Interviews were not strictly limited to the topics addressed by the questions, and we let the interviewees steer the conversation. This worked well because women often provided otherrelevant information, such as news that the government is planning to build a health post in Huamanzaña or information about how people collect water from the Puquio Reprisa or Reservoir 1982 when there is not enough water in the taps. Also, as we conducted more interviews, we saw some trends in the responses. Nearly all townspeople use the same types of firewood, though they do so in varying quantities. No one treats their water with chlorine or bleach, though many do use the chemicals to clean the buckets in which they store their water for the day. Moreover, women admitted that when Don Martín had chlorinated the water that ran to
the taps in town, people disliked the flavor.
The interviews also show many personal variations in the cooking times, fuel use, and difficulty of finding firewood within the different families. These results are
summarized in Appendix B. Though the variations will prove challenging to designing a stove that supports various cooking styles and techniques, it also highlights the important role that education can play in modifying these habits. In particular, it underscores the need for EWB–Princeton to develop an educational component for the stove implementation trip that deals with the proper amount of wood necessary to
stoke the new stoves. Visiting homes and talking to women on a one-on-one basis or with other women also afforded us the opportunity to observe another side of Huamanzaña life. We noticed that there is significant variation in how families store their water for the day: after filling their buckets or barrels at the various taps throughout the town, some people leave the water buckets uncovered, whereas others are careful to put lids on each bucket. Within the subset of families who leave their buckets uncovered, there is also variability in the cleanliness of the containers and the water itself. Nonetheless, because water-borne illnesses do not seem to be a significant health issue in Huamanzaña, these results may serve only as anecdotes.
Shannon and Ted conducted the majority of the interviews with women as a pair, though the latter interviews were conducted solely by Shannon. As the only female member of our team, we thought it was important that she lead the interviews because women might be more comfortable talking with someone of the same gender. We tried to conduct the interviews during mid-morning and mid-afternoon, two times of the day when women are less burdened by the tasks of cooking and would have more time to chat with us. Often the interviews took place in the kitchens themselves, with some occurring elsewhere in the home or outside on the stoop. Sometimes we participated in the cooking, learning how to defeather pigeons for lunch and cooking bread to be sold to other townspeople. In nearly allcases, we asked the women to pose for a photograph with their stoves so that we have a record of variation within the types of stoves in Huamanzaña. Furthermore, because photographs are highly prized, by having Shannon ask to photograph a woman with her stove is seen as a form of flattery.
10. Community Health Assessment
A thorough community health assessment was conducted in conjunction with the August 2006 solar energy project.37 We did garner some additional relevant information from the personal interviews with women, and that information has been summarized below.38
10.1 Indoor Air Pollution
Several—though not all—women interviewed noted that their current stoves cause smoke and indoor air pollution that damages their vision and causes respiratory problems. One of the mostharmful fuels is tusa, the corncob remnants from livestock feed that are used to ignite a fire. Tusa creates a particularly acrid and burning smoke that makes eyes water and breathing difficult. In one case, the smoke was so bad and the hole in the roof through which it should have escaped was so ineffective that the woman had moved her stove to each corner of the room in an attempt to find some location where the draft removed the heavy smoke. Nevertheless, women informed us that they often leave the room after adding tusa, and they keep their children
out of the kitchen while cooking. The veracity of the latter statement may depend on the amount of smoke; we often observed children in the kitchen—for they help their mothers with the cooking—and some parents reported spending money on expensive eye drops to treat the vision problems arising from the smoke.