September 15, 2010 | 14
Editor’s Note: Students from Dartmouth’s Thayer School of Engineering are working in Tanzania to help improve sanitation and energy technologies in local villages. This series chronicles work being done by the student-led group, known as Humanitarian Engineering Leadership Projects (HELP), to design "rocket stoves" in the village of Mwamgongo and top-light updraft design (TLUD) gasification stoves in the village of Kalinzi. The goal is to create a healthier, more energy-efficient cooking apparatus that these villagers will accept and use. HELP students are filing these dispatches from the field during their trip. This is their 10th blog post for Scientific American.
When we arrived, Jirani (Swahili for neighbor and the name we were told to call her) brought out a bench and smiled, "Karibuni (Welcome)!" As you may have noticed from our other posts, Tanzanians have a strong tradition of welcoming visitors into their homes. Once we sat down, Kevin explained the plan for the day: to cook beans. By measuring the amount of wood consumed during the two-to-three hour cooking process of a staple food, we are able to gauge the relative efficiencies of different stove designs.
As Kevin began to explain the process, Jirani sat down and started to breastfeed her baby, a common occurrence in a country where 44 percent of the population is under 14 years old. As Americans, a stranger breastfeeding their child in the middle of a conversation was new for us, but Kevin kept his composure while talking to her by looking in her direction to show respect, but not in a way that would make her feel uncomfortable. He continued to explain how we would be measuring the levels of "bad pollution" from each stove. Ryan demonstrated the combustion analyzer, a device that plugs into the laptop and measures the parts per million (ppm) of carbon monoxide levels in the air. Jirani nodded, "Sawa (Okay)."
I turned my head to the right, and I saw another neighbor entering the household.
"Hodi, (May I enter)?"
"Karibu, (Welcome)!" said Jirani. As the only local Wazungu (white people) in the village, we were used to often drawing crowds wherever we went.
Kevin began setting up the bean test, which would pit the traditional three-stone stove against our TLUD (top-lit up-draft) gasification stove in an efficiency battle. We started off by creating two piles of wood: one for the three-stone stove and one for our stove. Ryan calibrated our electronic scale with the fuel box (a small container that kept the wood steady as it was measured), and then added around 2.5 kilograms of wood to one pile. Jirani, who was very interested in the testing process, looked at the scale inquisitively.
Since we didn’t have enough firewood cut up for the second pile, I started chopping wood behind the house. A little girl, who seemed to appear from out of nowhere, watched me intently. A piece of timber flew off into the distance and she soundlessly ran over to grab it for me. When I thought I had chopped enough wood, we measured out a second pile of similar weight.
Another neighbor, also breastfeeding her child, and an older woman wearing a bright dress covered with sun patterns arrived to observe the process.
We added a liter of water and half a kilogram of beans into two pots of similar size, and Jirani started both fires at the same time. Our stove started off with a roaring flame, but then started smoking much more smoke than we would have liked.
Another woman with a full black headdress and an older man followed by an assembly of children entered the household. Our crowd was growing larger.
Ryan sat inside the cooking hut with Jirani holding the combustion analyzer while the three-stone stove spewed smoke into the air. Ryan desperately tried to fend off the acrid smoke by holding his shirt over his face, but even this had little effect.
"Time 12:36, CO 366 ppm," Ryan yelled to me, as I recorded the carbon monoxide data.
Jirani entered the hut and fed the fire, carrying her sleeping baby boy strapped on her back. She didn’t seem to be bothered by the smoke and the harsh particulates of the three-stone stove that engulfed her and her child. Judging by how well-behaved and polite Jirani’s children act, we knew Jirani was a responsible parent; sadly, she was unknowingly exposing her child to indoor air pollution. One of the fundamental goals of our project is to help educate people about the connection between indoor air pollution and health problems. Hopefully in the future Jirani will make an effort to minimize her family’s exposure to wood smoke.
Constantly breathing smoke from indoor stoves has been shown to be associated with increased risk for developing acute respiratory infections (ARIs) in children and chronic lung disease and lung cancer in adulthood. It was estimated in the year 2000 that indoor air pollution was responsible for 1.5-to-2 million deaths or 4-to-5 percent mortality worldwide.* Almost half of these deaths were in children suffering from acute lower respiratory tract infections such as pneumonia. Prevalence of ARI is high in the Kigoma region of Tanzania, particularly for children. In the most recent National Demographic and Health Survey of Tanzania conducted in 2004-05, 23 percent of children under the age of five in Kigoma had symptoms of an ARI within two weeks before the survey, compared with the national average of 8 percent.** The use of open fire, three-stone stoves in poorly ventilated areas is certainly affecting increases in these statistics.
I tried to remove these disturbing facts from my mind as a woman arrived with a hefty bundle of firewood on her head. We paid for the wood in order to reimburse Jirani for the sticks we burned during the test. A "bundle" of firewood cost the equivalent of around 75 cents. Although this doesn’t seem like a lot, it is a significant expense for people in the Kigoma region, many of whom live on less than $2 a day.
Once Jirani declared that each pot of beans was cooked (the most arbitrary component of the test), we measured the amount of remaining wood for each stove. The test showed that our stove used around 40 percent less wood. This was a great result considering our average was around 33 percent for bean tests and our stoves were made of scrap metal, but it was still less than the 50 percent reduction benchmark we were aiming to reach. While considering potential design changes to the current wood burning gasification stove, we also discussed changing our attention back to using only coffee husks as a fuel source in order to have a 100 percent reduction of wood fuel—this would surely have the greatest impact in terms of deforestation—but we would need to invent a new stove design and to determine issues of coffee husk supply. We certainly have more work ahead.
Photos courtesy of Wendy Hado
* Ezzati M, Kammen DM. The health impacts of exposure to indoor air pollution from solid fuels in developing countries: knowledge, gaps, and data needs. Environ Health Perspect. 2002 Nov;110(11):1057-68
** National Bureau of Statistics (NBS) [Tanzania] and ORC Macro. 2005. Tanzania Demographic and Health Survey 2004-05. Dar es Salaam, Tanzania: National Bureau of Statistics and ORC Macro