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 sixth blog post for Scientific American.
After hearing many rumors, we finally received confirmation that the famous Dr. Jane Goodall was actually in town to celebrate 50 years of chimpanzee research in Gombe National Park. This discovery came about after finding out that the Land Cruiser that we had reserved to drive to Kalinzi had been used to escort Dr. Jane Goodall to one of the villages. We took our unexpected delay with alacrity as we considered how incredible of an opportunity it was to be in the presence of a living legend. When we finally arrived in Kalinzi, we made our way past the cornucopia of emerald green bananas at the market to the Jane Goodall Institute (JGI) field station, which would serve as our headquarters for the rest of the summer.
Our first order of business involved collecting quantifiable emissions data from charcoal and three-stone stoves—the current standards among most Kalinzi villagers. The two main problematic components from stove emissions are carbon monoxide, which has been linked to maternity problems, and fine particulates, which contribute to Acute Respiratory Infection (ARI). We decided that our own kitchen was a good place to start and proceeded to take data as our cook, Tuma, prepared lunch and dinner. After a full day of monitoring the efficiency and particulate emissions generated from our stove, we went to the local cinema to watch a soccer match. The tiny building was set up like a church with a center aisle and about 15 rows of simple wooden benches containing 100 or so Tanzanians, with soccer as the object of worship.
The next morning, we woke up before sunrise to the crowing of roosters and began our first full day in the village. Our objective was to finish designing a top lit updraft (TLUD) gasification stove that could burn coffee husks. The TLUD concept was pioneered by Paul Anderson, an expert on Improved Cook Stoves (ICS) for developing societies, whom some previous HELP students were lucky to meet in the spring during an assessment trip. The main principle behind a TLUD gasification stove is the separation of pyrolysis (partial burning and releasing of flammable gases) and the combustion of the resulting gases.
Our TLUD stove not only burns wood more efficiently than traditional stoves, but also can be fueled by coffee husks to take advantage of local resources to even further reduce the impact of wood consumption for cooking. Coffee husks are waste products of coffee farming and are present in large quantities in the highland region. Our current stove design has a central bed of fuel that is lit at the top. There is a primary air intake at the bottom of the stove that passes a limited amount of air up through the bed of fuel to provide oxygen to allow for pyrolysis to occur at the top of the fuel. A secondary air intake, also at the bottom of the stove, allows air to flow up around the fuel cartridge directly to the combustion chamber. As the secondary air passes up through the stove, it is preheated by radiating heat, which insulates the stove and increases the efficiency of the combustion of the gases. As the stove burns, the pyrolysis travels down through the bed of fuel.
Thanks to information gathered from an assessment trip, we knew there was a man in Kalinzi called fundi (Swahili for "mechanic"), who has been making things out of metal since 1984. We left after breakfast with the intention of catching him before he headed out for the day. Although the sun had just risen, he had already left to go to work. To stay productive, we called some of the six women who had volunteered to help us test our stoves. We were immediately invited to come to the home of a woman named Hafsa, one more experience testifying for Tanzanian hospitality. We spent the morning talking with her and her husband and conducted some emissions and efficiency testing. Hafsa used mkaa (charcoal) and a mafiga matatu (traditional three-stone stove) to cook all of her meals. She preferred the three-stone stove because it used wood, which is cheaper than charcoal, and produced a stronger flame. However, she told us she doesn't like that the three-stone stove produces so much smoke since she always cooks inside. She said that when she starts cooking, her kids start running because of the smoke.
We did a simple water boiling test with her three-stone stove and calculated a thermal efficiency of 10.5 percent, which is close to the average for the three-stone stove. (The International Panel on Climate Change uses a default value of 10 percent for three-stone stove thermal efficiency.) In the afternoon, we went to the metal worker Fundi’s house a couple of times, but he was at his farm. We decided instead to fire up the stove that we designed at school at the field station, which generated much curiosity from villagers passing to and from the market.
Watching the chickens pecking away around our house and discovering the relatively high price of eggs, we were inspired to produce our own eggs. When a man came by the field station to sell both a chicken and rooster, we decided it was fate. We were going to raise chickens. As we would find out for the next few weeks, this would turn out to be a terrible decision.
Image of a three-stone stove courtesy of Parker Reed