The Setting: Rural Village in Rajasthan, India
There’s no sign of the sun yet, but the sound of Kamlabai, the wife and mother of our host family, slipping on her shoes means it’s not far from peeking over the horizon. Just like yesterday and tomorrow and virtually every day, she’ll bring an armful of wood into the dark kitchen, start a fire, and prepare her rotis, a round flat bread made with water and corn or wheat flour. She’ll prepare and cook each roti, one at a time, on a clay tawa over the flame in her traditional chulha. There is a certain charm in the routine: the rhythmic rolling and patting of fresh dough into consistently perfect rotis; the gradual awakening of the kids in the one-room house and of the livestock in the yard; the reliable illumination of the landscape complementing this chore.
In summer 2015, Kayley Lain, an engineering graduate student at the University of Iowa, Nidhi Baid, an Environmental Engineering student at the State University of New York, our son, Sushil Rao and I spent time in five Rajasthani villages to arrange the distribution of 1000 MAs and test the performance of the device in the field. Our local NGO partner, Foundation for Ecological Security (FES), was responsible for much of the distribution process. Instead of mild steel that was used in the tested prototype, we used high carbon stainless steel (SS304H) for the MA to guard against possible corrosion from the chemicals in the wood. To reduce the cost of the device, we removed the bottom plate from the design. Testing of the MA revealed an average of 33% reduction in wood usage in seven households. Particulate matter (PM) reductions as high as 51% were observed in one household, with an average reduction of 33%.
Due to the high variability in smoke production observed in the field, we conducted additional lab-field hybrid tests at the University of Iowa. For these tests, we built a traditional chulha from bricks and cement in an 8’x8’ outdoor tent, and heated a tawa to 350-400OC, measuring wood usage and ambient PM. These tests are more repeatable than actual field tests – distractions to the cook, house design variations such as placement of windows, and variations in wood moisture are eliminated – but they are more realistic than the lab tests, allowing us to better predict field outcomes and potential design improvements. With this setup, we can collect more data in less time than we could with field tests, without leaving Iowa City. In these tests, we measured a 31% reduction in large (~10 μm) PM, which is in line with field data.
A follow-up field visit was conducted six months after families had received their MAs, to get feedback from users and inspect the MAs. The enthusiasm for the devices took us by surprise. Cooks said they don’t cry from smoke anymore while they are cooking. They can make their meals faster and use less wood. None of the cooks we observed were ever excited about removing an MA so that we could record control data. A couple of them even tried to sneak it back into the chulha before starting the fire.
In a sample of 80 households in Rajasthan who received MAs, 71% of them used their MA regularly with no issues. None of these MAs had suffered any measurable weight loss or significant damage. Some women reported that they do not collect wood as many times a week as they did before they received an MA. Reasons for not using MAs included insufficient information upon receipt of the device and extra small chulha openings that could not accommodate the MA as supplied. Of the people who were able to use the MA, none reported any inconvenience induced by the device.
The Setting: Orphanage in Kitui County, Kenya
The school children in Nyumbani Village have just finished their lunch in the canteen. Githeri, a maize and bean stew cooked over a fire, is served for lunch every day. Most of the children play football barefoot in the afternoon sun, but one 7-year-old boy, aptly nicknamed ‘Little Engineer,’ builds a toy truck from salvaged trash instead. He secretly sells these masterpieces to his classmates and uses the profits to buy sweets. Little Engineer lives with his susu (“grandmother”) and nine other orphans in a house made of mud and concrete in Cluster 3. There are four houses in each cluster and 26 clusters in the village. Each house in the village is mostly the same as Little Engineer’s – ten orphans and a susu or emau (“grandfather”). Besides time spent at school and on his budding toy car business, Little Engineer will spend one to two hours a day collecting firewood for one of his siblings to cook morning and evening meals for the family, which requires three to four hours a day.
In Nyumbani, Fabio Parigi and Michele Del Viscio found a wider range of stoves than in Rajasthan. The efficiencies of these stoves varied significantly. Using the MA in the most efficient of their stoves (which resemble the U-shaped chulhas from Rajasthan) increased the thermal efficiency by 25%. Replacing less efficient stoves (which consist of three rocks placed in a triangular arrangement) with the most efficient configuration and implementing MAs increased the thermal efficiency by 78%. These improvements translate into an estimated 7500 km2 of local forest saved each year in Kenya alone.