When Dr. Larry Winiarski and I lived for a season at Rancho San Nicolas in Baja California Sur, Mexico we wanted to be helpful. We built cook stoves, solar cookers and other delightful inventions that we found interesting. But Larry was an insightful fellow and he started to listen to folks and ask them what problems they wanted to solve.
We had such a great time at the ranch, people were so nice, but Larry learned more than I did because he was born in Honduras and was more fluent in Spanish. It took me a couple of years to be able to understand what folks were saying. Speaking the language is important for many reasons!
After a while, Larry and I started working with the rancheros making rat proof boxes from available wire reinforced cement. Steel would have been great but was much too expensive and you couldn’t get it anyway. Rats were eating so much food and storage was a major problem. Stoves were great but homemade rat proof boxes took off like hot cakes.
We started making boxes and became more helpful. Folks loved Larry anyway but now he wasn’t just good company. After a couple of years, I started fixing holes in boats.
https://aprovecho.org/wp-content/uploads/2025/08/rodent-proof-box.jpg300400Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2025-08-27 09:11:112025-08-27 09:20:19Learning From People
Over the past 3 years, thanks to three grants from Fire Capital, Aprovecho has been working with CSIR (Council for Scientific and Industrial Research) in Ghana to expand their lab capacity. We have focused on teaching stove design principles through co-developing a stove retrofit for boarding schools in Ghana.
During the recent in-person workshop, Jaden visited the lab to help with the building of the prototype and plan for its installation at a local school. This prototype will go over an existing stove at the school, increasing thermal efficiency and reducing indoor emissions. With user, manufacturer, and lab result feedback, CSIR will finalize their design and give stoves to ten schools for a larger impact study.
The LEMS in Bangladesh
Sam went to Bangladesh to update their lab and provide training. The Bangladesh University of Engineering Technology in Dhaka now has a lab that can test cookstoves according to ISO 19867 standards. This provides a useful development tool for the area as well as way to teach the next generation about cookstove development. Sam observed that while urban and peri-urban areas had access to gas and electricity, households couldn’t always afford it, highlighting the need for clean biomass stoves even in areas with access to alternative fuels.
Sam also visited Life Green Energy, a stove manufacturer focused on forced draft stoves. Together, they developed a local Jet-Flame prototype aimed at saving fuel and reducing emissions. The prototype was able to burn green wood while other brick stoves could not. More development is planned to improve the product.
Aprovecho and Oregon State University paired with SunFire (Malawi), KIRDI (Kenya), and CSIR (Ghana) to conduct a total of 720 thermal efficiency tests on traditional wood and charcoal stoves. The goal was to compare the baseline efficiency of stoves with UNFCCC (United Nations Framework Convention on Climate Change) default efficiency, which had recently changed.
We developed a new test protocol, the UCET (Uncontrolled Cooking Efficiency Test), which measures thermal efficiency on any meal cooked. We found that the average thermal efficiency was between the new and old UNFCCC defaults. It was also found that firepower, pot/pan size, and cooking method are strongly correlated with efficiency.
https://aprovecho.org/wp-content/uploads/2025/08/UCET_test.jpg473600Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2025-08-13 11:55:502025-08-13 12:00:44What’s Cooking at Aprovecho
In my opinion, the WBT* cannot be used, especially in the lab, to improve a biomass cook stove because all of the important field variables are not represented.
A successful cook stove needs to be evolved from field tests, as we did in Southern India for the Shell Foundation. Cooks in eighteen villages kept on changing the Rocket stove until it was acceptable, useful, and even likable. It took a while but it was a lot of fun and a great introduction to Southern India!
The WBT, with severely limited variables, can be useful in the lab for international comparisons of stove performance. The same pots, same amount of water, same fuel, same procedures and protocols limit the confounding variables in an attempt to isolate the stove as the reason for perceived differences.
As we did in India, both field and lab data can inform stakeholders. The successful stove has to please cooks, retailers, distributors, etc. and, at the same time, meet project goals such as reducing adverse health effects. We used the WBT in the lab and the CCT* in the field. Marketing tests, as suggested by Baldwin (1987) were very important, as well. We learned right away that the stove had to cost ~$5 to capture sustainable market share.
The lab based WBT is best used to inform researchers how stoves might be improved. Then, iterations in prototypes are tried in the field including cost, weight, color, height, firepower, fuel used, etc, etc.
This combined use of the WBT, CCT, and KPT* for stove development was suggested in the International Stove Standards, (1985).
*Water Boiling Test “The Water Boiling Test (WBT) is a simplified simulation of the cooking process. It is intended to measure how efficiently a stove uses fuel to heat water in a cooking pot and the quantity of emissions produced while cooking.” – The Water Boiling Test Version 4.2.3
*Controlled Cooking Test “The controlled cooking test (CCT) is designed to assess the performance of the improved stove relative to the common or traditional stoves that the improved model is meant to replace. Stoves are compared as they perform a standard cooking task that is closer to the actual cooking that local people do every day.” – CCT version 2.0
*Kitchen Performance Test “The Kitchen Performance Test (KPT) is the principal field–based procedure to demonstrate the effect of stove interventions on household fuel consumption.” -KPT version 3.0
Cooking outdoors, making hot fires, burning the tips of sticks to use less wood and breathe less smoke (photo: Clean Cooking Alliance)
In 2003, Aprovecho was hired by The Shell Foundation to develop a Rocket stove in Southern India. We found a wonderful co-op of potters that was selling two-pot burnished $4 ceramic stoves with chimneys. They sold 250,000 stoves per year. Mahatma Gandhi promoted this kind of stove in 1934. The ARC staff thought that, while trying to introduce a new concept like a Rocket stove, helping the potters to update their facility and perhaps tweak the design might result in this established manufacturer with an existing market and distribution system becoming more successful. It was great to work with and learn from so many, highly motivated local folks!
Appropriate Technologists are encouraged to first survey technologies developed in the project area. ARC looked around lots of villages to try to find out what expert cooks were doing to use less wood and breathe less smoke. We were trying to find out what existing factories were making innovations, and which established markets and distributors were selling products. One constant was that almost every distributor said that stoves had to cost less than $5.
Appropriate Technologists read in textbooks that learning from local solutions is best practice. Hundreds of Indian women transformed the Rocket into a useful stove. ARC did not know so much information was needed to be successful! We had to learn from experts and try to get out of our own way (as Alan Watts titled his autobiography).
https://aprovecho.org/wp-content/uploads/2025/06/3-stone-fire.jpg375500Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2025-06-27 14:22:222025-06-27 14:22:23Supporting Best Practice
Sometimes it’s too cloudy for solar drying and a wood-fired dehydrator can help with large scale food preservation. In 2002, Dr. Larry Winiarsk helped farmers in the wet mountainous region of Nicaragua to design and build a prototype wood fired dryer for cacao beans. The ARC publication “The Winiarski Wood Fired Agricultural Food Dryer,” details construction of a rocket-style wood-fired dehydrator.
It’s estimated that the optimal temperature for drying is between 120 and 130 degrees F. Sustained temperatures over 130 degrees can begin to cook the food. (When starting to dry foods it can be most efficient to go up to 150 to 160 F. in the initial stages of drying when lots of moisture will be evaporating out of the food.)
A successful food dehydrator sustains these temperatures in dry air passing through food at a constant rate with even distribution for a variable period of time, depending on the food being dried. 1.) Hot air temperatures increase the rate of evaporation. 2.) Air flow through the food is equally important.
WHY?
Efficient drying moves the water inside the food into the surrounding air. Wet air cannot absorb more moisture. Hot, dry air picks up the moisture and air flow created by draft replaces moist air with dry air. In a Winiarski food dryer, air is efficiently heated and sufficient airflow of dry air through the food increases the rate of dehydration.
The food dryer features: a) burning biomass heating air b) is relatively air tight, c) has a large chimney or fan that removes moist air and moves dry air through the food. A large chimney usually creates the draft necessary for sufficient air flow.
In March, Jaden traveled to Ethiopia to assist in the installation of the LEMS and train lab technicians on ISO testing for cookstoves.
15 trainees from all over the country attended the training. The LEMS was procured by SNV and their sponsors and was given to Ethiopia’s Department of Water and Rural Energy at the end of the training and installation.
The installation of LEMS in different countries is vital in creating clean cooking solutions that can be used throughout the world. We hope to continue working with the lab in Ethiopia to design new stoves.
Proyecto Mirador in the Lab
Proyecto Mirador has been working on improving the efficiency of their Dos por Tres stove. After successful tests in their lab, they traveled to Aprovecho from Honduras to confirm their results.
They got the same results in both labs, showing how effective iterative design testing with the LEMS can be. Now they can install stoves that use less fuel and cook things faster in Honduras and Guatemala.
Field Testing Results Published
In 2023, we measured the emissions from cordwood heaters in Oregon. There are very few studies that evaluate emission measurements in the field for wood heaters. As seen from our experience in cooking stoves, emissions in the field are often higher than lab tests, and field studies help us understand how people use their stoves so we can make better designs.
We’ve been using the data we collected to create lab tests that reflect user behavior and design clean and efficient heating stoves that meet user specifications.
One of the biggest mistakes I have made was thinking that I could predict what stove would sell in a market. If only I had always followed Sam Baldwin’s advice and done market testing before manufacturing! In Southern India, as part of the 2003-6 Shell Foundation project, we had outspoken distributors who yelled in meetings that a successful stove had to cost $5, that 5,000 had to fit on a truck, and that it had to be designed by cooks! The stove had to be short so food could be stirred and work well at the low firepower required by villagers around Chennai, toast a chapatti, etc., etc.
When the carbon market crashes, affordable stoves continue to be sold and used. When stoves are purchased the consumer is convinced of their utility. The trick is to try to bring best solutions into marketable products but, luckily, engineers love a challenge!
A pot skirt, SuperPot, constant cross sectional stove top, stick support, keeping a fire hot, can all significantly increase heat transfer efficiency. Even Jet-Flames can be made for around $5. TLUDs can be inexpensive. There are many techniques to improve the market driven stove!
On the front porch of the house he built in West Eugene, Ken Goyer shows an example of the Six Brick Rocket Stove
Photo by Paul Neevel for the Eugene Weekly
I think about Ken making the lightweight, insulated bricks from Bailey Hill yellow clay for the Uganda submerged double pot stove in 2002. Exposing the sides as well as the bottom of the pot(s) to flame and hot gases increased fuel efficiency. The Rocket combustion chamber, also made from Ken’s recipe (clay and sawdust) was a 5” in diameter, 12″ high cylinder, placed under the first, larger pot.
We tested the stove using one pound of wood. 6.6 pounds of water in the first pot (12″ diameter) boiled in ten minutes. We had a great week of sunny, windy weather and it was great fun to work with Ken and Peter Scott (Burn Stoves), who was about to go to South Africa.
I met Ken when he was doing “Ken’s Ten-Buck Tune-Ups.” He first saw open cooking fires when he went to El Salvador in 1992 to help Sylvia Gregory with her women’s empowerment project. With funding from Rotary Club, Ken directed construction of brickmaking kilns for refugee camps near Lira in Uganda and Gulu in Darfur. He helped to start Aid Africa and is one of the inspirational people we miss and so fondly remember. He was one of Larry Winiarski’s best friends.
https://aprovecho.org/wp-content/uploads/2025/05/Ken-Goyer.png796770Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2025-05-09 11:21:382025-05-09 11:44:47Remembering Ken Goyer
In the first week of October, ARC Research and Development Engineer Jaden Berger visited CSIR-Ghana for capacity building training. The Council for Scientific and Industrial Research (CSIR) is the foremost national science and technology institution in Ghana.
The main focus of the visit was to teach them how to perform field testing using various sensor suites. CSIR was especially focussed on learning to perform KPTs (Kitchen Performance Tests) while using EXACT sensors from Climate Solutions Consulting. We also used other sensors CSIR already had: a PEMS (Portable Emissions Monitoring System) with a portable hood, an IAP (Indoor Air Pollution) meter, and an air quality sensor along with performing UCETs (Uncontrolled Cooking Efficiency Tests) during cooking to determine the efficiency of the stove.
Making observations of how cooks are using stoves.
Setting up a PEMS with a portable hood to measure stove emissions.
Testing was done at a secondary boy’s boarding school in Accra. The school cooks breakfast, lunch, and dinner for 3,000 students using a variety of improved and unimproved stoves. The stoves identified as the least efficient and highest emitters were the 12 wood stoves and 4 palm kernel stoves. (Palm kernels used to be considered agricultural waste from palm oil production but are now commonly used as fuel.) Several design meetings were held to determine a design that would increase efficiency, clean up emissions, and remove emissions from the room the cooks were in.
Palm kernel stoves in use for breakfast.
Weighing wood for three 24 hour-long KPTs.
Performing UCET measurements.
The next step is for CSIR to finalize a CAD model of the design along with some CFD analysis to predict if the prototype will work. ARC will then virtually meet with CSIR and their manufacturer to finalize the design and begin creating prototypes.
During the second week of the visit, ARC and CSIR worked on wrapping up older projects. This included gathering final data for a charcoal conversion efficiency study, creating a draft of the charcoal conversion efficiency protocol so that it can be published, and developing and using a durability protocol that is more applicable to conditions a stove will have to withstand in Ghana.
Taking measurements for creating a new durability protocol.
Overall, a successful trip with good progress made toward improving health and cooking conditions in Ghana.
https://aprovecho.org/wp-content/uploads/2024/11/Screenshot-2024-11-07-at-4.18.41-PM.png358390Kim Stillhttps://aprovecho.org/wp-content/uploads/2015/11/Aprovecho-Logo.pngKim Still2024-11-07 16:01:042024-11-07 16:20:19ARC Assists CSIR-Ghana in Capacity-Building
New SSM Health/Climate Biomass Heating Stove Buildings
Here is a video I made last week, introducing some of the the new things I saw on my visit to Shengzhou Stove Manufacturer (SSM). I keep on saying in the video (Sorry!) how much I admire Mr. and Mrs. Shen. Mr. Shen is a great engineer who has built the new buildings, installed the machines, and taken the ideas that Dr. Winiarski brought to him and manufactured over five million durable, affordable Rocket stoves. Mrs. Shen runs the business, does HR, sells the stoves, etc.
An amazing combination! Daughter, Kristina and nephew Chenkai, are being trained to assist the business. You’ll meet the younger generation in the video. Kristina went to the University of Oregon and is now a Vice President at SSM. Chenkai leads a team selling stoves out of his offices in Shenzen.
I walked around new buildings, tested clean burning stoves (including the Jet-Flame and forced draft TLUD) and saw a new wing being built (above) with huge machines to make health/climate biomass heating stoves, a new venture. Since 1976, Aprovecho has helped approximately one hundred stove projects, with SSM becoming the most commercially successful, rolling profits into expanding capacity.
