Would any manufactured stove that you know of work well for this woman? Maybe not?

Working with local women to design cooking solutions is not hard when the team is located in the project area. It’s only natural to include the user in developing the product. But when wood stoves are created by foreigners, that invaluable input easily goes missing and the stove, although technically fine, usually misses other necessary attributes. That’s why ARC tries to develop stoves in the field, while learning how fire works in the lab.

Researchers associated with the Regional Testing and Knowledge Center in Accra, Ghana might agree with this strategy. They recently published a paper in which 20 biomass cook stoves available in Ghana were evaluated for high-power thermal efficiency, low power specific consumption rate, turn down ratio, high power CO emissions, high power PM2.5 emissions, low power CO emissions, low power PM2.5 emissions, affordability, fuel saving potential, operations and maintenance cost, time saving, indoor CO, and indoor PM2.5 emissions.

The authors concluded that none of the cook stoves satisfied the conditions of all of the performance indicators. The forced draft stoves were generally high performing on the technical and environmental attributes, but low performing on the economic and social/public health metrics like affordability, maintenance and operation costs, and fuel saving potential. The more traditional stoves did not perform very well technically and environmentally but ranked highest economically, being more affordable than the cleaner burning alternatives like forced draft stoves.

Available natural draft stoves were a better alternative considering the economic, technical, and environmental attributes.  The high cost of forced draft stoves (most are imported), their operation and maintenance cost, and the requirement of electricity resulted in adoption rates being low. The suitability to prepare Ghanaian staples, which require rigorous stirring, were also generally underestimated. Locally made natural draft stoves did not score well in terms of emissions but were much less expensive, did not require the preparation of fuel, and were made to prepare Ghanaian staple foods. 

The study highlights the need to consider all the performance criteria simultaneously in order to choose the “best performing” stove. 
The authors conclude with the hope that locally made stoves can be technically improved while maintaining the other necessary attributes. (Gloria Boafo-Mensah, et al., Biomass and Bioenergy 150, 2021).

It just so happens that our General Manager Sam Bentson is at the Regional Testing and Knowledge Center in Accra right now, working with Ms. Boafo-Mensah and the rest of the team on some exciting projects. We look forward to sharing Sam’s report about his trip when he returns!

Paul Anderson TCHAR stove

In 2011, Dr. Paul Anderson described how the made charcoal in a TLUD could drop into a charcoal stove base and then be used to cook food. The top of the TLUD stove was removed after the charcoal was made and the pot was placed on the lower base to continue cooking. ARC used the same idea in a TLUD stove that was tested by Jim Jetter, but the wood burning and subsequent charcoal burning happened in the same combustion chamber. The TLUD was shorter, so the lower firepower in the charcoal supplied enough energy to a covered pot with a tight skirt to keep simmering. The ARC TCHAR stove was clean burning and scored well in a series of tests. (Jetter, et al., 2012, Environmental Science & Technology 46(19):10827-34).

Dr. Anderson’s 2011 TCHAR stove. The top (silver) portion is removed after the fuel has become charcoal, and the pot is placed directly on the base for simmering.

Using the made charcoal to simmer food to completion increases thermal efficiency. In cities where biochar may be less desirable, a known amount of fuel can bring the food to boil (burning the wood) and then gently simmer the food until it’s done (burning the made charcoal) without much tending. To preserve the biochar for agricultural use the primary air that goes up into the batch of fuel is limited and the fire is extinguished. In a TCHAR more primary air helps to decrease the smoke made during the transition from wood to charcoal burning and helps the charcoal to completely combust.

The Turn Down Ratio in a 2021 ARC TCHAR is about 5 to 1, so the pot needs a lid and a tight skirt to keep boiling. Using 700 grams of biomass pellets the stove boiled five liters of water in 27 minutes and kept boiling for two hours (covered pot/tight skirt). The TCHAR is another TLUD variation and, who knows, may be useful somewhere?

Burning wood and then made charcoal results in a large turn down ratio.
Selling LPG in Rwanda

LPG (liquefied petroleum gas) is among the most important fuels for achieving clean cooking. Many countries are actively developing intervention programs. In a five year project starting in 2007, an Indonesian program converted over 50 million households cooking with kerosene to LPG. In 2016, India intensified their campaign providing free connections to LPG cylinders to “Below Poverty Line” homes. In China, gas and biomass fuels, the dominant energy fuels for cooking, are used by 44.8% and 32.1% of households, respectively. In 2014, 47.6% of rural cooks used biomass, whereas urban households were more likely to cook with gas (65.8%) (Applied Energy 2014, 136:692-703 Duan, et al.).

Even older LPG stoves burn cleanly. Five different LPG stoves were tested 89 times and described in a 2018 article. Two stoves were manufactured in China and obtained in a local market near Beijing. One was manufactured in Japan and purchased in Kampala, Uganda. Solgas Repsol Downstream Peru (an international LPG distributor) disseminated another stove. A worn-out appliance was obtained from a rural household in Cameroon  (Environ. Sci. Technol. 2018, 52, 904−915 Guofeng Shen, et al.).

  • The average thermal efficiency for the LPG cook stoves was 51 ± 6%.
  • Approximately 90% of the PM2.5 data was below the level of detection.
  • The other 10% of the stoves had an average PM2.5 score of 0.20 ± 0.16 mg/minute. (The WHO Emission Rate target is 0.23mg/minute).

However, in a country like Rwanda the switch from wood and charcoal to LPG is slow. In 2019, only 2% of cooks were using LPG in the cities. 64% used a charcoal or wood stove and in rural areas “the use of clean fuels is negligible” (The World Bank, 2019). 93% of rural households use wood, 6% of charcoal, and 0.2% of gas (National Institute of Statistics Rwanda, 2019).

The cost of LPG is a big factor. “Prices are much higher in rural areas and upcountry towns as retail traders factor in transport logistics. Rising prices for cooking gas in the country have sparked concerns of likely reversing gains made in the push for a clean cooking solution as more households turn to wood and charcoal.”  

Marie-Jeanne Uwanyiringira, a businesswoman who sells LPG, says that the fluctuation in prices has caused frustration among consumers. “When someone buys gas from me at RWF 3,500 and the next month I tell them that it is RWF 5,500, ($5 USD) they don’t seem to understand that it is not the seller’s fault.” (Rwanda Today, April 9, 2021).

In addition to the recent Tibbetts Award, ASAT has just received EPA recognition for our success. ASAT (the for-profit arm of ARC) was awarded a 2021 EPA Administrator’s Small Business Program Award for Outstanding Accomplishments by a Small Business Contractor. This award recognizes ASAT’s contributions in Fiscal Year 2020 and our efforts to promote EPA priorities of protecting human health and the environment.

ASAT Inc. staff pose with their Tibbetts Award. From left to right: Sam Bentson, David Evitt, Jill Allen, Dean Still, Kim Still, and Dr. Nordica MacCarty.

EPA SBIR funding enabled ASAT to research and develop commercially viable inventions. We developed the Integrated Stove (seen below) that includes stand-alone accessories including the Jet-Flame www.Jet-Flame.com, an air cooled thermoelectric generator, and an electrostatic precipitator that reduces emissions of smoke from chimneys.

The Integrated Stove with Air Cooled 20 Watt TEG Prototype.