Cooking stoves and brick production – a burning problem

Fernando Martirena, Tom Miles, Kurt Rhyner   

Many rural dwellers around the world use firewood to cook their food, as well as for semi-industrial production like clay bricks and lime. Deforestation and growing urbanization result in high costs that affect them directly and immediately and we know that this problem is growing worse.

In the last 30 years many NGO’s have developed different models of kitchen stoves, and we are all aware of the fact that not all of those “inventions” have actually given tangible results. Unfortunately, it was often the best publicized models that fared worst. By the way, the same happened with brick and lime-kiln designs.

The EcoSur experience

Some of the people who later founded Grupo Sofonias were directly involved in what seems to have been the start of the much propagated “Lorena – stove” in Guatemala, which was a reasonable answer to a specific way of kitchen culture. When it was transferred to other countries and cultures, the results seem to have been less positive, and we found out quickly that it was not suitable for Nicaragua nor the Dominican Republic.

However, the idea of substituting open fire for an efficient stove is good and benefits everybody. We have worked with many adaptations and Sofonias Nicaragua has instructed hundreds of families how to build “adapted Lorena” stoves. Most recently, in Ecuador, EcoSur has produced the first prototypes of a simplified “Alpine type” cast iron stove that will help to heat the house, at the same time as it resolves the problem of smoke in the room.

A closely related issue is the investigation on briquetting biomass waste to be used for all types of combustion, directed by Fernando Martirena. It consists of wet-mixing clay and shredded biomass, and further shaping it with a hand press (for instance the CINVA-RAM type of press) into a solid fuel block. The resulting block is set to dry, which takes from 5 to 11 days, depending on weather conditions, and afterwards it is ready for use.

The main sources of biomass that have been studied are agricultural wastes, such as crops residue (sugar cane, coffee, banana, wheat, etc.). Besides, sawdust has proven to be a suitable source of biomass available almost everywhere. The finesse of the biomass plays an important role in briquetting, as well as the quality of the clay used. Before mixing, the clay must be set in water for at least 1 day, in order to collapse its internal structure and destroy clots formed in dry clay. The most frequent proportion is 20% clay and 80% biomass (per weight).

The Solid Fuel Brick reportedly has a calorific value similar to that of moist firewood. It successfully replaces most of the firewood in burnt clay brick production, and has also been used for cooking purposes. In comparison to wet firewood, the SFB produces less smoke, and the flame is more consistent, apparently because of the clay present in the block. The ash resulting from burning the SFB at high temperatures (for instance in a fired clay brick kiln) has proven to be an enhanced pozzolana. This enables producers to make proper use of a waste product whose disposal would be otherwise troublesome.

For the last few years we have been hearing success stories about vertical shaft brick kilns, a technology that was developed in China and is reported to have spawned several thousand kilns. They are working with coal powder and the people who have studied the technology have informed us that it was unlikely to work with firewood or with briquettes. However, Martin Melendez in Nicaragua has taken it upon himself to develop this new type of kiln. After consultations with the EcoSur team and other scientists and practitioners, he has built a miniature model of a kiln and has successfully fired miniature bricks. Now they are building a real life model to experiment with the technology, learn from the experience and improve it before taking the step of promoting it. If successful, this new kiln would allow bricks to be burnt in a much more efficient way.

The REPP experience

Over the last year a lot of interaction and mutual learning has been going on between EcoSur partners and participants on the biomass cooking stoves mailing list hosted by the Renewable Energy Policy Project (REPP). Archives for Stoves and the other bioenergy lists hosted at REPP can be found at:

Pictures, graphics, reports and reference materials for the Stoves discussion can be found at:

and in Spanish at:

The Stoves list is moderated by Ron Larson (USA), Elsen Karstad (Kenya) and Tom Miles (USA). Ron is particularly interested in charcoal stoves and wood gas stoves. Elsen is a charcoal producer but interested in all types of stoves. Tom is a fuels and energy consultant to industry with training and experience in wood and energy in Latin America and Asia.

The list brings together the experience of many stove improvement programs such as Prolena, the Asian Regional Cookstoves Program (ARECOP) and the Regional Wood Energy Development Program (RWEDP) of the United Nations Food and Agriculture Organization, the GTZ in Southern Africa, ARTI in India, Intermediate Technology Development Group (ITDG) in Africa, the Peace Corps and Winrock International/ESMAP. Individual organizations in the Americas include Prolena (Honduras, Nicaragua, Brazil) Trees Water and People (Mexico, Guatemala, Honduras, El Salvador), HELPS (Guatemala), Aprovecho Research Center (Costa Rica, El Salvador) and others. It is linked to other stoves discussions hosted by HEDON(IDTG/GTZ) and ETHOS (Engineers in Technical, Humanitarian Opportunities of Service).

There are individuals interested in improving existing and improved stove designs, adapting efficient combustors to local needs, like portability, and the developing and testing of new designs. Others are interested in quantifying health effects and impact of cooking on global warming. The stoves discussion has helped bring people and organizations together who before tended to work alone. Experience from the Himalayas has been shared with the Andes. Experience in Nepal of adapting the Guatemalan CETA technique of using molds to build clay stoves has been shared on the list. The successes and failures of metal and wood gas stoves are regularly shared between Asia, Africa and the Americas. Stove designers and testers like New Dawn Engineering in Swaziland and Aprovecho Research Center in the U.S. are finding ways to test and improve stoves with willing cooperators in many countries and sharing their results on the list. The list has led to the creation of new ad hoc organizations and loose associations for the purpose of improving stoves and health in particular areas.

The Stoves list brings together people who are creatively solving serious problems one brick at a time. They are open to questions, discussion and debate. Discussion lists are proactive: you have to ask the question to get the answer. To join the biomass cooking stoves discussion and ask the question log on to:
or send email to Ron Larson at This email address is being protected from spambots. You need JavaScript enabled to view it.

EcoSouth invites all persons interested in the subject of stoves to refer to one of the above addresses, as in our question and answer service we concentrate on the issues of producing and applying construction materials.

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Marcelino Castro
Civil Engineer (MSc)
Spanish, English, Russian.
MCR tiles, instruction, quality control, experience in many cultures.


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