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The Lorena is made of local materials of clay and sand easily accessible in most environments and usually comparatively cheap to other building materials. The stove is made of rammed earth, includes a chimney for ventilation, and sealed comals.. In the village of Majamout we found that the front comal is only used for tortillas and that the comal is taken off and a grate placed on when cooking in pots. This increases the amount of smoke in the house depending on the draft of the chimney, but increases the amount of heat directly hitting the pots and thus reduces fuel use. Also, canals redirect the heat from the combustion chamber to the back comals. We found in the village of Majamout the secondary burners are not used to cook on, but rather used as warmers. With our heat distribution tests this makes sense given that even after an hour these back comals are 6 times cooler then the front comal.
Critiscism of Lorena
"The Lorena stove was designed with the mistaken belief that rammed earth would act as insulation; there was a basic misunderstanding of the difference between mass and insulation. Good insulation resists the passage of heat; thermal mass does the opposite, it absorbs heat. Testing has shown that the rammed earth used in the Lorena stove does absorb heat, heat that should have gone into heating the cooking pot." The designers, Aprovecho, now state: “The Lorena has been tested over the years by many researchers and has generally been found to use more firewood than an indoor open fire. The stove has other attributes. Its chimney takes smoke out of the kitchen and it is well liked. It is pretty and a nice addition to the house. It is low cost and can be repaired and even built by the home owner. But, it is not a fuel saving or low emission stove.”
This harsh criticism ignores that even without the fuel reduction properties of other [improved cookstoves], its ability to reduce smoke in the house alone is an essential function. Also the rammed earth is a local, easily accessible material, which might be more important in reaching a wider number of people. It is then up to the community what are their priorities in what the stove is able to do and the costs they are able to pay upfront.
- 30 20 liter buckets of dirt (with a clay content of 20-30%)
- 6 2 liter buckets of sand (or less if you have a high sand content in your dirt)
- 5 meters chicken mesh
- 1 meter of wire for making hooks
- 1 bag of cement
- 1 bag of lime
- 3 comals
- 2 galvanized tubes for chimney
- A cap for chimney
- recycled wood pieces for 2 temporary wood frames
- 1 20 liter bucket for part of combustion chamber and large comal temporary mold
- 2 1.5 liter water bottles (filled with water) for back comal temporary molds
- tamper (can be metal tamper or recycled 4 by 4 wood pieces)
- 2 hand shovels
- 1 large sifter for sand and dirt (2-3 cm wide mesh)
- 2 shovels
- wheel barrow for moving dirt, sand, and cement plaster
- wood platform, tarp, or wheelbarrow for mixing cement plaster
- wire cutters
Preparation and building Base
- Clean Up site:
- Take out equipment and excess materials stored where stove will be built
- Building Mold and Mixing Dirt for Base:
- Collect 4 two-by-fours to build a wooden mold with inside dimensions of 130cm long by 80 cm wide by 30cm tall
- Nail the mold together and wrap the ends of your mold together with metal wire to prevent it from breaking apart from pressure of the filling dirt
- Sift sand and dirt for the mix
- Mix dirt with sifted sand, ratio: 5 bucketfulls of dirt, 1 bucketfull of sand. Have someone with a water bottle with holes on the cap, wet very little of the mix while 1-2 persons are mixing with shovels. Test the mix by binding some into a ball when squeezed in your hand, test by throwing the ball into the dirt pile to see if it holds its form.
Filling and Tamping Base
- Filling and Tamping the Base
- With the mix start filling in the mold. Each layer being approximately two 20-liter bucks.
- After laying out each layer, uniformally tamp down the mixture with force. This creates a rammed earth stove that is very strong.
- Creating Mold for Estufa
- wooden mold with inner stove dimensions...
- Placing in Comal and Combustion Chamber Molds
- Before filling the stove mold, place a 20 liter bucket where the large comal will be, 30.5 cm in diameter
- Then place two 1.5 liter water bottles (10 cm interior longitude) as the mold for the back two comales, with a 7.3 cm diameter.
- Fill wooden mold with the same mixture of dirt as the base, packing around the 20 liter bucket and water bottles, repeating steps 1 and 2 of "Filling and Tamping the Base".
- Digging the tunnels:
- Choose where the chimney tubes will be located. Use chimney tube as size indicator and start digging a hole 12cm deep.
- Remove the molds (20 liter bucket and two water bottles).
- Dig a tunnel big enough for your arm to go through connecting the large comal to the small left comal.
- Repeat step 3 for the small right comal.
- Dig tunnel connecting the small left comal to the chimney hole.
- Repeat step 5, connecting the small right comal to the chimney hole.
- Remove the mold from rammed earth.
- In the front of the stove, carve out a square where the combustion chamber will be located (20 cm wide and 15 cm tall). Dig through until reaching the hole of the large comal.
Its recommended that the distance between the base of the comal and the base of the combustion chamber be 20 cm.
Wire Mesh Cover and Hooks
- Wire Mesh
- Measure out exact dimensions of stove then cut out enough wire mesh to wrap over the stove.
- Lay out the wire mesh onto stove in order to give cement plaster a criss-crossing network to key into.
- Make hooks by bending wire and cutting with wire cutters.
- Tap the hooks in to keep wire mesh close to stove surface.
- Cut holes in mesh where the comales, combustion chamber, and chimney will be.
- Make slopes along the holes by cutting out dirt with hand shovels for comales to fit evenly. Comales go over the opening by about 3cm, this slope also helps expose more of the comal to the direct heat from combustion.
Plastering and Chimney Finish:
- Plaster Mix
- Make a mix of clay cement plaster with 2 parts fine clay:2 parts sand: 1 handful of lime:1/4 of cement. Spoon plaster on trowel.
- Splatter some water onto stove. Clay has a "memory" and if you simply apply the plaster without wetting the other clay/dirt surface your very wet plaster can just peel off.
- Spread clay cement plaster on Lorena moving from bottom up, 2.5cm thick. Start from the bottom up.
- Work your way through the sides then the top surface.
- Place pots on comales and press down to measure the ideal size.
- Let dry for a couple of days.
- Chimney Finish
- Pierce the laminated roof with the ideal size for the galvanized tube to fit.
- Connect the galvanized tubes to go through the roof.
- Someone will have to get on the roof in order to make sure the tubes are stable and to place on the chimney cap that prevents rain from entering.
- If there are open spaces around the tubes going through the roof, cover it with cement or clay in order to protect it from rain falling on the stove.
Organizations Building Lorenas
Otros Mundos non profit that defends indigenous peoples rights and works to offer alternative solutions to indigenous communities through appropriate technology projects like improved cookstoves, biodigesters, and rainwater catchment.
Communities installed at
San Cristobal, Chiapas, Mexico with Otros Mundos
- "Women farmers in Africa: rural development in Mali and the Sahel" By Lucy E. Creevey, Liaison Committee for Food Corps Programmes International
- Appropriate Technology Program with Humboldt State University and Otros Mundos in Chiapas
- LRWorld Lingo,"Biomass cook stove", http://www.worldlingo.com/ma/enwiki/en/Biomass_cook_stove