How to build a Rocket stove - a step by step guide

One of the problems that I've already mentioned about the solar cooker is shared by the Rocket stove, namely that the beneficiary families cannot be involved in its construction and therefore there is a risk that they will neither use nor maintain the cookers. On top of that there are a couple of possible improvements that would be interesting to try out - namely having separate and sloping fuel and air entrances to try and prevent people from choking the stove with too much fuel and hot ash and coals. The idea is that the fuel entrance slopes downwards to reduce the need for near-constant attention while cooking as the wood will "self-meter", falling down the chute as it burns at the tips of the sticks. Another benefit is that the stove can be used with charcoal, unlike the standard Rocket stove. The addition of a separate, upwards-sloping entrance for air should guarantee that sufficient oxygen enters the combustion chamber, while also helping to automatically empty the stove of ash as the fuel is burnt - thats the theory anyway!

The new design is the brainchild of Jerry, a technical genius who works for the CRC in Suchitoto. Some of his other ongoing projects include plans to install a micro-hydro plant to provide power for a community hospital and school with REDES, solar powered water pumps, biogas digestors and endless improvements for the Rocket stove - including an interesting idea for a hybrid Rocket, lit with biogas to help heat it up and burn damp wood as well as replacing the gas cookers that are often used for quick meals or hot drinks. Another idea of his is for a Rocket with two or three burners to accomodate multiple pots, or a large comal for cooking tortillas for extended families - there's lots of potential for REDES to adapt the designs to suit different families.

Yesterday Steph and I caught a bus up to Suchitoto to experiment with these ideas for the new design (and on the way she was serenaded by three teenage lads who happened to be carrying a guitar and ukulele with them!) We were somewhat lacking in the resources you might have in the UK for prototyping, so had to make do with recycling an old polystyrene board (ironically showing information about a CRC project building "Armenia" stoves which are mostly disused now) and some AIDS awareness posters, along with a cardboard box scavenged from the local shop for a mold. The idea was to stiffen the box with the polystyrene sheeting, which also serves to separate the wet adobe from the thin cardboard walls with the plasticised posters theoretically stopping water from seeping out...Jerry rather optimistically hopes to reuse this mold time and again for future stoves! The combustion chamber and various inlets for fuel and air are formed from empty drinks bottles filled with paper or water for stiffening and later removed once the cooker has dried.

The stove is primarily constructed from adobe, which requires clay-rich mud, so we were armed with a spade and pickaxe and sent off into the garden with a dustpan-sized sieve to produce a bucketload of fine-grained mud. Trust me, its a lot harder than it sounds as the clay makes the soil stick together in lumps and roll up into hard little balls that don't fit through our toy sieve. An hour or so later (and having provided a tasty feast for a swarm of mosquitos that suddenly appeared out of nowhere) we finally had enough mud to go with the sawdust that Jerry had been hoarding for months to make our adobe mix. The sawdust is a vital, if surprising, ingredient - ideally the finished stove would be fired to burn out all of the sawdust (any fine-grained organic material can be used) leaving a porous material not dissimilar to pumice. The trapped pockets of air provide the insulation vital for an efficient stove by reducing its effective thermal mass (the heat is confined in the combustion chamber rather than heating the whole body of the stove as happens in many designs of "improved" adobe stoves.)

After creating a dry mix of approximately 50:50 mud to sawdust we got to work on the remaining mud, adding water to make quite a moist adobe mix which was daubed around the base and up the sides of the mold to give a smooth surface finish about half a centimetre thick. This was then filled in with the mud/sawdust mix which was made up slightly wetter to ensure that it flows properly around the mold. At this point we ran out of both sawdust and time, so we agreed to return on Friday and rushed off to catch a bus back to San Salvador for our meeting with Seb and Edwin (who carried out the structural analysis of REDES' bahareque house) but thats a story for another time! [To be continued....]

As you've probably noticed Friday's come and gone now, and we now have a cardboard box of mud waiting for us in Suchitoto, slowly drying in the sun. The second day's work on the stove was a little frustrating - endlessly forcing mud through our mangled sieve until we had blistered fingers and decided that we must have enough to finish the stove, only for all of our adobe mix to be swallowed up by the mold without making a noticeable impact! We eventually filled it to a level where we could add the fuel and air chutes - old plastic bottles cut down to size and stuffed with newspaper, then balanced a square of polystyrene on top of the upside-down 2L bottle that forms the combustion chamber to try and stop sticks from sliding straight through and out the air inlet. Over the course of the afternoon we finally managed to fill the whole mould and ended up with a three centimetre cover of adobe at the top, which was a little less than we wanted, but once again we'd run out of time and mud. The mold was then covered in plastic to keep the water off it and left outside to dry in the sun.

Next week we'll return to finish the stove - the mold will be inverted so that our combustion chamber points upwards and hopefully we'll then be able to peel away the cardboard, paper and polystyrene layers of the mold to reveal a perfectly formed, dry adobe cooker! At least thats the idea.... [To be continued....]

Solar cookers - a culinary masterclass

In addition to the biomass stoves that REDES build as part of their housing projects they also recently started distributing solar cookers to rural communities. There is enormous potential for them here because of the abundant sunshine that El Salvador is lucky enough to have - there have only been two cloudy days in the six weeks I've been here (although there are daily afternoon thunderstorms) and this is supposed to be the rainy season! When we heard that REDES had a solar cooker project we were obviously really interested in finding out more - after all it offers an alternative to all of the improved wood burning stove designs that we're considering.

Our plan for the next two weeks in the communities with REDES stoves near Berlin and San Sebastian has become progressively more complicated - we now plan to interview 10-15 women every other day and invite them to a hands-on demonstration of both the Rocket stove and the solar cooker the following day when we'll ask them more questions about the two alternatives. During our time in Suchitoto we had already received training from the CRC in the use of the Rocket stove, so Monday morning saw us huddled around a rather dull-looking cardboard box in the garden with Franco who's in charge of the project.


The system proved to be incredibly simple to use - an aluminium foil-coated cardboard reflector quickly folds out to produce a quasi-parabolic solar concentrator. The box also holds a large refractive-glass casserole dish and a black pewter bowl which fits inside it snuggly. You stick your food in the black bowl, put that in the casserole dish with a lid on and leave it at the focus of the cooker for an hour or so. Easy!


The thing was that Franco was determined to show off the full potential of the solar cooker so instead of doing something boring like boiling water he produced an eski full of frozen Tilapia and ushered us into the kitchen to cook lunch. Parsley, corriander, garlic, spring onion and tomatoes were dutifully chopped, along with some leaves that he plucked off a weedy bush in the garden, all mixed up together and stuffed into the fish with a squeeze of fresh lime and pinch of salt. The lid went on and we moved on to dessert - chopped plaintain with a sprinkle of sugar and a couple of crushed cinamon sticks.

While our lunch was cooking Franco gave us the presentation that he does for training - an excellent participatory session that got us to identify the advantages of the solar cooker and also what meals it can or can't cook, along with a few pointers for maintenance. Many of the advantages are environmental and related to the reduction in firewood use - less deforestation, air pollution, global warming, stable rainfall patterns, improved soil fertility, protects biodiversity etc. There are also significant health benefits - reduced smoke inhalation prevents respiratory illnesses, less likely to burn oneself cooking and food is steamed rather than fried resulting in better nutrition. Less obviously it could also help to reduce the violent confrontations and sexual abuse of women that can occur when they wander into other people's land in search of scarce firewood.

Nevertheless it's no golden bullet - for a start the cost will prevent widespread use as the Mexican website selling them (http://www.ollasolar.com.mx/olla_solar.php) charges $690 each. REDES has a policy of always requiring some contribution towards the projects it runs from the beneficiaries, preferrably in the form of unskilled labour during the construction phase. This is very important as it helps to foster a sense of ownership over whats built, encouraging families to maintain them and helps to explain the benefits and problems of the technology, all of which help to ensure that the projects are ultimately succesful. Unfortunately this cannot be done with the solar cookers, so instead families are required to contribute $30 for the cookers - a significant sum of money in many rural comunities.

Perhaps a more serious problem is the total cultural change required in using the cookers - a very slow form of cooking which requires careful attention to timing as removing the lid too early to taste the food releases all of the stored heat and delays the meal by an hour or so! Although the elimination of oil for frying has great health advantages it does change the taste and texture of food which could hinder the adoption of the solar cooker. On the upside the pot is heated quite evenly from all sides and the trapped steam makes it impossible to burn food. The cardboard reflector also requires some care to ensure it doesn't get damp and delaminate, both from spillages while cooking and when stored. On balance I think its fair to say that there is huge potential for this project, but it will never totally replace biomass stoves - not least because there's no sun to cook breakfast with! However it does complement the use of an improved wood-burning stove and we hope to spend our last week of fieldwork visiting one of the first communities to receive solar cookers from REDES to make a direct comparison with their other stove projects.

La Carrera de Cintas - El Franco

After a quiet weekend last time around in San Salvador - partly spent recovering from staying up all night on Friday with the Imperials before they left on Saturday morning, but also including a day trip up to La Puerta del Diablo - The Devil's Door which overlooks the city, followed by an absurd tour of just about every Mall in the city (and trust me there are lots of them!) with a Salvadorean friend from the hostal we were keen not to waste this weekend.

Saturday started with a lazy breakfast before Domingo arrived to take us to Suchitoto. On the way there it emerged that we were actually going to a local festival in the little village of El Franco which he was confident had already finished but thought we'd try anyway...after asking about five different people who all assured us it hadn't finished Domingo was finally convinced, and so we arrived at the Carrera de Cintas - The Belt Race. The basic concept is a simple one - thread a pencil-sized skewer through a keyring hanging on a line overhead. The only tricky part is when you realise you have to do it while galloping past on a horse on a rough mud track! The undoubtable star of the show as far as I was concerned was the guy who did it one handed with his reins tied to his elbow-stub but still managed to win a number of prizes.

I guess that the tradition evolved from some type of courtship ritual - the main prizes (for which the ring in the cintas is smaller - about one centimeter across!) are nominally women, although nowadays they're more likely to be a $5 bill or piece of kitchenware. The Carrera de Cintas coincides with the maize harvest and the whole village turns out to watch the spectacle, along with a DJ for entertainment (loud Reggaeton inevitably), eskies full of cold sodas and beer and hot food. The riding winds down in mid afternoon to allow everyone to get ready for arguably the main event of the day - the evening's dance, where presumably the most successful riders will have flocks of ladies vying for a song together! As for the competitors - they come from all over the municipality, and the star horse of the show had come all the way from Santa Tecla, a suburb of San Salvador a good hour's drive away.


Sunday involved a quick trip down to El Tunco - the most famous Salvadorean surfing beach, which at times seems more like a little piece of Aus than Central America! Seb and I lathered on the suncream before going off to find a couple of long-haired, bronzed lads who were going to be our long-suffering surf instructors for the next hour...amazingly by the end of the lesson I could more or less stand up quite regularly - still quite a bit of practice needed before I tackle the 3m waves out in the deep where we could see surfers weaving up and down the white-topped crests for tens of seconds at a time.

Lunch with the Mayor of Berlin

The last week has seen a bit of a departure from our project on efficient wood-burning stoves as we've been supporting Seb Kaminski, an engineer from Arup in London, who's visiting for two weeks to lay the groundwork for a structural analysis of REDES' earthquake resistant bahareque houses. Bahareque is a traditional construction method, a type of wattle and daub that uses barra de castilla (a thin bamboo that grows to heights of 5 or 6m) for the woven frame of the walls. REDES' design incorporates a galvanised steel portal frame which is cheaper than using imported timber or bamboo and diagonal bracing with tensile wire. The barra de castilla is then attached the framework and left for a week or so to dry out - the projects are done in a participatory way with each beneficiary family providing someone to work as unskilled labour. Groups of 4 or 5 families work together on all the houses in their group which helps to provide the time needed between phases of construction (eg. for the barra de castilla to dry or the mud walls drying before plastering etc.) The finished houses are whitewashed and then painted by the families, resulting in a "modern" looking house far more desirable than their old adobe houses.

REDES are particularly keen to develop this bahareque design as it is 15% cheaper than the equivalent made from blocks, and more importantly the investment in materials goes to incredibly poor rural areas rather than the rich elite who hold monopolies on the block factories. Additionally it uses a much smaller amount of cement, which is both expensive and environmentally damaging (its production is energy intensive and a major source of industrial carbon dioxide emissions) and barra de castilla is a fast-growing, sustainable and carbon-neutral resource. A structural analysis has already been carried out by an independent local company, but in order to secure international donor funding and governmental support for rolling out a larger bahareque project REDES would like certification from an internationally renowned company, which is where Seb and Arup come in.

As well as a number of technical meetings with the REDES engineers who designed the houses Seb has a questionnaire for families who have participated in the project, so over the course of the fortnight that he's here we will visit three different communities to do a visual assessment of the houses and hear the families' views. As a result we spent last Friday visiting Loma Fria where REDES are currently building rainwater collection tanks for the bahareque houses. It was very interesting talking to the families, the vast majority of whom were delighted with their houses and no longer worried about the threat of earthquakes. For those who don't know, El Salvador suffered two major earthquakes (6-7 on the Richter scale) in 2001 which killed hundreds of people. Everyone we talked to in Loma Fria had their old adobe houses severely damage during the earthquakes, although none of their relatives had died. One of the supposed advantages of bahareque is that it is extremely light and flexible - certainly when compared to the traditional adobe walls with loose blocks and tiled roofs it is easy to see the improvement in the design.

Another advantage of the new houses is their resistance to insects, in particular assasin beetles (los chinches) which tend to live in the nooks and crannies of old adobe houses and emerge at night to bite the sleeping residents. These seemingly harmless bites can transmit Chagas disease - it often goes unnoticed for tens of years, but eventually damages the nervous and digestive systems and can also cause heart failure - something that we are particularly aware of after there was a worry that one of the group from Imperial was showing symptoms, luckily it turned out to be a false alarm.

Nevertheless there are also some problems with these houses - the quality of the welded joints is dubious, most are only spot welded together and their resistance to earthquake loading will be minimal at best. The houses are also prone to surface cracking as the plaster dries so quickly in the roasting heat, and the thin, light walls desirable for earthquakes heat up much more quickly making it uncomfortable to sleep inside during the day. On top of that there's a problem of social acceptance that is harder to overcome than all the technical challenges - some people simply do not want a house made out of mud, whether its been nicely painted or not, and would be much happier with blockwork walls.


Jumping back to Wednesday and the title of the post, we attended the inauguration ceremony of the second phase of a batch of 70 REDES houses in Berlin (where Steph and I will be returning in a couple of weeks time to interview families from the first phase about the stove that came with the house) where the funding has come from Castilla La Mancha with support from a Spanish NGO - Terra Pacifica. It turned out to be a very interesting day listening to the various speeches from all the players - the Mayor and Town Council, comunity leaders, Terra Pacifica and finally REDES.


I also picked up a few pointers on how to get the comunity involved in this type of event - for example reading out the contract for the next phase seemed like a good idea, but perhaps some of the finer legal details could have been omitted! The ceremony was followed by lunch at a little restaurant perched at the top of the hill overlooking the whole valley and Embalse 15 de Septiembre - one of the main hydropower sources for El Salvador. Douglas even managed to rustle up a group of Mariachis to serenade us and celebrate Jose's (one of the Spanish delegation from Terra Pacifica) birthday.