Science in Society Archive

The Community Cooker Turns Rags to Riches

An extraordinary recycling project turns rubbish into energy and potentially transforms slums into resource rich communities Sam Burcher

The disturbing scenes of human deprivation in the highly acclaimed movies Slum Dog Millionaire and The Constant Gardener [1] show the real-life slums in India and Africa overflowing with people and with refuse.  But what if the piles of stinking rubbish could be converted into what urban slums need most of all: hot water for washing, pure water for drinking and heat for cooking?

Nairobi-born architect Jim Archer has designed and implemented with the help of his Kenyan fellow Director Mumo Musuva and their Planning Systems Services team the 2008 World Architecture Festival (WAF) award-winning project in Kibera, Africa’s largest slum, which does just that.  The locals in the Laini Saba district in Kibera have been instrumental to the success of the project they call the “Jiko ya Jamii,” that translates from Swahili into the “Community Cooker”.

Agnes Aringo is a caterer at Jim’s architectural firm in Nairobi.  She works on the community cooker and reports [2] that the cooker is versatile, and that it boils water, cooks vegetables, stews beef, bakes cakes, fries food, and can be used to prepare breakfast, lunch and dinner, and make cups of tea. The two ovens cook cakes very quickly and each is large enough to grill a whole goat.  You can’t tell that the fuel used to cook this food is the waste products from the slum. Agnes says, “Nothing is thrown away or should be thrown away in our environment.”

The community cooker in use

A community-led cooker

The slum dwellers themselves have solved several of the practical problems presented by the cooker project. Volunteers from various local youth groups collect, sort and store the garbage in metal racks adjacent to the cooker where it can dry.  Materials that cannot be burnt such as rubber and glass are put to one side. Biodegradable scraps that fall through become compost manure [3].    

The really useful solid waste materials like paper and plastic – bags, drinks bottles and packaging -  and food scraps from banana, cassava, maize cob and sugarcane peel, sawdust and even the discarded carrier bags of human and animal excrement colloquially known as ‘flying toilets’ are forked up to the top level of the racks ready for incineration. All these items would normally be left to rot in the street, thrown into water courses, or dumped in local rivers.

At first, Jim was baffled as how to reward the sorters for their time and effort. “It’s very simple,” they said. “We will do the sorting for the public from say 6 am until midnight.  But from midnight until 6am we will work the cooker for ourselves.  We will make bread and we will bake buns and we will heat water. We will sell these and that’s how we will make our money.”  From that moment on, Jim knew they had a working project. 

Two simple taps are the only moving controls on the cooker, which has deliberately been kept very, very simple to operate and to maintain.  One tap controls a drip flow of recycled sump oil (dirty and discarded oil from vehicles) and one tap controls a drip flow of water.  A drop of each falls in equal amounts onto a heated steel plate at the face of the firebox, where the water vaporises into hydrogen and oxygen, which causes a combustive reaction with the flames and increases the temperature.  As the firebox gets hotter it heats the network of steel pipes that pass around the cooker. This resourceful technical innovation was the idea of a local man and self-taught furnace builder Francis Gwehonah, who has helped double the firebox temperature from 300oC to 600 ˚C. 

How the community cooker cooks

The cooker is made entirely of welded steel and has eight circular hotplates on the top. This is similar to a ‘traditional’ hob design except that the big metal cooking pots can be partially submerged into the hotplates to gain and retain heat from the firebox below. Hot food is served directly from the saucepans, or can be taken back home by the person who has collected rubbish, or purchased a token to exchange for cooking time.  The cooker has two ovens under the hob, one either side of the firebox. 

A tall and narrow chimney rises out of the firebox between the hotplates and reaches high above the slum. White vapour emerges like papal smoke wafting away the almost odourless fumes from the spotlessly clean kitchen area. Sliding down below the hob, a wide metal chute feeds a constant supply of rubbish from the storage racks into the firebox’s hungry flames.

In theory, the community cooker should be operated 24 hours a day providing there are people to collect, sort and burn rubbish. A by-product of the incinerator-like cooking process is the relatively small amount of ash that collects beneath the firebox which it is hoped will undergo a second transformation into material to reduce fly menace in pit latrines and the smell from open sewers, once toxic levels of the ash have been tested and if found acceptable.

Hot water for washing

It costs Sh5 (5 Kenyan shillings, about US$ 0.06) to use the cooker to make a family meal.  A local woman Elizabeth Mumbi reckons it’s a bargain. She says [4], “I come here quite often, I find cooking at this communal place quite cost cutting. The Sh5 I pay to use the communal “jiko” is nothing.  Imagine how little kerosene or charcoal this money can buy.  Nothing costs this little any more.” 

The cooker heats up water for washing which can be taken to a communal bathroom known as a “bafu”.  Four large water filled tanks are connected by pipes to each corner of the cooker roof.  They act as a reservoir for up to 160 gallons of water at any one time. On average 50 people a day take hot water into the bafu closet, while as many as 200 people could wash from the rain water stored in the tanks. 

Since the Laini Saba community cooker became operational in 2007, Jim Archer has drawn up plans to continue to improve the social and environmental conditions in Kibera further [5]. He wants to increase the number of cookers to one per every 50-70 households, which can contain as many as 20 members per household.  Jim is planning to recycle waste water from bafu closets to flush through the open pit latrines that often block and overflow which are to be redesigned as “aqua privies”. The runoff from the “aqua privies” can then be bio-digested and the resulting matter and moisture gravity fed to support the growth of vegetables, fruit trees and shrubs to create green spaces within the slum.  

In this system, waste from one activity is simply a precious resource for another. By recycling the flow of wastes in the environment, the levels of water consumption, ground pollution, fly and mosquito breeding grounds and disease are all reduced.

Kibera as it is and as it could be with planning

UNEP funds cooker project

The United Nations Environment Programme (UNEP) is a major supporter of the Community Cooker initiative and has stumped up $10 000 towards its installation.        The project is part of the Nairobi River Basin Programme (NRBP) [6], designed to rehabilitate and restore the Nairobi rivers ecosystems to improve livelihoods and enhance biodiversity.  UNEP and the Kenyan based Paint Manufacturers BASCO who have also generously contributed to the construction of the prototype are keen to fund more cookers around the slum, which has a population of well over 800 000 [7]. Jim’s team has made the World Health Organization’s 800°C minimum temperature requirement for incinerators in the Developing World their bench mark for operational acceptability within the cooker’s fire box.

Until the current temperature of 600 ˚C is increased a further 200 ˚C the rubbish will continue to pile up and the majority of people in Kibera at least will go without basic sanitation. However, Jim Archer is confident his team can raise the temperature, but until his patent pending design reaches 800°c, he reluctantly accepts that there should be no new community cookers. 

Cookers not charcoal

About 91 250 tonnes of charcoal biomass are used for energy every year in Kenya [7].  Contributing to this are several ‘temporary’ displaced persons camps, which permanently shelter well over 110 000 people each.  Women and children in these camps travel further and further every day to find wood and fuel for cooking, denuding the countryside for miles around and creating health problems for themselves from the smoke of the firewood.

 Recent research findings show that black carbon (BC), the black soot resulting from the incomplete combustion of burning fossil fuels contribute to warming the planet 55 percent as much as CO2, and that reducing black carbon emissions may be the quickest, cheapest way to save the climate (see [8] Black Carbon Warms the Planet Second Only to CO2, SiS 44). Community cookers will contribute a great deal to reducing BC emissions, and hence earn carbon credits if BC reduction is included in the Clean Development Mechanism of the Kyoto Protocol.

The German aid agency GTZ has expressed an interest in placing community cookers into the refugee camps they manage and Jim reckons that each camp would need a thousand cookers to sustain their populations. He believes that the money that could be earned through carbon credits from these cookers could be reinvested into a massive reforestation project of native trees undertaken by the refugees themselves.

An engineering company in the UK has offered to loan Jim the sensitive equipment he needs to establish much more precisely how much carbon is emitted from the community cooker and how that compares to the use of charcoal and kerosene plus the emissions from the piles of rubbish in Kibera.  The Engineering practice ARUP and an NGO called JHPIEGO who are an affiliate of John Hopkins University, the Kenyan Red Cross and the Centre for Sustainable Engineering in the UK, and the British based Charity Glad’s House are also actively interested in the slum cooker project.

Low tech is the future

There are seemingly infinite uses to which the basic concept of the community cooker can be applied for local development. These include kilns for clay bricks, pottery and tiles, small hot water systems for homes, hot food and water for hospitals, schools and colleges, hotels and lodges. However, Jim’s low tech and socially inclusive vision of change under challenging conditions may not appeal to everyone in an increasingly complicated and technologically driven world. 

But what this relatively low cost and labour engaging project does do is to give people something that they have never had before, hot food and hot water on a regular basis.  In addition, it demonstrates that local solutions to specific problems such as the global scourge of plastic and other waste can be transformed into the basic comforts necessary for human wellbeing.

It is another example of the affordable, distributed, decentralised generation of renewable energy that gives local communities energy autonomy, which is a key to truly Green Energies [9] (ISIS publication).

Article first published 30/09/09


  1. Burcher S.  The Constant Gardener.  Science in Society 30 2006:4
  2. Agnes Aringo’s report. Jiko ya Jamii, The Community Cooker.  Simple Heat Generation from Local Rubbish Collection.  The prototype model operational, March 2008
  3. Amos Kareithi.  Hidden treasures in garbage. The Standard, Saturday August 28 2008 p23
  4. Barry Moody RPT Feature - Slum cooker protects environment, helps poor. Reuters 3 April, 2009.
  5. Personal interview with Jim Archer September 2009, in London.
  6. United Nations Environment Programme. Environment for Development The Nairobi River Basin Project
  7. Ministry of Nairobi Metropolitan Development
  8. Ho MW. Black Carbon warms the planet second only to CO2. Science in Society 44.
  9. Ho MW, Cherry B, Burcher S, Saunders PT, and Others. Green Energies, 2010, The Institute of Science in Society (Forthcoming).

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There are 12 comments on this article so far. Add your comment above.

Sam B Comment left 1st October 2009 19:07:43
Burning any organic matter including biomass such as wood can cause health problems, but crucially uses up finite resources. The incineration of infinite rubbish is probably marginally better than refuse left to rot in the streets and rivers as far as health and ecological problems are concerned. I am sure that there will be studies that can decide that. Of course the best solution would be energy derived from sunlight and also biogas from wastes. Until then, the WHO has issued guidelines around incineration to destroy harmful dioxins and filter systems are in place to deal with fumes.

Rory Short Comment left 1st October 2009 23:11:48
It is not clear from the article what types of waste are incinerated and as a previous commentator pointed out the incineration of plastic waste can lead to pollution problems with dioxins. That said however the intention to localise resource usage, in this case rubbish, is most exciting and commendable.

susan rigali Comment left 2nd October 2009 00:12:02
Jim, Mumo and Agnes are cleaning up the slums and creating resource for a better life. Green spaces in the slum and possible areas for gardens will employ others to action. While toxins may be present through incineration, it certainly can not be worse than the depleted uranium others experience through wars. Brilliant work that needs support in order to continue improvement. It seems that the future of resource development comes from helping others instead of acquisition through destruction.

Flavio Lewgoy Comment left 1st October 2009 17:05:25
Sure the project is a good one. But it has a darkside, too. Incineration of organic matter and plastics generates many health problems through air pollution with dioxins, particulate matter, toxic metals, etc.

Marian Weaver Comment left 8th October 2009 15:03:36
While this is a great stop-gap alternative to festering piles of trash and unsustainable use of scarce wood resources, I'd have to say that getting solar cookers into wide use should be a top priority anywhere in the world they are appropriate. Many of the places in the world currently experiencing catastrophic deforestation are also blessed with very reliable sunshine. My husband and I live in southern Arizona, with a climate not unlike the sahel, and we cook with the sun probably 300 days a year. No smoke, no emissions, no trees cut, dead easy once you get the hang of it.

marie-paule nougaret Comment left 6th October 2009 18:06:18
dioxins only come from chlorine loaded pstic (pvc) which might be banned world wide in a few decades… as weel as cadmium and other toxic metal additives to plastics. The rest is goid clean fuel (fun). Packaging may be the problem and it's rather new mpn

dooberheim Comment left 7th October 2009 15:03:57
One other issue they may want to be careful of is the use of used motor oil in their firebox. Motor oil contains high levels of lead from bearing wear, that will volatilize and contaminate the surrounding area. However, the benefit of safe water and good food may well outweigh that for them. In rich countries, we lose sight of how hard it is to live in the third world. People who can complain about dioxins, or lead, are usually not the ones that are complaining about not having enough to eat. DK

cjohnson Comment left 7th October 2009 16:04:06
Burning this garbage for energy is a much better option than leaving it to rot on the streets. When it comes to emissions such as dioxins and PAHs that people are concerned about, A steady, hot fire in an enclosed unit with a draft (supplied by a chimney) will yield fewer of these pollutants than hundreds of wood fires smoldering all day long even if waste materials are being used as fuel. They aren't burning vinyl siding from suburban house remodels, last year's cell phone fashion trend, crusty BFR-treated couches, CCA lumber, mercury switches, NiCd batteries, and other items found in developed world garbage.

John Irvine Comment left 7th October 2009 15:03:05
Forget the burning - install a gas pilot light -use solar to heat the plate - drip in the water and presto you have hydrogen power for electricity generation...

Derek Comment left 7th October 2009 21:09:20
There is a physics problem here, though it may be left purposefully obscure to safeguard the idea (technology transfer reasons?), or the author doesn’t quite get the processes and so glossed the details, either way water does not dissociate into hydrogen and oxygen gas when heated! In order to dissociate H2O into H2 and O2 you need to perform electrolysis, this is what all the major research at MIT, Stanford, CalTech, etc. is trying to develop in an economical way to usher in the hydrogen economy (hint: no success yet). In all honesty I don't have access to the whole report (pay site...I know for a good cause and all) so the details should be hidden in there (let's hope). But what I think is really going on, and why the 'oil' is mentioned VERY briefly, is essentially an external diesel engine (as opposed to an internal combustion engine). Heat is supplied by the fire; dripping diesel onto the plate wont ignite it because compression is needed, so the water vaporizing to steam (NOT dis-associating), increases the pressure in that sealed area around the fire box, and presto, a small bang, pressure and heat double the temp. of the cooking stove. No hydrogen, but maybe a nice way to get rid of waste oil.

keith allies Comment left 17th September 2010 15:03:30
This is an excellent project.Can you please provide me with the architect James Howards e-mail address? We ould like to buy the plans of the community cooker for our slum community in Namibia. Thanks keith allies

Felix Staratschek Comment left 18th February 2010 06:06:52
Hallo! Greatings from Germany! Cooking with waste is no solution. There is to much energy- input in the substances. Only recycling can safe this energy. Whats about solar- cookers and more efficant cooking- places? I have made an informationpage about an german recycling- and waste- management- idea for plastics and e- waste in german and english language (kryo- recycling). Pleace spread this infomation to all persons, you know, that many people get knowkedge about this idea and good alternatives to incineration. If you and others have some more or new information, pleace send the information to my adress. . Here is the link to my informationpage: With best Greatings, Felix Staratschek, Freiligrathstr. 2, D- 42477 Radevormwald