'Improved' Cookstoves May Do Little to Reduce Harmful Indoor Emissions

Black-carbon emissions from newer stoves, designed to be safer, were higher than those from traditional fire hearths, a new study finds















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Image: Barbara Fraser

TOTORABAMBA, Peru – Smoke swirls around the hearth and hangs in the sunny doorway of the adobe kitchen where Espirita Lima Bautista crouches by an open fire, toasting barley grains. Soot dangles from the thatch roof in six-inch stalactites, a grim reminder of the particles she inhales whenever she cooks.

For this 80-year-old grandmother, breathing while cooking for an hour is like inhaling the second-hand soot from 400 cigarettes. Although it only lasts as long as the meal is being prepared, exposure began when she was a baby, slung in a blanket over her mother’s back.

Two decades ago, concerns about cooking fires centered on deforestation from firewood. Now research shows that cookstoves can kill people, too.

Indoor smoke from coal, wood or dung – used as cooking fuel by more than 3 billion people worldwide – ranks ahead of unsafe water as a cause of death in low- and middle-income countries. Almost 2 million deaths a year are caused by cooking smoke, which is linked to pneumonia in children, chronic obstructive pulmonary disease, low birth weight babies and lung cancer, according to the World Health Organization.

These fires also help heat up the planet, emitting greenhouse gases as well as the black carbon that creates the stalactites on Lima Bautista’s ceiling

“There are health and climate co-benefits to changing the way a lot of people in rural areas around the world cook,” said Jennifer Burney, a postdoctoral fellow at the Scripps Institution of Oceanography in San Diego who studies the links between energy and food in poor countries.

Faced with global public health threats, governments and non-profit development organizations are encouraging families to install “improved” stoves. The United States has donated $105 million to a United Nations-led effort that aims to put safer cookstoves in 100 million households by 2020. In addition, leaders of the G8 countries pledged in May to take measures to reduce short-lived climate pollutants that include distributing more efficient cookstoves in developing countries.

The problem is that many newer models on the market do little to reduce harmful emissions and some actually make matters worse.

“It’s a case of the policy getting ahead of the science,” said William Checkley, a researcher from Johns Hopkins University’s Bloomberg School of Public Health, who is coordinating two studies in Peru, including a comparative study of cookstoves in Lima Bautista’s village near the Andean city of Ayacucho.

Research published in March points to huge differences between stove models. Black-carbon emissions from some newer stoves were higher than from traditional fire hearths, said Burney, who co-authored the study.

Cookstove research was originally designed to reduce deforestation, said Tami Bond, an engineering professor at the University of Illinois. Now, she said, “health is really the driver” of clean-stove research.

Indoor smoke mainly affects women, children, the elderly and indigenous people, who have the least political and economic clout, and the least access to safe water, sewer systems and health care, said Agnes Soares, environmental epidemiology adviser at the Pan American Health Organization in Washington, D.C.

For many diseases, indoor cooking fires rank between active and passive cigarette smoking as a risk factor, according to Kirk Smith, director of the Global Health and Environment Program at the University of California, Berkeley.

 Globally, the World Health Organization attributes 35 percent of chronic obstructive pulmonary deaths and 21 percent of lower respiratory infection deaths to indoor air pollution from solid fuel.  In China, where coal is the main fuel, they are the second-highest factor linked to lung cancer, after smoking. Women who cook indoors over open fires also have thicker carotid artery walls and more arterial plaque buildup than urban counterparts who use liquefied petroleum gas stoves, according to Checkley’s preliminary data. Both are signs of heart disease.



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  1. 1. homelessonwheels 05:56 PM 7/11/12

    Is there any reason nobody has considered the simple act of exhausting the smoke to the outdoors? Even if the cost of a proper flue is prohibitive, how about locating the hearth near an open window, or maybe a hole in the roof above the fire? DO they really not know any better than to let smoke accumulate indoors? It seems that everyone forgets education and prefers technological solutions. Could that be because of the profit motive? After all, new stoves, or whatever, will have to be designed, built, and sold, putting money in somebody's pocket. While quality of life could be greatly enhanced simply by teaching people how to more safely use the existing technology, there's no money in it so who's going to do it?

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  2. 2. DanYHKim 06:31 PM 7/11/12

    While the worst emissions levels from the worst "improved" stove session exceeded the best emissions level from the traditional stove, this does not mean that adoption of improved stoves "may do little to reduce harmful indoor emissions," as the title states. The data show that improved stoves produce generally lower emissions than traditional stoves. While it is true that indoor pollution can be greatly reduced if cooking were done using propane, methane or electricity, this may be an insurmountable leap for people who are now using mud-constructed traditional stoves with no external ventilation, as described in the linked paper (Environ. Sci. Technol., 2012, 46 (5), pp 2993–3000). This may be especially true due to the individual nature of home-constructed traditional stoves, many of which may have much worse performance than the stove used in the test. Do not let the best become the enemy of the good.

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  3. 3. dwbd 08:50 PM 7/11/12

    It would be much more energy efficient to connect them to the grid and give them a $100 microwave. Amazing how greenies are always promoting energy efficiency, but those archaic methods of cooking are terribly energy inefficient.

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  4. 4. Essau 09:38 PM 7/11/12

    For these folks, a $1.50 stove is a luxury that many cannot afford. A "proper flue," that is a modern metal chimney attached to a stove is not in their budget. Cooking "next to a window" is not going to make much difference, and a "hole in the roof" lets rain in. These people are the poorest of the poor, they don't have a lot of options, but they need something to cook on. Educating them is great, but it doesn't change the physical reality of their world.

    The price of charcoal (or wood) is a significant cost in the lives of these folks. An improved cookstove can reduce fuel use by as much as 50%, which is roughly analogous to you cutting your power bill (gas+elec) by 50% -- except that at their level of income, the proportionate difference that an expense reduction of that amount makes a much bigger difference in their lives.

    Give them a microwave? Are you serious? They don't even have electricity. Their whole families are living on $1.50 per day -- if they are lucky. Giving them a microwave would be a bizarre and enormously ineffective form of "assistance."

    A $10 or $20 mass produced solar stove would be a great help for them -- on days when the sun shone, but it won't solve all their needs. It would be beyond their reach unless someone else donated it, and it wouldn't work on extremely cloudy days, but it would help. A similar help would be a small solar hot water heater, but again, they can barely afford a $1.50 improved stove, let alone a piece of equipment that would cost them half a month's wages.

    We need to promote and build sustainable, distributed, appropriate technology power sources for these folks. Roughly 2.5 Billion people in the world have no power or almost no power -- they are going to come "online" at some point, and if they do it in a sustainable way, that will save them from making the same damaging CO2 contributions that we in the west have made through our mindless energy gluttony.

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  5. 5. Steev 08:21 AM 7/12/12

    We promoted the African ceremic-lined stove made locally from scrap metal. People bought it not for the health or environmental benefits but because it saves money and is more "modern" than the regular stoves. We used advertising to convince some consumers that even though the improved version costs 5 times as much, it pays for itself in a month and lasts over 2 years. It was measured (in actual homes) to reduce charcoal consumption by 46%, and by extension smoke also. Your article has me wondering about black carbon and how much healthier the ceramic-lined stoves are.

    The WHO and the International Standards Organisation can devise all the standards they want, but I don't see how that will benefit poor households.

    Your article hints at a nightmare in which international organizations go around handing out free or subsidized stoves, which will of course be mis-used or not used at all. The real challenge is to convince people that improved stoves or alternative fuels produce enough of the kind of benefits they care about (i.e. financial savings) that they warrant the investment. Only then can you have local suppliers sustainably serving demand from the users themselves. That takes a lot of promotion, which international organizations could support, and not the sort that sounds like public service notifications, but real private sector-style advertising.

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  6. 6. Essau 08:54 AM 7/12/12

    One other aspect of helping people implement a sustainable energy lifestyle that Steev touched upon is the demand for fuel that cookstoves place on the local environment. In many places, gathering of fuel (i.e. wood, or wood turned into charcoal) is environmentally detrimental because it results in deforestation, leading to problems with erosion and habitat loss. This is especially the case in areas of very dense population. In India, there are examples of group kitchens that use large solar ovens to cook food for hundreds of people. Providing something like that on a small (individual) scale would be helpful for many people around the world, but they will need financial assistance in order to access the technology (raw materials, transportation, implementation.)

    I agree with what Steev brings up about the disconnect between the theoretical advantages that a product may have and the utility of that product in a given society. Solutions to this problem have to take into account cultural and practical issues. For example: while biogas (animal waste methane) generators are accepted readily in some central asian countries where animals are kept in close confinement (pens), the technology does not transport well to places where people practice herding in open country -- the "poop" is spread out too far to practically collect and use in a home biogas generator. Additionally there are cultural issues that may arise surrounding the handling of animal waste.

    The real issue, IMHO, is that some 2.5 Billion people need access to energy to improve their lives, and the best way for them to access that energy (for the planet, and in the long run) is through some kind of appropriate technology sustainable energy program. Of course, we in the more developed countries need to "get our house in order" at the same time.

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  7. 7. InquiringConstructivist 10:27 AM 7/12/12

    I teach workshops on how to make solar cookers from scrap. Admittedly it may be hard for some to find reflective material and clear material, both being necessary for any decent solar cooker. But solar cooking will be the permanent solution for most of us, a technology that works today and will still be as cheap and plentiful ten thousand years from now.
    A reliable power grid will be another part of the solution, as well as better combustion of biomass; but I and other critical thinkers have discovered that even in the land of reliable power, solar cooking has many benefits, from cooler kitchens in the summer to more social cooking.

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  8. 8. Essau 12:37 PM 7/12/12

    What are the solar cookers like that you build? Webpage? I'm working on converting my school bus (home) to solar heating (as I have time to do things.)

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  9. 9. singing flea 01:39 PM 7/12/12

    The problem with cook stoves in third world countries is more complicated then just cooking food. In most places the cook stove does double duty as the only source of home heating and hot water for bathing and sanitation. An energy efficient cook stove is fine in the tropics but cooking can be done outside under a canopy in tropical climates. For thousands of years Polynesians cooked in communal pits called emus. Cooking was a weekly celebration where everyone help in some way or another.

    In colder wetter climates this becomes impractical just as cooking with a small efficient wood stove would be. A good example is the hearth that was once the central feature of the early settlers in America. The hearth was built for heating a log cabin or sod house and cooking was a secondary consideration.

    Having traveled extensively I can state with conviction that solar cooking would not eliminate the need for q2wSaz
    .



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  10. 10. outsidethebox 02:47 PM 7/12/12

    Where do the real poor in this world live? Mostly in very warm countries. I have lived in "Sunbelt" states exclusively since graduating college. In over 40 years, 90% of my meals have been cooked outside for that reason. Just as in the pre-electrical and pre- air conditioned South. This was not to be "green". Just not to put heat into the house.

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  11. 11. Steve3 in reply to dwbd 04:10 PM 7/12/12

    The grid goes no where near where these people live. They collect and burn whatever grows nearby.

    And "Greenies" are not promoting old unhealthy cooking and heating methods like open stoves and coal. At this moment in time people with and environmental outlook and people more concerned with rural development in the poorer south are staring to come together to share experience and offer solutions. New stoves are an important meeting point. Do you understand what I'm writing?

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  12. 12. Steve3 in reply to outsidethebox 04:16 PM 7/12/12

    Hi.... TOTORABAMBA, Peru where the lady in the foto lives has a temp range today of 7°C at night and 20°C as the highest daytime temp.
    Not exactly sunbelt I would have thought.

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  13. 13. dwbd in reply to Steve3 08:51 PM 7/12/12

    Greenies are promoting whacky energy non-solutions that throw 100's of $billions down the sewer, a small fraction of which could supply electricity to these poor communities. Perfect example is Germany, one of the stupidest places on Earth to install Solar power, and yet Greenies have made it #1 Solar Power country in the World. Take a small fraction of that wasted capital and supply Solar panels and microwaves to these countries with no electricity. Providing cheap electricity is the foundation of building a civilization. It is not a difficult task if you ignore Greenie Religious Dogma and optimize Electricity production according to the local environment. i.e. Nuclear Power for high tech Germany. Solar power for low tech, sunny developing nations. Logical, Rational but the Greenie Religion does not accept that.

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  14. 14. bfraser in reply to homelessonwheels 11:06 PM 7/12/12

    There are some studies that show a reduction in particulates when stoves are vented properly, but people don't always vent the stoves properly, keep the chimneys clean, use the damper correctly, etc. There are a lot of human variables, as well as technical variables, in cookstove use.

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  15. 15. bfraser in reply to Steev 11:11 PM 7/12/12

    According to the people I interviewed, the ceramic lining isn't as important as the air flow inside the stove - some are more efficient than others. 50% particulate reduction is better than nothing, especially when coal is the fuel, but Smith's point was that the goal should be truly clean indoor air.

    The WHO and UNDP published this report on energy access in developing countries, and what it would take to expand the grid: http://bit.ly/bC6KJO

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  16. 16. Essau 12:55 PM 7/13/12

    Both singing flea and outsidethebox make valid points. In the back-country of Buryatia, a stove is just as much about heat as it is about cooking, while in rural Viet Nam, food production is the main function. And the Polynesian weekly outdoor cooking sounds very similar to neighbors getting together to can food in the US deep South.

    Solar cooking is not *the* solution for folks who don't have access to "modern" gas and electric ranges (or the corresponding utility infrastructures.) It can be a *part* of solution, and it can be a *significant* part of the solution. A self tending solar rice cooker would be a huge blessing for many people in Bangladesh. (Stream of consciousness thought: what if, as a part of it's social welfare programs, the US developed a cottage industry of manufacturing such devices, which would then be distributed as foreign aid; thus, promoting sustainable development abroad, while employing folks here who might not otherwise have work?)

    Currently, nearly half the world population has little or no access to distributed power (electric or mechanical.) The standard response in supplying the demand for power is to install generating stations and grids. There have been problems with this approach in some of the less developed countries, where the ability to maintain such an infrastructure is marginal (both from the standpoint of having an educated and technically skilled population, and from the standpoint of endemic governmental corruption.) The investment in infrastructure that is required to supply a diffuse rural population is extremely expensive, and the delivery of power to limited areas in order to encourage urbanization for the sake of minimizing infrastructure costs brings with it another host of problems.

    I would argue that a more "sustainable" approach is the development of modules of appropriate technology that could be distributed more quickly and easily than a grid system, and that would not incur the inefficiencies attendant upon grid transmission. This would not necessarily be less expensive, but it also would not, once developed, necessarily be more expensive. The issues of technical training and maintenance would still need solving, but the level of both required, in "lower-tech" systems, would not need to be as high as they would for a grid system.

    Such an appropriate technology distributed sustainable power system would, however, be a giant step to reducing the environmental effects of bringing another 2.5 billion people "online."

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  17. 17. singing flea 04:27 AM 7/15/12

    Sorry for the corrupted post in No.9. I'm not sure how that happened.

    What I meant to say was, "Having traveled extensively I can state with conviction that solar cooking would not eliminate the need for indoor stoves in many places.

    BTW outsidethebox, millions of poor people do not live in warm countries. Those people who cook indoors on wood or charcoal or even peat and dung live in modern countries too, even America.

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  18. 18. singing flea 04:37 AM 7/15/12

    "Greenies are promoting whacky energy non-solutions that throw 100's of $billions down the sewer, a small fraction of which could supply electricity to these poor communities."

    You are confusing electricity with economical energy. Solar is by far the the least expensive way to heat a home and even cook. It is truly astonishing how someone who professes to be a know-it-all about energy has never even heard of passive solar heating. This is the same kind of person that would live in an air-conditioned wood frame house rather then an adobe house with a cement floor in middle of Death Valley.

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  19. 19. dwbd in reply to singing flea 09:16 PM 7/15/12

    Nope, I never said anything about passive Solar Heating, which I am a big fan of. The interesting thing if you look at the extraordinary 100's of $billions being dumped into "clean energy", most are going into nutty Scams like Solar PV in cloudy Germany. And unbelievable, actually shutting down their perfectly good, zero emissions Nuclear Power plants to install more idiotic, ultra-high priced Solar PV and Wind Turbines - running at a pathetic 18% CF. Just throwing money down the sewer, money that could provide zero emissions electricity for poor Africans in high Solar areas, and save lives. Win, Win except for the Greenie Cult dogma.

    So the bizarre thing is, what would actually be economical like Passive Solar Heating and Solar Hot Water is getting ZIP to NIL in subsidies or promotion. The only rationale is that the whole purpose of this Wind & Solar SCAM is to prevent Nuclear Power from displacing fossil fuels for electricity production. Wind & Solar power mates well with Natural Gas not Nuclear or Coal, so the big proponents of Wind & Solar have been Big Oil/NG.

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  20. 20. singing flea in reply to dwbd 02:40 PM 7/16/12

    "...Passive Solar Heating and Solar Hot Water is getting ZIP to NIL in subsidies or promotion."

    Actually this is a totally erroneous statement. There is many very generous tax benefits available on both the state and federal level for anyone with enough gumption to look into them.

    The problem is that 'for profit' corporations that produce the dirtiest and most expensive forms of energy have absolutely no incentive to promote conservation and free energy sources. As long as there is oil and coal to exploit, and as long as big industry invests in ships, trucks and aircraft that run for 30 years on fossil fuel we will be stuck with automobiles that use gasoline too. The fact of the matter is that gasoline is a by product of the distillation process that makes heavier fuels for industry. It's really not safe to burn this fuel in anything bigger then a V8 or a vehicle that needs to carry more then 30 gallons at a time and is driven by amateurs.

    The biggest impediment for passive solar for heating and cooking needs is simply that 20th century homes were not designed that way, in spite of visionaries in the mid century. They were stomped to extinction by big business that had other visions for the future when the building booms were in full swing. Housing developers had infrastructure like pipelines and electrical transmission lines to fund for the next 30 years and this infrastructure simple wasn't going to be profitable if homes didn't need huge appetites for the energy. It is ultimately a banker's dilemma. If hindsight were foresight we wouldn't be in this mess, but investment bankers don't concern themselves with profit beyond the terms of their loans.

    Now is not the time to defend such wasteful practices anymore, nor is it time to build more waste inspiring energy plants. Now is the time to get behind legislators that that will help get rid of these parasites and get American on the road to self sufficiency in the years to come. It is going to be sink or swim in the very near future and that becomes a personal challenge. Big oil isn't going to help anyone when the oil runs out and the pitfalls of fracking become glaringly obvious.

    Passive heating and solar electric for new homes will eventually become law, and it won't be republicans that will figure that out. They will continue to fight it all the way to the bank at least until we all go broke and can't pay the utilities anymore. When that happens, they will be busy peddling all the patents on alternative energy that were bought up by these same corporations years ago.

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  21. 21. llmystic 05:48 PM 7/16/12

    Unfortunately this is a common problem. Field testing of products is harder and more expensive. Even if a business is conscientious enough to test their products at all (and many are not), lab testing is cheaper and easier. But it does not replicate field conditions, so the results are suspect. Good design is meaningless if the people using the stoves (or any "improved" products) do not use them as the designers intended.

    It seems obvious to me that open hearth fires are often cleaner because more air can get to the fuel. Stoves block off the air, so unless the design is exceptional, the stoves will not burn as cleanly. There is a solution, not mentioned in the story. Fluidized bed designs force air under the fuel and add both more air and turbulence, insuring hotter, more complete burning. (The same principle allows a blacksmiths forge to get hot enough to melt iron -- or a blast furnace to make steel.) While fluidized bed designs usually use electric motors to force the air, I suspect bellows could be used in places where there is no electricity. Or maybe a solar array could provide electricity -- a fan does not take much power, for a small cook stove, and it would only be needed for an hour or so. Anyway, it seems to me there are more and simpler technology solutions here than trying to install electric or gas fired stoves everywhere -- that is going to be extremely expensive and will not be accomplished any time soon.

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  22. 22. dwbd in reply to singing flea 07:55 PM 7/16/12

    Bull. The West has already spent a $trillion subsidy on Wind & Solar Electricity. Show me any significant Solar Hot water expenditure. Good example is Ontario, you could once get $1200 Federal, now expired for Solar Hot water one time payment, but a homeowner can get $186,000 per yr for a Solar PV installation that Ontario doesn't need and is ZERO benefit to Ontario. Passive solar is more difficult since it really would be part of good building design.

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  23. 23. Essau 11:38 AM 7/17/12

    I would have to see some information regarding any efficiency comparison between open hearths vs. traditional cookstoves vs. improved cookstoves. The improved cookstoves claim roughly 50% less consumption of fuel than traditional cookstoves. If that is true, then they are obviously more efficient than regular woodstoves. From reading I have done, I recall (but am not going to the trouble of citing) some UN projects in Thailand where people did actually save substantially on fuel by using an improved stove -- actual, in the field savings.

    I am not aware of any comparisons between an open hearth and a cookstove of any kind (I'm sure they exist, but I haven't seen any.) I *doubt* that an open fire is more efficient than a woodstove, but have no proof of that, either. I know many people still use open fires, but what proportion in relation to those who use cookstoves, I don't know.

    However, for folks who are already using cookstoves, not open hearths, the question is one of improving the cookstove. I can think of at least two good reasons NOT to use an open hearth in a house: open fires are easier to fall into, and open fires are more likely to cause a house-fire. Since some folks are already using cookstoves, increasing the efficiency of those stoves makes a big difference for their users.

    Passive solar is a hallmark of good building design, I think. But what would be really helpful to someone using a cookstove would be a simple 10 gallon solar water heater and a 10 gallon solar distillation unit. Both are low tech solutions capable of greatly improving life in homes that depend on the kind of cookstoves we have been talking about. Such items are beyond the means of many poor folk, but they are a paltry expense for someone here in the US.

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