08 Mar 2010

World’s Pall of Black Carbon Can Be Eased With New Stoves

Two billion people worldwide do their cooking on open fires, producing sooty pollution that shortens millions of lives and exacerbates global warming. If widely adopted, a new generation of inexpensive, durable cook stoves could go a long way toward alleviating this problem.
By jon r. luoma

With a single, concerted initiative, says Lakshman Guruswami, the world could save millions of people in poor nations from respiratory ailments and early death, while dealing a big blow to global warming — and all at a surprisingly small cost.

“If we could supply cheap, clean-burning cook stoves to the large portion of the world that burns biomass,” says Guruswami, a Sri Lankan-born professor of international law at the University of Colorado, “we could address a significant international public health problem, and at the same stroke cut a major source of warming.”

Sooty, indoor air pollution from open wood or other biomass fires has long been linked to health problems and deaths. More recently, scientists have been surprised to learn that black carbon — not only from biomass fires but from dirty diesel engines and other sources — is a far larger contributor to global warming than previously suspected: The dark particles absorb and retain heat close to the Earth’s surface that might otherwise be reflected.

Primitive stoves and open fires pose serious health risks, particularly among women and children.
Some two billion people around the world, Guruswami notes, do most or all of their cooking and heating with fires from simple biomass — dried dung, wood, brush, or crop residues. In India alone, the ratio is much higher — about three-fourths.

“Think about that,” says Guruswami, who directs his university’s Center for Energy and Environmental Security. “Two billion people, one-third of the people on Earth, are caught in a time warp, with no access to modern energy. They got energy from Prometheus a long time ago, and that was it.”

Public health scientists have been pointing out for years that open fires and primitive stoves for cooking and heating used in much of the developing world pose profound health risks, particularly among women and children. Women typically spend hours cooking multiple meals beside smoky fires and stoves, with infants and small children in close proximity.

The public health implications alone are profound: 1.5 million lives are lost to respiratory, heart and other soot-related harm every year, according to World Health Organization estimates.

As for the climate aspects, atmospheric scientists have more recently reported that ordinary soot — or black carbon — plays a surprisingly large role in global and regional warming. Some scientists now estimate that small, solid particles of black carbon are responsible for about one-fifth of warming globally and, as such, are the second-largest contributor to climate change, after carbon dioxide gas.

In addition to soaking up heat in the atmosphere, the tiny, dark particles — or aerosols — are blown poleward or up mountains, where they settle on snow and ice and absorb warmth. Although dirty diesel engines, power plants and other more advanced technologies produce black carbon, cooking fires appear to be the largest source of soot in developing nations.

More alarming, extra warming driven by black carbon appears to be especially amplified in the high country of Asia’s Tibetan Plateau, home to
Some scientists now estimate that particles of black soot are responsible for about one-fifth of warming globally.
the world’s highest mountains. There, in a region sometimes called the “Third Pole,” summer melt-water from thousands of glaciers forms the headwaters of major rivers that provide water to more than a billion people in teeming cities and small farms below, in India, China, and smaller nations like Burma and Vietnam. In fact, the plateau has been called “Asia’s water tower,” feeding the Ganges, the Indus, the Brahmaputra, the Mekong, the Yangtze, and the Yellow rivers.

Already, glaciers on the plateau have declined by about 20 percent since the 1960s. Scientists have predicted that with rising Asian populations and more open fires, diesel engines, and burning of forests, the glacial melt will accelerate, eventually diminishing the rivers below.

Beginning in 2007, scientists at the Scripps Institute of Oceanography helped establish just how profound warming boosted by black carbon might be in the Tibetan Plateau. While previous hints had come from computer models, Scripps scientists working in India measured soot levels and dispersion by flying three unmanned aircraft equipped with sensors across the region. Using this data, the Scripps team, headed by climatologist Veerabhadran Ramanathan, concluded that black carbon was probably contributing at least as much to the Tibetan Plateau’s glacial melt as were greenhouse gases. A separate study last month estimated that black carbon was responsible for at least 30 percent of glacial melt in the Himalayas.

Late last year, NASA reported that black carbon rises into the atmosphere, attaches to dust, and moves with warm-season air patterns to the Himalayan foothills. Heat from the sun warms this “brown cloud,” accelerating its typical monsoon season rise up the slope, essentially pumping heat up the mountains, according to William Lau, who heads research in atmospheric sciences at NASA’S Goddard Space Flight Center.

This NASA image shows brown haze over Northern India that scientists say is mostly caused by human activities, including the burning of biomass.
“Over areas of the Himalayas, the rate of warming is more than five times faster than warming globally,“ Lau said at a press briefing in December, noting that the heating problem is most dramatic in the western part of the Tibetan Plateau. “Based on the differences, it’s not difficult to conclude that greenhouse gases are not the sole agents of change in [this] region,” he added. “There’s a localized phenomenon at play.”

Enter the cook stove. A November 2009 study published in The Lancet, the British medical journal, estimated that a decade-long, all-out effort to equip about 90 percent of Indian households that burn biomass with clean-burning cook stoves by 2020 would reduce premature deaths by 17 percent annually, essentially saving 55.5 million years of human life.

But there’s a key reason the world’s poor have long cooked with biomass over sooty fires, often nothing more than a “three-stone fire” with dried dung or brush smoldering under a pot sitting on a triangle of stones: They couldn’t afford anything better.

The University of Colorado’s Guruswami says that to be workable for billions of people who might live on as little as one dollar a day, a better cook stove has to have three main attributes: It has to reduce soot, it has to be long-lived, and it has to be cheap — ideally $10 or less. The good news is that inventors and engineers have come up with various versions of efficient cook stoves, some of them both simple to use and inexpensive.

In the early 1980s, Oregon-based engineer Larry Winiarski developed what he called the Rocket Stove, designed for cleaner combustion and more heat using a fire that burns the tips of a long bunch of small wood sticks: To feed the fire as the tips burn away, a cook need only push the bundle in further. The Rocket stove is designed to take advantage of natural convection to burn its biomass more efficiently, and in fact uses about half as much wood as a primitive three-stone fire or simpler stove.

The Aprovecho Research Center, a nonprofit where Winiarski serves as technical director, estimates that more than 40 stove projects in many nations have since built Rocket stoves, and estimates that more than a quarter-million Rocket stoves are now being used worldwide.

Fort Collins, Colo., home to a major university-based combustion laboratory, is a hotbed of cook-stove advocacy and dissemination.

Envirofit, a nonprofit started by two engineering graduates of Colorado State University and two professors, has developed a modified, patent-
The promise that improved cook stoves hold has triggered government action in India.
pending Rocket stove that it claims is exceptionally durable. A problem with past designs is that metal combustion chambers tend to quickly fail due to high heat and caustic fumes. But Envirofit worked with Oak Ridge National Laboratory scientists to develop a combustion chamber made of metal alloys that give it an exceptionally long life — long enough, it says, that it can issue warranties on the chamber for five years.

The group works closely with Colorado State’s world-class Engines and Energy Conversion Lab to develop other combustion-chamber and stove efficiency features. The engineering focus, says Envirofit Vice President of Engineering Nathan Lorenz, has been to “control the geometry of the combustion chambers and heat transfer.” The more heat you transfer, the faster a pot heats up, the less fuel you burn.

About 100,000 Envirofit stoves have already been sold in India, at prices as low as 700 rupees, or about $15. The stoves quickly pay for themselves in fuel savings alone, allowing households to save $50 to $75 annually that would have been spent on wood or other biomass, even while using 60 percent less biomass and eliminating about 80 percent of soot.

Another Fort Collins-based nonprofit, called Trees, Water, and People, focuses on Central America, Mexico, and Haiti, where it promotes local construction of Rocket-type stoves. Working with local partners, the group says it has built more than 35,000 stoves.

In India, Scripp’s V. Ramanathan has helped pioneer a newer program that adds a layer of science. Dubbed Project Surya, this nascent effort is conducted in partnership with the United Nations Environment Programme. Its first community-wide experiment, launched last March in a village in Uttar Pradesh state, will provide cook stoves, along with solar lanterns (to replace sooty kerosene lamps), to every household that wants them.

Envirofit says its cook stove will cut smoke and carbon emissions by 80 percent.
The unique feature: The project is designed to collect a wealth of data. A small sensor on the roof of the home of the village leader will provide the first accurate measurements of how much carbon is actually reduced in the local setting. Regional sensors and satellites will eventually help scientists learn more about more widespread pollution effects.

The Energy and Resources Institute in India also has launched a “Lighting a Billion Lives” campaign designed to replace soot-producing kerosene lamps and dung or wood fires with solar-powered lanterns. Begun in 2008, the campaign has so far supplied more than 6,000 solar lanterns to people in roughly 200 Indian villages.

Elsewhere, two of Europe’s largest industrial corporations, Phillips and Bosch, also have high-efficiency cook stoves in development. At Yale University, mechanical engineer Allesandro Gomez, director of the school’s Center for Combustion Studies, has begun to work on other designs.

But a conundrum remains. Researchers have found that it can be difficult to convince people to switch from traditional cooking methods to more advanced stoves, for a variety of reasons that range from uneasiness with unfamiliar or finicky technology, to upfront costs. Working with Yale development economist Ahmed Mushfiq Mobarak and a local NGO, a team of researchers at Stanford University has found that many households in Bangladesh simply do not regard the high-efficiency cook stoves as great improvements. The group found that even when offered completely free stoves, more than 30 percent of households refused the offer.

Envirofit’s Lorenz says some of those stoves are simply too cheaply made. That’s why his nonprofit focuses on charging at least minimally for its more durable products, and even paying attention to product aesthetics. “People would rather be treated like customers than victims,” he says.

More from Yale e360

Coping With Climate Change:
Which Societies Will Do Best?

As the world warms, how different societies fare in dealing with rising seas and changing weather patterns will have as much to do with political, social, and economic factors as with a changing climate.
In India, the promise of improved cook stoves and reduced black carbon have triggered high-level government action recently. In December, New and Renewable Energy Minister Farooq Abdullah announced a new “National Biomass Cook-stoves Initiative.” Given that the world’s wealthiest nations are overwhelmingly responsible for planet-warming greenhouse gas emissions, it seems reasonable to suggest that these countries could launch micro-lending programs to underwrite the widespread adoption of clean stoves.

India and the world have at least one good reason to move quickly to reduce black carbon: Compared to greenhouse gas reductions, slashing black carbon offers a much quicker and cheaper fix. While climate-altering carbon dioxide can remain in the atmosphere for many decades, solid soot generally falls from the sky in days or weeks.

“It’s a faster fix, and when you think about the humongous cost of fixing even one power plant to reduce carbon dioxide, it’s really cheap,” says Guruswami. “This is what economists like to call low-lying fruit. Let’s find a way pick it.”


Jon R. Luoma, a contributing editor at Audubon, has written about environmental and science topics for The New York Times, and for such magazines as National Geographic and Discover. His third book, The Hidden Forest: Biography of an Ecosystem, has been released in a new edition by Oregon State University Press. In previous articles for Yale Environment 360, he wrote about new technologies to harness the power of the ocean and about the challenge of storing excess electricity produced from renewable sources.

SHARE: Tweet | Digg | | Reddit | Mixx | Facebook | Stumble Upon


The author does not discuss small biomass-burning stoves that make biochar.

See for instance, the presentation at:

And, enter stove into the search engine at the International Biochar Initiative's web site.

Posted by S.W. Ela on 09 Mar 2010

I wonder about the advisability of continuing the use of wood for cooking. It's great that this new system uses considerably less wood, but it's still based on a rapidly diminishing supply of wood and continues the problem of deforestation. Wouldn't it be smarter to take the technology used in the solar lamps and use this for cooking?

Posted by Shirley Nelson on 09 Mar 2010

In-depth studies of deforestation have actually shown that the link between rural wood use by the poor and deforestation is often wildly exaggerated, raising significant questions about the anecdotal connection often made between rural wood use and deforestation. See, e.g., Deepak Bajracharya, "Deforestation in the Food/Fuel Context: Historical and Political Perspectives from Nepal," Mountain Research and Development Vol. 3, No. 3 (Aug., 1983), pp. 227-240. Bajracharya found that, at least in Nepal, deforestation tended to result from overexploitation and mismanagement of forest resources by governments and industry over many decades, not people living on the edge of survival.

As to solar cooking technologies, there are a number of techs that work quite well from an engineering standpoint, but many users found them unsatisfactory because they change the taste of the food, removing the taste of the wood and smoke and replacing it with a metallic taste (think about eating eggs from your titanium camping pots every morning of your life). Even improved cookstoves have had difficulties associated with changing the taste of traditional dishes, which are a central part of the culture in many rural areas.

Posted by Adam Reed on 09 Mar 2010

The solar technology used in solar lamps is presumably photovoltaic and unsuitable for use with
cook stoves, however solar thermal energy can be utilised -

It's good to see that the link between rural wood use by the poor and deforestation being shown to be wildly exaggerated.

Posted by Scribhneoir on 09 Mar 2010

Black carbon pollution is alive and thriving in upscale, wealthy U.S. communities. The unfortunate trend to cook over wood-fired grills is expanding as concern for the "time-warp" habits of Third World countries increases. We also pay inordinate homage to the antiquated, polluting fireplace and think it is healthy to have our children sit around campfires. So who is ahead here?

Posted by mary power giacoletti on 09 Mar 2010

What happens when these cook stoves or lanterns break? Do the people know how to repair them? The Thaksin government in Thailand gave rural communities solar panels for household electricity. Great idea, but now most of them are broken and no one knows how to repair them. Also if you're making under a dollar a day, ten dollars is a lot of money to spend on something. What of solutions that allow people to make it themselves. These "solutions" ought to be locally adapted and economically viable, something people can create with local resources.

Posted by Kim on 10 Mar 2010

It seems to me that getting a rocket stove into the hands of someone who will use it in place of more traditional cooking technologies is one of the most cost effective carbon offset strategies available. The going rate for offsets seems to be about $10/ton, but I suspect a rocket stove does better than that considering reduction in both fuel consumption and black carbon output. Is there something individuals in developed countries can do to help get these stoves into use (ie to help get this low lying fruit picked)?

Posted by Rob on 14 Mar 2010

Mr. Luoma’s article does great justice to the pioneering work stove engineers whose designs form the foundation of the improved cook stove industry, yet the reader was left with little information about the financial mechanisms currently transforming how the world’s poor cook. E+Co’s clean energy work in the developing world has proven that the industry’s future, and its ability to deliver improved stoves to the 2 billion people for whom the technology means life or death, lies with carbon finance.

With society and governments increasingly placing monetary value on clean air, companies such as Goldman Sachs, JP Morgan, and other leading investment banks are purchasing the carbon credits created by cleaner burning stoves. As a result, an inexpensive, well designed cook stove in Ghana or Mali yields more than twice its value in the form of carbon credits. The funds go to the stove manufacturers, enabling them to sell more widely and cheaply. What was once a razor thin margin industry that peddled homemade contraptions is becoming a high finance endeavor in which quality, life saving products are sold at deep discount to the world’s poorest households, with polluters in the developed world footing the difference.

See and for more details.

Erik Wurster
Carbon Finance Manager, E+Co
Posted by Erik Wurster on 14 Mar 2010

The world is not aware of extensive agricultural residue burning here in South Asia, especially in harvesting season, when millions of square kilometers of agricultural fields are on fire for weeks. Diesel is adulterated with government subsidized kerosene and the vehicles spew tonnes of jet black smoke. All the domestic waste, rubber tires, tree leaves and other waste is openly burnt and it keeps on slowly smoldering for hours and in the process generating huge volumes of smoke.

It is the don't care attitude of public and government, intense selfishness aggravated by illiterate population and lopsided government subsidy policies that encourage this global problem of black soot from Asia. Here even in summers the sunlight is dimmed.

Posted by AJAY on 18 Mar 2010

In continuation to my last submission, i would like to say that in addition to creating the new technologies it is the motivation factor that drives the public to use these technologies. For that INFORMATION, EDUCATION AND COMMUNICATION and then more and more IEC to the public by intense government and international funding is needed.

This black soot has disrupted the monsoon patterns here. the winter rainfall is almost negligible now. The water availability for human consumption and crops is drastically falling. Pakistan in south Asia is on verge of war with India over water scarcity. The Taliban is motivating the drought ridden public to fight jihad for getting water. in India we have sucked dry our aquifers for feeding the teeming population. Global warming should have increased the monsoon rainfall by 5-7 percent by now but for this black soot. Which by blocking the sunlight and also absorbing it is rapidly drying up this whole region in a very complicated manner.

Additionally it is melting the glaciers. The whole hydrological cycle is in crises. it is when the population understands that what their behavior patterns, lifestyle and selfishness is doing to the environment and killing their and their children's future ; it becomes malleable to the new propositions and technologies. The time for using the atmosphere as an open sewer is over. most people here suffer from chronic respiratory disorders.

But the whole process is leading us nearer to drought, war, inter and intra population conflicts, ill health and a bleak future. Only the intense honest awareness efforts can reverse this trend.

Posted by AJAY on 19 Mar 2010

I have been wanting to go back to burning wood for cooking to save on electricity but the smoke and time has prevented me from taking it to heart. Nice to hear about the rocket stove.

Posted by Elatia on 22 Mar 2010

I wonder about the advisability of continuing the use of wood and biomass for cooking. Doesn't this continue to exacerbate deforestation? Wouldn't it be smarter to develop solar power instead in the form of simple cooking units?

Posted by shirley nelson on 15 Aug 2010

A lot is being said on improving life & reducing carbon emissions with improved woodstoves but the biggest road block its adpotion by rural communities. Poor do not have money to buy improved stoves,which costs $25 versus humble chulha (traditional mud stove) which is almost free.

The real concern here is not great products but great advocay & implementation.In Indian context a Govt.campaign (on the lines of Polio eradication campaign) & adoption incentive can go a long way to further adoption by rural communities(like transferring subsidy from Kerosene to improved stoves).

Posted by Pawandeep Singh on 27 Aug 2010

Inexpensive wood burning, gasification stoves can be made from tin cans or round duct; they burn with a blue flame. Gasifiers have been around for a long time. (During WW ll thay used wood and biomass gasification burners to run trucks in the USA and Australia.) Why do we have to invent a new technology that fits our comfort zones, when we wound be using the stoves? If managed properly, trees and other biomass are a wonderfully renewable resource. Case-in-point: the privately owned hardwood industry and superefficient family farms in Pennsylvania.

Posted by Pat Cinotti on 28 Sep 2010

Envirofit stove prices are way above what poor can pay in India; the agency is tapping the urban lower middle class, and not the poor landless rural folk. They can sell millions of stoves with their high-tech strategy like the MFIs lending at usurious rates of thirty to fifty percent- all under the social marketing banner.

600 million Indians live in over half million villages and it will be a logistic nightmare to reach them the stove without increasing the cost. And their dependency on outside sources for supply.

The solution is to make the stove with locally available material like the French rocket stove that can be made with just six bricks that cost rs.3o[15cents].

The reason the improved stove has not found favor under the CDM is the difficulty to monitor it; with the sensors system of the Surya project mentioned above, monitoring becomes feasible; envirofit claims that one stove reduces CO2 emission by one to one and half tonne and that will be a carbon credit of 10 dollars; enlisting the strength of over two million self help group in the villages with the monitoring system of surya, a village of 100 stoves can earn carbon credits of a 1000 dollars; when they earn this money more will be converted to improved stoves.but let the stoves be made locally.

Posted by RKRAO on 12 Nov 2010



Soil as Carbon Storehouse: New Weapon in Climate Fight?
The degradation of soils from unsustainable agriculture and other development has released billions of tons of carbon into the atmosphere. But new research shows how effective land restoration could play a major role in sequestering CO2 and slowing climate change.

As Uses of Biochar Expand, Climate Benefits Still Uncertain
Research shows that biochar made from plant fodder and even chicken manure can be used to scrub mercury from power plant emissions and clean up polluted soil. The big question is whether biochar can be produced on a sufficiently large scale to slow or reverse global warming.

Greenpeace’s Kumi Naidoo on Russia and the Climate Struggle
In a Yale Environment 360 interview, the outspoken executive director of Greenpeace discusses why his organization’s activists braved imprisonment in Russia to stop Arctic oil drilling and what needs to be done to make a sharp turn away from fossil fuels and toward a green energy economy.

The Trillion-Ton Cap: Allocating The World's Carbon Emissions
The U.N. climate panel concluded last month that carbon emissions should be capped at a trillion tons, a total the world is rapidly approaching. Now comes the hard part: How will we decide how the remaining emissions are apportioned?

Black Carbon and Warming: It’s Worse than We Thought
A new study indicates soot, known as black carbon, plays a far greater role in global warming than previously believed and is second only to CO2 in the amount of heat it traps in the atmosphere. Reducing some forms of soot emissions — such as from diesel fuel and coal burning — could prove effective in slowing down the planet’s warming.


Donate to Yale Environment 360