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Cooking and Climate

April 27, 2009


Twenty years ago Donald Johnson, an animal-nutrition specialist at Colorado State University, published a study about how much methane gas is emitted by cows and how that release of gas could adversely affect the atmosphere. He concluded each cow emits 200 to 400 quarts of methane gas per day, or 50 million metric tons per year. A Washington Post article about Johnson’s study was headlined “Feed, Animal Flatulence and Atmosphere.” Cows and their flatulence have been getting a bad rap ever since. The world’s self-proclaimed “smartest man,” Cecil Adams, posted a blog about the article. He wrote:

“According to the story, animal flatulence ‘contributes in a large way to the potentially catastrophic warming of the globe, the “greenhouse effect.”‘ Just one little problem. Cows don’t emit 400 quarts of flatulence a day. According to Professor Johnson, they emit 400 quarts’ worth of burps, known in polite circles as eructation. The Post, in other words, doesn’t know one end of a cow from the other! … Details aside, animal methane does present a definite threat to the biota. It’s believed 18 percent of the greenhouse effect is caused by methane, putting it second on the list of offending gases behind carbon dioxide. Methane breaks down in the atmosphere to form carbon dioxide, ozone, and water, all of which absorb heat. The temperature of the atmosphere rises, the ice caps melt, and next thing you know you’re pumping the Atlantic Ocean out of your basement. There are several major sources of methane: rice paddies (methane-producing bacteria thrive in the underwater environment), swamps and wetlands (ditto), mining and oil drilling, landfills, termites (although there’s still some controversy on this one), ‘biomass burning’ (notably in the Amazon rain forest), and animals. Ninety percent of animal methane is produced by ruminants (i.e., cud-chewers). These include sheep, goats, camels, water buffalo, and so on, but most of all cattle, of which the world has an estimated 1.2 billion. Ruminants eat hay and grass and stuff containing cellulose, which can be digested only by special microbes that, to minimize commuting problems, live in the ruminants’ guts. Unfortunately, the microbes tend to make a mess, and about 6 or 7 percent of what they eat winds up as methane. Thus the problem.”

Despite efforts to produce feed that reduces the need for cows to burp [see “New Cow Diet Reduces Methane Emissions…and No, It’s Not M&Ms], Adams asserts that the methane challenge is “another largely insoluble problem that threatens to end life as we know it. Sometimes I wish one of these looming disasters would go ahead and happen, just to end the suspense.” We know, of course, that there are other sources of greenhouse gas emissions that can be more successfully addressed. One of those is the soot and gas that are created by cooking methods used by people mired in poverty [“Third-World Stove Soot Is Target in Climate Fight,” by Elisabeth Rosenthal, New York Times, 15 April 2009]. It seems unfair to point fingers at the poor when so many people in wealthy countries are driving by themselves to their local grocery store. Addressing the challenge created by the primitive cooking methods, however, could have an immediate and beneficial effect on the health of the poor as well as on the long-term health of the planet. Rosenthal writes:

“While carbon dioxide may be the No. 1 contributor to rising global temperatures, scientists say, black carbon has emerged as an important No. 2, with recent studies estimating that it is responsible for 18 percent of the planet’s warming, compared with 40 percent for carbon dioxide. Decreasing black carbon emissions would be a relatively cheap way to significantly rein in global warming — especially in the short term, climate experts say. Replacing primitive cooking stoves with modern versions that emit far less soot could provide a much-needed stopgap, while nations struggle with the more difficult task of enacting programs and developing technologies to curb carbon dioxide emissions from fossil fuels. In fact, reducing black carbon is one of a number of relatively quick and simple climate fixes using existing technologies — often called ‘low hanging fruit’ — that scientists say should be plucked immediately to avert the worst projected consequences of global warming. ‘It is clear to any person who cares about climate change that this will have a huge impact on the global environment,’ said Dr. Ramanathan, a professor of climate science at the Scripps Institute of Oceanography, who is working with the Energy and Resources Institute in New Delhi on a project to help poor families acquire new stoves.”

As Rosenthal states, black soot is a problem primarily associated with the developing world while carbon dioxide emissions are a greater challenge for the developed world. “In Asia and Africa,” she reports, “cookstoves produce the bulk of black carbon, although it also emanates from diesel engines and coal plants there.” She goes on to explain why soot is a problem.

“Like tiny heat-absorbing black sweaters, soot particles warm the air and melt the ice by absorbing the sun’s heat when they settle on glaciers. One recent study estimated that black carbon might account for as much as half of Arctic warming. While the particles tend to settle over time and do not have the global reach of greenhouse gases, they do travel, scientists now realize. Soot from India has been found in the Maldive Islands and on the Tibetan Plateau; from the United States, it travels to the Arctic. The environmental and geopolitical implications of soot emissions are enormous. Himalayan glaciers are expected to lose 75 percent of their ice by 2020, according to Prof. Syed Iqbal Hasnain, a glacier specialist from the Indian state of Sikkim. These glaciers are the source of most of the major rivers in Asia. The short-term result of glacial melt is severe flooding in mountain communities. The number of floods from glacial lakes is already rising sharply, Professor Hasnain said. Once the glaciers shrink, Asia’s big rivers will run low or dry for part of the year, and desperate battles over water are certain to ensue in a region already rife with conflict.”

The answer to the challenge is widespread adoption of low-soot cookstoves [“Fresher cookers,” The Economist, 6 December 2009 print issue]. The Economist estimates that “between two-and-a-half and three billion people—nearly half the world’s population—use a stove every day, in conjunction with solid fuel such as wood, dung or coal. Yet in many parts of the world the stove has barely progressed beyond the Stone Age.” If, as the old adage states, necessity is the mother of invention, one would have thought that innovative stoves for the poor would have been developed years ago. The Economist notes that efforts are now being made to build stoves that address emission and health problems associated with traditional cooking methods.

“After an initial wave of stove design that sought to reduce deforestation through improved efficiency, scientists and engineers have turned their attention to stoves that minimise the levels of noxious emissions to which stove users—mainly women and children—are exposed. Crucially, they have also recognised the need to take account of the way in which stoves are actually used.”

Rosenthal also pointed out that cultural preference affects resistance to using cleaner and safer stoves. Foods cooked on safer stoves have a different (and not necessarily better) flavor — just ask any American who loves the flavor of food cooked on his or her backyard grill. Most poor people, however, would like to have a stove that reduced the amount of smoke they had to inhale and the amount of fuel they had to use. The ultimate answer is a solar cooker — no smoke, no fuel costs. Of course, you can only cook on days when the sun shines! The Economist‘s article details the challenges associated with designing a cooker that reduces indoor pollution and increases thermodynamic efficiency.

“One of the principal problems the designer of a stove must solve is to optimise the thermodynamics. Typical stoves—including the basic ‘three-stone fires’ still used in many parts of the world—draw in too much air during the combustion process, which cools the fuel and means more of it is needed. Even with more advanced designs, poorly insulated combustion chambers can add to the cooling effect and thus to the inefficiency. The challenge, explains Bryan Willson of Envirofit, an organisation developing stoves for India, is to optimise a stove’s air-fuel ratio and minimise heat transfer to improve combustion efficiency.”

The article recounts several methods being experimented with in India. One model uses “a carburettor design, with chimneys that draw air in through precisely calibrated inlets.” Another model “has an integrated battery-powered fan to direct air to wood pellets in the combustion chamber, improving efficiency.” Increasing efficiency, however, does not necessarily reduce indoor pollution. “One solution,” the article notes, “is the ‘rocket stove’, a simple design that diverts the smoke outside. Other options include stoves that run on propane gas or pellets, or reflect solar radiation onto a cooking vessel.” But specialist fuels, like propane and wood pellets, can reduce the appeal and affordability of cookers for the poor. Whenever you discuss the poor, affordability is a huge challenge. Rosenthal reports that experiments are underway in India that address affordability, reliability, and availability.

“In March, the cookstove project, called Surya, began ‘market testing’ six alternative cookers in villages, in part to quantify their benefits. Already, the researchers fret that the new stoves look like scientific instruments and are fragile; one broke when a villager pushed twigs in too hard.”

Experiments were also taking place in Darfur (although they may have stopped since relief organizations have been ejected from Sudan). Those experiments, The Economist reports were also enlightening:

“In the refugee camps of Darfur, the dough for the staple food, assida, requires vigorous stirring of the cooking pot. ‘None of the stoves we tested had been built with this in mind,’ says Ashok Gadgil, the head of the Darfur Stoves Project. Only after the stoves were seen to tip over during cooking did Dr Gadgil and his researchers go back to the drawing board and refine the design. Other findings from the Darfur project shone new light on cooking habits. The original stoves had been designed to boil water, but researchers found that for each meal, two-thirds of the fuel was used to make sauces by frying onions, a process that requires a more intense, continuous heat.”

The Economist also addresses the reliability issue noting that innovators must deal with the competing challenges of making a cooker light enough to be portable but strong enough to withstand the rigors of daily use in less than ideal conditions.

“Mild steel is the natural choice for a stove chassis, but such stoves do not last for more than a few weeks in the field. Nickel-content alloys are a better choice for durability, but more expensive. For insulating the stoves, ceramic linings are the materials of choice in the lab, but they are difficult to ship and present problems of consistency for mass production. Materials are therefore often limited to those available locally.”

The “perfect” cooker has yet to be invented. When it is, there will be profits made by its manufacturer because the so-called bottom billion represent a huge market for such products. The poor will also benefit because current cooking methods generate enormous health risks. The Economist reports:

“The World Health Organisation (WHO) estimates that toxic emissions from cooking stoves are responsible for causing 1.6m premature deaths a year, half of them among children under five years old. In China 83m people will die from lung cancer and respiratory disease over the next 25 years, according to a recent report from Harvard University. Research from the University of California, Berkeley, on stoves in India, Guatemala and Mexico has found links between indoor air-pollution from stoves and increased incidence of pneumonia, cataracts and tuberculosis.”

There are few challenges in the world whose solutions represent “low hanging fruit” for two critical areas — in this case health and climate. People in the developed world should be excited to support efforts to invent a better stove because doing so will help save the planet. The poor who must actually use the stove should be excited to do so because its use will save their families. It would be nice to solve this challenge so that we can get back to discussing burping cows!

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