The Greenhouse Hamburger
February 2009 Scientific American
Most of us are aware that our cars, our coal-generated electric power
and even our cement factories adversely affect the environment. Until
recently, however, the foods we eat had gotten a pass in the discussion.
Yet according to a 2006 report by the United Nations Food and
Agriculture Organization (FAO), our diets and, specifically, the meat in
them cause more greenhouse gases‹carbon dioxide (CO2), methane, nitrous
oxide, and the like‹to spew into the atmosphere than either
transportation or industry. (Greenhouse gases trap solar energy, thereby
warming the earth's surface. Because gases vary in greenhouse potency,
every greenhouse gas is usually expressed as an amount of CO2 with the
same global-warming potential.)
The FAO report found that current production levels of meat contribute
between 14 and 22 percent of the 36 billion tons of "CO2-equiva-lent"
greenhouse gases the world produces every year. It turns out that
producing half a pound of hamburger for someone's lunch‹a patty of meat
the size of two decks of cards‹releases as much greenhouse gas into the
atmosphere as driving a 3,000-pound car nearly 10 miles.
In truth, every food we consume, vegetables and fruits included, incurs
hidden environmental costs: transportation, refrigeration and fuel for
farming, as well as methane emissions from plants and animals, all lead
to a buildup of atmospheric greenhouse gases. Take asparagus: in a
report prepared for the city of Seattle, Daniel J. Morgan of the
University of Washington and his co-workers found that growing just half
a pound of the vegetable in Peru emits greenhouse gases equivalent to
1.2 ounces of CO2‹as a result of applying insecticide and fertilizer,
pumping water and running heavy, gas-guzzling farm equipment. To
refrigerate and transport the vegetable to an American dinner table
generates another two ounces of C02-equivalent greenhouse gases, for a
total CO2 equivalent of 3.2 ounces
But that is nothing compared to beef. In 1999 Susan Subak, an ecological
economist then at the University of East Anglia in England, found that,
depending on the production method, cows emit between 2.5 and 4.7 ounces
of methane for each pound of beef they produce. Because methane has,
roughly 23 times the global-warming potential of CO2, those emissions
are the equivalent of releasing between 3.6 and 6.8 pounds of CO2 into
the atmosphere for each pound of beef produced.
Raising animals also requires a large amount of feed per unit of body
weight. In 2003 Lucas Reijnders of the University of Amsterdam and Sam
Sorer of Loma Linda University estimated that producing a pound of beef
protein for the table requires more than 10 pounds of plant protein‹with
all the emissions of greenhouse gases that grain farming entails.
Finally, farms for raising animals produce numerous wastes that give
rise to greenhouse gases.
Taking such factors into account, Subak calculated that producing a
pound of beef in a feedlot, or concentrated animal feeding operation
(CAFO) system, generates the equivalent of 14.8 pounds of CO2‹pound for
pound, more than 36 times the C02-equivalent greenhouse gas emitted by
producing asparagus. Even other common meats cannot match the impact of
beef; I estimate that producing a pound of pork generates the equivalent
of 3.8 pounds of CO2; a pound of chicken generates 1.1 pounds of
CO2-equivalent greenhouse gases. And the economically efficient CAFO
system, though certainly not the cleanest production method in terms of
CO2-equivalent greenhouse emissions. is far better than most: the FAO
data I noted earlier imply that the world average emissions from
producing a pound of beef are several times the CAFO amount.
What can be done? Improving waste management and farming practices would
certainly reduce the 'carbon footprint" of beef production.
Methane-capturing systems, for instance, can put cows' waste to use in
generating electricity. But those systems remain too costly to be
Individuals, too, can reduce the effects of food production on planetary
climate. To some degree, after all, our diets are a choice. By choosing
more wisely, we can make a difference. Eating locally produced food for
instance, can reduce the need for transport‹though food inefficiently
shipped in small batches on trucks from nearby farms can turn out to
save surprisingly little in greenhouse emissions. And in the U.S. and
the rest of the developed world, people could eat less meat,
The graphics on the following pages quantify the links between beef
production and green-house gases in sobering detail. The take-home
lesson is clear: we ought to give careful thought to diet and its
consequences for the planet if we are serious about limiting the
emissions of green-house gases.
Nathan Fiala is a doctoral candidate in economics at the University of
California, Irvine, focusing on the environmental impact of dietary
habits. He also runs evaluations of development projects for the the
World Bank in Washington, D.C. In his spare time he enjoys independent
movies and sailing. In his study of the environmental impact of meat
production on which this article is based was recently published in the
journal of Ecological Economics.
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