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Do Food Miles Matter? Reducing Meat & Dairy Consumption May Be Even
More Important

http://www.organicconsumers.org/article ... _11662.cfm

Red meat and dairy are responsible for nearly half of all greenhouse
gas emissions from food for an average U.S. household

By ERIKA ENGELHAUPT
Environmental Science and Technology, April 16, 2008

The benefits of eating locally grown food may not extend to curbing
global warming, according to a comprehensive study of greenhouse gas
emissions from U.S. food.

On a typical spring day, lunch for Seattle-based writer Sage Van Wing
includes pasta with pork sausage from a small local farm. The
peppers, cheese, and shallots on top come from the nearby farmers
market. Van Wing is a locavore-she tries to eat only locally grown
foods whenever possible.

Red meat and dairy are responsible for nearly half of all greenhouse
gas emissions from food for an average U.S. household.

Van Wing, who coined the term locavore with a friend 3 years ago,
says curbing global warming is one of many social and environmental
reasons for eating locally. And for many people, "food miles", the
distance food travels from farm to plate, are a simple way to gauge
food's impact on climate change.

But it's how food is produced, not how far it is transported, that
matters most for global warming, according to new research published
in ES&T . In fact, eating less red meat and dairy can be a more
effective way to lower an average U.S. household's food-related
climate footprint than buying local food, says lead author
Christopher Weber of Carnegie Mellon University.

Weber and colleague Scott Matthews, also of Carnegie Mellon,
conducted a life-cycle assessment of greenhouse gases emitted during
all stages of growing and transporting food consumed in the U.S. They
found that transportation creates only 11% of the 8.1 metric tons (t)
of greenhouse gases (in CO2 equivalents) that an average U.S.
household generates annually as a result of food consumption. The
agricultural and industrial practices that go into growing and
harvesting food are responsible for most (83%) of its greenhouse gas
emissions.

For perspective, food accounts for 13% of every U.S. household's 60 t
share of total U.S. emissions; this includes industrial and other
emissions outside the home. By comparison, driving a car that gets 25
miles per gallon of gasoline for 12,000 miles per year (the U.S.
average) produces about 4.4 t of CO2. Switching to a totally local
diet is equivalent to driving about 1000 miles less per year, Weber
says.

A relatively small dietary shift can accomplish about the same
greenhouse gas reduction as eating locally, Weber adds. Replacing red
meat and dairy with chicken, fish, or eggs for one day per week
reduces emissions equal to 760 miles per year of driving. And
switching to vegetables one day per week cuts the equivalent of
driving 1160 miles per year.

Several other recent studies have analyzed particular foods and poked
holes in the food mile concept. For example, it can be more energy
efficient for a British household to buy tomatoes or lettuce from
Spain than from heated greenhouses in the U.K.

The new work expands on those studies by providing a comprehensive
look at the U.S. food supply. Weber used an input-output life-cycle
assessment, which counts not only the CO2 produced when food is
shipped but also all greenhouse gases, including methane (CH4) and
nitrous oxide (N2O), emitted from farm production. This means
counting all the way back to the fossil fuels used to manufacture
fertilizer and tractors.

"There is more [total] greenhouse gas impact from methane and nitrous
oxide than from all the CO2 in the supply chain," Weber says. In
large part, he adds, this is because N2O and CH4 emission in the
production of red meat "blows away CO2". Cows burp CH4, and growing
their feed uses large amounts of fertilizers that are converted to
N2O by soil bacteria.

Edgar Hertwich, an expert on life-cycle analysis who is at the
Norwegian University of Science and Technology, calls the
results "quite convincing" but notes that consumers should still keep
an eye on food flown on airplanes, which have very high greenhouse
gas emissions. "Food miles are a very good idea, but not for the
faint of heart," adds Gidon Eshel, a Bard Center Fellow at Bard
College. "Counting transport alone won't do the trick; you need a
full life-cycle analysis."

"It's still useful to think about transport," says David Pimentel of
Cornell University, an ecologist who has conducted life-cycle
analyses of food's energy use. He recently calculated that if a
typical American drives home with a 1 pound can of corn, 311 calories
of fossil fuel energy are used to transport the 375-calorie corn in
the can.