http://environment.newscientist.com/...meat-does.html
Quote:-
That locally-produced, free-range, organic hamburger might not be as
green as you think.
An analysis of the environmental toll of food production concludes that
transportation is a mere drop in the carbon bucket. Foods such as beef
and dairy make a far deeper impression on a consumer's carbon footprint.
"If you have a certain type of diet that’s indicative of the American
average, you're not going to do that much for climate while eating
locally," says Christopher Weber, a researcher at Carnegie Mellon
University in Pittsburgh who led a comprehensive audit of the greenhouse
gas emissions of our meals.
Gassy foods
His analysis included emissions such as transporting and producing
fertiliser for crops, methane gas emitted by livestock, and food's
journey to market. All told, that final step added up to just 4% of a
food's greenhouse emissions, on average.
But some items, particularly red meat, spewed out far more greenhouse
gases than other foods, Weber and his colleague Scott Matthews found.
Environmentally savvy shoppers may want to take note.
"It seems much easier to shift one day of my beef consumption a week to
chicken or vegetables, than going through and eating only Jerusalem
artichokes for three months in the winter," says Weber, a "vegetarian
bordering on vegan."
Every last molecule
Other researchers have quantified the greenhouse gas budget of foods,
but most studies looked at a single food item, such as an apple, or
ignored greenhouse gases more potent than CO2, such as methane and
nitrous oxide.
Weber's team combined statistics on greenhouse gas emissions for
different foods with estimated greenhouse footprints for transport for
each step in a food's production and final delivery.
Food travelled an average of 1640 km in its final trip to the grocery
store, out of total of 6760 km on the road for the raw ingredients. But
some foods log more kilometres than others. Red meat averaged 20,400 km
– just 1800 of those from final delivery.
Accounting for greenhouse gas emissions made those contrasts even
starker. Final delivery "food-miles" make up just 1% of the greenhouse
emissions of red meat, and 11% for fruits and vegetables.
To drive his point home, Weber calculated that a completely local diet
would reduce a household's greenhouse emissions by an amount equivalent
to driving a car 1600 km fewer per year. He assumed the car travels 10.6
km per litre of petrol (25 mpg). Switching from red meat to veggies just
one day per week would spare 1860 km of driving.
"The differences between eating habits are very, very striking," Weber says.
Edgar Hertwich, a researcher at the Norwegian University of Science and
Technology in Trondheim, agrees that the obsession with food miles can
obscure more significant environmental impacts of our food.
"Why not focus on what actually happens on the field and how much
fertiliser we use," he says.
Whatever the source of greenhouse gas emissions from food, many are now
calling for labelling that lets shoppers know how much carbon went into
their goods. In the UK, the government-supported Carbon Trust offers a
voluntary carbon label, and a proposed California law aims to regulate
such labelling, much like organic food standards.
"Our goal is to get the most accurate information that’s available in
the hands of consumer so they can make informed purchasing decisions,"
says Matthew Perry, head of Carbon Label California.
But based on Weber's study, consumers will face decisions tougher than
buying local well water over bottles shipped from Fiji.
"If you're interested in the hamburger you're not going to switch to
tofu, but you might switch to a chicken burger," Perry says.
Journal reference: Environmental Science and Technology (DOI:
10.1021/es702969f)