Correction:
Earlier versions of this story, including in the April 22 print edition of The Washington Post, mentioned the World Resource Institute, which should have been stated as the World Resources Institute. This version has been corrected.
It’s something of a green truism: Reduce your carbon footprint. And if you can do so as you trek along the grocery aisles, all the better on this 42nd Earth Day.
That was the thinking behind splashy announcements that started coming out a couple of years ago from a handful of corporations such as PepsiCo and smaller firms saying they had carbon-footprinted cartons of orange juice, six-packs of beer and other goods.
Tesco, the British supermarket giant, even began slapping items with big black footprints stating the number of grams of carbon dioxide supposedly emitted while churning out that swig of juice or mouthful of chips.
A low rating is intended to indicate a product you can eat without guilt, because its production generated fewer of the greenhouse gases that are responsible for climate change.
Two years on, handicapped by uncertainties about how to calculate those ratings — or whether it’s even possible — carbon-footprinting schemes struggle to be recognized as the standard stamps of eco-consciousness that the FairTrade, Energy Star and LEED systems have become.
Nonetheless, several countries have labeling schemes in the works, and U.S. proponents of labeling argue that even flawed systems are better than none. More and more U.S. consumers crave such information, proponents say, and in the absence of government action to reduce carbon emissions, pushing consumers toward lower-carbon choices might be the best climate change-fighting tool available.
“We only need fairly small changes in consumer behavior to make a dent in the growth curve of carbon emissions,” said Michael Vandenbergh of Vanderbilt University, who advocates carbon labeling of products.
So far, though, few people agree on how to measure the carbon footprint of, say, a kilogram of beef. “All those companies making announcements in 2009 bit off more than they could chew,” said Rita Skank, who directs a rapidly growing professional organization of number-crunchers who calculate ecological impacts of goods.
Green-leaning consumers — hoping to estimate the carbon impacts of eating more vegetables and less meat, as well as activities such as choosing to ride a bicycle instead of driving — are left to supplement what little information U.S. companies offer with online carbon-footprint calculators.
No standard math
A recent study of carbon emissions generated by Brazilian beef cattle illustrates the difficulties in calculating carbon footprints. Estimated emissions vary greatly depending on how many environmental ripples are included in the equations.
And deciding that is a matter of choice, not math.
Consider: Brazilian beef raised on long-established pastures generates about 28 kilograms of carbon dioxide (or its equivalent in other greenhouse gases, such as belched methane) for each kilogram of beef under wrap at the grocery store.
But the study’s international team of authors say that this figure fails to account for a dramatic indirect cost of Brazilian beef: the deforestation of the lower Amazon region to create grazing land for cattle.
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