A vegan in a Hummer has a lighter carbon footprint than a meat eater in a Prius

That’s the assertion made by author and food activist Michael Pollan while speaking on a panel as part of last weekend’s PopTech 2009 conference.

What a notion!

The EPA estimates that a 2009 Toyota Prius generates about 0.56 lb. of CO2 emissions for each mile driven (taking into account all aspects of operating a vehicle but not its manufacture). Assuming 12,000 miles driven annually, a Prius generates approximately 3.5 tons of emissions each year. While the 2009 Hummer H2 eludes EPA testing through its truck classification, independent emissions testing reports estimate that the HUMMER H2 expels 1.46 lbs of emissions per mile. Multiply this by the 12,000 estimated annual miles and the H2 delivers nearly 9 tons of annual emissions.

Similar methodology can be used to calculate the carbon footprint of our diet. Fossil fuels go in (feed, fertilizer, processes) and emissions are released (adjusted for both plants’ absorption of CO2 and the negatively impactful effect of methane gas released by farm animals).

A typical American diet gets 47 percent of its calories from animal sources, resulting in a carbon footprint of 2.52 tons per year. By far the worst emitter in our diet is beef, so if a diet is especially heavy in red meat rather than fish or chicken, you can add another ton to the year’s emissions. Vegetarians can easily knock a ton off, and vegans drop another ton.

At 9 tons from the vehicle and a half ton from the diet, the vegan in the the Hummer is contributing 9.5 annual tons of CO2 while the meat-eater in the Prius generates about 6 tons. So strictly speaking, there is a bit of hyperbole to Michael Pollan’s statement (although on a per household basis or with an especially carnivorous eater it holds true), but it still makes the point that small shifts in diet can have a big impact on our environment.

Grain-fed beef results in 3.04 lb. of CO2 emitted per 100 calories. Compare that with the CO2 emitted by 100 calories of chicken (0.37), apples (0.06), eggs (0.64), and soy (0.01). With the carbon equivalent of a gallon of gas in every hamburger, beef is pretty much the Hummer of the food world. Giving up that burger on a weekday or practicing meat-free Mondays as they do in England is the equivalent of riding your bicycle to work a few times a week.

Of course all of this begs the real question: do vegans even drive Hummers?

This low carbon diet calculator can help you compare the relative carbon impacts of your food choices.