Little things can have a surprising impact.

Take global warming. Increasingly, we’re being asked to think about our “carbon footprint,” the amount of greenhouse gas produced to do the things we do: emissions from our cars, emissions from the power plants used to generate electricity for our homes, emissions from our air travel, and so on. These kinds of activities all have the benefit of looking dirty, so it’s very easy to imagine that there’s a bunch of carbon dioxide coming out along with the soot and smoke from engines and furnaces. But the big, obvious sources of greenhouse gases aren’t the only ones out there; in fact, nearly everything we do has a carbon footprint. Take, for example, the humble cheeseburger.

If you’re like me, you occasionally wonder what the bigger story is behind everyday activities and products. A couple of years ago, I wondered aloud (in my blog, Open the Future) what the carbon footprint of the more prosaic parts of our lives might be — and I used, as an example, a cheeseburger. Now, I’m no enemy of the cheeseburger; I picked the cheeseburger as my example because I like them, and I wanted to know its impact. We’re not yet at the point where it’s easy to go Google up the carbon footprint of whatever you want, and nobody else had investigated the impact of something like a burger. I knew what my task would be.

After a bit of research, I found numbers laying out the energy demands of producing burgers — not just the energy for cooking, but everything, from raising the cattle to processing the meat to growing the wheat, lettuce and tomatoes. It’s not hard to find information showing how much carbon dioxide gets emitted by various energy sources, so converting that data on energy demands to data on carbon footprints just took a bit of simple math. Adding it all up, I got a number adding up to about 4-5 pounds of carbon dioxide emitted in the lifecycle of each cheeseburger — not a huge amount, but not insignificant.

But it occurred to me that carbon dioxide isn’t the only greenhouse gas out there. There are quite a few others, but they’re either too minimal or cycle out of the atmosphere too quickly to make a big difference. All but one, that is: methane. Methane (CH4) doesn’t last as long as CO2 in the atmosphere, but it makes up for it by having a much stronger greenhouse impact. One unit of methane is roughly equivalent to 23 units of carbon dioxide, when it comes to trapping heat. Fortunately, there’s not a huge amount of methane in the atmosphere; unfortunately, one of the bigger sources of methane is cattle.

Cattle gas, to be precise, or what the US Environmental Protection Agency politely calls “enteric fermentation.”

The beef industry is big business, and there are millions of steers out there, waiting to be turned into cheeseburgers. It turns out that when you take into account the methane produced by gassy cows over the several years before they get turned into burgers (and divide that methane by the number of burgers you get per cow), the carbon impact of each burger more than doubles: more than ten pounds of carbon dioxide equivalent per burger. (Because CO2 is the most common and important greenhouse gas, environmental scientists like to convert the impact of other greenhouse gases to “CO2 equivalent” levels — in this case, multiplying the amount of methane emitted by the cattle by 23, to get the CO2 equivalence.)

Okay, ten pounds or more per burger, that’s something, right? Well, maybe. Ten pounds isn’t a whole lot in comparison to the average annual carbon footprint of an American, which is about 20 tons. If you only eat one or two burgers a month, you’re not adding much to your footprint.

It turns out, though, that if you’re only eating one or two burgers a month, you’re way below average. According to a diverse array of sources, including the sober UK news journal The Economist, Americans eat on average around 3 burgers per week. Now, that’s the average — meaning, all of the burgers consumed in the US divided by all of the people. Some of us eat less than that, but some of us eat even more. When you run the numbers, that little footprint of around ten pounds per burger becomes almost 200 MILLION metric tons of carbon dioxide equivalent, every year, from the lowly cheeseburger. If you want to see the math, check here. To put that in perspective, the total annual tailpipe emissions from all of the sport utility vehicles on the road is about 150 million metric tons.

Think about that for a minute: the lifecycle impact of burgers, all added together, is greater than the tailpipe impact of SUVs, all added together.

So, does this mean that we all need to stop eating cheeseburgers?
Well, cutting down wouldn’t hurt, for health reasons alone. But the point of this little exercise isn’t to make you feel guilty — it’s to trigger a bit of a realization. Everything we do has an impact — including the things we eat — and sometimes, that impact is far greater than we might think. But if we don’t have good information, we can’t make good choices.

It’s likely that, as we become a more carbon-conscious society, we’ll get a few more surprises like this. Not all of them will make us change our behavior. What they will do, though, is give us a better recognition of the implications of our actions. And that will let us take a little bit more responsibility for what we do.

And ultimately, it’s that link — from knowledge to recognition to responsibility — that’s how we’re going to save the world.