Ing Electronico

The Cheeseburger Footprint
by Jamais Cascio
We're growing accustomed to thinking about the greenhouse gas impact of transportation and energy production, but nearly everything we do leaves a carbon footprint. If it requires energy to make or do, chances are, some carbon was emitted along the way. But these are the early days of the climate awareness era, and it's not yet habit to consider thegreenhouse implications of otherwise prosaic actions.

So as an exercise, let's examine the carbon footprint of something commonplace -- a cheeseburger. There's a good chance you've eaten one this week, perhaps even today. What was its greenhouse gas impact? Do you have any idea? This is the kind of question we'll be forced to ask more often as we pay greater attention to our individualgreenhouse gas emissions.
Burgers are common food items for most people in the US -- surprisingly common. Estimates for the average American diet range from an average of about one per week, or about 50/year (Fast Food Nation) to as many as three burgers per week, or roughly 150/year (the Economist, among other sources). So what's the global warming impact of all those cheeseburgers? I don't just meancooking the burger; I mean the gamut of energy costs associated with a hamburger -- including growing the feed for the cattle for beef and cheese, growing the produce, storing and transporting the components, as well as cooking.
The first step in answering this question requires figuring out the life cycle energy of a cheeseburger, and it turns out we're in luck. Energy Use in the Food Sector (PDF),a 2000 report from Stockholm University and the Swiss Federal Institute of Technology, does just that. This highly-detailed report covers the myriad elements going into the production of the components of a burger, from growing and milling the wheat to make bread, to feeding, slaughtering and freezing the cattle for meat -- even the energy costs of pickling cucumbers. The report is fascinating inits own right, but it also gives us exactly what we need to make a relatively decent estimation of the carbon footprint of a burger.
Overall, the researchers conclude that the total energy use going into a single cheeseburger amounts to somewhere between about 7 and 20 megajoules (the range comes from the variety of methods available to the food industry).
The researchers break this down byprocess, but not by energy type. Here, then, is a first approximation: we can split the food production and transportation uses into a diesel category, and the food processing (milling, cooking, storage) uses into an electricity category. Split this way, the totals add up thusly:
Diesel -- 4.7 to 10.8 MJ per burger
Electricity -- 2.6 to 8.4 MJ per burger
With these ranges in hand, we can thenconvert the energy use into carbon dioxide emissions, based on fuel. Diesel is straightforward. For electricity, we should calculate the footprint using both natural gas and coal, as their carbon emissions vary considerably. (If you're lucky enough to have your local cattle ranches, farms and burger joints powered by wind farm, you can drop that part of the footprint entirely.) The results:
Diesel --350 to 800 grams of carbon dioxide per burger
Gas -- 416 to 1340 grams of carbon dioxide per burger
Coal -- 676 to 2200 grams of carbon dioxide per burger
...for a combined carbon dioxide footprint of a cheeseburger of 766 grams of CO2 (at the low end, with gas) to 3000 grams of CO2 (at the high end, with coal). Adding in the carbon from operating the restaurant (and driving to the burger shopin the first place), we can reasonably call it somewhere between 1 kilogram and 3.5 kilograms of energy-based carbon dioxide emissions per cheeseburger.
But that's not the whole story. There's a little thing called methane. It's a greenhouse gas that is, pound for pound, about 23 times more effective a greenhouse gas than carbon dioxide. It's also something that cattle make, in abundance.
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