I wondered a couple of days ago what the carbon footprint of a hamburger might be. It’s the kind of question we’ll be forced to ask more often as we pay greater attention to our individual greenhouse gas emissions. Burgers are common food items for many people; it’s said that the average American eats three burgers per week, or about 150 burgers per year. What’s the global warming impact of all that? I don’t just mean cooking 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 clues provided by my friends
Martin Kelly and
Kim Allen sent me looking in the right direction, but then I stumbled across an absolute treasure:
Energy Use in the Food Sector (PDF), a 2000 report from Stockholm University and the Swiss Federal Institute of Technology, looking at the life cycle energy use associated with… a cheeseburger! 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 in its own right, but it also gave me exactly what I needed to make a relatively decent estimation of the carbon footprint of a burger.
Based on a variety of sources, 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 by process, but not by energy type. Here, then, is my first approximation: I 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, I could then convert the energy use into carbon emissions, based on fuel. For electricity, I calculated the footprint using both natural gas and coal; if you’re lucky enough to have your local burger joint powered by a wind farm, you can drop that part of the footprint entirely.
Diesel—90 to 217 grams of carbon per burger
Gas—37 to 119 grams of carbon per burger
Coal—65 to 209 grams of carbon per burger
...for a combined carbon footprint of a cheeseburger of 127 grams of carbon (at the low end, with gas) to 426 grams of carbon (at the high end, with coal). Adding in the carbon from operating the restaurant (and driving to the burger shop in the first place), we can reasonably call it somewhere between a quarter-kilogram and a half-kilogram of carbon emissions per cheeseburger.
Or, over the course of a year, between 37 and 75 kilograms of carbon emissions from the average American’s cheeseburger habit.
If each of the 300 million Americans hit that “average” burger consumption, we’re looking at 75,000-150,000 tonnes of atmospheric carbon annually from burger consumption alone—that’s the equivalent of the annual carbon output from 7,500-15,000 SUVs.
IEET Blog