So many reasons to not eat cheeseburgers. Here is a contemporary one.

From:  Deliver us from cheeseburgers

Peter Aldhous, San Francisco bureau chief

My climate guilt is complete. Not only did I expand my personal carbon footprint by flying from California to attend the AAAS meeting, but yesterday I ordered a cheeseburger on room service at my hotel here in Chicago.

Regular readers of New Scientist will already know that agriculture makes a bigger contribution to global warming than the entire transportation sector, and that you can help manage the problem by choosing low-carbon foods.

My guilt trip stems from the fact that cheeseburgers are among the most climate-unfriendly foods imaginable, as multiple speakers reminded me this morning at a AAAS session on “life-cycle assessments” of the total greenhouse gases emitted in putting food on our plates.

The good news is that some organisations are making better choices than me. At this morning’s session, Helene York of the Bon Appetit Management Company described her efforts to bring low-carbon menus to its network of some 400 cafes on college campuses and in corporations across 29 US states.

In April 2007, Bon Appetit adopted a two-year target to reduce the use of high-carbon beef and cheese by 25 per cent. For beef, this target has easily been achieved. But York admits that the cheese target will be missed, because chefs have struggled to find acceptable alternatives. “It will take more time to educate the palates of our customers,” she says.

The complexity of calculating total greenhouse gas emissions for foods was revealed by other speakers at the session. Even for the same end product, total emissions can vary widely depending on how the food was farmed or caught, transported and processed.

For instance, if I order salmon at a Chicago restaurant this evening, I’ll do nearly five times more damage to the climate if it was farmed in Chile and flown in fresh, compared to fish frozen at sea by a seine-net vessel from Alaska. I wouldn’t have thought to ask.

The science of calculating the greenhouse emissions associated with food is still too young to provide answers to many of the questions that York and other innovators are asking. Is canned better than frozen? Should chefs in northern US cities choose produce grown in hothouses, or trucked in from Mexico?

For anyone embarking on a career in research, there seem to be some clear opportunities. In the meantime, if you want a meal that induces less guilt than my cheeseburger, try Bon Appetit’s low-carbon diet calculator.