Backyard barbeques – one our favorite simple pleasures, right? And even here, there’s opportunity to cut back on our carbon footprint. Here’s how to limit the CO2 output of your next summer get-together.

Slow Food
It’s said that 30% of the greenhouse gases causing global warming can be traced back to the production of food. So if we’re smarter, more efficient about how and what we eat, there’s big potential to cut back on our carbon footprints.

Sad but true, it’s the staple of the backyard BBQ that’s one of the biggest offenders: Beef creates 19 kilograms of carbon dioxide for every kilogram served, according to studies. And the livestock industry alone is responsible for 18% of the world’s greenhouse emissions, a 2006 UN study showed. Calculating that takes into account everything from gas used by delivery trucks in getting the beef to a store to the amount of methane cows emit by burping.

Produce is much less “carbon evil,” if you will. For example, a kilogram of potatoes, by the time they’re served up baked on your patio table, equates to just 280 grams of emitted CO2.

Chicken is a relatively carbon friendly meat, representing 32% of the meat consumed worldwide but contributing only 8% of meat’s carbon footprint, according to a study out of Canada’s Dalhousie University.

Fish gets more complicated, with so many factors coming into play it’s tough to say which is the most carbon friendly. But generally, you want frozen fish, because it’s been trucked in to your store instead of flown in (as fresh fish is).

Overall, what you really want to do for a low-CO2 BBQ is limit the meat, max out the veggies and fruits, and make sure you buy from a farm close to your house.

For a fun exercise, check out the Bon Appétit Management Company’s Low Carbon Diet Calculator. It puts together a sort of greenhouse gas scorecard of a variety of meals.

Briquettes or Propane?
If you’re aiming for a green BBQ, here the answer is clear: Charcoal grills are far less environmentally friendly than gas grills.

According to a study released last year, charcoal grills have a carbon footprint almost three times those of propane grills (998 kg CO2e vs. 349 kg CO2e). (By the way, “CO2e” means “Carbon Dioxide Equivalent,” basically a way to universally express units of global warming, so it can include things other than just carbon, such as methane.)

A lot of that has to do with the efficiency with which the heat sources burn. Liquid propane gas, according to study author Eric Johnson, burns at near 90% efficiency, while charcoal is closer to just 20%. So you’re wasting almost 70% more energy right off the bat just using briquettes. When you include production and transportation of the two sources, it tips the scales heavily in favor of propane being the greener choice.

Eating It All
Perhaps the simplest way – certainly the most logical – to cut back is to finish your food. Instead of eating what we buy, we throw a lot of it away, which ends up producing methane – a particularly hazardous greenhouse gas – as it breaks down in landfills. According to a 2007 British study, the amount of emissions we’d save simply by eating our food instead of tossing it in the trash would equal taking 1 in 5 autos off the road.

So salute your host, get your fill, and clear your conscience all at the same time just by licking your plate clean!