Of all the things that an individual can do to help slow the process of climate change–change lightbulbs, turn down the AC, ride a bike–few if any have as much impact as eating less meat.

So, at least, says the Environmental Working Group in its new Meat Eater’s Guide to Climate Change and Health.

Yes, this is a guide for meat eaters, not an argument for a vegetarian or vegan diet, which may be too much to ask of a nation of carnivores. But just eliminating a meal or two or three of meat can have a big impact, according to EWG:

If everyone in the U.S. ate no meat or cheese just one day a week, over a year, the effect on emissions would be the equivalent of taking 7.6 million cars off the road. 

Or

If you eat one less burger per week, over a year, it’s like taking your car off the road for 320 miles or line drying your clothes half the time.

Or, as Mark Bittman notes, if for two days a week you don’t eat any meat or cheese until dinnertime, you’ll accomplish something similar.

You’ll also save money–vegetarian meals generally cost less–and do your heart a favor, since most vegetables are lower in artery-clogging fat than meat.

I don’t entirely trust EWG, which tends to see risks everywhere. But this report strikes me as both solid and useful. To produce the report, EWG teamed up with CleanMetrics, an environmental  consulting firm, to calculate carbon footprint assessments of 20 types of conventionally raised (not organic or grass-fed) meat, fish, dairy and vegetable proteins. Included in the tally are pesticides and fertilizers used to grow animal feed as well as the grazing, processing, transportation, cooking and finally, disposal of unused food.

Different meats, it turns out, have dramatically different impacts. Beef, for example, generates more than twice the emissions of pork, nearly four times that of chicken, and more than 13 times that of vegetable proteins such as beans, lentils, and tofu. Here’s a chart:

Notice that a kilogram of cheese has a higher carbon impact that pork, turkey or chicken. That came as a surprise to me. I was pleased to see lentils at the low end of the chart; they’re a favorite of mine.

Citing USDA data, the report also  said 20% of uneaten meat in the U.S. ends up in landfills. Percentages vary by type:  40% of fresh and frozen fish were tossed, 31% of turkey, 25% of pork, 16% of beef and 12% of chicken.

While there’s no evidence that meat, when consumed in moderation, is unhealthy, most Americans eat far more than they need to get their daily recommended dose of protein.  Eating too much meat can contribute to heart disease and obesity, and a  2009 National Cancer Institute study cited by the EWG that found people who ate the most red meat were 20% more likely to die of cancer and 27% more likely to die of heart disease than those who ate the least.

When consumers do eat meat, EWG says, they should try not to buy or order too much and, where possible, seek out grass fed or pasture-raised meat, certified organic or unprocessed meat.

Celebrities who endorsed the guide include author Michael Pollan, author and physician Andrew Weil and chef Mario Batali. Batali is quoted as saying: “Most people in the U.S. eat way more meat than is good for them or the planet.”

For more, including recipes, check out the excellent Meatless Monday website, which is produced in association with the Johns Hopkins Bloomberg School of Public Health. The EWG told me it didn’t take money from food-industry companies to support the Meat Eaters Guide.