A plant-based diet beats a traditional meat-based one hands down when it comes to trimming one’s contribution to greenhouse gases, but not everyone is willing to plunge head-long into a life of tofu dogs.

The good news for meat eaters with an environmental conscience is that meats and dairy products are not all created equal when it comes to the quantity of greenhouse gases (GHG) produced. In fact, a study just released by the nonprofit Environmental Working Group (EWG) and titled “Meat Eater’s Guide to Climate Change + Health” reveals that by avoiding just the three worst GHG offenders — lamb, beef and cheese — even hard-core meat eaters can make a sizable dent in their diet’s climate change footprint.

EWG, in partnership with CleanMetrics, an environmental analysis firm, examined the “cradle to grave” lifecycle, from farm to retail to plate to disposal, of 20 popular foods in four categories — meats, fish, dairy and vegetable protein — and compared the GHG produced by each.

To get as complete a picture as possible of a product’s lifecycle GHG emissions, EWG included emissions from cooking and even from disposal of uneaten food in their analysis. For example, the study accounted for the 20 percent of meat that goes to waste, according to figures from the U.S. Department of Agriculture.

The study focused on the conventional kinds of foods most Americans eat, i.e. grain-fed and non-organic. Fish were represented by farmed salmon and canned tuna; and the four dairy products included were cheese, milk, yogurt and eggs. Among the vegetable proteins were common favorites like nuts, lentils, dried beans and tofu.

The two ruminants, lamb and beef, clearly stand apart as the greatest GHG producers, in large part because of the methane they release through flatulence: methane is a 25 times more potent greenhouse gas than CO2.

Perhaps surprising, cheese came in as the third biggest GHG emitter, though its emissions were under half that from lamb or beef but were racheted up nonetheless because cheese also derives from a ruminant. Pork, farmed salmon and turkey all trailed pretty closely behind cheese. The harder a cheese the greater are the GHG emissions because hard cheeses require more milk.

With the exception of yogurt and milk (2 percent) — with emissions between one 10th and one 20th that of lamb or beef — chicken, canned tuna and eggs produced the smallest quantities of GHG among the animal products. Of all the meats, chicken generated the least (even 37 percent less than turkey) because chickens generate no methane and the amount of feed they require is relatively small.

Emissions associated with canned tuna were lower than those from farmed salmon, in large part because wild tuna catch their own food whereas farmed salmon eat prepared fish meal which is energy-intensive to produce.

GHG emissions from lamb or beef were at least nine times (and as high as 44 times) that of any of the plant-based products. Especially good news perhaps for vegans is that plant foods considered high in protein, like nuts, lentils, beans and tofu, were all among the very lowest GHG emitters.

EWG also detailed where in each product’s lifecycle the greatest GHG emissions occur. For meats, fish and eggs, the lion’s share of emissions occur during the “farming” phase before products undergo any processing. In addition to obvious emission sources like running farm machinery, every step in farming produces GHG. As example, nitrogen fertilizers used to grow feed grains emit nitrous oxide (N2O), a GHG with 300 times the global warming potency of CO2, and the fastest growing source of atmospheric methane is animal manure.

For plant products, however, most emissions come about after crops have left the farm and often stem the most from cooking. A pressure cooker can cut cooking times way down, not only for dried beans, lentils and vegetables, but also for meals based on meats.

The EWG study report is rich in many other details about how foods compare in their effects on the environment and human health (www.ewg.org/).

It also lays out how meat eaters can make seemingly small changes in eating habits, besides just avoiding lamb and beef, which measurably reduce one’s climate change footprint. For example, if a family of four skipped meat and cheese just once weekly, the impact would be equivalent to taking a car off the road for five weeks.

The per capita GHG emissions of Americans are double that of people in the European Union, and the fact that we consume 60 percent more meat contributes to this difference.

However, the EWG report points out a sobering fact, that individual actions like eating less meat will not suffice to stop global warming. If all Americans converted to a vegetarian diet for example, the country’s GHG emissions would be reduced by less than five percent, according to EWG calculations.

EWG stresses that achieving the necessary cuts in GHG emissions will require bold political actions which trigger comprehensive shifts in national energy policy and put the nation on a resolute path to green energy.

Sarah Mosko, Ph.D., is an environmental writer living in California who blogs at sarahmosko.wordpress.com.

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