The Environmental Impact of Animal and Plant Protein Sources

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We’ve all heard that eating less meat is a great way to reduce our environmental impact by cutting carbon emissions. On average, it takes more than 11 times as much energy to produce one calorie of animal protein as it does to create one calorie of plant protein. The meat and dairy industries require large amounts of pesticides, chemical fertilizers, fuel, animal feed and water to operate, and in return they produce large amounts of greenhouse gases and toxic manure that pollutes our waterways. Worldwide meat consumption has more than doubled in the past 60 years, with global meat production reaching 600 billion pounds in the last few years.

Dairy and meat production take a heavy toll on the environment, but not all protein sources are created equally. For its 2011 Meat Eater’s Guide, the Environmental Working Group conducted lifecycle assessments on 20 popular types of protein from meat, dairy and vegetable sources and found that different sources and different production systems have varying environmental impacts.    

Lamb, beef, cheese, pork and salmon topped the list for highest amounts of greenhouse gas emissions produced. On the opposite end of the scale, plant-based sources such as lentils, tomatoes and beans, and dairy-based sources such as yogurt and milk created the fewest amount of emissions.

protein sources chart 
Image Courtesy The Environmental Working Group 

It’s no surprise that meat-based protein sources created the most greenhouse gas emissions as ruminant animals such as sheep and cows create methane through their digestive systems. While lamb and beef generate about equal amounts of methane, lamb produces less edible meat relative to the animal’s weight, earning it the top spot on the EWG’s list. Thankfully, lamb constitutes just one percent of all meat consumed by Americans. Unfortunately, conventionally farmed beef, which generates the second highest amount of greenhouse gas emissions, makes up 30 percent of all meat consumed by Americans. Vegetarians who eat lots of cheese should note that cheese comes in third on the list of biggest emissions producers. Cheese ranks so high because it takes about 10 pounds of milk to produce one pound of cheese.

For a more in-depth look at the health, climate and environmental impact of various protein sources, check out the EWG’s 2011 Meat Eater’s Guide.