Food production in general is an inefficient process; the US expends roughly 10 units of fossil energy to produce just one unit of food energy. Indeed, about 10 percent of the US energy consumption goes into raising, distributing, processing, preparing, and preserving the plant and animal matter that Americans eat.
Meat production, however, requires and produces a greater amount of energy. In 2006, the Food and Agriculture Organization of the UN announced that 18 percent of global emission results from the livestock industry. This is equivalent to 7.1 billion tonnes of CO2. For context, a single tonne of CO2 weighs as much as 10 baby elephants, and is produced by flying to Paris seven times or breathing for 500 days.
In a report published in the journal Climatic Change, researchers found that a meat eater’s diet releases greenhouse gas emissions approximately double that of vegan’s. This is primarily a result of the enormous amount of toxic gases produced by the livestock industry. Indeed, merely reducing the amount of meat subjects consumed reduces greenhouse gas emissions associated with an individual by between 920 and 1560 kg CO2-equivalent/yr.
Although the livestock industry accounts for only 9 percent of the global emission of CO2, this sector also generates 65 percent of human-related nitrous oxide and 35 percent of methane. These gases have 296 and 23 times the Global Warming Potential of CO2, respectively, meaning they are even more dangerous to the environment.
So where do these gases come from? The main culprits are the animals themselves, especially cattle. As cows digest, they produce methane during a process known as enteric fermentation. This methane accounts for almost a third of the emissions from the agriculture sector. Another major source is from manure management, including storage, which can affect how these gases are produced. Manure management contributes to nitrous oxide levels, which rise during the breakdown of manure and urine.
The meat industry also requires massive amounts of water, both to feed its animals and to process the meat. Beef production requires six times more water than tofu production, and even four times more than chicken. Each processing step, aside from final packaging and storage, requires water, in addition to polluting the waterways with blood, manure, fat, and other animal byproducts.
How can we make a difference when these huge industries dominate greenhouse gas emissions? One way is to reduce wasted food. At least a quarter of the food grown is wasted annually, accounting for 2.5 percent of the annual US energy consumption. Merely by eating what we buy, monitoring our food spoilage, and making informed decisions about portion sizes could be more effective than expensive and controversial energy supply policies that have been proposed.
Another key to the problem is to reduce our meat consumption, replacing energy-intensive meats with less energy intensive fruits, nuts, beans, vegetables, and grains. You’ve probably heard about Green Monday, a new initiative spearheaded by the Office of Sustainability that encourages members of the community to eat vegetarian one day a week. Indeed, if everyone at Washington University in St. Louis, faculty, staff, and students alike, participates in Green Monday, the institution could collectively reduce its carbon emissions by as much as 5,000 metric tons per year. This is equivalent to taking 1,053 cars off the road. Even giving up meat for just one day a week makes a significant difference when done consistently and communally.
 Webber, Michael. “More Food, Less Energy.” Scientific American Jan. 2012: 74-79. Print.
 “More Food, Less Energy”