December 29, 2009
Peter Spendelow, NW VEG President
People who eat meat but are worried about global warming and the environment have considered grass-fed beef as a possible way to reduce their environmental impact. It turns out, however, that grass-fed beef is a key contributor to global warming and, pound for pound, is responsible for more greenhouse gas than grain-fed beef.
Livestock's Long Shadow, a major 2006 report by the United Nations Food and Agriculture Organization, pegs the livestock sector as responsible for 18 percent of all human-created greenhouse gasses--a larger share than the entire transportation sector. There are four main ways that livestock creates global warming gasses: energy used directly to grow the animals and their food, methane produced in the stomach of livestock, nitrous oxide derived from fertilizers to grow their feed, and carbon released from trees and from the soil when land is cleared for grazing or for growing grain to feed the animals.
Of these four, it is methane production with which the grass-fed beef has the most problems. Methane is 23 times more potent than carbon dioxide as a greenhouse gas, and is produced when cows digest grass in a special part of their stomach called the rumen. Like humans, cows cannot digest cellulose directly, but special bacteria living in the cow's rumen ferment the grass and digest the cellulose, releasing methane as a byproduct. The cows just burp out this methane. Grains, which have much higher concentrations of proteins and starches, digest more quickly and do not produce as much methane. The cattle also grow faster on a grain-rich diet due to the higher concentration of calories, and so they take less time (and produce less methane) in growing to the size at which they are sent to slaughter. The net result is that cattle produce two to four times more methane per pound of beef when raised to market weight on a grass-fed diet.
For some of the other factors, grass-fed beef produce fewer greenhouse gases. There is much less direct energy use when cattle are allowed to graze as compared to the energy used to grow crops to feed cattle. Cattle pastures are often fertilized, but there is probably less fertilizer use in pastures than in growing grains for cattle feed. As far as carbon released from the soil, though, the difference is not clear. Pastures do store a bit more carbon in the soil than do tilled crops, but when natural forests are cut down either for grazing land or for growing crops for animal food, massive amounts of carbon are released from both. When you add up all the greenhouse gasses, though, the increased methane production outweighs the other factors, and Nathan Pelletier, a greenhouse gas/food science researcher from Dalhousie University, recently estimated that grass-fed beef results in roughly 50 percent higher greenhouse gas emissions.
One advantage to grazing animals instead of tilling the soil to grow food crops is that pastures are a more natural habitat for other species, and allow more native birds, rodents, and other animals to live. Contrarily, ranchers are often relentless in eliminating competing or predator species through trapping and poisoning. A recent very disturbing Audubon article described farmers being forced to use a very toxic poison to kill prairie dogs on their property even when they wanted to keep it natural (see article at www.audubonmagazine.org/features0911/incite.html).
In the humanitarian aspect, feedlot-raised cattle clearly have it much worse than free-range grass-fed cattle. Switching animals from grass to grain is upsetting to their digestive systems and requires that they also be continually fed antibiotics, plus they are given all sorts of supplements and growth hormones to grow quickly. John Robbins, in The Food Revolution, describes how 75 years ago it would take four to five years to raise cattle to slaughter weight. Now, today's grain- and hormone-fed animals are slaughtered when only 14 to 16 months old. But today's grass-fed cattle are also slaughtered at a much younger age--as young as 18 months. Wild species of cattle such as water buffalo and bison have a lifespan of 20 years or more and take five years to reach maturity, so both grain- and grass-fed animals are commonly slaughtered when still very young.
One thing is clear in the grain- vs. grass-fed debate: Neither form of beef is environmentally friendly. In a sidebar to Mark Bittman's article "Rethinking the Meat Guzzler" in the New York Times on January 27, 2008, Eshel and Martin provide data showing that producing 6 oz. of beef steak produces 24 times more greenhouse gas than does producing an equivalent number of calories of vegetables and rice. If you are worried about the greenhouse gasses produced by the food you eat, you shouldn't be worrying about grain- vs. grass-fed beef. Eating grains and vegetables directly yourself, instead of passing them through animals to produce meat, is far more efficient and less damaging to the environment.