OK, let’s get all the giggles and smirks about cow flatulence out of our systems, shall we? I admit this topic probably brought a smile to my face when I first read about it years back. Upon examination, however, it turns out animal agriculture is humankind’s second-largest source of greenhouse gas emissions.
As for cow flatulence – and burps – it’s mostly a matter of methane. Methane is a greenhouse gas that comes from many sources, but cattle digestion is a primary contributor. Methane has about 23-34 times more greenhouse effect (trapping of longwave infrared radiation in the atmosphere leading to warming) than carbon dioxide, though it trails carbon dioxide emissions in volume by a considerable margin. Also, methane in the air combines with oxygen to form additional carbon dioxide, the longer lasting greenhouse gas.
The UN Food and Agriculture Organization (FAO) keeps tabs on global food production and relevant scientific and economic issues. The FAO calculates 39 percent of all agricultural greenhouse gas emissions come from cattle, with beef cattle producing quite a bit more than dairy cows. (Grass-fed cattle produce significantly less methane than corn-fed cattle per animal.) This cattle methane outweighs greenhouse emissions from the use of synthetic fertilizers and deforestation. In the last decade, methane from livestock increased 11 percent. Globally, meat and dairy product consumption has been increasing, as you might expect with population trends and a growing middle class in countries like China. In general, the FAO reports meat consumption is growing fastest in developing countries.
The FAO has calculated a third of the earth’s ice-free land and 16 percent of global freshwater is devoted to growing livestock. As of now, a third of grain production also is used to feed livestock. Maybe most concerning of all, an FAO study projects global meat consumption will increase 76 percent by 2050, and dairy products will go up by 64 percent.
Domestically, the average American’s beef input produces 1,984 pounds of carbon dioxide annually. Replacing beef with plant food would reduce that number by 96 percent. But expecting such mass conversions is, in my opinion, from the movie “Fat Chance.”
In fact, the FAO appears to be somewhat fatalistic about this. FAO natural resource officer Francesco Tubiello told NPR that asking everyone to drastically reduce meat consumption is simply unrealistic. That is not to say more modest reductions are not likely and are, in fact, happening in millions of people’s lives. That may be more due to health concerns than those of the environment, but such reductions will have some benefits for the environment regardless of intent.
There are also other greenhouse gas side effects from our current land use in raising livestock. Animal manure releases significant amounts of greenhouse gases as well. Livestock-induced impacts include loss of carbon stored in trees and soil when additional land is cleared for agricultural expansion. The FAO calculates such expansion puts an additional .65 gigatons of carbon dioxide into the air. Roughly 2 percent of the world’s energy is used annually to make 100 million tons of nitrogenous fertilizer, much of it to grow corn.
Animal agriculture, partially through heavy nitrogen fertilizer use, produces 44 percent of anthropogenic/human activity-induced emissions of the lower volume but strongest greenhouse gas, nitrous oxide. There are also the separate issues of animal agriculture making the largest contributions to water pollution globally, as well as air pollution apart from greenhouse concerns. Antibiotic resistant bacteria, a grave public health concern, is strongly tied to overuse of antibiotics in cattle production.
There are some mitigating actions that can be taken in the way we produce our food to cut back some of the greenhouse impacts. Tubiello says increasing crop yields through more efficient use of land can reduce emissions. Research is ongoing in this field in places like land grant colleges, the USDA and agricultural technology centers in many other nations. The FAO reports there is still fairly widespread inefficient use of costly nitrogen fertilizers, and believes efficiency can be improved. Fortunately, farmers in developed nations are among the best-educated segments of society in the sciences as well as in economics, so it pays for them to be the quick learners they are.
What we feed cattle can make some real inroads as well. The notion that grass-fed cattle emit less methane per animal is true. But in global meat consumption trends, grasslands are a less efficient land use. Grass-fed cattle are smaller cattle. The FAO calculates with meat consumption trends, the smaller cattle would lead to greater number of cattle being raised to satisfy meat demand. The total methane emissions would actually end up increasing with major conversions to grass fed. Between the corn and soy feed that makes cattle very gassy and the less-nutrient-rich grass lies alfalfa. Research indicates that kind of feedstuff switch might solve some of this gassy conundrum. Surprisingly, cattle emit more methane through their belches than through their rear exhaust. Alfalfa reduces belching. As Johnny Carson used to say, “I did not know that.” Other feedstuffs are being examined as well as realistic and efficient substitutes.
Finally, we’ll end on the tawdriest topic: manure. Manure can be managed better (tell me about it!). Since it is a significant contributor to nitrous oxide emissions as well as water and air pollution, such efforts are important and doable. Research is underway to increase use of manure as a fuel.
Imagine if we could do the same in the political dialogue. I see managing manure as a worthy goal for humanity.