Here is the other part of my husband’s presentation at our community gatherings.
OK, before we really get going here, we have to talk about cow farts. Because cows (and other livestock) fart a lot of methane, which just happens to be a potent greenhouse gas. It is much more effective, pound per pound, at warming the planet than carbon dioxide. Fortunately, we humans (and cows) aren’t adding nearly as many pounds of methane to the atmosphere as we are of carbon dioxide. And the methane breaks down in the atmosphere relatively quickly, in only a few years, rather than in many decades. But methane is still a very important greenhouse gas, and all of the climate models that attempt to predict global warming include estimates of methane emission and decomposition.
A widely cited 2006 report by the United Nations Food and Agriculture Organization, Livestock’s Long Shadow, estimated that 18 percent of annual worldwide greenhouse gas emissions are attributable to cattle, buffalo, sheep, goats, camels, pigs, and poultry. That’s more than the entire transportation sector (13%). A 2013 update came up with a similar figure. To come up with those numbers, the UN included not just livestock farts, but also emissions from a) clearing land to graze livestock and grow feed, b) keeping livestock alive, and c) processing and transporting the end products. The UN FAO has lots of other reports and resources here.
A Worldwatch report, “Livestock and Climate Change” by Goodland and Anhang (2009) estimates that livestock and their byproducts actually account for 51 percent of annual worldwide greenhouse gas emissions. How did they get from the UN’s 18%, all the way up to 51%? Well, it’s all in how you do the accounting. Basically, to the UN estimates, they add the effects of animal respiration (producing CO2), the loss of carbon-sequestering forest, and other factors. Some of those you might want to quibble with, but most seem pretty reasonable.
But wait! The U.S. animal agriculture industry claims to generate only 2.8% of U.S. greenhouse gas production! But they only include methane from digestion, excluding all the other factors listed above. Perhaps more importantly, they conveniently include only animal agriculture inside of the US, meaning they exclude, for instance, all of the beef that we import from the Amazon. But isn’t that part of the impact of the American diet too?
Like other issues, this is one that you can read about “until the cows come home”. But the material above is a pretty good introduction, covering most of the territory. Personally, it seems clear to me that the UN reports are reliable, but probably underestimate the actual climate impact of animal agriculture. If that’s true, and if the world’s appetite for animals continues to grow, then even if we somehow eliminated all fossil fuel usage by our transportation systems and buildings, animal agriculture alone could push us over the UN greenhouse gas targets, risking catastrophic impacts, particularly to the world’s poorest. Seems like a pretty good reason to try some new sauces and substitutes.