Monday, November 2, 2009

Are cows worse than coal?

Just when the "clean coal" public-relations campaign seemed to be losing momentum, the Worldwatch Institute came out with a report blaming livestock for over half of all greenhouse-gas emissions. I can't imagine a better gift to the coal industry; the consensus has always been that burning coal is the single largest cause of warming, but now more confusion threatens to push the debate backwards.

The report makes a number of questionable claims, but one stands out: Worldwatch contends that since livestock have been domesticated, even their breathing should be counted as a human-caused emission. This ignores the reality that huge numbers of wild animals, especially methane-producing ruminants, used to roam the earth without ever registering the 25-gigaton CO2 impact ascribed to modern livestock. For example, the American buffalo population two hundred years ago likely exceeded the current population of all American dairy and beef cows combined. A report with so little concern for consistency resembles propaganda more than research.

The second half of the article reads like an extended advertisement for veggie burgers, with the implication that replacing meat with "soy analogs" could eliminate those inflated greenhouse-gas emissions. Meat has become a pretty easy target for a variety of activists and I won't try to defend it, but I do reject the claim that all animal proteins cause terrible environmental impacts relative to a vegan diet. Here are some reasons why dairy is at least as sustainable as soy:
  • Production of soy protein does not use materially less land than production of dairy-farm protein; this holds true for both industrial and organic production. I encourage any reader to run the numbers--for industrial methods, both end up at about 750 pounds of usable protein per acre.
  • Up to half of dairy cow diets typically consist of forage crops--alfalfa and grass that require minimal spraying, cultivation, and processing; in contrast, row crops like soybeans must be tilled and planted annually.
  • American farmers produce twice as much milk with half as many cows as they kept in the 1920s. This smaller dairy population has less absolute and per-capita impact in every area.
  • Manure in less-mechanized dairy farming is typically handled as a solid that produces little methane; farms that handle their manure as a liquid also have the ability to extract energy from that manure with an anaerobic digester--which not only destroys the methane but also can replace fossil sources of energy.
  • Dairy farming provides its own fertilizer; while soybeans fix their own nitrogen, they still need regular doses of phosphorus and potassium (along with micronutrients) to stay in production.
Taking this report at face value should lead to calls to kill off our livestock while continuing to burn coal; hopefully, cooler heads will prevail and remind us that thousands of years of agriculture have fed us without cooking us.