Global Mooing

Jacob Leibenluft (AKA "The Green Lantern"), tries to answer the question: "Which is better for the environment, soy milk or cow's milk" in Slate.

I think he's saying soy milk wins, but it's a lot closer than conventional wisdom and more complicated than farting cows:

... it's not easy to compare the two products: Soy milk may be packaged and marketed as a substitute for dairy, but environmentally speaking, it's a very different product. Start with the basics: The calcium in soy milk has to be artificially added, and you won't get anything remotely looking like milk from soy until you've ground up the beans; removed a fiber the Japanese call okara; and added water, vitamins, minerals, and sugar. Most cow's milk needs to be pasteurized and packaged, of course, but what you buy in the store is much closer to what comes off the farm.

...According to research by Cornell University scientist David Pimentel, it takes about 14 calories of fossil-fuel energy to produce one calorie of milk protein on a conventional farm. Organically produced milk might require a little less than 10 calories of fossil-fuel energy, under the most optimistic assumptions, and better farming techniques could cut down greenhouse-gas emissions by at least 25 percent.

By comparison, Pimentel's data suggest that it takes about 0.26 calories of fossil fuel to make a calorie of organic soybeans—which are used by most soy milk manufacturers. Soy protein accounts for about 35 percent of those calories, so let's say you'll need to put 0.75 calories of energy into farming soy to produce a calorie of protein. That makes soy protein approximately 13 times more energy-efficient than even organic dairy protein under a best-case scenario.

...Of course, as we've already discussed, you don't drink raw soy beans. Not only do the other ingredients in soy milk need to be shipped from elsewhere; the process of adding them requires energy and produces a significant amount of waste. As one British government report put it, manufacturing soy milk is closer to making fruit juice than cow's milk. (And as the Lantern has noted before, producing fruit juice takes quite a bit of electricity)

...niche products have their environmental downsides, too. A specialty product like soy milk—despite its growing popularity, its market is about one-twentieth the size of regular milk's—is probably going to have to travel farther to the average consumer simply because fewer people produce it. With more centralized production, that means the soy travels farther to the plant, too. Production probably has a much bigger environmental impact than transportation, but it's worth keeping in mind: Environmentally, it hurts to be in the minority.