There's also a disagreement on methane, the powerful greenhouse gas that cows belch (and excrete, but to a lesser extent). Capper believes that a corn diet and a shorter life span results in one-third the methane output of a grass-fed cow. Other researchers, however, have suggested that grass's ability to sequester carbon may compensate for the difference.
Even if Capper is correct on all counts, it isn't a TKO for the CAFOs. There's more to environmentalism than greenhouse gases. CAFOs produce 300 million tons of manure per year, twice the volume of human feces. Even if it were spread out, that would be a lot of bullshit. But it's particularly bad when concentrated on small patches of land. CAFOs usually capture their waste in lagoons before spraying it back onto the fields as fertilizer, but the storage units sometimes fail. Large volumes of manure can kill aquatic plant life, the base of the marine food chain. Massive dead zones from CAFO runoff exist in the Gulf of Mexico and the Chesapeake Bay. Based on some estimates, we spend more than $4 billion (PDF) annually trying to clean up CAFO manure runoff. In addition, the long-term, low-dose antibiotics CAFOs give livestock can lead to antibiotic-resistant bacteria, further undermining our dwindling supply of useful medicines.
May the Lantern make a humble suggestion? Stop eating so much beef. Whether grass- or corn-fed, it's pretty bad for the environment, and it's not that great for your body, either. If your palate simply can't resist grassy notes, get them from a nice sauvignon blanc. Locally produced with a natural cork, of course.