Grass-Fed Beef and Methane, Part Deux: Still More Armwaving

I've written several times about grass-fed beef not being the climate nightmare that grain-fed beef is, and possibly a better alternative than eating plants. In the comments to one post, Michael Tobis and I engaged in much speculating about whether the methane emissions from cattle were worse than the carbon emissions involved in agricultural production of the same amount of calories. (And I never answered his final point that on already-cleared (regularly plowed) land, farming should be carbon neutral - the response is that it still takes energy inputs to farm, transport, and process the production, and soil carbon is not neutral relative to the possibility of converting the land to pasturage.)

Anyway, it was a data-free discussion, which is fine for what it's worth. Now comes a cattle rancher to make the same argument at Grist. To his credit he raises the methane issue, but after asking questions as to ways that, maybe, somewhat reduce methane emissions, concludes as to whether the methane is a problem, "The fact is clear. It is not the livestock; it is the way they are raised."

I may have been guilty of armwaving in my discussion with Michael, but at least I didn't jump from that to a conclusion. I left a comment saying as much, and a later commenter said it better:

It is conceivable to me that a steer that eats only grass from naturally fertilized pasture could have a negative carbon footprint. Root structures of grasses can be quite large, and soil can become a carbon sink, so the pasture could possibly sequester enough carbon to make up for the methane emitted by a steer during digestion. I'm also open to the idea that manure decomposes differently on pasture than at the feedlot. But someone needs to demonstrate it with some actual measurements and some real science.