PG&E has been doing this is California for years and they generate a good amount of power off it, while also capturing all the methane from the cow manure. If the cows are going to be raised, you might as well mitigate their emissions and put that methane to good use.
Gonna need a source on your 1000x. I can find 27.9x the potential, per unit mass. I think my point still stands: they're taking a problem and merely converting it into a different form of the problem, and calling it a solution.
I think you need to compare the greenhouse effect from methane as compared to that CO2, NOx and SOx released by burning off the methane. There is a reasone the EPA requires waste water treatment plants to flare off methane rather than freely releasing it.