It seems like a faulty way to analyze the problem in any case. Atmospheric methane devolves into CO2 in about eight years, "on average." CO2 emitted into the atmosphere appears to stick around for 300-1000 years. The heat-trapping of methane is obviously much greater during that eight years but then it devolves into CO2. I guess the only way to draw a real conclusion would be comparing the amount of Methane+subsequent CO2 resulting from traditional animal husbandry with the amount of CO2 produced by this lab process.