There's no reason to do that. You do not want to create more methane, and the possibility of even a trickling of it getting into the atmosphere. This methane to methanol is purely to get rid of the methane we produce, and hopefully the methane stored in the atmosphere. We've got plenty of hydrogen, it's one of the most common elements (iirc) in the known universe, but to convert some into methane? Hydrogen is clean, and then make it toxic methane? It's much better to just use the hydrogen as fuel. I remember seeing an article one time about a method to convert hydrogen into fuel, and so it's much better to do it that way. Though how costly or doable on a mass scale either conversion is, we don't know yet.