@Aredwood: How will a fart tax actually reduce emissions?
It won't. In just the same way that carbon taxes don't reduce the amount of carbon being outputted. But it gives a select few a great cash windfall, and a bunch companies can puff themselves up with [false] pride and say "we're doing our bit".
If a tax doesn't work you may just have to legislate for methane reductions, staged reduction by quotas etc. One way or another this needs to be controlled, even if we may be indifferent as a country, markets and politics will demand it eventually.
Nitrogen caps are gradually coming in. Controlling nitrogen outputs ultimately reduces cattle numbers and this will reduce methane as well.