KSN: In an effort to clean up air pollution, the federal government has a new proposal on the table: a tax on gas, but not the kind you put in your car. Instead, the tax would be aimed at ranchers and the bodily emissions that come from their livestock. Big factories and cars are what you typically think of with air pollution, but what about livestock? Cattle, hogs and sheep produce greenhouse gases like methane, nitrous oxide and carbon dioxide through their digestive systems. Now, …