Methane burps are created through the process of enteric fermentation. First, the food sheep and cows eat goes into a chamber called a rumen. There, up to 200 different organisms (like fungi and bacteria) get to work processing, breaking down and fermenting the food. This gives the animal a bit of energy before being passed along to the next stomach for more processing. As the plants and grasses are fermented in the rumen, methane is created, which the animal then burps out.
Methane is a powerful GHG that is nearly 34 times better at trapping heat than carbon dioxide (or CO2). But while carbon dioxide can take thousands of years to break down, methane only remains in the atmosphere for about 12 years.
Nitrous oxide is also a potent GHG, about 298 times better at trapping heat than carbon dioxide. It’s created from nitrogen on the ground – 20 per cent from fertiliser and 80 per cent from livestock’s urine and dung. But it also doesn’t last as long as CO2, breaking down within 114 years.