If we can capture landfill gas, why can't we capture cows' burps and farts and use them as a source of energy too? It's the same methane after all
How do you propose capturing methane laden cow burps?
Land fill sites are stationary and inanimate. Getting methane out of a land fill site basically involves putting some pipes into the back fill site and running the pipes to a central collection point to process the gas. Some pumping of the gas may be required.
Cattle however, are live mobile creatures. They move around, they eat grass, they lie on the ground, they chew cud, drink water, bellow and interact with other members of the herd. With so much activity, how does one collect methane laden burps?
A collection mask could be placed on the cattle and a collection container, whether rigid or flexible, could be placed on a cow's back or side but all this would interfere with the normal activities of a cow and could be regarded as being cruel.
Cows could be restrained in a cage with limited movement or confined to a barn where the air inside the barn is filtered for methane. In such scenarios the animals would not see daylight or engage in normal activities for cattle and would definitely be regarded as cruel.
Methane-reducing feed additives and supplements inhibit methanogens in the rumen, and subsequently reduce enteric methane emissions.
Methane-reducing feed additives and supplements are most effective when grain, hay or silage is added to the diet, especially in beef feedlots and dairies.
You're right, it's a similar gas, so it could theoretically be used for energy. The problem with doing this is two-fold:
There is no currently known non-cruel way to capture such gases. The most feasible way would be to surgically insert tubes in the animals. I don't think anyone wants to see that happen, especially the cattle.
Collection would likely interfere with cattle depositing their feces on the ground. In most areas, animal feces are an essential part of the ecosystem. However, since cattle or similar animals aren't endemic to many ecosystems in which they are currently present, the effect would vary depending on the region.