What is the science behind the moo-ve from cattle methane emissions?

FILE PHOTO: A dairy cow is seen at the South Mountain Creamery farm in Middletown, Maryland U.S., May 19, 2020. REUTERS/ Carlos Barria/File Photo

(Reuters) - Scientists have worked for years to reduce methane emissions from cattle burps by changing what cattle eat, or through research on vaccines, genetic modification of cattle and even forehead-mounted masks and backpacks to trap vapors.

WHAT IS THE PROBLEM?