Agriculture contributes about 20 percent of total greenhouse gas emissions in the world

At her farm nestled in the green hills of northwestern France, Marie-Francoise Brizard is helping to curb a planet-wide menace: farting and belching cows implicated in global warming.

This year, Brizard said, she has cut methane emissions from her herd of 40 Normandy cows that are equivalent to 32 metric tons of climate-changing carbon dioxide.