From the Washington Post:
Meat that's raised according to "alternative" standards (about 1 percent of meat in the United States) might be a better choice but not nearly as much so as its privileged consumers would have us believe. "Free-range chickens" theoretically have access to the outdoors. But many "free-range" chickens never see the light of day because they cannot make it through the crowded shed to the aperture leading to a patch of cement.
"Grass-fed" beef produces four times the methane -- a greenhouse gas 21 times as powerful as carbon dioxide -- of grain-fed cows, and many grass-fed cows are raised on heavily fertilized and irrigated grass. Pastured pigs are still typically mutilated, fed commercial feed and prevented from rooting -- their most basic instinct besides sex.