Pasture-raised beef is better for the environment
Eatwild.com has a page dedicated to showing studies published in various journals and science magazines about the impact of pasture farming and pasture-raised animals versus feedlots.
Here's an excerpt:
When properly managed, raising animals on pasture instead of factory farms is a net benefit to the environment. To begin with, a diet of grazed grass requires much less fossil fuel than a feedlot diet of dried corn and soy. On pasture, grazing animals do their own fertilizing and harvesting. The ground is covered with greens all year round, so it does an excellent job of harvesting solar energy and holding on to top soil and moisture. As you will read in the bulletins below, grazed pasture removes carbon dioxide from the atmosphere more effectively than any land use, including forestland and ungrazed prairie, helping to slow global warming.
It’s a different story in a confinement operation. Here, the animals are crowded into sheds or kept outdoors on barren land and all their feed is shipped to them from distant fields. On those fields, the crops are treated with fossil-fuel based fertilizers, sprayed with pesticides, and planted, tilled, and harvested with heavy equipment. Each of these operations requires non-renewable fuel. Then the feed is shipped to feed manufacturers where it is dried, flaked or pelleted, and mixed with other ingredients and then, finally, shipped to the waiting animals, using yet more fossil fuel.