One of the places that Pollan works to bring out the contrast between progressive or green-minded agriculture and traditional, industrial agriculture is in Chapter 8 where he describes Joel Salatin's farm. Here Salatin raises cows, hogs and chickens and focuses on the relationship between all of these animals and the grass that sustains them at a basic level.
Though Salatin's farm is a particularly interesting case, Pollan highlights it in order to contrast the practices that Salatin uses to yield healthy meat from animals that are not subjected to the conditions of a concentrated animal feed lot or confinement in the way we understand it and the practices of industrial, conventional agriculture.
He notes that industrial agriculture requires huge amounts of inputs such as fertilizer and even diesel fuel just to move everything around and transport it but on Salatin's farm the animals all work together to fertilize the grass with their own excrement and they spread it naturally so there's little need for large amounts of diesel or fertilizer. In this chapter Pollan makes the argument that large amounts of animal protein can still be raised but without the seemingly destructive and unsustainable practices of the industrial, conventional model.