Agricultural societies, I imagine, have always fed waste products to livestock. On diversified farms, pigs and chickens get lots of kitchen scraps and "culls"–produce that can't be sold. And it's worthwhile to keep cows around if you have access to pasture–cows convert a wild, low-input perennial crop (grass), which humans can't digest, into highly nutritious beef and milk.

But as agriculture industrialized, the waste products that farmers serve to farm animals have industrialized, too. Before the rise of massive facilities that house thousands of chickens and vast feedlots that confine thousands of cows, I doubt anyone thought of feeding "chicken litter"–feces mixed with bedding, feathers, and uneaten feed–to cows. Chicken litter was a valuable fertilizer; it added not just nitrogen and other nutrients to soil, but also plenty of organic matter.

But with the rise of industrial chicken production, farms produced way too much litter to be absorbed by nearby land (not that they don’t often severely overload the land around them).

So what was once a resource has become a waste problem–and one solution has been to feed chicken litter to cows. Cows consume between 1 million and 2 million tons of chicken waste per year–and then we consume those cows.

 

Read article at: http://www.grist.org