What do they do with orange peels?

I was making fresh-squeezed orange juice today (an occasional indulgence - yum) and I wondered what commercial juice making operations do with the orange peels.  After all, they produce a lot of them.

Not hard to find the answer to that one -- they are converted to cattle feed.

I couldn't find much of a description of that.   Just this from Tropicana (from this Web page):

"Tropicana's production process aims to utilize the full life-cycle of the orange. For example, Tropicana recycles peel and seeds to make 150,000 tons of beneficial cattle feed, avoiding more than 700,000 tons of raw peel becoming landfill waste annually."

They also have potential to be used as a feedstock for biofuel production. The citrus peel oil, of course, can be used in envirosafe cleaning products.

Here's a longer article:  Fruit's pulp, seeds, oil all involved in making a variety of products  (also discusses the peels)