The paper today has an article about how the price of sawdust has tripled recently, and industries that use it are starting to look for alternatives. One paragraph reads:
Farmers have come up with perhaps the most unusual tactic: using processed cow manure as bedding instead of wood shavings. Many dairy farms have a process to convert cattle waste into methane gas that they sell to electric generators. The byproduct is basically the hay the cows ate. Lee Jensen's Five Star Dairy in Elk Mound, Wis., uses an aerobic digester to render manure into stall bedding, and has so much on hand after the process that he's selling the excess to neighbors.