If you don't mind downloading a huge PDF, you can find a copy of the first Discover magazine article
here, which describes the process and potential benefits. The costs turned out to be higher than that article projected (in part because the US didn't ban feeding turkey waste back to turkeys, which means they have to pay for the waste rather than being paid to dispose of it) but there is an update in the current issue of Discover that explains where things stand, how they are finally getting the subsidy issue worked out, and where things are headed.