I assume they're getting out more potential energy than they are consuming in the process, otherwise what is the point?
//////////////////
I think they're 85% efficient meaning that of the energy potential of 100 lbs of turkey offal --15 lbs is used in the conversion process. The other 85 lbs becomes oil.
Here's a link to the original discovery magazine article back in may 2003
http://www.p2pays.org/ref/32/31035.htm