These food bags do contain foil.  And many I think burn them then pack out the foil, unfortunatlly many don't pack out the foil.  I have done both burn and wash bag and pack out.  These bags are the same type bag the freeze dried food comes in.  The reason we tend to burn them is to get rid of the food smells.  More ansd more people are using them we found lots of foil in the Q last year.  I think we packed out more that we found than what we had outselves.
By the way they also have ham in these bags. (cubed) I take a bag of ham and add it to the dried cheesey spud meals.
qp