Actually, Sarbar's Freezer Bag "Cooking" method isn't cooking at all, just rehydrating. The food was cooked before dehydrating.

You don't cook the food in the bag, you just boil water and pour it in the bag. By the time you've gotten the pot off the fire, made sure the freezer bag is open wide but won't fall over (takes a little adjusting) and pour in the water, the water is well below the boiling point. It's probably no warmer than blanched vegetables when you bag them before freezing, the standard way of home-freezing your veggies. The bag then sits in your cozy for 15 minutes or so until it is rehydrated. By that time, it's generally cool enough to eat.

Of course you can rehydrate in your cooking pot, but then you have to wash the pot!

Since I pack out everything, the freezer bag from my dinner carries the garbage for the next 24 hours. It's not a good idea to burn plastic even where campfires are legal--leaves residue in the fire ring. Aluminum is even worse and I am sick and tired of seeing fire rings full of it. I swear that half the garbage I pack out is junk that other people have left in fire rings!

The biodegradable feature of the cellulose bags, though, sounds really good! I probably should consider using them, bite the bullet and wash my cooking pot nightly!