I recently made a pillow out of packing peanuts. Here is a picture:
I simply filled a .6 ounce stuff sack with them. They weighed about 1 ounce so the the total weight of the pillow is 1.6 ounces. The pillow is about 6" in diameter and 12" long. The packing peanuts are soft and flexible and more like closed cell foam than styrofoam.
This pillow isn't for everyone. The peanuts make a crunchy sound when I move around. This doesn't bother me but might bother my wife when she camps with me. It also takes up about 300+ cubic inches of pack space. I use a large pack and have plenty of extra volume so this doesn't matter to me. If you are down to your last few cubic inches of pack space this won't work for you.
I dare you to say that ten times as fast as you can.
I have seen/tasted packing peanuts made from some sort of edible corn starch. They literally melt in your mouth. Add some hot sauce for a tasty dual use meal after your last night out!!! And if you ever crave a midnight snack........
_________________________ If you only travel on sunny days you will never reach your destination.*
* May not apply at certain latitudes in Canada and elsewhere.
There are older packing peanuts that used to be made out of cheezies, sans cheese. So like blank corn pop type dealies.
I've tried them, dry and bland and yucky. They were in a parcel I got during Christmas a decade ago, yea I was young thats why I ate them... However, if you try to sleep on them, they will compact into dust. So use the styrofoamies or closed cell foam or whatever the heck you mentioned.
As for a pillow. I have a memory foam square, its not toooo light, but I can put it under my bottom when I am sitting, or under my head. I jsut have to remember not to eat the beans...........