Did some research and found this.
Being biodegradable and nontoxic, they are also safe for humans and pets to ingest accidentally. However, they are not produced in food-safe conditions, and are not recommended for eating. Also, during the manufacturing process, the nutritional value is removed from starch-based packing peanuts. This removes edible components, such as sugars, that would otherwise attract rodents and bugs.
So they may be biodegradable but they may not have much if any actual boost for a compost pile.
[url=https://www.engineerguy.com/comm/3294.htm]Bill Hammack on Cornstarch Peanuts[/url]
My wife and I got a package in the mail that fascinated me. I don't even recall its contents, because I was taken with the the green packing peanuts used to protect whatever it was from damage. As I scooped up the pellets to toss them in the trash, my wife said, with a very knowing voice, "Just toss them on the compost pile." What! Plastic in the compost? No. She showed me a slip of paper that explained: There was no "plastic or polluting gases" used to make these peanuts; they were made of cornstarch.
from this that they should be safe.
[url=https://itotd.com/articles/540/biodegradable-plastic/]Joe Kissle's take on the matter[/url]
The thing is, this is generally not in the nature (so to speak) of synthetic polymers. The interesting solutions, therefore, are largely to be found in biopolymers, a class of materials that look, feel, and act like the plastics we all know and love, but which, owing to their natural sources, can also serve as food for bacteria. Products made directly from cornstarch, other starches, or cellulose certainly fit that description. And such materials, which are used not only for packing peanuts but for things like fast-food containers, do show a great deal of promise. But if youÃ¢â‚¬â„¢re looking for something bacteria might like to eat, how about the food they make themselves?
Many different kinds of bacteria (and other organisms, for that matter) create a substance known as polyhydroxybutyrate, or PHB, that they store as an energy source in much the same way humans store fat. PHB, it turns out, is a rather versatile plastic. It can be produced in quantity quite quickly simply by feeding sugar to the right kinds of bacteria in what amounts to a fermentation process; it can also be produced by genetically modified plants (including a type of potato). Because it is, in fact, a bacterial food product, itÃ¢â‚¬â„¢s completely biodegradable. Another often-mentioned biopolymer is polylactic acid, or PLA, made from lactic acidÃ¢â‚¬â€which, in turn, is produced by the fermentation of cornstarch.
This sounds promising though it also make you think about what the future has in store for us. Even better biodegradable products across the board. Wouldn't that be nice, I suggest if you have an interest in this you at least read then entire story by Kissel.