And 500 years...so like 8-10 generations of people until it breaks down. And what does it break down into?
Styrofoam is 95-98% air, which is part of the problem why nobody recycles it. It costs a fortune to load up and transport all that material that is essentially air. I am not a chemist, but I learned that Styrofoam could be recycled and reused, but it's just not worth the effort.
The building block of Styrofoam is styrene, which is naturally occurring in some foods like strawberries. Last time I checked, strawberries are good for you. There does not seem to be much concern of ingesting small amounts of Styrofoam in the wild. The problem seems to be that nobody will recycle it and therefore it is just more waste for the landfills.
McDonalds used to be one of the biggest consumers of Styrofoam using those containers for their food, but in recent years they switched over to paper and light cardboard containers. I think that is good because those paper products can be composted. I shred almost all the paper and light cardboard packaging we get at home and throw it into the coop, into the run, or into the compost bins.
Until now, I did not know I could shred Styrofoam and use it in potting mix. Since I can no longer get Vermiculite at our local Menards, I think I will start to shred our Styrofoam packaging and mix that in the potting soil. If I come up with some way to shred it at home that works well, I might even do some dumpster diving and retrieve Styrofoam that others throw into the recycling bins (even though they are not supposed to put Styrofoam in those bins).
If I can't find a way to shred Styrofoam at home that makes it worth my effort, then I'll just buy a minimum order of 6 bags of bagged loose fill Styrofoam insulation. For $50.00, I would have enough Styrofoam insulation to last many, many years for amending my potting mixes.