Sure you can compost them. If you require urgent compost for some reason then hold off on them, but otherwise, no problem. They make a good mulch too.

Dave

I put some in my compost last Christmas--and they are still very much intact. So I do think they will take awhile to compost, but that's okay!

We occassionaly get Pistachios and the shells always go into the compost. Just how long they may take I am not sure but I do know that when I empty the bin, about a year after, I find none of those shells.

I throw anything like that in the bin. If I am harvesting finished compost and they have not broken down, I just toss them back in.