Plastics contain things like BPA and Pthalates..chemicals that are hormone mimics and can leach into food/worms. Good choice. Plastic bins are all too common and everybody acts like they are safe when they really aren't. The plastics industry doesn't care about your health.

I just made a wood bin of cedar bought new from the lumber yard. I don't trust things like cedar fence posts on craigslist, I figure those could be treated too..or any used wood. I called the supplier to make sure it wasn't treated. Just cut and dried. Cedar is naturally rot resistant. Redwood works too although I'm not sure how sustainable that is, depends where it comes from.

Pressure treated wood has arsenic in it and copper too. Stay away from it.

Some particle board has formaldehyde in it.

Not sure about plywood, but that's glued together in some way too.

There are probably other woods that work. Pine is untreated but it probably rots fast.

I'd recommend calling your lumber yard and asking. After that, ask for their supplier's phone number and they should give it to you, for a double check. I did this and ended up getting cedar. It was expensive, $40 for a 12 foot plank that is 12 inches wide and 7/8 inches thick, but I made a bin out of it. I avoided using nails, and went for wood joints. Much more effort and time but worth it to me.

Ps, the bin was 2ft x 2ft x 12 inches deep - enough for two people to use every week. Almost the same price as the wooden ones on the internet. I think they go for $30-$40.

I was hoping that the 24 years its been out in the weather would be long enough for the wood to be safe. Guess I'll have to come up with a plan B.

I dunno, I guess it just depends how safe it is. It's hard to say how much of the deadly arsenic has leached out although there must be some kind of research on the issue..just hard to find.

Maybe there are some cheaper options other than cedar? Maybe pine won't decompose that fast? I mean if you spend $20 for pine and it lasts 4 years, maybe that's worth it to you. Maybe there are other options like oak. Not sure. Do some research and see what's available - I would suspect that pine would be ok, I mean it can't crumble that soon, you'd think.

I've found a lot of free pine on craigslist, the question is has someone put something on it. Most often you can see with your eyes whether that's been the case. I just found it easier to buy some new wood. Gave me piece of mind because I'm uptight about this kind of stuff.

Thanks for the info. Spoke to DH and he said he has some cedar that he can cut into boards. He's had it in blocks for a couple of years and hasn't needed it for anything. Looks like I will have cedar boxes for the worms and grow boxes too.

I am sure you could build a 3'x6' bin out of that old pressure treated wood. I would not use treated wood if I planned on using the vermicompost on food crops, although they would probably be fine. If the bin is open bottom, the worms would be fine and the vermicompost good for landscape and houseplants. Cedar would be better and safer, but will not last as long. I like re-using things.

Good Luck! Pete