I have a plastic kitchen trash can (13 gal size) that I keep filled with hay in our laundry room. That's what I use every day.
I have a secondary, larger plastic tub (55 gal) out on my porch that is filled with hay and is used to refill the kitchen trash can. It can refill that trash can about 5 ? times.
The full bale of hay is covered with a tarp in the back part of our property and can fill that 55 gallon tote about 5 ? times.
We live in the desert, so mold isn't a problem with the plastic. But I believe that the plastic doesn't work so well in more humid areas unless punched with air holes.