moldy wood chunks

I am thrifty so I would try using it. Put the wood in a little earlier than usual , during VOC burn off, to burn off the mold. Try it first on a small, casual cook.

Small loss if you toss

If it's just a bit of surface mold here and there, I've actually cooked that off in the egg.  I actually piled as much would fig on the cooking grid, got the egg up into the 300s for a bit, and then just closed the vents.  

I've never seen smoking wood at the store sold in air-tight containers, so I wouldn't store it in a sealed bucket.  I suspect it should be allowed to breath, but also needs to be stored in a reasonably dry place.  I'm in FL (so high humidity).  Smoking wood left out on my covered patio will mold.  Smoking wood left in an open box in my garage doesn't.  So, that's where I store it now.