RE: All Work and No Play...

Great, now you reminded me that I have to screen (filter? sift? sieve?) the compost. Good thing that I actually like that work - whatever includes a shovel, count me in :-D

I'd say that the black mulch is either just some kind of mold, or that carbon is used. Would be the cheapest, cheaper than any other dyes I think.

Sounds like a busy, but satisfying weekend :-) Thank you for sharing!

Edit: Brave LLM says - "Black mulch dye is typically made from carbon black or iron oxide. Both materials are safe for people, plants, and animals in the landscape."