I wouldn't do it. Juglone, the toxin in black walnut trees, is in the bark, leaves and wood although not in as high a concentration as it is in the roots. It is supposedly possible to use a compost that includes black walnut leaves if they have been allowed to cure for long enough. But a couple years ago I used six-month-old compost that included small amounts of walnut leaves as a small part of a container mix for tomatoes. About a month into the season, my tomato plants collapsed and died. No signs of disease, just complete wilting and sudden death.

Here is a link that might be useful: Toxicity of black walnut

Walnut is a valuable timber wood that you could probably bring you some $$$. If a local mill isn't interested, you bet some hobbyist woodworkers would be!

Yeah, I think you can get that tree taken down for free at least, and maybe even paid for.

We have already had 3 companies come out to give us estimates for taking it down...2 of them certified arborists...and they all told us the same thing, that saw mills around here won't touch our tree because we live in a large urban area (Chicagoland), and they would be afraid of nails or something in the tree that could break their saw blade! I wish I could find someone who would be interested in it.

I've had the same experience. I heard that there were people who would pay us to take the trees. But the arborists I've contacted said It would cost us hundreds of dollars for each of the five trees at the edge of our yard to be removed. That's why I grow almost everything in containers and can't even use my own leaves to make compost. And I live in a tiny village.