I don't really know the answer to your question. But I do know that there is some kind of chemical in black walnuts that prohibits growth of a lot of plants. Therefore I wonder if compost with black walnuts in it would do the same?
Thanks Gingerlily. But that sure isn't what I was hoping to hear. We used about two truckloads of it on a steep hillside garden. The compost has held extremely well.The plants there are doing quite well for the most part. Maybe its because the drainage is so good and the bad chemical washes away. But it may also be affecting the flatter gardens adversely. Sure wish we'd have thought of this earlier.
The compost is 3 to 4 years old depending on where in the pile you dig. The shells don't seem at all broken down and I pick out as many as I can when I put it down as they aren't nice to step on with bare feet, either. You can get the compost by the pickup load for free and its such great stuff! So hoping your info is correct. It gives me hope!
Well, now, what I was referring to is the black walnut tree inhibiting growth of some plants. In other words, certain plants don't grow well under or near a tree. Maybe the walnuts themselves don't have that same chemical. On the other hand, as old as your compost is, that might make a difference too. If some things are growing well in it, just pay attention to what doesn't grow well and don't use it for those plants.
Can't turn down free compost if it's good for some plants.
... the juglone in black walnut trees is highly concentrated in the roots, a little less in the bark & nuts, and even less in the leaves. Water doesn't do much to juglones, but oxygen breaks the compound down. The consensus seemed to approve of composting black walnut leaves, as long as the compost gets plenty of exposure to air for at least four weeks.
As for the nuts? I guess you could burn 'em. The juglones would be thoroughly oxidized, and you'd be left with charcoal & ashes.