I either use mine for pathways or dump in the "stump dump" from when we cleared to build the house 20 years ago. That dump has rotted away to just mounds and weed trees now. I'd suggest on those walkways, you keep any walnut out from under even large trees.
OBTW, scrap cherry, oak, maple, etc (not BW) always gets custom made into chunks for the grill and smoker. Hardly ever cook without it.
Rich