Glad to see the gardening application info, thanks @FridayYet .
ETA: don't see a place to purchase and am curious about their cost.
Knew the PDZ was probably safe for the garden/compost, and figured but didn't know if the nitrogen absorbed in it would be available to plants or not.
I use a lip on board and is lined with vinyl sheet flooring which also helps with 'sticking', especially in winter.
Gets sifted out 2-3 times a week, depending on population, and goes to a friends compost.
Mixed with sand and about a 1/4" - 1/2" deep (any deeper and they tend to dust bathe in it) it lasts a long time just needs topping off once in a while.