Hi Nereus
WE have a cat and dog on board. Although we use the usual kitty litter, we have used sand from beaches, but a visiting yachtie did use a piece of synthetic turf with an eye hole in one corner for attaching
line to wash overboard.
She trained her cat and dog to use the turf by (for cat) placing turf into litter box and gradually reducing the litter until there was none and the cat was used to the turf on its''own.
I have yet to try this as we are stationary and not cruising at this time.
Hope this works for you.
Kind regards
Gail
Yacht Ramona
Austalia