Years ago when we had cats there was a pellet product on the market that was made from alfalfa. We found it to be the least offensive as far as smell. (My DH has allergies, as it turns out to CATS!) Haven't had a need for it in years and don't know if they still make it but one thing that we liked about it was that it was environmentally friendly and broke down easily. You could even flush it down the drain into the septic tank unlike the clay product.
Ann in TN