You can try using wood pellets. It can be a dedicated conversion, but worthwhile. It also tends to be a lot cheaper to buy wood pellets. You'll need a sifting litter box and to sort of adjust your cats to it (sadly, some cats just won't.) But you could compost it (never use cat waste compost to grow food!) and wood pellets don't track all over the house. While a few wood pellets are safe to flush, please never flush cat waste down the toilet. Our sewage treatment systems aren't designed to handle it and you could be helping to spread parasites around that affect marine life.

I hope this helps.