We’ve been using “sWheat scoop” which is made from wheat, compostable, clumping, and available at Walmart or Amazon. Some say it’s expensive, but it’s very pleasant to work with and makes an excellent addition to the compost pile.
Interested to learn more. We have an outdoor near feral cat that is aging and starting to use a litter box on the porch or in the house for a nighttime warm up.
I use this stuff. It's made from corn cobs mixed with some pine, smells great, clumps well, etc. Much prefer it to clay. For being made of an inexpensive, sustainable base it is not cheap but lasts for a good while.
We love feline pine. It’s the pellet kind. But our cats are indoor outdoor and only use it for pee. God only knows where they poop. When it’s getting a bit mushy I scatter it all in the meadow.