We used wood pellets for a long time with great success but I stopped due to number of reasons, one being that I guess they must use some clumping agents plus something to glue the particles into pellets and I am not sure what ingredients the companies use for that;
I also used corn clumping litter, which I suspect caused lower respiratory disease in my cat - although I have no proofs to support this claim, just my own observation.
After much research and many trials we now use grass seed litter - Smart Cat and the petco brand, So phresh, which is basically the same as smart cat but a bit cheaper. This litter is the most expensive I've bought so far and still far from perfect, but it's natural, less dusty (although recent bag was way dustier that previous ones), clumps very well naturally, cats don't seem to carry it around on their paws (although it's messy around their litter box, but not that much on couch/beds etc - robot vacuums does a great job with this). I am still looking for healthier and safer option, but I don't believe it exists at this point. I think I would never use clay (dust plus I imagine cats eat it while cleaning themselves) nor pine litters (alleged toxicity).
I also used corn clumping litter, which I suspect caused lower respiratory disease in my cat - although I have no proofs to support this claim, just my own observation.
After much research and many trials we now use grass seed litter - Smart Cat and the petco brand, So phresh, which is basically the same as smart cat but a bit cheaper. This litter is the most expensive I've bought so far and still far from perfect, but it's natural, less dusty (although recent bag was way dustier that previous ones), clumps very well naturally, cats don't seem to carry it around on their paws (although it's messy around their litter box, but not that much on couch/beds etc - robot vacuums does a great job with this). I am still looking for healthier and safer option, but I don't believe it exists at this point. I think I would never use clay (dust plus I imagine cats eat it while cleaning themselves) nor pine litters (alleged toxicity).