“Tofu litter” sounds like one product. It isn't quite.
Tofu-style litter is made the way tofu is made: plant fiber left over from processing beans, pressed into small pellets with a starch binder and a little stone powder for hardness. Which plant the fiber comes from is where brands part ways — and the two you'll actually find are soy and pea.
Soybean fiber
The original, soy fiber pellets carry more leftover protein and oil than pea fiber pellets, and that shows up a day or two in, when the box starts to smell sour and beany. The pellets also powder more as they rub against each other, and the clumps tend to cement to the bottom of the pan.
Tofu litter made of soy fiber is the most common, because soy fiber is the cheaper raw material. It's the fiber left after soy is processed for food.
Pea fiber
What we use, and the only fiber in our pellet. Pea fiber absorbs more per pellet, so you get through less of it. It holds almost no leftover protein or oil, so it stays neutral when it's wet instead of turning.
Pea fiber breaks down into powder more slowly than soy fiber, which means less dust. Pea fiber clumps set faster and lift off the pan instead of sticking to it. You can even see the difference before you use the litter — pea pellets are paler and smoother, soy pellets are yellower.
So which fiber should you buy?
Both work. The difference shows up on day three, not day one — whether the box has gone sour, whether the clumps still lift whole, whether there's a layer of powder at the bottom of the bag.
The more cats you have, the more this shows. More digging puts more dust in the air, and more waste gives the litter more odor to hold — so a multi-cat home notices the fiber it's using faster than anyone.
Whichever you pick, check how much stone powder is in it. That varies more among brands than the fiber does, and too much stone powder ruins the litter — here's how to check yours in three minutes.