Best eco-friendly cat litter?

[Roundaboot]

We're adopting two rescue kittens (age about 5 months) this weekend. They'll be kept in until they're settled (and the female cat spayed) so we need to install a litter tray and suspect we'll get through a fair amount of litter.
I'm looking for something that is a) eco-friendly b) not too expensive and c) doesn't get tracked all over the house! We used to use wood pellets for our old cat, on the rare occasions he was kept in (he usually did his business outside) but I've been reading reviews on Pets at Home and it looks like the quality has gone down?
Would really appreciate some recommendations!

I use worlds best cat litter which is brilliant and I think bio degradable. Not cheap but lasts an age. One of my cats is a furious litter tray digger so it does end up everywhere, but it doesn’t track that much. And doesn’t smell!

Breeder Celect recycled paper cat litter, 30litres, about £12 or £13 from Amazon

Super Benek corn litter, made from the middle of corn on the cobs, so a waste product. Fantastic at trapping smells & lasts ages. Clumps well & doesn't stick to long haired DCat's floofy bum

Worlds Best is amazing.
It is expensive but a bag lasts ages and ages.
i have two kittens and the litter box never smells with this and it is so easy to clean. It clumps well so you never get the layer of wet at the bottom.
I use a bag every 6 -8 weeks with two indoor kittens (7 months old).
I also have a lidded litter tray and a mat so it is all contained.

We also like Benek, I buy it from Zooplus

We use this one. I prefer it to the wood tbh and just put it on repeat delivery.

They'll be kept in until they're settled (and the female cat spayed)

Does that mean you have one of each sex, both unneutered? Eek. At five months, kittens having kittens is not that unlikely, even if the other one is her brother.

Or does it mean boy cat has been done but not girl cat?

Boy cat has had the snip already!

Thanks for the recommendations everyone!

If you have an equestrian/country stuff shop nearby, try getting the wood pellets for horse bedding! I used to use Sainsburys or Waitrose wood pellets which my cat preferred @ £4.50-5.00 a bag. Dad was paying £7 for his 10 litre sack of wood pellets! Nicked a bag a few weeks ago and was blown away by how much more moisture they hold and by how much cheaper they are! unfortunately had to have cat PTS a couple of weeks ago but wish I had twigged about these horse bedding pellets earlier!

We have three indoor cats and use Greenwoods - it lasts forever, doesn't smell at all and it's not too harsh on their paws.

We buy from ZooPlus but I'm sure you can get it elsewhere.

We use Nature's Calling made from walnut husks. Flushable. No smell

@Roundaboot

I have a thread on litter, this week. I won't use corn based litter as it seems to be causing an allergy (Worlds Best and Benek). Used both in the past, Benek was the better of the two, Worlds Best, if not stored correctly during manufacture, can be smelly and contain mould. Not great if you have the really big bag. It is soft on paws but I think the health issue is something to consider from mites and fungus spores and am not keen on it. Maybe Benek would be the same, but I couldn't find it again, other than the perfumed versions so gave up on it.

Cats Best is a good one, Greenwoods do not specify what it is made of and it is a bit hard, so I no longer get that.

Clay can clump when licked off paws and clog up the digestive system in kittens. Bentonite is also clay.

Perfumed litter can cause allergies or put them off using the tray. Paper litter is soft but goes everywhere and doesn't clump.

Silica is hard and crunchy, doesn't clump. You can also get tofu based litter which I have not tried, and don't want to.

I would go with a clumping wood based litter (Cats Best, Natusan).

I was recommended Natusan and have bought it, looks pretty good and ethical.
natusan.co.uk/