Litter advice - indoor cat

[ObelixtheGaul]

Our new beautiful rescue boy is an indoor cat as he has health issues. I have never had a cat that doesn't go outside.

My question is about litter. We use wood pellets in an open tray at the moment. I am loath to get a lidded one as apparently a lot of cats don't like it. I empty solids out every day, often more than once and empty the whole thing every two or three days, but the litter odor hits me when I come through the door after being out.
I want to use a biodegradable litter rather than a sillica-gel based one.

Should I empty the whole thing every day, or is there a better biodegradable litter I could be using? Have any of you used a covered tray, and were your cats OK with it? He's an older street cat who is great at using the tray, I don't want to put him off using it altogether by introducing a lidded one.

It's not that we never used trays before, our other cats were always in at night so I kept a tray for them on case they got caught short, but have never had a cat who will only be using an indoor tray.

I would appreciate any advice.

I have had a couple of cats who liked to eat the clay-based ones so watch out for that (weirdos), and the cereal-based ones apparently sometimes have little critters living it!

I have this litter box from Pets at Home, it's been amazing.

I also use Fit Litter, it's colour changing so tells you if urine is not right. No smell and only change it monthly. Costs £18 a month. You just scoop poo out and then stir it.

It really is the best litter I've ever used, and I've tried loads!

I looked at those litter boxes, did your cats use this from a kitten, or were they introduced to it later in life?

Ivy Cat is 10, I've had it for three years. I got it in the sale, it's the best one I've had. She's quite a large cat to, over 5kg and she's been fine with it.