Cat Litter Compost, Installment #3


No, our cats aren’t privileged or anything.

A gentle reader reminds us that it’s been too long since we updated you all on the cat litter compost.

For background, see Installment One and Installment Two

Long story short, cat litter composting can work (under the care of an experienced composter, mind), especially in conjunction with a worm bin–but I’ve found a method I like better.

On the composting experiment:

In our last episode of Cat Box Madness, I discovered my kitty litter wasn’t breaking down very quickly, so I added nitrogen to the mix. That seemed to work well. All except the first 7 inches or so is really nicely broken down all the way through. I still wouldn’t put it as it is anywhere near food crops, even though it is two years old, just to be safe.

To make it extra safe — and useful — I’ve been letting the worms have at it. I’m using it as part of the mix that forms the worm bedding, so cat poo will become worm poo and the garden will be delighted.

That’s how I plan to dispose of all of it, bit by bit. If I didn’t have the worm bin, I’d call it done and spread it under fruit trees or ornamental plantings.

Lessons Learned:

1) Make sure your pile is accessible and easy to turn. Due to lack of yard space, I put my litter in a 50 gallon drum in a narrow, hard-to-access–and hot!–side yard. This meant I never wanted to tend it, and when I forced myself out there, I was pretty unhappy. There wasn’t even enough room to wield a shovel comfortably.

2) A big pile is a good pile. While I made this work in a 50 gallon drum, the best compost comes from a bin which is about 1 cubic meter/yard in size. Smaller bins just don’t heat up sufficiently, and are invariably pokey and hard to work with. If you want to do this, do it big.

3) Careful with the litter you choose. Not many litters make the grade. You can’t use clay litter, or any litter made with deodorants or coloring or “magic crystals” or tiny unicorns. It must be made of 100% plant based material. I approve of both World’s Best and S’wheat Scoop. Pine pellet litter, like Feline Pine, is much less expensive than the clumping brands, and suitably plant based, but under ordinary circumstances, since its not scoopable, you have to dump the whole tray rather often, which leads to a fast build up of material. If you have room for it, this might be okay.  (I’ll have more to say about pine litter further down, though.)

4) You have to add extra nitrogen to your pile to make it work. Even though it’s plenty stinky, the nitrogen present in cat waste can’t balance the heavy carbon loads of the litter by itself.

(Note: You should be an experienced composter before you try composting cat litter, as I’ve warned before, and so you will of course know what I mean by all this talk of carbon and nitrogen–but for those of you who are incorrigible, or simply curious, nitrogen sources you might add to your pile include urine, natural seed meal fertilizers, dried alfalfa, fresh grass clippings and other plant material, fresh chicken, horse, or cow manure, and vegetable trimmings.)

Other than those caveats, cat litter composting works pretty much like regular composting. Keep the pile moist. Keep an eye on it, fix it as necessary. Let it sit for two years at least before you spread it. And then spread it around non-edible plants, or under fruit trees. The fruit trees won’t uptake anything nasty.

It’s totally do-able and I’d do it again. But I’d rather do it again in a larger yard, where I could have a big, accessible compost bin. So now I’m doing something new.

The New Paradigm

I heard about a new kind of litter tray made specifically to work with pine pellets. I hate to be advertising–I get nothing out of this–but there’s only one and it’s called the All Pine Self-Cleaning Litter Box. (And that name is pretty dubious, btw, because I spend plenty of time cleaning the boxes still.)  Anyway, it’s basically a nesting system, two trays nested together. The inside tray has a perforated floor. The lower tray is solid.

The way it works is that pine litter, when it meets moisture, expands and crumbles into sawdust. This dust just builds up in a regular box, but in these perforated boxes the dust falls through to the bottom bin. You help it along  by giving the box a shake when you’re scooping. This construction isolates the pee-soaked dust from the poo–and the clean, intact pine pellets. Once you scoop the poo out you’re left with clean, whole pellets.

The following photos will probably explain this better:

litter box

The nesting boxes filled with pine litter. (Another prize winning photo from Root Simple!)

perforated floor of the litter box

The entire floor of the upper box is filled with holes like this. The dust falls through to the box beneath.

dust view

An unsavory photo of the dust collection area. This box was is need of changing. I dump the dust every 2 days. DIYers note the little support legs.

You could of course DIY this system. See some notes at the end for tips on that. I considered it, but for various reasons decided to throw money at the problem instead of making it a project.

I really like this system because

a) It’s much neater. Pine litter is less dusty than clumping litter, which means less tracking, less dust on surfaces, cleaner cats.

b) And it’s cheaper. Pine litter cost less than clumping brands, and I’ve heard that Equine Pine, bought in bulk, is much, much cheaper per pound than the kitty brands. Next time we go to a feed store I’m going to check it out.

c) The urine soaked sawdust can be sent to the normal compost pile. The urine dust forms the majority of the waste material generated by the cat boxes. So I’m still composting say 80-90% of their waste, but with much less trouble.

(Note: It’s the poo which has the scary stuff in it, after all. If there’s any residual traces of scary stuff (that’s a scientific term, by the way) in the sawdust, carried along  by microscopic pieces of poo,  I don’t really mind, because between the cats bathing on our dining table, sleeping on our bed pillows, and the one cat that likes to stick his paw in my mouth, I’ve met all their bacteria and parasites already. And anyway, it’s all going to go through good long composting cycle.)

In sum, this is a good way to go for anyone who wants to recycle at most of their cat litter.

The weak spot, of course, is the poo. The poo can go in the toilet or into the garbage. Even with three indoor cats, day to day this doesn’t amount amount to all that much.

I understand that sea lions are impacted by toxiplasmosis, which is why I don’t flush our cat poo. I don’t know how much this caution is worth, actually, considering the staggering amount of cat poo is laying around in yards and parkways all over Los Angeles, ready to roll down the storm drains with the next rain. But nonetheless, as of now I send their poo to the landfill.

It’s a compromise. I’m pretty happy with it.


DIY IDEAS:  Some preliminary notions that I considered: Make sure you have enough clearance between the lower and upper box. You’ll want at least two inches to accommodate the dust. You need tons and tons of holes on the bottom of the inside tray for it to work correctly. It might be difficult to balance the structural integrity of the floor with a sufficiency of holes. And speaking of structural integrity, the bought boxes have many little legs on the bottom of the inside tray to keep the tray firm under the feline foot. You’ll need to improvise some sort of support to keep the floor from sagging.

Leave a comment


  1. I applaud your efforts but once upon a time I used wheat and corn cob litter and tried to compost it. Then my dog ate a whole litter box full of the corn cob stuff. He became very very ill. He had to be transfused and that’s how I learned that they use strong dehydrating chemicals to prepare those vegetable materials as litter.

    Once I learned about the desiccants in it it didn’t seem so important to compost it anymore.

    I also ended up passing on the wheat stuff when we got an infestation of those grain weevils.

  2. How is living with a cat cleaning itself on the table and living in such close quarters all the time any different than using not-quite-composted compost? Cats allowed on the table, counters, and beds are spreading fecal matter whether anyone wants to acknowledge it or not. I have not had a cat in the house since I was fourteen-years-old and discovered I was allergic to cat dander. Now, I would not have one because of the pathogens scattered on objects and in the air.

    I really don’t care if anyone lives with fecal matter, so this is not an admonition. Plus, all the cat poo in yards and dirt anywhere does get walked back into homes, even hospitals. Where does caution begin and end? (Just leave the chicken poop I just walked into the house out of the discussion.)

  3. My two cats and I reside in Belize where cat litter is rare. I quickly tired of crossing into Mexico and having to lug the containers of clay based litter through customs. After reading your cat com-postings #1 & #2 I decided to switch to a plant based litter, one that could be found locally, and try my own cat compost experiment. Wood shavings and chips work. Easier to find, use as litter and then to compost are grass clippings which I rake into bags and are free. It isn’t absorbent and has to be emptied daily but a small amount provides the medium in which the cats do their business. (By the way my cats are particular about their toilet. For a couple of days they were confined to a small bathroom with their litter pan until I made sure they would use it.) Cleaning is as easy as dumping the litter box contents into the bin, a trash can composter. Rinse water is dumped in as well. Occasionally I throw a few food scraps in before the litter. There hasn’t been any odor. Fluid does leach out onto the ground through the holes in the trash can. So far this has worked out well for me. If I can set up a worm bin I will do that for phase 2 although I haven’t seen a worm here in Belize yet. Thanks for your information!

    • Interesting! Grass clippings! I’d never have thought about that–but it sounds like it works. The advantage is that the clippings won’t be as carbon heavy as litters, so will promote faster decomposition. If it’s too fast, ie too stinky/slimy, one can always add some more dry stuff to balance it out. So glad you’ve found a system that works!

  4. Just LOVE all the pictures of your kitties! I can’t add any info about litter but am interested in seeing what works for you. My cats are inside cats who will used what ever litter is put in their litter box and personally I like to make sure it ‘scoops’.

  5. Unicorns!!!

    Awesome post. 🙂 I had to switch from the pine to the paper liter – my little Miss has the *worst* allergies, and the pine seemed to be contributing. She’s a million dollar baby, that one!

  6. So impressed with your efforts and diligence, and knowing things like sea lions are affected by toxoplasmosis, which affects your decision about the ultimate fate of the cat poo. Glad there are people out there going the extra mile on behalf of the environment

  7. My husband made a DIY pine litter sifter with 2 nesting storage tubs & hardware cloth. Scoop poop, then dump contents of box into sifter. Shake. Dump dust straight into compost.

    • So you have a regular litter box, but manage the dust with this sifter — right? That’s a great idea. I spend a good deal of time sifting in the boxes, and that sounds like a faster system. DIYers take note!

  8. Hello just started using the litter box and needed to know how much, or high, should the litter be in the box, I feel i am putting to much in. Thanks

    • Yeah, you don’t need a lot. Maybe 2″? The trick is to shake down the dust every day. If you skip it and it builds up and gets all dusty and harder to deal with.

  9. This question isn’t exactly on point, but I was hoping you might be able to provide some insight since it’s related to the feline pine litter box. I recently switched my litter to feline pine, and love the idea of the “Self Cleaning” box they make. However, I’m in a pretty tiny apartment and my cats are large, so I use a Petmate Jumbo box 21.8″x18″x18.5″ since we need the cover and high sides…

    I was wondering if you could provide some insight into whether you think it might be possible for me to fit the sifter portion of the box into my regular box? Thanks 🙂

    • The boxes I have are pretty small: 17 long x 13 wide x 5 deep. Seems like there’d be too much room around the edges if you put one of these inside your boxes. A better plan would be to make your own system using two nested jumbo boxes. There’s an Instructable on it somewhere, I believe.

      I’m thinking about adding some more info to the post on what I’ve learned using the pine litter boxes for a few months now. I’d warn that it is no less trouble to use than clumping litter — it’s just different. I didn’t like clumping litter because the natural sorts were expensive and they also generated lots of dust. Pine pellets are cheaper and much less dusty. I can also compost some of the pine dust, which I like. Finally, I think it is less stinky overall.

      But on the maintenance side, it is work. The dust does not fall through the holes in the inner tray on its own– it must be shaken or raked to encourage it to sift through. So, every day, a least once a day, I scoop poop and rake the trays of our two boxes to get the dust to fall into the lower tray. Then, every other day I have to empty the wet sawdust out of the lower trays. That’s in the case of two boxes for three indoor cats.

      The trick, I’ve found, is to use a minimal amount of pellets in the top tray — just an inch or so. If that layer gets too deep, it’s almost impossible to get the sawdust to shift down, and you may as well be using a regular box. But if you keep on top of it, keep that top layer minimal and shake and rake diligently, the box is always full of a nice tidy layer of whole pellets. This is also the most economical use of the pellets, since no whole pellet is ever thrown away.

      Good luck on your box quest!

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  11. I found your articles very informative and entertaining! I am new to composting, but I get the gist. I thought in one of your earlier blogs you stated that the nitrogen was supplied by the urine and the poop? In this last installment it sounds like you send the poop to the landfill? Did I miss something? I am going to pursue this further and try to find a composting class/seminar I can take here in Anchorage. Thanks for all of the great info!

  12. I built a composter a year and a half ago and live in New England. Ive found it seems to rot and break down fine, but all that stops when winter hits. Also will begin using some form of sifting litter box as you suggested. Seems the easiest, safest and cheapest way to combine cats, composting and environmental health. Since I have Lyme Disease and already have suffered from Bartonella, I can tell you all that you don’t want to increase your chances of getting it anymore than you have to (by getting too close to cat poop) I’ll be happier using the contents of the next cat compost bin which includes no feces, and know I can safely use it on vegetables down the road a piece. Here’s to a safer compost pile, healthy cats, vegetables, and a lighter landfill. As you said at least digesting the feces seperately seems the best option.

  13. To clear the dust and poop from pine pellet litter, we use a basic plastic scoop into which we drilled lots of small holes. All we do is scoop, shake out the dust to remove, and return the intact pellets back to the litter box. Any poop is easily scooped from the litter box.

    … just thought I’d contribute our simple and inexpensive solution. 🙂

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  16. I use the pine pellets. Love them. I only have one little indoor kitty so I just change every few days by dumping into garbage. I feel compelled to say that one should be wary of clumping litters, as kitties lick their feet and that CLUMPING stuff goes into their intestines, where it can CLUMP. Seriously. I researched the heck out of litters after I had a lovely Maine Coon die from standard litter silica that got in her lungs. X-rays were identical to the lungs of miners. And why? Because I added those covers to keep my floor cleaner, but cutting ventilation. Big mistake. So, no silica litters and no clumping ever allowed in my life. And no covers. Just the pine, which is easy to use.

  17. Have you tried the Walnut shell litter? It’s amazing. I swear that it smells like I’m baking muffins when I scoop the box (I have three cats so I really stay on top of it). I have been composting the urine for a few months in a good old compost pile (kitchen waste plus dryer lint, coffee grounds, egg shells, hair brush debris, bits of cardboard and paper products… pretty typical). I am blown away at how crazy awesome the compost is with the addition of the litter. I turn it every couple of days and it’s steaming and smells amazing. I only use it on ornamental plants so I have no worries. I use all different litters and mix them– wheat, corn and walnut. I haven’t tried the newspaper yet, but I will. My logic is that a little bit of everything is better than all one thing– so if I find out that the one thing is bad, I was only using a little. Right? Thanks for your posts on compost. And for your cat pictures:)

  18. This is wonderful! thank you so much for this page. We are attempting to become a zero waste home and we have it narrowed down to a couple non-recyclable plastics and cat litter. I have since learned that composting cat poo is a big no no. with the pine pellets method i can still compost and simply dispose of the poo the same way my own poo gets disposed of. Thank you again!

  19. Thanks for that.
    We have an indoor ferret, and use a rice byproduct (Coprice Max’s cat litter) which smells quite nice, like ricebran, and is good and absorbent. Ferret wee and poo is much less stinky than cat stuff. We do just dump it all in the compost or the worm farm. I admit I haven’t looked into the safety of that. But I did look hard for info about the effect of anti-flea stuff in composted animal poo. Our vet recommended a particular topical flea and worm killer, but I actually found online a detailed description of one person’s data regarding the relative toxicity of various flea killers via cat litter towards garden worms. Have very rarely used the stuff but we did choose the product that killed the least worms, as we wanted to keep composting the litter.

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