Cat Litter Composting

Pocket Nitrogen Generator

 Mrs. Homegrown here:

Apologies to you googlers looking for solid answers. This is what Erik calls a probe. I’ve decided to compost our kitten’s litter box waste, and this is how I plan to go about it. However, I’m sure I’ll learn a lot as I go, so this post isn’t instructional. I will post a report once the system gets going.

The real reason I’m posting is because I’d love is to hear from any of you who do this already–tips are much appreciated! I’m particularly interested in finding a good brand of litter that composts well.

The basic gist:

Okay, first, anyone who’s gone through Composting 101 knows they say not to put pet waste, especially dog and cat waste, in your regular compost bin. This is because cat and dog poop contains pathogens. We never composted our late dog’s waste, and for 12 years we sent at least two big plastic bags of poop to the landfill every day. Parents who use disposable diapers got nothing on me in terms of environmental guilt.

Now we’ve got this cat, and I’m looking in her litter box and seeing nothing but carbon and nitrogen. I can’t stand it. I’m disregarding Composting 101 rules because I know this can be done, if done carefully. Over the years I’ve learned to be amazed by the Cleansing Power of Compost & Time, especially since we started doing some humanure composting. Check that link for more info on Jenkins’ good work in that area–research, technique, message boards, etc. It’s all there. Human, cat and dog waste are all more tricky to work with than your more benign chicken and bunny waste. This isn’t something one should do in a half-assed way, but it is possible.

The plan I’m going to follow is the basic humanure model, which is classic composting, but with lots of attention and care, followed by a 2 year rest period for the full bin, during which time worms and bacteria do their scrubbing magic to help remove any lingering nasties. When the first batch is done, I’ll have a sample lab tested, just out of curiosity.

Whatever I do, I won’t spread my finished compost on food crops, but instead under our trees and around our perennials. 

I have considered doing this via a worm bin, but as I understand it, the worms don’t like the fresh pet waste–and understandably, too! They like to come in when it’s broken down a bit. I’ll definitely add worms to the bin when the rest period begins. But if anyone has a pet-waste worm bin, let me know how that’s going!

Now I have to find a spot for (yet another) bin of poo in our yard.

(Do I hear the soundtrack to Deliverance playing, or is that just my imagination?)

Update: Read what I decided to do in The Cat Poop Portal

Leave a comment


  1. When I read the humanure part of your new book, my first thought was, “Wouldn’t this work for kitty litter?” It’s on my list of things to try…I’ll be interested to hear how this works for you.

  2. I haven’t attempted to compost the solid waste, but I use Trader Joe’s compressed pine sawdust litter and all the litter and urine go into my compost pile. The package says it’s safe to use as a mulch as is.

  3. I think your plan sounds really solid. I have never done it, but if I was going to, it would be like this.

    Nit pick here, but won’t you need to find place for 2 poo piles? Just one to start with, but when that one is full and it enters the 2 year rest you’ll need another pile to put the poo in.

    Are you going to combine your humanure pile with the cat poo pile?

    You’ll want to remember to keep pregnant ladies away from that poo pile, just in case the toxoplasmosis bug doesn’t immediately die. (I think.)

    Good luck! Do keep us in the loop!

  4. Good luck. What about drying the litter and manure first to kill pathogens and then composting? I will be interested in your results.

  5. You should read “Holy Shit: Managing Manure To Save Mankind” by Gene Logsdon. He covers most types of manure, including cats, dogs, people, worms, cows, chickens, horses, rabbits, etc. I have mine loaned out at the moment or I would relay his recommendations on cats.

  6. We don’t compost our kitty’s waste, but we -do- use Yesterday’s News litter. It’s compressed pellets of newspaper and once it soaks up a bit of moisture it turns into wet paper pulp – I am sure it’d break down pretty fast if you watered it. Our cat was used to sandy kitty litter, so we had to mix the two together for a while until she got used to the pellets.

  7. @Jennie: Yes, I will need two bins. I didn’t mention it, but you’re absolutely right–one for aging, one for active. Folks with dogs who don’t have the litter would need three–one more bin to store carbon material. It takes space, for sure.

    @Ches: I trust the composting process itself to kill pathogens. We have a good friend who’s been doing lots of humaure composting–big projects with multiple families, and her compost always tests clean. It’s totally possible to kill pathogens through heat, bacterial processes, and time. Drying would work, true….but how to do it? I’m imagining cat poop spread out on dehydrator screens! Wouldn’t our neighbors love us?

  8. @David: thanks for the tip!

    @Rena: We’re using Yesterdays News right now. Don’t know if I’m satisfied enough with its odor controlling properties. As a first time cat owner, though, I don’t know if it gets any better than that! It is nice to use paper instead of trees, though…

  9. @Mr. Homegrown: Did my traveling husband sneak in a comment? He’s talking about these vertical worm towers that are planted in the ground–we’ve posted about it before. I’m not sure if the worms will be happy getting loads of cat litter poured down their tube. I think they like it to come to them a little broken down first.

  10. Great site, I had heard about it yesterday. My mate and I are also doing similar lifestyle things. We are no were near the pro you two are, but we hope to be someday. Sorry I don’t have any input on this other than, I have heard about burying The poo in some remote area of the yard and allow it to compost on its own(wont be reusable which your going for im guessing). PS We find your blog very empowering.

  11. @Janna: Yes, I know people who scoop the poop and compost the litter and urine. That makes sense.

    I’m surprised the bag says it can be used as mulch as is. I’m not sure if I would do that. If you put carbon-rich material on the ground, raw, like sawdust, for instance, it will leach nitrogen out of the soil as it breaks down, robbing your plants. The urine may offset this some, though. Hard to say. IMHO it would be better to send it though the compost cycle.

  12. You know, I’ve used stove pellets in place of Yesterday’s News…you can buy a 50 pound bag for under $10 here. I’d imagine you can find them where you are…just another alternative to the spendy Yesterday’s News.

  13. You can use sand, wash, and dry and reuse. Now, if you contact meetsy At Yahoo dot com, she does this all the time, washing sand, that is. You save packaging, product, and composting costs and time. I think you just dry it in a pan in the sun, another pathogen killer–the sun. Mrs. H, you could ask her and she would be glad to tell you. A forty pound bag of play sand should be enough for two boxes, one to use, one to dry. Although, I think she said it dried fast. I should have paid better attention. But, I only have hens. Of course, you dip the poop first.

  14. No recommendations regarding compost, but regarding litter, I switched from Yesterday’s News to Feline Pine/off brand pine cat litter. I find it has superior odor stifling abilities.

  15. We use small animal bedding or wood fuel pellets (no additives – pine) as litter and our cat loves it. You just need a very large scooper. Use the edge of the scooper to pick out the poop. Then dig into the wet sawdust piles, sift the dust into the bag and throw back the pellets. Sounds like work, but it’s easier and less messy than cleaning clumping litter that sticks to the scooper. Also – very cheap and long lasting, no odor.

  16. @Mrs. Homegrown: The TJ’s compressed sawdust litter does not smell much. I think it’s refuse from milling, rather than virgin trees – at least I really hope so! I agree that composting it is the way to go. Mulching with it doesn’t make sense to me either.

  17. We use Feline Pine – or essentially pine sawdust squished into pellets. It has the same texture as Yesterdays News, but controls urine odor better.

    And since we have maaaany cats, we get the “premium pine pellets” or “pelleted horse bedding” at the local feed shop for about 1/8th of the cost of actual Feline Pine, and it’s completely identical. Comes in bulk bags, so less packaging, too. If you get the special two-tray system, you’ll throw out only the spent pellets, and the kitty will be happier walking on fresh pellets always.

    Been composting the litter for about 2 years now, (flushing the poops) and have even put it directly in flower beds with no problem to the plants. Those pellets crumble when wet, and hold a ton of urine. I’d say it’s a nitrogen boost more than anything.

  18. I haven’t done it yet but I was totally thinking of the scoop the poop/compost the rest tactic. I await with bated breath and pinched nostrils to see how your experiment goes.

  19. i don’t have any advice in this department, but i do use pine cat litter and like it. but i am totally open to being able to make use of my kitties poops. please keep us posted! i would love to know what you find out in your process. i might have to try myself (although we were considering having our cats learn to go potty in the toliet). congrats on NY article! and that is one super cute kitty!

  20. I haven’t read the responses, but we use the “feline pine” and I’ve often wondered about composting at least the nitrogen-rich sawdust that’s left at the end (the pee breaks down the pellets into sawdust, and you scoop out the poop). I haven’t added it to my compost bin yet just because I know there’s still, like, poop particles in there. I guess I wonder how pathogenic they are?

  21. Hi Kelly,
    cityfarmer,org (very cool canadian website!) has an instructional video on how to make a pet waste composter. I discovered it right after I had spent 130 or so bucks on a commercial one, only to find that I could have built the same thing myself practically for free! See below:
    or go to and scroll down halfway through the page.

    BTW., I heard your husband speak at the statewide Master Gardener Conference in Santa Rosa yesterday: it was the most entertaining presentation we had all day – thank him for that: I really needed some comic relief!
    Hope your migraine is better –
    Gabriele ([email protected])

  22. With three cats, we use Sweat Scoop (although I’d like to try the cheap pine pellet suggestions here) which has done a great job with managing odors and is easy to clean up. We added some (poop scooped) to our fledgling experiment compost pile. When turning it, the litter seems ashy- is it possible it’s burning? Composting is our newest adventure of zillions to come.

  23. Well, pine litter seems to be winning the day…

    @Jessbot: Love the two tray system!

    @b80: Toilet training kitties intriguing (and it’s pretty darn funny to see them sitting on the toilet), but we live in a very dry place and would rather save the water.

    @Anon: We are on the coast and I’ve never heard of this sea otter thing. Jeez! You think they could put up a sign at the vet or something. I’ll have to look that up.

    @Sarah: I’ve only done some random googling, so I’m no authority, but as I understand it, the toxo bug is really only dangerous to the unborn and people w. impaired immune systems. I’ve read that if you have an outdoor cat, you’re probably already exposed and immune to it. If you’ve got indoor cats, they probably don’t have the bug.

    @Anon: Thanks for the tip on the compost system–I’ll look into it. Glad you liked Erik’s talk!

    @Lea: Ashy? Huh. It’s pretty unlikely your pile got hot enough to burn it. I wonder if what you’re seeing is some kind of ashy mold/mildew/fungus. Lots of strange things happen in the pile. It’s best just to let it roll–or if what’s happening is gross, turn it under and let nature break it down.

  24. After it has broken down, I dump the feline pine litter (minus the poop) on my lawn and around nonedible plants. I don’t see anything wrong with it and it’s better than wasting it in a landfill. I wouldn’t use it in compost.

  25. Have a look for toxoplasma gondii and why you shouldn’t flush cat litter down the loo. I would strongly recommend not to follow through with this.

  26. For cats, SWheat Scoop is awesome as is World’s Best Cat litter. But, as a cheap alternative to World’s Best, many people with lots of cats use chicken laying crumble. It is virtually the same as World’s Best and has a nice mild corn smell. Cats love it and it clumps perfectly.

    Toxoplasmosis is an extremely misunderstood issue. Cats can only get toxo from going outside, eating rodents or raw meat. If you have an indoor cat and no rodents and they aren’t on a raw diet, there is no exposure. You can have them titered to see whether they have been exposed before you get them. But, even if they have been infected, their feces will only be infected for 2 weeks! And it is quite rare for them to ever become reinfected because they develop an immunity. In the rare event that you have put two weeks of toxo-infected cat poop in your compost, no worries – toxo can only survive in soil or litter for, at best, 2 years – that’s why you compost it for 2 years. Most people get toxo from undercooked meats. It is rare to transmit from cat to human and there has never been a documented case of prenatal transmission from a cat despite the scare tactics. There are many great articles out there like this one: and this one Let me jump down off my soap box now. 🙂

    • Hello
      I have recently acquired a cat on loan from my daughter and have so enjoyed reading all these posts. this one especially, thank you so much for this info, it makes so much sense. I dont know why I didnt consider where they would be getting toxoplasmosis. Anyway, my visiting kitty is an indoor kitty, always has been, thank you for your post.

  27. Can’t you just combine the kitty poo with your humanure compost bin? I don’t see a huge reason to keep them separate, especially since you’re letting it age a whole two years (we barely do 12 months). And, you’re pressed for space. Two large bins is much easier than four separate bins…

    We use sawdust instead of kitty litter when we need to have a cat indoors (when they are ill or when they really want some human love). Sawdust is great with odor and does ok with compost. And, it’s free. And, it’s a waste product that can be turned in to something useful!

    I dump the sawdust + pee/poo on ornamentals as is; but, we have a ton of space. I may start dumping it into the compost toilets unless I can figure out a reason that this would be a bad idea.

    (An aside: I really enjoyed the photos and article in the NYtimes yesterday. What a great success for you both to be written up in such a major publication! yay!)

  28. @midnightgardener: Thanks for the toxo rundown. I’ve seen similar info and haven’t been worried about it. I’ll age the compost to be a good citizen, but somehow I’ve seemed to survive the feral cat poop in our garden for all these years!

    @Bosque: Thanks. And sure, we could combine the cat litter with the human litter–that would make total sense. But we don’t have an active humanure pile now, just a resting one. Erik and I have to have a Compost Talk and decide how we want to manage all our piles–do we want to start a combo kitty/human pile, kitty only, or do we want to scoop the poop and put urine and litter in the regular pile. No matter what, there’s way too many bins in the yard!

  29. Assuming you are using a good, natural cat litter, composting this in it’s own pile is no problem at all. I’ve been doing this for years in a corner of my yard. I really don’t anticipate using the soil that will eventually be there, but for me, that isn’t the point. Having used cloth diapers exclusively on my two kids, I certainly wasn’t going to start throwing out little plastic bags of poop everyday! Not even if those bags were “compostable.” AND, it would have messed up my infrequent garbage pick-up, too! So I just scooped the poop and took it to its special pile and tossed it on after every clean-up time. And when it came time to change the litter, too, I just added it to the pile. I never cared how long this process was going to take, so I didn’t add anything, check on it, stir it – nothin’. Admittedly, not everyone has the space for this approach and some may want to be able to make the process happen faster or in a prettier way, but this is certainly the easiest way if you have a tiny bit of extra space in a discreet part of your yard. Good luck! And don’t be afraid!!!!

  30. Kelly i don’t see that anyone has mentioned black soldier fly composting?

    Visually alarming the first time you spot them in your pile but pretty voracious and they don’t mind fresh manure one little bit. I understand everything is a little soupy when the BSFs are done so it’s best to feed their leftovers to the worms for a nicely finished product.

    Check out question #5.

  31. I’ll be interested to see how you get on with this. I’ve been trying to find a solution for a couple of years, but my problem is with quantity- I have 2 largish dogs and 3 cats…

    I read the city gardener instructions and then a week later found a plastic dustbin in a skip. I felt very smug, especially when I then learnt to bokashi waste using fermented newspaper, which meant I could use the juice from that instead of septic tank additive. Free, and a closed loop cycle (well, pretty much!) And it was all great until it filled up. And 2 years later it’s still full. No smell, no flies, just…sitting there. (And that’s just from the dogs.)

    I did have a bit of a poke about with a stick about a week ago and noticed some brandling worms have moved in, so I added a few more with a little semi-decomposed straw from the regular heap (couldn’t fit in much), and hopefully that will speed things up a bit.

    We’re on clay, so I suspect the poor drainage (though it’s never flooded) along with the quantity has been too much for it.

    Re: cat litter, we use a pelleted pine one, but last summer the children had great fun making our own from old newspaper. Not the quickest process in the world, though we did speed it up from the initial instructions we found online, but it kept the children entertained in the garden for a while! Should you ever be at a loose end…

  32. For any dog owners out there without the outdoor space for composting, definitely consider flushing your pet’s waste instead of sending bags to the dump. That way the waste gets treated instead of possibly contaminating groundwater down the line. There are flushable bags made of corn that will eventually degrade.

  33. I just got the Urban Homestead book and love it. I have not tried composting my animal’s waste but I use the World’s Best Cat Litter and think it would be a great choice for composting since it’s natural.

  34. What a fascinating topic. We inherited a cat this winter who had been an indoor/outdoor cat but has to stay inside in our apartment. We are using the Worlds Best Cat litter and really like it – we use the multi-cat formula even though its just one cat because it is less dusty (so less dusty kitty paw prints on the carpet and couch). I am going to try composting the spent litter when I change the box every month… what a great idea. Thanks for all the food for thought!

    • woah~ did you say that you change the litter once a month??
      I have 2 trays and have to change those at least once every two days. If i don’t, the cats will end up doing their business somewhere else!

  35. I hadn’t thought about a dedicated bokashi bin- that link is interesting, Marti, thanks.

    It is easy to make your own Bokashi system- there is lots of info on the web- and to make it much cheaper it’s really easy to ferment newspaper in live yogurt whey and molasses, so you don’t have to buy the innoculated bran. I did a huge batch so I only need to do it about every 12 months for my regular bokashi.

    It doesn’t say what the accelerant they sell is on the website- I wonder how much quicker that makes the process, and it also doesn’t give you numbers of pets per system that I could see. I think I still have too much poop to make it viable, but for one or two animals it could work well.

  36. Toxoplasmosis is a parasitic protozoan. You do not become immune to it. It is possible to have an asymptomatic exposure. However, each exposure increases the number of bradyzoite cysts in your brain tissue and lymph nodes. It is linked to psychiatric disorders and current research suggests that it can lead to behavioral changes.

    It’s true that most infection of humans occurs through under cooked meat. However, that meat was infected by the food animal being exposed to cat feces.

    The oocysts are extremely small and light and could be airborne. They are also longed lived (a year or more).

  37. I appreciate this post and all the comments. I use stove pellets for litter and absolutely hate throwing bags of the stuff into the landfill. I do worry about toxoplasmosis. I may try long term composting of the litter (feces removed) and putting it on ornamentals and the lawn. I’ve got woods behind my house and thought of just dumping it there, but don’t think it’ll be good for the environment. Need more info….

  38. We’ve been using natural based litters for several years, but only started composting this past January. Since I use coco peat (coir) for my humanure toilet, I also use it for the cats’ litter box. Even though it doesn’t clump, I don’t have the odor issues I did using pine, corncob, or sand. It may be that the cats like to dig in it and so cover it up better. Additionally, the worms like the coco peat and it takes ALOT of nitrogen to break it down.

    I personally like the texture and look forward to adding the finished goods onto my various plant projects around the yard.

  39. I noticed a post about sawdust litter looking like ash. I’m not sure where you kept it, but a friend of mine volunteers at the animal shelter and they used pine shavings. They scooped the poops and started a pile out back for the shavings with full sun exposure. After a few months the ammonia levels rose so high that the heat of the sun caused them to ignite. It almost burned the shelter down. Just something to consider; I’d hate to see it happen to someone else.

  40. I guess my concern is one of the original food. It seemed to kill my worms. I wondered if a de wormer had been added to the feed. Your technique of composting the poo first will be my next step. Nice to know there’s options to kitty litter. I’ve been using composted forest mulch to help the process. That two tray system looks worth investigating. Thank you, all!

  41. I have both Breeze litters boxes & a Smart Litter Box. With the Breeze one I do waste the pads for now(would like to find a compostable one), the poop I put down the toilet after being sure all the pellets are off it. If not ok to flush poop, why aren’t the toilet training systems removed from the market ? – I see them in most pet stores now. But anyway I barely dispose any accumulation of litter volume with Breeze – the pellets do not absorb liquid & they can be washed. They won’t compost but they are innert as far as I know so can be buried, and I keep them for about a year before I can’t seem to destink them. Even better, after using the Breeze boxes for awhile, I came across the Smart Litter Box. It uses a small tank that collects the urine & then can be pored down drain & flushed. The litter is safflower seeds that also do not absorb liquid. I scoop poop & flush it, and don’t even use the tank: I have an extra bathroom tub that I don’t use, and took the tank out, the pee goes right down the drain & I just run a little water down it once a day to keep urine from pooling around it & smelling. Love this system!

  42. There is a brand new biodegradable litter on the market now from Blue Buffalo. It is made from crushed English walnut shells. I like this option much more than corn or wheat b/c the corn and wheat is used in grain as a feed source for livestock. When you deplete those sources from the environment, the price of feed is becoming significantly higher. Crushed walnut shells clump better (within 15 min), less tracking, no smell, and NO DUST-much better than World’s Best! Also, no worries from kitties eating the litter (by the way, corn, wheat and soy are highest linked ingredients to animal allergies)! Keep it out of their food AND their litter!! This litter is also made in USA and made from annually renewable agricultural resources.

  43. I’ve been composting cat waste for a couple of years. I have a nature mill composter in the back room where the cats do their thing. Pricey but worth it. When the bin fills up, it goes into the yard to continue breaking down and age. Some food waste (veg/fruit) also goes into the mix. So far, it has been great. I have three, indoor cats and use the Worlds Best.

    I understand the concern about micro-organisms, but I think it all has gone a bit overboard. Neighborhood cats are doing what they will in my garden. Their waste is much more likely to be infected with toxo and other bad stuff. My guys’ stuff, while indisputably rank initially, is broken down, aged and not likely infectious since they’ve never gotten a chance to acquire a taste for brain-addled rodents. No more plastic bags in the landfill. I like to think about archeologists in the future puzzling about the millions of packages of carefully wrapped shit. I’m sure they’ll think it is some kind of deification of our beastie friends. Not so far off.

  44. Pingback: Cat Litter Compost, Installment #3 | Root Simple

  45. Thank you for all the info!

    I am about to get a cat and am trying to make learn how I can make the smartest decisions.

    I live in an apartment and do not have room on my balcony for a compost. Where I live there is a weekly compost service where I put my normal food compost in compost bags and then put it into the bin.

    I will be using compost-able litter. My question is can I put either pee or poo in my city’s compost bin? I was thinking maybe I could flush the poo without the litter and then compost the pee in my citiy’s compost bins?

    I live in Switzerland and have a bit of a language barrier in trying to find my answers. Thank you for any help!!

    • Hi Jenna,

      Cat poop has potential diseases in it, so no city facility would want it in the compost. I would use urine soaked litter in my own compost (though to be safe I would not put the compost on food crops). However, I’m pretty sure no city would want the urine, either, just to be safe. You could ask your city what their guidelines are for disposal of cat litter. Perhaps they have an enlightened system we don’t know about.

      I love pets, but they are environmental disasters. 😉 I can’t imagine how many plastic bags of poop I threw in the garbage when we had our dog, and though I try to compost some of the cat litter, much of it still goes in the garbage.

      Good luck! And enjoy your new kitty friend!

    • Gruëzi Jenna. Have the same problem like You. Your comment is from “2014”…may be, some news in this topic?? Please share ;D…Thank You

  46. Katerina, are you in Switzerland? Germany? That litter works. But you can buy wood pellets that are used for burning and heating homes. You can buy them at home and farm stores like Jumbo or Landi or Migros doit It is much cheaper, only 5 CHF for a large bag

Comments are closed.