Is spent cat litter an appropriate source of nitrogen for compost?

  1. The cat litter used is made of recycled paper pellets so is rich in carbon.
  2. It doesn't contain the cat faeces because that is fished out once or twice daily with a net to make the litter last longer, so should not contain any significant source of pathogens.
  3. It has quite a ripe ammonia smell to it (hinting it's rich in nitrogen, thanks to cat urine) by the time it's replaced in the litter tray, making me wonder if it could be added to the compost to hasten the breakdown.

If not good for compost, could it be useful anywhere else in the garden?


I wouldn't use the compost anywhere I was going to grow food or walk barefoot, or where children might play.

The primary dangers of cat feces would be:

If I was going to use kitty litter in my compost, I would probably build use it in the lower layer of a sheet mulch garden bed and then grow cover crops on that bed -- maybe buckwheat, winter rye, or a perennial like clover, depending on the time of year I started the bed. Note that roundworm eggs can survive for years in soil in some climates.

As a side note, by the time you smell ammonia, you are losing significant amounts of nitrogen into the air.

  • Right. On balance, the answers are skewing towards "no, inappropriate" unless there's no chance of it going towards a food crop. – Lisa Jul 13 '11 at 6:48
  • Marking this as answer because it provided the concrete reasoning behind the answer and allows me to go ahead and use it knowing the risks... or not use it at all. – Lisa Jul 13 '11 at 6:50
  • I might recommend a more thorough study of toxoplasmosis (a protozoan infection that can be spread via cat urine). I think it could be more dangerous than the answerer seemed to think. – Brōtsyorfuzthrāx Oct 9 '14 at 17:20
  • This link may be helpful in showing how even latent infections can be dangerous (car accidents; increased mortality for the mentally ill; possible increased risk of mental illness, etc.): en.wikipedia.org/wiki/Toxoplasmosis#Research – Brōtsyorfuzthrāx Oct 9 '14 at 17:34
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    @user2962794: more dangerous indeed. I'd note that the wikipedia reference for the latent infections dates from 2013, or 2 years after the original answer. I'll remove the "probably only dangerous" qualifier and link to wikipedia – bstpierre Oct 10 '14 at 18:16

The usual recommendation I see for faeces and urine is not to put it on the compost due to the possibility of disease. Urine might also be a bit concentrated. From a disease point of view you should be okay if it gets hot enough. For the question of concentration, then you can use small quantities and dilute.

You say your litter is based on recycled paper (which should rot), but a lot of other cat litters use zeolites for their 'structure'. These should make a good base for soil/compost, although you may have to watch for any chemical treatments.

  • Thanks. As I said, there are no faeces except trace amounts so am less concerned about diseases. Thanks also for the note re zeolite/diatomite type litter - not relevant in my case but may be helpful to others. – Lisa Jul 13 '11 at 0:45

I do not have any experience with putting used cat litter in a compost pile, but from your very! specific stated details I would say it would be safe (at least I would do it) and a good thing to put on your compost pile (plenty of nitrogen to help the cooking process).

You will want to balance out all that nitrogen with plenty of brown matter in your post pile. For brown matter there is nothing better than shredded, fallen Autumn (Fall) leaves, IMHO.

I would also make sure the compost pile is kept moist enough by adding water as needed.

Why do I say the above is safe?

With our second son we used compostable diapers. Pee-pee ones went straight on the compost pile. Poo-poo ones were emptied & flushed down the toilet (you never want to deliberately add fecal matter to a compost pile).

For what it is worth, Bob Flowerdew from BBC Gardeners’ Question Time podcast is constantly encouraging people (especially males) to pee in their compost pile, maybe not directly, but his point is, pee is wasted if it doesn't end up on the compost pile. Personally I haven't gone down that route...

Now the flip-side, below are (just) a few places that advise against putting cat litter in a compost pile:

Now that I may very well have gotten you even more confused on what to do for the best, I'd say it really is your choice to make one-way or the other...

  • Thanks, and I'll remember the nappy advice for the future (and the toxoplasmosis advice from bstpierre too of course). – Lisa Jul 13 '11 at 6:47
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    "Pee-pee diapers" or people urinating on a pile are different: in the absence of disease, urine is sterile when it leaves the body. In the diaper case, you're taking away the urine before it is mixed with feces. If Lisa had pure cat urine, it would probably be ok, but with the fecal contamination it may have roundworm eggs or coliform. Personally, I would use humanure before I used cat litter. – bstpierre Jul 13 '11 at 11:49
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    I've found cats pee and poop in my garden, especially on dry turned or raked earth, away. So the faecal contamination will happen anyway. Add to that all the foxes, birds and other wild animals that will be dedicating there and perhaps we are all being just a little prudish. – Rincewind42 Jul 13 '11 at 15:39
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    That urine is sterile (at any point) is a myth. – Brōtsyorfuzthrāx Oct 9 '14 at 17:52
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    @user2962794 I didn't know that. Here's a cite for your claim: sciencenews.org/blog/gory-details/… – Philip Oct 10 '14 at 18:26

I'd say it depends a bit on what will be grown later. If you are putting the compost onto vegetable plots, especially vegetables that you are going to eat raw, then you need more care to avoid pathogens and such bugs. However, if it's going on a flower bed then I might worry less. Where I live - China - people open up cesspits and use human waste to fertilise plots, so cat poop has less to worry about than that.

The one thing that would worry me is the litter itself. It may be made of recycled paper but how many preservatives and other chemicals are in that paper? You might find that it doesn't readily decompose at all.

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    The litter product used claims to be "100 biodegradable" and be made out of "99% recycled paper" and to contain "no added chemicals" and really my question is limited to these supposedly biodegradable type pet litters. – Lisa Jul 17 '11 at 4:23
  • Also, I know it degrades swiftly as I've been keeping a compost pile exclusively made of this stuff and water, which may or may not be useful for the future, but it seems to be high in nitrogen -- looks a bit like guauno. Can provide photo if interested. – Lisa Jul 17 '11 at 4:24

If not good for compost, could it be useful anywhere else in the garden?

If you don't go the composting route ... it can be used to deal with groundhogs. It might work as a replacement for predator urine in keeping away other animals.

  • Now that is something I would NEVER have known. I'll keep it in mind in case I ever try to do gardening in North America. – Lisa Jul 25 '11 at 23:40

I have areas in my garden that are shaded where I have dug trenches 18 inches deep. I have put the cat litter in the trench, and then covered with soil. Because the area is shaded, it is unlikely to be used later by any subsequent owner for vegetable production. Also, the pathogens are unlikely to persist after two years.


Be safe. Use the used litter only to fill holes; that's about it.

There are a lot of bloggers who demonstrate you CAN compost cat litter (wood and clay), growing even leafy ground crops like lettuce. But they have not tested their cats or their worked soil.

My property is a little wild, and I've spent a few years leveling out some of the larger dips and holes. I do this by digging up the topsoil (one foot down), filling it some, then returning the topsoil. If I need to relocate a lot of soil, I'll use a pick and dig a small pit on the edge of the property (so I immediately have topsoil + sand to mix with clean compost. I can then take my time filling that pit, and eventually cap it with topsoil. Note that if you do this with wood/paper litter, the decomposition will eventually cause the topsoil to "sag" so you may want to balance the paper/wood with clay, or mound a hill of topsoil in anticipation of settling.

Beware that insufficient "normal" topsoil depth over this will present a walking hazard (boots punching through the topsoil into wet contaminated clay). Depending on your locale and laws, it MAY be considered some form of improper waste disposal so use sense and don't create a hazard for yourself or future owners of the property.

I've only dug holes around the treeline as "a" I don't want to see a pit from the home windows, and "b" I don't want a mess where someone may walk over (however the freshly leveled space is OK for planting trees, flowers or other non-edible plants). 4" of sandy topsoil followed by 2" of mulch seems like a reasonable compromise for areas not normally walked on.


I have a rural property with an acre of pine trees that I have been using as an area to spread cat litter for years.The area is unused - untrodden by humans except me. The fallen needles with added grass clippings and leaves are annually tilled lightly to stir into the ground soil. There is no odor whatsoever in any season (Colorado mountains). This is purely an experiment I guess on my own long-owned land. I can say having many tree types around that this section of pine looks vibrant-well nourished and taller! than some others I have planted.

Eventually the wood may get harvested for a planned cabin. Do I expect the cabin to smell of cat - lol no. Just a personal observation of no real consequence.

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