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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?

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5 Answers 5

up vote 9 down vote accepted

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:

  • Toxoplasma gondii, which is probably only dangerous if you have HIV or are pregnant
  • Fecal Coliforms
  • Roundworm (Toxocara cati or related species), which can cause visceral larva migrans aka Toxocariasis, the symptoms of which sound unpleasant. Even though you say you're scooping the feces, it's possible for eggs to be remain in the litter.

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.

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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 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...

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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
    
"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

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.

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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'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.

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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

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