Indoor Cat Poop Vermicomposting?

Thinking about how to kick things off with my Urban Worm Bag 2.0, I knew I needed to come up with something different.

I asked for feedback from the Red Worm Composting Facebook community – mentioning that I had been toying with the idea of a (compostable) cat litter experiment – and received some great feedback/ideas.

But the discussion seemed to keep coming back to the cat poop…lol

In the end I decided that’s what I was going to do (and will be using some of the suggestions people had for making it a bit more “worm-friendly”).

When I told the worms about my idea, they weren’t quite as excited about it as I’d hoped. Below is a dramatic re-enactment of the conversation (thanks to Will Ferrell and Fred Armisen for agreeing to help out on such short notice!)

In light of this rebellion, I have decided to only use worm cocoons to stock the system.

Another twist is that I won’t be using any shredded cardboard (my go-to bedding material for virtually all smaller systems). Instead, I will be using mostly wood chips (which do at least have some shredded leaves mixed in as well) and stove pellets. Some well-aged, dry-ish horse manure will also be used to help make sure I don’t end up with any bad odors.

The compostable kitty litter I use is chick starter feed. Really awesome stuff (works very well as a clumping litter, and is relatively inexpensive), but obviously pretty high in protein (and thus nitrogen). Not a great way to balance out the high-N of the urine and cat poop. FB group all-star, Erin May suggested just using the poop, not the urine clumps – and I think this is great advice, especially for an enclosed, home-scale bin like this.

Previous systems where I’ve dumped everything in were larger outdoor systems, exposed to the elements. The worms were allowed to move into the material on their own (beds were never even stocked with worms).

I have started collecting just the cat poop (with small amount of loose litter) and layering it with wood chips and a small amount of aged manure in an old cat food bag (which has a plastic liner inside). Hopefully I don’t get it mixed up with the cat’s regular food bag! hahaha

This will provide a bit of a “pre-composting” phase for the material – hopefully making it even more inviting for the worms.

Speaking of of the worms – part of the reason I want to use cocoons is that it means the worms will be born into this system, likely helping them to adapt even more easily to the conditions and food source (not that I’m all that worried, especially with no urine clumps in there). And I think it will just be fun watching the population develop over time.

Hoping to get this system started a bit later in the week (as I type this on Dec. 10th). Should be fun!

Let me know what you think in the comments section below.

WARNING: Adding cat (or dog/human) feces to a typical indoor worm bin is NOT a recommended practice, especially if you are fairly new to vermicomposting! I have nearly 20 years of experience and this is intended primarily for “entertainment purposes” only. Various precautious (eg wearing gloves) will be taken, and any vermicompost produced in this system will be used for ornamental plants only.

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    • Kristina
    • December 11, 2018

    I’ve been wondering the same about pet fish and parakeets and dove poop…we have a compost bin out back too but as for the worms I’m new to this and mine are doing super good just by winging it lol
    Hooray for experimenting!! And btw thank u for your site

    • Bentley
    • December 11, 2018

    Thanks Kristina!!
    Bird and fish manures are another can ‘o’ worms altogether. Challenging for somewhat different reasons. I would actually pre-compost both types (fish and bird) in a larger (ideally outdoor) system for a while before attempting to feed to the worms since ammonia release (deadly for worms) will be very likely otherwise. In larger systems with excellent ventilation you may be able to get away with some of these moistened, mixed with bedding materials sitting up above the worm zone, though!

    • Karen M
    • December 11, 2018

    One of the other things you need to consider is whether the cats have been treated for fleas/worms.
    If the cats have been treated with the type of drops that also kills worms then you can’t use the poop or peed litter as it will also kill your worms.
    If you know a vet, I would ask them how long the flea/worm treatment stays active.

    • Bentley
    • December 11, 2018

    Interesting point, Karen!
    It has been ages since this cat has had any sort of treatment for anything – but it is definitely worth keeping these sorts of things in mind!
    Thanks for sharing that

    • kayla
    • September 17, 2021

    Please let me know how this went. I was considering composting cat poop and taking sample of compost to be tested.

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