Manure in a Home Worm Bin

I received this msg from Melissa

I am wondering if it would be a good thing to add manure to my indoor
vermicomposter, in addition to the normal fruit and vegetable waste I
add?

I appreciate your expert opinion!

Hi Melissa,
Great question – something I’m sure a lot of others have wondered about as well. I know I talk a lot about the value of “aged manure” here on the blog – but I probably don’t spend enough time on the “DOs” and “DON’Ts” of manure use.

Generally, my blanket recommendation for those who are new to vermicomposting is to steer clear of any type of manure when using a typical plastic, enclosed worm bin (whether located indoors or outdoors). While there are certainly types of manure that CAN be used in these systems, it’s probably not worth the risk since even relatively small concentrations of ammonia and various salts can harm or kill your worms.

It’s important to remember, though, that “manure” is just a word – a single word that refers to many different materials. Even the term “aged manure” is pretty non-specific. In my case, what this usually refers to is horse manure (originally bedded with straw or wood shavings) that’s been left to sit in an outdoor pile for at least a month. It is dark, earthy smelling stuff – and it’s a fantastic material for a wide range of uses. There is no issue using it in any type of bin. The challenge for a newcomer, however, is trying to figure out if a given heap is aged “enough” (I’ll offer some recommendations in a minute).

Another type of “manure” that people often associate with the word is the bagged manure you can buy at garden centers. I’ve done some testing with these materials (again, there are many different types – so you can’t make generalizations) and the results have been mixed at best. Some types seem to be well-received while others are not. Since these manures are typically composted in some manner before being bagged, I don’t think it’s as much an ammonia issue as it is a salt issue. Worms are very sensitive to low concentrations of salts (such as those present in urine), and some farmyard manures (eg. cattle/steer manure) seem to have higher concentrations than others.

Before offering some additional pointers and suggestions, I do want to point out that most manures would probably be fine if added to larger, open (or at least very well ventilated) vermicomposting systems with good drainage – especially those that are exposed to the elements a bit. If the worms have a quality, established habitat already and the manures are simply layered over top there is much less chance of causing any harm.

OK – getting back to the smaller, enclosed systems…

Here are some suggestions:

1) If at all possible, add manures that have been mixed with some sort of bedding materials and left to sit outdoors for at least a few weeks.
2) Always test manures on a very small scale to see how the worms respond before adding too much. If they move into it immediately and seem to be actively feeding on it, gradually add more.
3) Manures added to smaller enclosed bins (especially plastic ones) should never have much of a manure smell – aim for more of an “earthy” smell.
4) Never use manure as an initial bedding material unless you are very confident that it is going to be well-received by the worms (again, testing out on a small scale first is never a bad idea).
5) Aim to steer clear of ALL avian (poultry etc) manures since they tend to be even more potent than those from the larger animals. If you soak/drain them, mix them with shredded cardboard (or another bulky, absorbent bedding) and let them sit for a bit, they MAY be ok – as always, be sure to test out on a small scale first.

AGAIN – these recommendations are intended primarily for those using typical, enclosed plastic home worm bins, and none of this is set-in-stone! The key is always to test things out for yourself – just be sure to do so on a small scale first.

Hope this helps!
8)

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Comments

  1. If I get some horse manure that dosen’t smell…Heck yes I will add to an indoor bin!

    • Milwauken
    • August 2, 2012

    Aged horse manure works well for my small plastic bin. It’s mostly hay, straw, and bits of feed oats. Though it tends to be dry, so I add a little moisture.

    Thanks for your website! I’m new to worm composting, and have learned a great deal from your videos and articles.

    • Gina
    • August 4, 2012

    Does llama manure work well for worm composting?

    • Matt in Haiti
    • August 5, 2012

    I use a lot of very well aged pig manure mixed in as bedding and the worms love it. In setting up indoor plastic bins, I will mix fairly even amounts of coir and manure, with some coffee grounds, pulverized egg shells and rock dust. And occasionally when feeding I will mix in a healthy amount of manure as “living material”. The worms move in immediately. And, I do also notice that worm size increases with heavier feedings of manure. The manure generally is several months old, having sat exposed to the elements here in the tropics for that time, and then I store it outside in a sack, so the end result is a product that is pretty unrecognizable as manure, but works like a charm.

    • Dina
    • August 5, 2012

    I got most of my worms from a well aged manure pile. It’s been sitting out for at least a year. However I didn’t add a bunch of it to my indoor Rubbermaid bin (maybe 4 or 6 cups worth along with lots of shredded carboard & newspaper). I’m happy to report that the bin took off after adding the manure. I’ve harvested it, sorted worms, eggs & babies into a new bin and everyone seems to be happy. I’m still finding babies in the vermicompost so for now I’m keeping in moist and checking it every couple days.

    • Dina
    • August 5, 2012

    Forgot to tell you I’ve learned a lot from your website and really appreciate all the helpful advice everyone has given!

    • Bentley
    • August 7, 2012

    GINA – Llama manure is a great “worm food”, and you’d probably be ok adding small amounts at a time to an enclosed, plastic bin (since tends to be a bit more “mild” than some other manures) – but I’d recommend creating a quality, established habitat for the worms before using it (i.e. don’t just try to force them to live in the manure right off the bat)
    —————-
    MATT – sounds great! I’ve read that pig manure is phenomenal for growing composting worms. I think the key there is the aging ahead of time.
    —————-
    DINA – Like yourself I’ve discovered that outdoor, aged manure piles can be the “ultimate” composting worm habitat (and I have my own secret pile at a horse barn that I still collect manure/worms from). Your cautious approach is definitely the way to go with a smaller, indoor bin though.
    8)

    • Ben
    • May 5, 2014

    Will Aging the manure outdoors ensure that there wont be any salt content? Or are we relying on it being in the elements (rained on) to wash away ammonia and various salts?

    • Bentley
    • May 6, 2014

    Great question, Ben!
    That’s part of why I recommend outdoor aging – since it will (hopefully) be exposed to some rain as well. Salts aren’t always going to be an issue – but with some manures (such as poultry) it can be really important. The ammonia doesn’t need rain – it will either be released as a gas or converted to something else.

    • Ben
    • May 7, 2014

    Thanks for the reply Bentley,

    It would be great to know the exact process that you use on the manure. Your recent videos on food optimization were fantastic and covered every possible question i had.. Except how did you end up getting the manure to that stage prior to adding it to the mix. My wife owns a horse and i have tried aging the manure outside for quite some time and i never got it looking anywhere near what the stuff you added to the mix does. it ended up being hard lumps that were difficult to break up and wouldn’t absorb much moisture so im obviously doing something fundamentally wrong.
    Any information would be great. And im sorry if it has already been mentioned i have looked around and couldnt seem to find anything on the topic other thatn the above post.

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