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
I appreciate your expert opinion!
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!