Vermicomposting C:N Ratio

A question from Joyce:

I read about the C:N ratio. How do you increase the C? How
do you make sure the N doesn’t get too high? I am not a scientist or
chemist. I lost my worms to the “ammonia smell”. Thank you.

Hi Joyce,
Sorry to hear about your worms! They are indeed very sensitive to ammonia – even at very low levels, this gas can kill them quite quickly.
The good news is that keeping the C:N ratio pretty high is not very hard. One thing I should mention before getting into C-rich materials though, is that it is very important that whatever you are adding to the bin is not already emitting ammonia.

For example, you can have all the c-rich bedding you want, but if you add fresh manure to a standard worm (enclosed) worm bin you will almost certainly kill your worms. Same goes for any really foul, rotting material. The larger the system and the more air flow there is, the greater the chance it will be able to buffer the negative impact of the material being added.

Ok – getting back to C-rich materials…

Any of the typical worm bin ‘bedding’ materials, such as shredded cardboard, shredded newpaper, coco coir, peat most etc are great for boosting the C:N ratio – they also help to provide an excellent habitat for the worms since they are highly absorbent, and also allow good air flow (although the latter two, should be mixed with one of the bulkier types for best results).

The ultimate material however will be something that is ‘living’, such as really well-aged manure/straw, rotting leaves etc. These materials have the added advantage of being loaded with microbes, and potential sites for the conversion of ammonia into much less harmful nitrogenous (N-containing) compounds. This is why composts can work so well as a biofilter medium.

So you end up with the triple bonus of inoculating your system with lots of microbes, providing your worms with an excellent protective habitat, as well as helping to keep your system up in the optimal C:N range.

Hope this helps!
8)

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Comments

    • Tony ELlis
    • January 10, 2011

    Hi Joyce,

    I have the same dilema as you only my pro ject is for a grade in my high school ecology class. My question is what is a descent ratio to work with that won’t have too much affect if it is slightly altered?

    • Alice Beetz
    • March 22, 2011

    I have a client with a question about composting vermicompost.
    How much carbon material should be added to have a proper C:N ratio (25-40:1)for composting?
    They’re considering sawdust or hay or rice straw for the carbon part.

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