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I know that for 'regular' composting without worms you need a carbon-nitrogen ratio of something between 25:1 and 30:1. Is the same true for vermicomposting? I'm not sure if it matters, but I'm using tiger worms in a closed worm bin.

EDIT: I tried google and found mixed results. On this page and this one they say that the specific C:N: ratio doesn't matter, but Wikipedia mentions a ratio of 30:1 and on this page they say you should have a 70:30 ratio (of browns:greens).

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FWIW, I think that last link is saying that 70% of the volume should be browns and the rest should be greens; that's not the same thing as a 70:30 C:N ratio. – bstpierre Feb 11 at 12:05
@bstpierre you're right! I misread it. – THelper Feb 11 at 12:13
Also, I'd guess that you would want a higher ratio (than the 30:1 for regular composting) to avoid having it heat up too much and killing your worms. Though in a small bin, you're less likely to achieve critical mass to getting a hot pile; there the issues would be more along the lines of smell and excess liquid. – bstpierre Feb 11 at 12:37

2 Answers

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I haven't ever worried about it, here are my general guidelines:

  • plenty of cardboard and pulp egg cartons, the structure gives worms places to escape to and lay egg capsules.
  • no citrus or fresh pineapple.
  • no tropical fruit skins (pesticides).
  • no dairy or meat.
  • nothing too oily
  • worms never eat anything that is alive, including seeds.
  • best to chop up or dry out fresh veggies, because many will just start growing and never get eaten
  • watch your worms, if they are climbing out something isn't right.
  • add ground up egg shells, they provide calcium and a buffer against organic acid buildup.
  • make sure you have plenty of air, and not too much water, drain holes in the bottom are a must.
  • most pungent/strong food has herbs and spices that are antihelmetic... Don't add any dried wormwood, rosemary, etc.
  • no hair.

The worst horror stories I have heard involve either pesticides from banana peels or ant invasions.

The old timer that sold me my worms has been vermicomposting for 30 years, and always makes sure his worms have access to alfalfa pellets, because, he claims, the worms can eat them directly without first being digested by fungi... I don't know if it is true.

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Thank you for your answer. I guess you are saying it doesn't matter much. However your remark on the fungi got me thinking. Since worms eat stuff that has to be digested by fungi and bacteria first, I guess the best C:N ratio depends on what the fungi and bacteria prefer? – THelper Feb 12 at 12:23
and which prevents anoxia and keeps everything in a good pH range... – Grady Player Feb 12 at 18:00
up vote 2 down vote accepted

I stumbled upon this scientific paper in which they say that

different earthworm species are impacted differently by C-to-N ratio and feed mixture type.

For the Eisenia fetida (tiger worm) the result of their study was:

A C-to-N ratio of 25 resulted in the highest stability of the product, the best fertilizer-value of the product, and also a product with the lowest potential for environmental pollution

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