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Office Copy Paper and Worm Bins


February 10, 2018

I live in a fairly built up outlining area from you but wanted to ask about carbon to nitrogen ratios and office copy paper. Search google and get answers all over the place. I have worm bins and have had a heck of a time getting a good balance on them because of wildly varying values. One person says coffee grounds are browns, another it's greens. Some say office paper is fine, others say it's bleached so it's toxic. Newprint varies from 175:1 all the way up to 800:1, same with sawdust. Also wondered if feed stocks contribute more than just carbon or nitrogen? Do they also affect pH?


Answer by JZ: Here are my thoughts:

  • Composting worms ingest decomposing organic materials and the microorganisms on them. Sure, a variety of greens & browns in a worm setup is useful, but keep in mind that that worms will consume anything that is in the process of decomposition or decomposed already.  In their natural environment, generally speaking, eg. a forest floor, they would have mostly decomposing moist carbonaceous materials available to them, eg. brown leaves.

  • In an aerobically maintained composting setup the pH will self-adjust, over time, usually ending up neutral in the humus end product. In my opinion, when worm castings reach a depth of 6 to 8 inches, then the bin should be harvested. Deeply compacted worm castings may create anaerobic conditions in a bin - creating unpleasant odors. Bins contents may also be "fluffed" from time to time, to aerate them.

  • The  ideal C:N ratio in a composting setup is 25-30:1. If this ratio is maintained, then it provides balanced nutrition for microbes, which then proliferate in the setup. This ratio is most relevant to hot process composting (thermophilic) operations.  Worm composting setups are a cold process and so rigid adherence to the ratio is not so important. Whatever organics you add will begin to microbiallly decompose, get softer, then worms can ingest whatever is decomposing - green or brown.

  • Yes, info. on paper products may be confusing. The easiest, very natural organic material to add to a worm set up is shredded moist brown leaves. Then you have no issue with contents of paper products.

  • An important consideration is “how are your worms doing”?  If they are reproducing, most likely, their environment is fine.

  • We consider coffee grounds nitrogenous (green). Nitrogen will escape from any organic material when the material is left exposed to air & sun over period of time. So, fresh coffee grounds most likely have more nitrogen than old, exposed grounds.

  • We consider the following acceptable for composting setups, including worms: newspaper, egg carton, paper towels, napkins tissue, brown bags, filters and cardboard - all shredded before adding. Printer paper, would be your choice.

We avoid glossy, slick, colored, wax / plastic coated papers. Any paper contaminated with chemicals, eg. paints, oils, etc..

Let us know if this is helpful.  Keep up, worm composting is a fine process.  

Answer by JH: Firstm while I think the google search engine is a wonder of our modern world I would not rely on it for compost information for the desert. Many good composting sources do not differentiate on climate. Our website however has excellent resources and information specific to a high desert climate. One of these resources is our compost mix calculator. Another is our lists of browns and greens.

As for coffee grounds, they are an excellent source of nitrogen (greens) and are bountiful and any coffee shop will likely provide them - free nitrogen! And while shredded copy paper is fine as a brown addition to a compost pile, it would not be a good choice for worm bedding for the reason you mention.

And if I understand your question, you’re asking specifically about worm composting. If so the C:N ratio is not important. You do not want to overheat a worm bin but you do want to provide your worms food and bedding all of which they will consume. Yes, pH is a concern in the worm bin so limit amounts of additions like coffee grounds.

Please read the excellent how-to resource on our website about worm composting. Here is the link.

If I’ve misunderstood your question feel free to reply all and clarify. Thanks for your inquiry and best wishes.

Response from Questioner: Recently had populations declining pretty sharply so trying to trouble shoot and narrow down the cause.With the c:n ratio for the worm bins, I was worried that it would start to smell bad like standard compost if the ratios got out of balance... and since I live in pretty dense urban/suburban area (desert coastal) don't want neighbors noticing anything. I usually stir the contents of the bins weekly just to keep them from turning anaerobic, sample counting worms to get an idea of population health (#'s falling/climbing). Again, thank you both. Greatly appreciate your time and help!

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