Storing Castings, Worm Tea, Egg Carton Cardboard

Three questions from Ursula:

1. How can I store worm castings for use later in the spring?
I already know you can’t let it dry out as it turns into
a cement like mix. I would like to preserve the beneficial
organisms without drowning or suffocating them.

2. When I make worm tea (1 cup to 1 gallon) for watering
house plants the castings accumulate on top and eventually
form a crust. Do I need to break this up?

3. Do those gray egg cartons which organic eggs are sold in
have any chemicals in them that may harm the worms?
I use the torn pieces for bedding but the worms have never
even nibbled them!

Hi Ursula,

1) Storing worm castings is relatively straightforward – the main goal should be to store the material at a moisture content that’s dry enough that it doesn’t feel moist, but not so dry that it becomes crispy and lifeless. When you squeeze it in your hand it shouldn’t release water, but it should be able to partially hold its form (poking with your finger should easily break it apart though).

Using some sort of enclosed bin similar to a worm bin would likely work very well – it’s important to have air flow for the sake of keeping everything aerobic, but also some ability to maintain humidity (storing in a wooden box probably won’t work so well). Plastic bags would probably be fine as long as you added lots of tiny holes in the sides.


2) I’d be interested to learn about your worm tea making process – sounds like you might simply be dumping the vermicompost right in the water. My suggestion would be to submerge a permeable bag (cloth, nylon stocking etc) in the water so that most of the vermicompost can actually be removed afterward (i.e. you aren’t left with sludge in the bottom) and the tea itself doesn’t have much particulate material in it. If you are getting a crust on top of your soil this is perfectly fine but breaking it up and mixing it in with the soil a bit will likely be the best approach – it will be easier to water the plant, plus you will end up with more benefits from the material itself.


3) Excellent question – unfortunately I don’t really have a good answer for you. I can only share my own experiences in this department. Egg carton / drink tray cardboard is actually my favorite for vermicomposting systems. It is easy to tear up, holds water really well, and seems to break down fairly easily (in comparison to other cardboards etc). I have seen no evidence of harmful effects, and in fact, the worms always seem to thrive in systems when I use it. I’ve noticed that this type of cardboard (especially the drink trays, and the stuff used to pack electronics etc) can have a rather strong, almost vinegary odor to it, so I have little doubt that it contains some form of “chemical” – likely some sort of binding agent. My gut feeling is that it’s not really anything to be concerned with, however – again, the worms just seem to love the stuff, and will happily convert it into grayish worm turds over time.

That’s odd that you are not seeing any evidence of worm “nibbling” – perhaps they’re simply more interested in other materials you have in the bin?


Anyway – hope this helps, Ursula. Thanks for the great questions!

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    • Steve K
    • February 15, 2011

    “gray worm turds” cracked me up.

    I have also used all sorts of egg cartons, paper based packing materials, etc in my bin, and they have broken down pretty easily. The only exception is that the egg cartons are a little thick on the bottom of each egg-holding cell, so there are leftover paperboard rings that sometimes take longer to break down than the rest of it. Still, everything seems to break down faster than corrugated cardboard, but slower than newspaper.

  1. Hi Ursala,
    My personal research (which is as far from scientific as you can get),
    is that if the VC stays moist it should be ok. My evidence is: when I get a tub of finished VC, I toss in a dozen or two of worms. The way I see it, if those worms stay alive, the VC is ok. I have a tub from last June that is still moist and the worms are still alive. On the other hand, I have several tubs in my garage that froze. I guess I’ll find out how that VC is when it thaws.

    • Lonnie
    • February 17, 2011

    When you purchase worm castings from a local person or over the internet (eBay),
    how can you tell if worm castings are “good” or alive? Mark, how are you going to tell if your frozen bins of worn castings are any “good”? Thanks

  2. Hi Lonnie,
    I don’t really sell anything but, I think you pointed out a good business practice should I decide to go retail. There are ways to test for microbial content and that comes with a big price tag. I not sure how the cold affected the VC. I think in the future, I will have to find a way to store my tubs inside so I can have an assurance of quality VC.
    Thanks for pointing that out.

  3. Hi,

    I just wanted to say that I store my worm castings in the empty 1lb. lettuce containers that you get at Whole Foods. These are clear plastic but any leftover worms (and there are always some of those!) and any worms from cocoons left in there seem to do fine. I go through the castings periodically or before I am going to use the castings in my garden and take out any worms that I have missed. I always keep the lid on but pushed down on only one side. I leave the other end “ajar” or unattached for oxygen. I think that is a great idea from Mark to have some worms in there to test if the vermicompost is OK. In effect I always have worms left in there: either I missed them or they hatch after I separated the castings from all the worms. It is a good way to recycle those lettuce containers!–Sandie Anne

    • Lorne
    • February 22, 2011

    i’ve read somewhere something about letting castings or it might have been vermicompost sit for a period of time to ‘cure’ – something like 6 weeks?

    page 63

    my first gift of worms came with these ‘instructions’ – still some of the best out there

    • Mike From Kansas
    • March 13, 2011

    — 1. How can I store worm castings for use later in the spring?
    I have very good success storing castings in large autoclavable gusseted bulk spawn bags that are widely used in mushroom cultivation. They have a micron filter that allows gas exchange without loosing moisture content (which KEEPS them from going anaerobic and keeps mold spores out, as well as pests!). I have only used the “Large” size which holds a little over a gallon. Only downside is that you need an impulse sealer – can find them on ebay & mushroom cultivation supply stores for around $25 (plus shipping). I reccomend looking for one that seals bags up to 12″ wide and has a seal of 2mm or wider. They ARE reusable (I just clean them out well with water and let them FULLY dry before re-use). After filling and sealing I store in a cool dry place, I have an old fridge set at around 60 which seems to work well.
    NOTE: I DO NOT “Pasturize or Sterilize” – Which is what these bags are intended use for. I simply have not tried this out… Pasturization is supposed to kill all “evil” spores/microbes but leave the good ones.

    — 2. When I make worm tea (1 cup to 1 gallon) for watering
    house plants the castings accumulate on top and eventually
    form a crust. Do I need to break this up?
    It sounds like you empty your whole “concoction” in the watering/folier process. The process I do is simple and VERY effective. Here is my formulas and steps for the proccess of brewing. Note: I mix this in a “Food Quality” 2 gallon bucket, but only make 1 gallon batches as I only have a 1 gallon sprayer (I am an avid vermi-aquaponic grower and in which requires me to folier feed, so not that much tea is required)

    SUPER Worm Tea:
    – 1 — Food safe/food quality bucket w/lid, that can hold at least 1 gallon (I reccomend a 2 gallon – 5 gallon)
    – 1 — Air Pump (I reccomend one that is sized for a 50 gallon aquarium – mine has 2 outlets which works best in the following plans)
    – 1 — Nylon paint strainer (Found in the paint section at your superstore/hardware store)
    – 2 — Small air stones (the little blue ones found in the aquarium section/pet store)
    – 2 — Large air stones (make sure that they will fit in the bottom of the bucket)
    – 2 — 1/4″ T fittings (used for the air line – found close by the air pump)
    – 2′-4′ — 1/4″ air line (I reccomend 4′ just in case you mess up, also give u more line to locate the air pump)
    – 1 gallon — Fish Aquarium Water (I use this from my aquaponic system – distilled water will work just as well. I DO NOT reccomend tap water as it contains chlorine/florine/and other nasty stuff I just dont want in my system!!)
    – 1 cup — High Quality Vermicompost
    – 1/2 oz — Unsulphured Organic Blackstrap Molasses
    – 1 oz — Natural apple cider vinegar
    – 1 oz — Maxicrop Liquid Seaweed Plus Iron (I need the extra iron for aquaponics)
    – 1 oz — Maxicrop Liquid Fish
    – 1/2 oz — Unsulphured Organic Blackstrap Molasses
    1) Drill two holes 1/2 inch each in the lid.
    2) Cut four lengths – 2 inches each and 3 lengths – 1 foot each of air tubing.
    3) Attach one airstone to each 2 inch length of air tubing.
    4) Connect the 2 small air stone/tubing assemblies to 1 T fitting and repeat for the large air stones.
    5) Connect one each of the 1 foot tubing to the T fitting asseblies made in step 4 (you should have a large stone assembly and a small stone assembly)
    6) Thread the end of the 1 foot tubing through the holes in the lid (making sure the air stones are on the “inside”) and connect it the outlets on your air pump.
    7) Fill bucket with the 1 gallon fish water/distilled water, add one portion of the 1/2 oz molasses, and mix it up.
    8 ) Load your paint strainer with the 1 cup of vermicompost, add to it the small air stone assembly, and tie off. (should resemble a tea bag)
    9) Drop in the large air stone assembly and the tea bag.
    10) Plug in the air pump. IMPORTANT NOTE: make sure your air pump is located ABOVE the bucket… just in case it gets shut off or unplugged – it wont create a syphon and ruin your air pump!!
    11) Brew over night in a cool location (12 hours)
    12) Shut off air pump. Remove the Tea Bag assembly (air stones included – simply remove at the air pump)
    13) Remove the T assembly connecting the 2 large air stones and simply connect each to the a 1 foot tubing section (you should have an extra length cut earlier)
    14) Add in the vinegar, seaweed, liquid fish, and the 2nd 1/2 oz of Unsulphured Organic Blackstrap Molasses.
    15) Plug the air pump in again and brew away!! I reccomend at least 12-24 hours.

    NOTE: If you dont want to make “SUPER Worm Tea” – Simply stop at step 11 but brewing for 24 hours and not 12.

    Also Note: I use this as a folier feed, any extra that is left over I use a drench. I only apply when plants show a nutrient deficiency or pest problem. All these products are safe to use in aquaponics and havnt noticed any adverse problems. My plants LOVE IT.

    — 3. Do those gray egg cartons which organic eggs are sold in
    have any chemicals in them that may harm the worms?
    I use the torn pieces for bedding but the worms have never
    even nibbled them!

    As far as I’m aware, there is no harmfull binders/chemicals in the cardboard. I have also never noticed them not munch on them… they love it!! Maybe try smaller pieces?
    Note: I also throw them in my with my SUPER Tea for a copule hours while it is in the last hours of brewing. Then I ring them out really well before adding them to my worm bin. Because as you might know, the tea is a microbe heaven!… The worms dont fully eat the food and bedding – the microbes do – they break everything down and the worms then eat the microbes. So loading up the cardboard with microbes, in theory, should speed things up. I havnt done side by side comparisons (tea soaked and plain water soaked), but this is something I have always done from day one. It works, dont see why I need to change.

    • Brad I. from Portland, ME
    • October 11, 2013

    On storage of vermicompost/castings

    I was thinking of what I could use for storing VC over the winter that is
    breathable & that I could add more VC during the winter months easily.
    What about using burlap coffee bean sacks available for free at local
    coffee bean distributors/retailers? The sacks are large in capacity with
    plenty of room for ventilation and the burlap may help dry the VC that might be a little wet/clumpy. I picked one up today and will update with
    my results.

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