Walnut Shells and Banana Peels?

In the spirit of continuing to dust off long lost RWC experiments (I swear I feel more like an archaeologist than a vermicomposter half the time! lol)…

Near the end of January 2017 I set up a small experimental zip lock bag system using walnut shells as a main bedding/food material. Then…wait for it…I basically forgot all about it for the better part of a year. (Shocking, I know! 😉 )

Well, just before the Christmas holiday, for whatever reason I started thinking about vermicomposting walnut shells again – and I decided to start up a bigger, “fancier” experimental system. We’ll talk more about that in a minute.

Of course, it only made sense that I should check on the original system as well!

It seems as though most of the walnut shells are still intact, but basically everything else originally added (shredded cardboard + dry beans and rice/barley mix) has been converted into rich, earthy-smelling compost.

Interestingly, the label on the bag seems to indicate that I added ONE worm on Feb 21 (2017). Guess I didn’t get around to blogging about that! lol
Digging through the contents of the bag I was able to quickly find about 10 Red Worms and quite a few empty cocoons. The split between adult and juvenile worms seems to be about 60:40 (young:adult). I would say the adults are fairly close to “normal” size, but they are very dark in color.

I had actually planned to add the contents of this system to my new system, but I noticed there seemed to be fungus gnats in the old one. So I’ll just keep it going independently. Speaking of which – just for fun, I decided to sprinkle in some chick starter feed and add some water to see if I can accelerate the break down of the shells (and development of the Red Worm population).

[Oh, and in case you are wondering how I ended up with 10 or more worms yet only started with one – my guess is that the “living material” I added when originally setting up the system contained one or more cocoons in it. Either that or the one worm was an adult, and already fertilized.]

Moving on…

For the new system I definitely wanted to add something that would (hopefully) balance the less-than-ideal walnut shells. The first thing that came to mind – something we have a good supply of in this household – was banana peels. My rationale is that the peels should offer much more food value than the shells, and should break down into a nice habitat material for the worms.

Over the past few weeks I have been stock piling both materials in preparation for getting this system set up – and yesterday I decided to get the ball rolling.

Step 1 involved dumping in all the walnut shells – 3.7 lb worth! If you’ve ever felt how light a walnut shell is, you’ll know that this translates into a LOT of shells!

Next I dumped in 5.46 lb of banana peels. Some of these have been sitting for quite some time, so there was a fair amount of liquid down in the bottom of the holding bag.

I then mixed the shells and the peels really well.

Originally, I had planned to then leave the shell/peel mix to age for a while before adding any worms. But for the sake of jump-starting the experiment, and to reduce the risk of problematic conditions developing (eg excess fungal growth, funky smells, fruit flies etc), I decided to add some worm-rich material right away.

As it turns out, I had the “perfect” material for the job! Last fall I brought in some feed bags of worm-rich material from outdoor beds with the intention of concentrating the material for the “worm-mix” product I sell up here. I ended up shutting down early, simply leaving the bags to sit in the basement.

These are breathable bags and no water or food has been added since they were brought in, so the material itself has dried out a fair bit. The worms have shrunken down quite a lot as well. But it is a beautiful, crumbly “living material” (with loads of tiny worms in it) so it ended up being the perfect addition to the new system.

I mixed in maybe 5 or 6 handfuls of the material, and then layered a little more over top.

Apart from stocking the system with Red Worms, this mix will add all sorts of other beneficial organisms, and will help to wick up any excess moisture from the banana peels.

Similar to my “Tiny Red Worm Rehab” system, this bin will only have a garbage bag as a cover.

I am really interested to see what happens with this system. I am confident that the shells will break down a lot more readily with a steady influx of banana peels, I have little doubt that the worms will thrive – and I suspect that the finished compost is going to be really nice stuff (with maybe a nice extra boost of K from the peels).

Stay tuned!

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    • Caleb
    • January 12, 2018

    Awesome stuff on the followup from the previous walnut experiment! Can’t wait to see the future results of this one! I hope you don’t get too many fruit flies, that’s always my annoyance with banana peels – a lot of times they come with the fruit fly eggs in the peels already when you get the from the store, so they just hatch up real nice in my bins. I always try to bury them now and cover with a good amount of dry cardboard on the top as a result.

    But banana peels are an amazing food material, they break down easy, lots of sugars and starches… good stuff!

    • Caleb
    • January 12, 2018

    Oh 2 other questions:

    1) Have you considered using a food processor to pre-chop the walnut shells at all?

    2) How do you feel about other nut or similar products? Peanut shells? Apricot/Peach pits? Pistachio shells? How about the nuts themselves? I had a whole bag of pre-shelled pistachios go bad, I washed them off with water for the salt, then threw them in too.

    • Mads
    • January 13, 2018

    Hi Bentley,

    wonderful to see some blog posts from you again. I’ve missed it and have been a bit worried for you.
    This experiment is you in a nutshell and I’m curious to follow it. My own experience with nutshells is that they take forever and a day to break down. When I sift the harvested material from my flow through systems the shells are still there. They are a bit softer and I can break them apart by hand, but they go back in as excellent living material when feeding. The insane amount you’re putting in this tub will require years – 3-4-5 years is my guess. But as mentioned it’s a kick ass living material you can use again and again …and again …and again.

    • Bentley
    • January 13, 2018

    CALEB – Yeah I think this one is going to work out a lot better! I agree re: fruit flies, but thankfully during colder times of year they don’t seem to hatch out of the peels. During warmer months I will more than likely freeze all peels before adding them to the bin.
    As for using a food processor – while this would definitely speed up the process, I tend to prefer a more “lazy” approach! lol
    Other tree nut shells will be similar in terms of resistance to breakdown. I suspect peanut shells would break down a lot more readily, since it is more like a fibrous pod than a hard shell. And just to be clear – I am not really expecting this material to get completely coverted to worm castings the same way the banana peels do. I will almost certainly be left with partially broken down nut waste that can then be screened and used as a great “living material”.
    As for the nuts themselves, while they will certainly break down, keep in mind they are very high in fat, so they may be more resistant than typical fruit and veggie wastes and if you have a lot of them they may get a bit rancid.
    I’ve never really tried adding a lot of nuts at once. I’ll be interested to find out how it works for you!
    MADS – Thanks for your kind words and concern. That is funny – “forever and a day” – lol. Yeah, as touched on in my last response, I’m definitely not expecting them to be converted into castings. I am actually more excited about their potential as a great future living material to be added to other systems (which it seems you have been doing, and are recommending, as well – cool!)

    • Amy Drummond
    • February 5, 2018

    Hi Bentley,
    I am really enjoying learning about all your worm experiments! I was a biology major in college, worked a little, then took 2.5 decades off (HA!) to raise my 6 kids and homeschool them. I just started my first worm farm in the fall, and I think it is going well. It is wonderfully reassuring to me to hear you totally forgetting and neglecting things sometimes and coming back to find that the worms are still hanging in there. Maybe mine will survive my mistakes too! I had steered away from banana peels, but now I will just make sure to freeze them before adding. My family is not sharing my enthusiasm yet, so I don’t want to fill the house with funky smells and more bugs just yet!

    • Bentley
    • February 8, 2018

    Hi Amy – sometimes we just need a decade or two to figure things out! 😉 I can definitely relate! haha
    I also understand the lack of enthusiasm other family members can feel (partially from my own experiences, but largely from all the feedback I have received on the topic). Just keep at it and show them the amazing results (grow some healthy plants etc). Hopefully that will get them to come around!
    Either way, you’ll always have your online “worm-head” friends to fall back on for support.

    • indano
    • February 9, 2018

    run banana peels through a blender, add enough water to blend well, worms seem to thrive, in the moist food.

    • Sue
    • July 7, 2018

    I made a mistake by adding Chestnut shells ca. 3 or 4 yrs. ago and I’m still picking them out when harvesting compost. So I agree, Walnut shells might take a life time and a day.

    • Bentley
    • July 11, 2018

    Haha – that’s funny, Sue!
    I have seen some evidence of them breaking down, but it’s pretty clear that the level of resistance is similar to that of wood (if not even more resistant).

    • Robert
    • November 27, 2018

    I use an old coffee grinder to grind egg shells and today I decided to give the walnut shells a try the are hard to blend up for sure but I broke most of them down to a heavy grit

    • Sue
    • November 29, 2018

    Hello all;
    revisiting this page gives me an idea to do the same with pumpkin seeds that will take a lot less time to break down, I hope. I sell my vermicompost so seeing lots of pumpkin seed shells is not attractive. Was going to put them through the (manual) grain grinder but now I change my mind and will start a 3 gal. bin with it. Could have saved me the trouble of drying them; but now this will save me the trouble of grinding. The light bulb didn’t turn on until today.?
    Every time I used my manual grinder, I can’t help thinking about the poor donkey of olden days, walking round and round to work the grinder, haha.

    • Bentley
    • November 29, 2018

    Hey Sue!
    This comment reminds me I need to post an update for this one! Over time the shells seem to have become really brittle. And I have decided to convert this one over to a more “normal” system with regular inputs and more moisture. I suspect they will break down pretty well. But screening is always important when selling. Anyway – good luck with the grinder!

    • Sue
    • November 29, 2018

    Bentley: Now that your shells have become brittle, I agree with your decision to run it as a normal bin. Shouldn’t be too long now and please keep us updated. Thanks.

    • James Gililland
    • January 14, 2019

    I use a leaf blower-vac to break down pecan shells. I get produce (tomatoes, cucmpers, lettuce, cabbage, carrots, celery). An run them through a juicer. Takes a while, but the smaller the better. I put the veggies on top of my worm bin filling half the bin. Then topping it off with ground sweet feed, an chicken feed. Then with ground pecan shells w/ the pecan meat. Takes time getting all that together. But the outcome beautiful vermiculture.

    • Debbi Bothe
    • January 8, 2020

    I have some walnut shells that I was wondering about adding to the vermi-bin. I was thinking I’d give them a good pre-soak for 24-48 hours first …. Thoughts? Updates?

    • Bentley
    • January 14, 2020

    Hey Debbi – they are ok in moderation. Basically same as something like wood chips. They will take a LONG time to fully break down but they can become a sort of “living material” over time – screen em out and re-use to inoculate new systems. If you have a lot it is probably better to toss in the garden or in a bigger outdoor system.

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