DIY Worm Harvester

I meant to write about this topic quite some time ago, but it somehow fell by the wayside during the summer. Thankfully a reader email re: worm harvesters reminded me about this overdue post.

For anyone who becomes even semi-serious about vermicomposting it is inevitable that the issue of separating worms from vermicompost will arise. I’ve found that with high enough densities of worms in my tubs I can harvest using the ‘light method’ quite quickly, but this is still far from the ideal method. I have also written about my ‘garbage bag harvesting method‘, which seems to work reasonably well, but isn’t really helpful for actually harvesting worms – it is better suited for transferring all your worms to a new system.

Earlier in the summer I had an enjoyable conversation with one of my worm customers (who came to pick up his order). Like myself this person has a keen interest DIY ‘eco’ projects – like worm bins and aquaponics systems – and is always on the lookout for cheaper ways to make really useful equipment.
At one point the topic of worm/vermicompost harvesting came up, and he told me about an article he had come across outlining how to make your own trommel harvester. Long story short, I asked him to pass along the link when he got home so that I could check it out for myself.

The article in question is called “A Homegrown Worm Harvester” and is found on “Bishop’s Homegrown” blog. I’ve had the pleasure of exchanging a few emails with Alan Bishop, the owner of the site, and I must say he is one of the nicest guys you could ever hope to meet online. His ‘homegrown’ site contains a wealth of fascinating information about his ‘ecologically-managed’ farm located in Indiana – I highly recommend you check it out. Unfortunately it looks as though he hasn’t been adding new posts for a few months, but hopefully he’ll get back to it once the cold weather arrives (and the harvest is finished). Just so you know, Alan also owns a really interesting looking forum called “Homegrown Goodness” – also definitely worth a visit if you are interested in homesteading and related topics.

Ok, back to the topic at hand…

Alan devised his home harvesting system after testing out a smaller version he built based on plans he found online. While certainly functional, he found that it took too long to harvest the quantities of material he had on-hand, so he decided to improve upon the design.

Alan’s new system is really cool, and it apparently also works very effectively. The trommel screen is basically just a plastic garbage bin that has been cut in half and then re-attached via a length of 1/2″ screen (with 1/4″ screen on the outside). To attach the screen to both halves of the garbage bin he simply used plastic cable ties.

I must admit that I became a little muddled trying to get through the rest of the instructions – while I’m certainly a DIY person at heart, that’s not to say I have any talent for building things. Part of the reason I emailed Alan originally was in fact to see if he could help me understand how the unit was actually constructed. He ended up sending me this helpful email:

Sorry about the confusion with my post, I think I was pretty sick when I actually wrote that and looking back, it is pretty hard to follow, I’ll try to elaborate here.

I turn it by hand basically.

More or less the basic premise is to cut a large plastic trash can in half and cut the bottom end out, buy some small gauge chicken wire and wrap it around one end of the trash can using those plastic lock in straps to attach it tightly to the trash can (you will have to drill some holes in the trash can in which to insert those lock straps) about an inch or two up from where you made the cut, take the other end of the trash can and do the same thing with the chicken wire on that end.

Then you build a frame to hold it off of the ground, we re-used some old deck boards we had lying around. The next step is to find a pipe or some other type of metallic rod that you can use to suspend the harvester through the middle of the frame at a 40-45 degree angle.

You will have to bore a hole in middle of the support board on each end of the frame, on the end in which you add worms and compost you want it to be high and on the end in which the unfinished material and worms will fall out you will want it to be lower (40-45 degree angle). You will then have to place a couple of wooden braces in each end of the trash can, cut them to size (to fit the diameter of the trashcan) and then use screws to hold them in place you will then bore two alligned holes through those for the metal rod. Since the trash can is held at an angle you will have to place some type of brace on the back side of one of the wooden braces to keep the trash can from sliding. We used some Koetter pins I believe.

So there you have it! Thanks again to Alan for sharing all this great info. I definitely want to see if I can build one of these myself, and encourage all you DIY worm buffs out there to do the same. Of course, if you DO make one (or some other type of harvester), please let me know!

[tags]worm, harvesting, harvester, vermicompost, worm castings, compost, red worms, compost worms, trommel, trammel, compost screen, screening, harvesting worms[/tags]

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    • vermiman
    • September 14, 2008

    How is the tube held in the center of the harvester? That is since the bottom is cut out.

    • Bentley
    • September 15, 2008

    Hey vermi,
    He has two wood paddles (one on either end) with holes drilled through them. These are attached to the garbage can. To top it from sliding I think he has some sort of kotter pin, but I imagine there are other ways one could do this.


    • Charles
    • September 15, 2008

    I am going to make one of these but using a 5 gallon bucket. I think it will work best for me since I only have 1 bin and it needs to be harvest badly. I am also using another 2 bins to catch the compost. I will take some pics when its done. Hoping this week to get it done. I already cut of the bottom and cut it in half. Not the straightest cuts but they will do.


    • Bentley
    • September 24, 2008

    Sounds good, Charles – let me know how you make out. Someone else sent in some pics of their system. Will post those shortly.


    • Brad
    • March 5, 2009

    I built one yesterday out of a 5 gallon bucket, I don’t know what I did wrong but the material went way too fast… I then build a set of screen boxes to sift it we’ll see how that works out. I am going to build a larger version of the bucket with a barrel to see if size really does matter 😉

    • Gatis
    • June 30, 2010

    Hi guys,
    Can anybody explain me one thing: when you decide to separate worms from castings, I mean, these castings are quiet wet and the question is: how do you get it fall through the screen into box?

    • Bentley
    • July 1, 2010

    Great question, Gatis!
    Vermicompost coming from an enclosed plastic tub bin (and many types of bin/beds for that matter) will often be pretty wet and not really well suited for screen harvesting. Your best bet will be to let it sit and dry out on some cardboard (or something else to help wick away moisture) for a few days. Just make sure to break it up as it dries, or you might end up with some vermi-concrete!
    You may also want to test out some of the other harvesting methods found in the harvesting section of the “HOT TOPICS” page (see upper navigation)

    • Gatis
    • July 1, 2010

    Ok, thanks Bently! The reason why I`m asking is, that I was told that if it drys, then it looses valuable elements, but it seem like not to be true – ok if I can dry it, then it all makes sense!
    Thanks! : )

    • Bentley
    • July 1, 2010

    Hi Gatis,
    The key is not to let it become bone dry, or to simply leave it sitting out in the sun since both of these can result in a lower quality material.
    Dry it slowly and break up the larger chunks and you should end up with some decent stuff.

  1. One thing I do when I harvest my BOMs is stop feeding for 2 weeks then I put 2 – 3 brown paper bags or boxes in another plastic tub. I then put the bin contents (worms and all) in the bags or boxes for 48 hours to soak up the moisture. If it is still wet, I dump it in another box for 48 hours.

    • Gatis
    • July 2, 2010

    Mark, could you put some photos of this process?
    (sorry, but english is not my native language, there for I`m not sure if I got the main idea of what you said)
    Thanks! : )

  2. Gatis,
    what is your language?
    Es el español su idioma?


    • Gatis
    • July 3, 2010

    No, no! : )
    It`s Latvian!

  3. Gatis,
    Ielieciet bin saturu kartona kast? uz 2 dien?m. Lodzi?? b?s absorb? mitrumu.

    J?su draugs,


    • Gatis
    • July 4, 2010

    Ok, thanks! I`ll try to do that!

    • Jay
    • July 30, 2010

    Hello everyone

    I’m somewhat new to composting….. just to briefly explain to you guys what I have…
    I stacked 4 cinder blocks on top of each other in one row and 3 in the next I placed 2x6x8 ft long boards across them. This gives me a raised area to stack plants on top of.

    Underneath this area is where I compost. After spending 100 bucks on a fancy tumbler composting bin with a crank I gave up for two reasons It can not hold much material and it attracted flies like crazy with or without the air holes open. I finally drilled small drainage holes on the side and bottom on an 18 gallon storage bin. After Google-ing for ideas I undoubtedly stumbled onto red worms and purchased 2 pounds for 40 bucks with free shipping. Well worth the investment. There are four people in my house so I actually decided to get another bin going and purchased 2 more pounds of worms for the 2nd bin. I notice a huge difference in how quickly scraps and junk mail get broken down with the worms compared to without. I will try and attach pictures in my next post. I Have pictures of a tumbler I made to sort through the castings.

    • Jay
    • July 30, 2010

    A fairly cheap easy way for worm harvester is to get a sauna tube (this is a cardboard cylinder with no bottom,they use these to make cement footings) Or you can cut a 5 gallon bucket or something round. Then you buy 1/4 inch screen. The one i bought was 24inches by 5 feet long it was seven dollars. I cut 18 inches off the sauna tube and then cut that in half. So each end you will be using will be 9 inches. I then rolled the screen over the tube so it overlaps 3 inches. I purchased large zip ties and zip tied the screen to the tube. This gives me and 18 inch area for the compost to be sifted over a bin. Think recycle people ….. I had an old pool handle lying around so I drilled holes through it. I also drilled holes in the sauna tube and ran the thread I purchased all the way though the pole out the other side of the sauna tub. I used washers and nuts so it won’t move around. and it really adds strength to the cardboard tube and screen. I ran 2 threads all the way through on each end so it makes a X
    The stand i screwed a board to my shed and made the opening double wide. This allows me to screen the compost flat and then lift the pole up to get the worms and not ready compost up into another bin separate from the casting bin I hope you all enjoyed the pictures and good luck if you decide to make your own.

    here is a link in case the photos I posted did not work

    • Frank
    • December 4, 2010


    I know this is an old post, but I just saw it today. Many thanks for the excellent photos and a great idea. Do you find that the 1/4″ cloth lets a lot of cocoons and small worms through?

    I had an idea to have 2 set ups: one with 1/4″ and one with 1/8.” Then, sift the contents from the 1/4″ event with the 1/8″ set up. Double work, to be sure, but maybe less cocoon loss..


  4. [IMG][/IMG]

    Here you’ll find plans to build an inexpensive, compact, and light weight hand trommel. It is designed to classify quantity material for your dry-washer, highbanker, sluice, pan, or garden, and can also be used as a worm harvester, gemstoner, or even an arrowhead sifter. The cost of parts is around $50 US. If you’re anything like me then this DIY is at the right price! Have fun finding gold! Be sure to check out the videos on the trommel site. They’ll show you the trommel in action along with mesh change ideas.



  5. Sorry, here is the picture of it standing.


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