John W’s Rotating Screen Harvester

What is it with people named “John” and their harvesters?! (see also “John’s Passive Worm Harvester” and “John’s Homemade Worm Harvester“)

Regular RWC reader and discussion participant, John White, recently told me about the success he was having with his new DIY vermicompost/worm screener. This nifty piece of equipment (shown above) is based on the “Low Cost Homebuilt Worm Casting Harvester” design (freely) available on the Washington State University website.

Here is what he wrote :

A while back I sent you an email that had some links on it for compost tumble harvester plans. You told me to send you some pics if I ever made one. Well I made one; and I have to say that I LOVE it. It is much faster than what I had been doing before. It was very easy to make and only cost maybe $30ish. It gets about 95% of the worms out and I would say almost all of the unfinished compost.

Anyways here are the pics…

The green one is the starting product. It was from my WF360. The small yellow tub was all the worms and unfinished compost that came out of the end. and obviously the clear container is the finished product that came through the screen.

What I did last time i used this was gave it a few weeks after I harvested the material and then put some watermelon on top and harvested all the little worms that made it through the screen.

And from a follow-up email (responding to some questions I had):

Almost all of the worms ended up in the container of bulk stuff. Only the really small worms fell through the screen.

I have done this twice now. The first time I took the time to really let it dry out a lot. It worked, but this time I need some room cause my worm inn is full and I am trying to get casting for replanting my yard this year…so I took the lid off of my 360 for 2 maybe 3 days and just let it air dry a little. I probably could have gotten more casting had I given it more time to dry…but after looking at the bucket of bulky material…I don’t think I would have gotten to much more castings. Now I will just dump these back onto my 360 and let the worms finish it up.

I was really pleased with the speed. If you get the right bucket underneath you can really spin the barrel quite fast and process a lot in a short time.

The harvester uses 1/4″ “hardware cloth” screen, and John mentioned that he already had the screen and paint rollers – so a more realistic cost for someone starting from scratch might be closer to $50.

Thanks very much to John for allowing me to share this. Definitely seems to be a great (and afforable) screening option!

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    • John Duffy
    • March 22, 2013

    Way to go John. The paint rollers were a brilliant solution for bearings.

    • John w
    • March 24, 2013

    Yeah. It was one of those “this has to be to simple to work” things that actually worked!!! I have been using the turbo light harvesting method for a while now but kind of dreaded it cause I don’t have much work space. This really speeds up the process though!

    • Kim from Milwaukee
    • March 25, 2013

    John, how are you turning it?? Do you use a knob or just rotate it by hand? This is really brilliant, I think I have everything at home to make one!

    • John W.
    • March 25, 2013

    I just do it the old fashioned way and spin the bucket as you see. It turns very easily on the pvc pipe. I have seen where some people make similar contraptions and put handles on it, but for me i wanted to keep it simple as possible.

  1. Looks great! I know I will be building one in the next few weeks and getting ready for my first (EVER!) harvest! Can’t wait! Thanks!!

    • John W.
    • April 3, 2013

    the only real trick is to make sure you have the right size bucket under the screen. After this pic was taken I replaced the blue bucket for a bigger one. You could also put a tarp under it. If you have to small of a bucket you just have to spin it slower; otherwise you spin casting out of the bucket.

    • oneman
    • April 10, 2013

    Two bits of thin flat board in a V screwed underneath ( like a long funnel does the trick. the tarp is another good idea. If using the board, remember to give enough room underneath to catch the cast.

    • Susie Kayser
    • April 23, 2014

    John, I love the paint roller idea! I was trying to think of an easy, cheap (relatively low-tech) way to roll the aerobic composter I plan to make from a plastic barrel. I also want to harvest my worm castings, and this thing can work for both! I will let you know what my costs are, but I think I can do it pretty cheap – we never throw anything away that might have a new life left in it! I’m excited!

    • Texgal
    • October 19, 2014

    Finally got around to making this harvester. THANK YOU! It took about 10 minutes to harvest the castings and it was done!!! Quick and easy. I did a demo with some of my “worm” friends and they were all excited over it. Thanks again.

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