Wheelie Worm Bin

For a while I have worked on a design for a flow through worm farm. I have looked into several commercially available systems but they were either too cumbersome, did not produce both worm wee as well as vermicompost or were just ridiculously expensive. However, by looking closely at all these systems I started to get a picture in my mind of what I wanted and how it could work.

As with any such idea I decided that a prototype was the best way to go before spending a lot more money on a bigger system. I was lucky to find a 60 litre wheelie bin on sale at a variety discounter and this gave me the idea of building a mini system to test the idea. The cost of this small wheelie bin was only $12 compared to $75 for a full-sized bin.

The planned flow through system is to have a collection basin for the worm wee, an access door for the spent vermicompost and top access to feed the worm and add any bedding materials.

Starting Bin for 60L Vermicomposter 28th August 2010

The bin shown above is one of four I purchased for various applications including my vermicomposting prototype. You will see a couple of screws already inserted as I had already installed the internal frame before remembering to keep a photographic record.

Tap installed to bottom of the bin to drain the worm wee from the collection chamber.

I installed a tap to the base of the bin so that the worm wee that has collected in the bottom of the bin can be drained into a suitable container for use in the garden. The tap needs to be positioned so that the internal opening is as close to the floor as possible, allowing for the fitting of the flange, to remove as much of the liquid as possible.

Battens for the floor of the false bottom.

Interior of the 60L wheelie bin with false bottom shown. Tap fitting can just be seen middle front.

The next step is to fit a wire mesh floor to create a self draining false bottom. The battens were installed first using 25mm x 25mm hardwood with four pieces fitted to each wall. They are positioned about 15cm above the floor to give a liquid storage capacity of  about 10 litres. The tap fitting can be seen through wall below the front batten. Cut a wire floor to fit neatly to the top of the battens. There is no need to fasten it down but make sure it is strong enough to support the mass of vermicompost that will be sitting on top of it. The next stage will be to fit some shade cloth or similar netting to prevent material and worm falling through.

Mesh Floor covered to prevent worms falling through but still allowing good drainage.

The shade cloth is now wrapped around the mesh floor. Time now to cut out an access door just above, 15mm or so, the floor to allow periodic removal of the vermicompost for the garden. Initially this door will show the start-up bedding but once the worms finish with it, it will all be good compost. Cut the door mostly the full width of the wall and high enough to allow a garden trowel to be used to remove the material. A height of about 100mm will do and a width of 200mm.

Access door cut into front of the bin. Hinge fitted and a latch system.

The picture above shows the position of the access door. I have already fitted a hinge to the top edge and a simple latch to the bottom to keep critters out and compost in. My access door is fitted to the front of the bin, same side as the tap but you can fit it to any side you prefer. The hinge is fitted to the top so that compost won’t get caught up in the hinge when you are clearing it out and it will naturally fall closed if you are distracted. I have found that 1/4 inch gutter bolts are ideal for the hinge while the latch is a galvanised (could be brass) screw screwed into the wooden batten with a washer to prevent the head pushing through the plastic wall. Only tighten the screw enough to control the latch effectively but not so tight as to lock it.

Vent holes drilled in all sides to give good air flow.

I then drilled air holes in all sides to make sure there is adequate ventilation. I used a 1/4 inch drill and made three rows of 4 holes are so. The next step will be to add pre-soaked bedding.

Soaked bedding added to the false bottom.

The bedding is made up of used egg cartons torn into small pieces and well soaked. Egg carton paper makes excellent bedding as it holds enough moisture but is light and holds a bit of air. My layer is about 50mm deep.

Shredded office paper is put on top of the soaked egg carton bedding.

Simply get hold of some shredded office paper or packing material, put this on top of the shredded egg carton paper and then soak with a small sprayer of some sort to get everything nice and wet.

Wet down the shredded paper with a sprayer or watering can.

I used a special little sprayer made from an old Coke bottle. The spray nozzle comes from Diggers Club who sell these and they are great for jobs where you need a small gentle spray such as for seedling trays and in confined spaces like this.

Add a layer of finished compost for a food and bedding for the worms.

Worms will happily work away on soaked cardboard but get very little nutrition from it and it will not feed them much. Adding some finished compost is ideal as it gives them something to chew on, so to speak, until they are fed their first lot of kitchen scraps or manure. A 50mm layer is enough to get them started. The thickness of the bedding, after settling, is now about 120mm and that will give a couple of thousand worms a good home to settle into. We will now wait a few days for the materials to settle and age a bit then add some worms and the new bin is under way. I will add about 1000 worms to see how it performs compared to my first system which also has only about 1000 worms in it after being harvested to supply the worms for the wheelie bin.

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5 Responses to “Wheelie Worm Bin”

  1. Dave Says:

    How did the prototype go?

    • Adrian Kuys Says:

      Stay tuned Dave and I will organize an update. In short it works very well provided you keep the bin out of the sun as it gets too hot when the sun shines on it directly, even for a short time. I had it under the side verandah which is shaded by a large powton tree and I thought that would be a good spot. Unfortunately it dried out so fast and the worms did poorly and many died. I have since decided that there was also too much air movement through having too many air holes. I now have it in a dark shed with no wind although temperatures still get warm but the worms love it here and have now increased tremendously and also produce plenty of worm wee!

  2. farmer_liz Says:

    Thanks for the detailed post! I have an old full-sized wheelie bin, so I’ll be trying your method using that. Have you tried a full sized bin yet?

  3. Dave2 Says:

    Great design, but I really think they need a soil section (around 20mm deep). This allows the worms to retreat to the centre of this when it does get hot (although your spot in the shed seems ok you might want it closer to the house). I’m going to use your design but with one modification; a mesh level 150mm above the first with a thick layer of cardboard on top. Then add potting mix on top. By the time the cardboard breaks down the potting mix will have become a solid block of castings that will slowly fall down to the level below to be scaped out. I need this mod for two reasons; it needs to be on the west side of the house where my current redundant worm farm is and this gets quite hot on a summer arvo. Also I am doing a second one for dog poo only and I don’t want to scape out from the bottom until fully broken down.

  4. Allan Colquhoun Says:

    Hi Adrian – I have been thinking about flow through systems and have seen many problems & unknowns.
    Here is what I am going to try for a start. A wheelie bin very similar to yours. A leachate collector under the false bottom and that is it. Then the worm food (semi composted organic matter) and bedding in laundry bags working up from the bottom adding at a rate that encourages the worms to finish what they have first (???). A bit of trial and error there.
    Any way when it comes to harvesting the castings just remove the bags putting the very lowest bags to one side and replacing the rest in the bin. Hopefuly the bags at the bottom will have no worms or eggs – some won’t matter. Putting the bedding and food in different bags maybe?
    Still a lot of unknowns but it will simplify things. The bags themselves may break down I just hope they are synthetic.

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