Wheelie worm bin

I'm going to move my existing compost bins due to a planned house extension. They are just a couple of pallet bays which I throw everything in and empty/turn once a year. It suits my lazy style but does have drawbacks - no lid means the heap is always wet and cool and doesn't kill weed seeds, the birds and dogs fish out anything they think is interesting (our pup has a few upset tummies I think due to eating something she shouldn't, like overripe pears), and I think a rat family lives in one side. So I have an old wheelie bin maybe 18 in section 4 ft tall. It has a lid and wheels, but has a split up one side. I've been using it for garden rubbish - ie plastic /metal bits that I find or generate in the garden, but I'm wondering whether I can make it into a worm bin.
I think if I only use the new bin for kitchen scraps I won't need such a big compost bin. I do compost most garden weeds and such in situ - chop and dropping etc. Actually I chuck the nastier stuff under my willow fedge and let them fight it out, slowly the soil is building there.

So this (attached) is my schematic of how I'm imagining the bin. I'll find or make a suitable tray that fits in the bottom of the wheelie bin, above that is a mesh which holds the worm chamber material above, but lets finished compost fall into the tray. New scraps, cardboard, charcoal? are loaded at the top. I'll fish some likely looking worms out of the existing heap when I empty it to start my population.

Questions -
How big should I make the holes in the mesh?
Are rats likely to get in - how could the risk be reduced?
What have I forgotten, is that how a worm bin should work?

My climate is mild and moist all year (usually between 5 and 15 deg Celcius), so I'm not too worried about the worms getting too hot or cold. I can make sure the bin is out of the sun (should it ever return!)

Hello Nancy, there is a company in NZ that sells wheelie bin worm farms and you might be able to get some ideas from their set up https://www.hungrybin.co.nz/

I have considered making something like this with an extra rolling trash/recycling bin. My main holdup is cutting plastic which always sends microtrash flying everywhere, but of course this could be mitigated. I look forward to seeing your results!

Megan Palmer wrote:Hello Nancy, there is a company in NZ that sells wheelie bin worm farms and you might be able to get some ideas from their set up https://www.hungrybin.co.nz/

(edited to add picture from above link)

Thanks Megan, I'd seen some of these in some of the websites I looked at. Their design looks much shallower than a full size bin, and has a taper but no mesh as I understand it. Seems to be a well thought out and practical bin (speaking as one who has never kept worms as pets, only free ranging!) The natural compression of the taper is supposed to give the worm compost enough structure to stay in place until harvested.
Most of the designs for reusing bins have pipes as the lower retaining structure, but a) I don't have pipe and b) it would involve more cutting of plastic to install. I do have some 1 inch galvanised mesh left over from shop shelving which should be durable to last for a few years, but I don't know whether the worm residue will fall though too fast or not at all, It wouldn't be so easy to rake it out as the pipes in the normal designs I have seen...I'm assuming the extra depth (potentially) of my design is not a problem as such.

Ben Zumeta wrote:I have making something like this with an extra rolling trash/recycling bin. My main holdup is cutting plastic which always sends microtrash flying everywhere, but of course this could be mitigated. I look forward to seeing your results!

Great (Permie) minds think alike! Maybe you can share your progress too! As regards cutting plastic, probably something that would melt as much as cut will give the cleanest cut. Bins are normally made of polyethylene which has a very low melting point. I think I'll have a go with a nibbler type tool. That has a scissor action and cuts out a thin strip rather than swarf, but I'm not sure whether the blades have enough open bite for the plastic width. Maybe someone already has experience to share.

This fellow made something very similar to your idea, complete with a tutorial. I love Captain Matt's channel. His enthusiasm is so contagious. https://www.youtube.com/watch?v=2cqjmCNGhfM&t=912s

I've been making something similar for years.  11-gallon kitchen trash can is my biggest seller.  I start out with a layer of cardboard and several layers of newspaper, formed as a basket to keep things 'in'.  After several months, the compost has built up enough to not all fall down if you take that false floor out.  One thing I found out is you need a lot less support pieces than you think.  I had them every 2" and nothing was coming through.  I took every other one out and things worked fine.  Good luck.

Now presenting my completed worm wheelie bin:

Starting materials

The bin is the original one we had for the shop. We got a new one because this one had nasty splits, but I've been using it as a garden rubbish bin for years. Judging by the moulding marks it was made in 1983, so has done it's duty as a bin. I can't remember where the fridge shelves came from - again I think they were from the shop. Not pictured are 4 lengths of batten wood, a few screws, tools and tiewraps, and a door handle.

Having checked that the shelves and trays would do the job, I sketched on the side of the bin where the shelves would go. I made a good distance between the shelves, so as to get in with a hand for loosening compost if necessary. There is a fair amount of space under the lower shelf to the floor.

a view inside

I used a large drill to make a hole, and then my reciprocating saw with a fine toothed blade to cut the door and slots for the trays. There was a bit of swarf from the drilling, but the saw seemed to generate very little; I think it melted the plastic as much as cutting it. On one side the shelves sit in a slot on the wall of the bin, on the opposite side the trays are supported by a wooden batten, which is screwed through the plastic into another batten.
Drilling holes at the ends of the cracks ought to stop them propagating more, and small holes at strategic places hold tie wraps to hold the crack closed.

Stopping cracks with drilled holes and tiewraps

Two larger tie wraps form crude hinges for the door, and I found a little metal mushroom and bolt to make a knob. The door is just wedged in position. At the moment the bottom of the wheelie bin doesn't have any cracks (although the axle is seized so it doesn't actually wheel, just drags) so it should collect worm juice nicely. I may lift it onto a plinth and fit a tap (faucet) to drain the worm juice.

finished worm bin outside kitchen

There are rather large gaps between the edges of the fridge shelves and the sides of the bin. I've put a sheet of cardboard and some layers of newspapers as a base layer before putting in a few inches of compost. Some of this is new (bought) potting compost and some is from failed plant pots (which included a couple of worms). I've put a bit more shredded cardboard on the top, but I guess a sheet of cardboard to cover the vegetable waste as it's added will make the worms more comfortable. I'll start adding the contents of the kitchen compost bin to this rather than the compost heap, which (all being well) can now be dismantled and some suitable worms relocated.

cardboard and newspaper support compost worm home

The whole job took about 3 hours.

I thought I'd give a little update on my worm bin, how I've used it and success or otherwise.

During the year I have been using it for most of our kitchen waste (although I found out my husband has been continuing to use the old compost bin too..) Probably a caddy (about a gallon) full of waste about twice a week or so. The problem has been that this is far too much waste for the worms to digest - there has been very little sign of them and the bin has been full of fruit flies over the summer. I thought it wasn't working at all, however I emptied it today and there actually were quite a few worms under the surface.
I'm going to set it up again, but put less than half the volume of waste in this time. I'll also try and put more 'browns', cardboard type waste, to get a better aerated mix and hopefully fewer flies. This does mean I'll need to dispose of the rest of my kitchen waste elsewhere. I'll probably set up another slow compost bin elsewhere, rather than build another worm bin I think

I've finally got round to moving my compost bins (reported here). So I've also set up my worm bin with some of the worms relocated from the old compost heap. I'm going to try and take it very slowly and not overfeed the worms this time. I've got a source of clean wood shavings I can add to keep the worm bin from getting unbalanced. Hopefully I can do better keeping the worms happier.

worms in new home

Nancy, rock on!  That looks really great!