Making a Composting Wormery

Research

A composting wormery is, essentially, one or more containers that house composting worms into which suitable kitchen waste can be thrown in order to produce compost. Wormeries generally consist of somewhere for the worms to live, somewhere for food waste to be thrown, and optionally an area to collect liquid by-products.

A wormery can be constructed from sealed stacking boxes, or nesting boxes or containers. Remember, the tighter the 'seal' of your containers the more vital it is that you add sufficient air holes. When deciding what you want your wormery to look like it is well worth doing a quick image search online to research existing wormery designs of both home-made and commercial products.

I've seen a variety of different wormeries available, and they are mostly either two or three tier designs - though following the same principles. I decided that the additional expense of a third tier was so minimal, that I might as well construct a three tier wormery.

The basic design of a three tier wormery is to have a base, and two interchangeable composting levels. The top composting tier, when filled, becomes the middle tier, and when it does so the middle tier (which should contain compost by this point) is emptied out onto the garden and becomes the top tier. The top tier then has your vegetable (and other compost suitable materials) waste added into it until it eventually turns into compost and fills, at which point the process repeats.

Over time, and as the composting process is carried out, liquid composting by-products collect in the lower/base tier, from which they can be collected and used on your garden as a liquid fertiliser.

Plan Your Design

Before making your wormery you need to put together a coherent plan. Some people might be able to play it by ear and design something on the fly, but I always think it is worth spending a little time at the start to work out exactly what you're doing. This ensures you have all the right equipment to hand, can prevent you making an irreversible mistake, and can save time.

If the price of materials is a factor, and frankly for something like this it really ought to be, I advise to not have too rigid a design in mind until after you visit some shops and check out prices. Depending on special offers or your precise size requirements you may find containers/boxes quite suitable for the task that you hadn't initially considered.

I went to the shop looking for a great deal on individually sealable stackable boxes, and ended up buying garden planters instead.

Once you have your basic materials take some time to measure up your containers and draw yourself some blueprints to guide your process.

I'll describe the components of my wormery and the construction process below, but to start with here is a copy of my design blueprints. Note the drainage tap measured for fitting in the base, a means to raise the middle tier so it doesn't sit all the way into the base, and air holes for the middle and top tiers.

My design shows (right hand side) a front elevation of the base (see tap position) which includes air holes. After further consideration I omitted air holes from the base tier as being unnecessary. The positioning of air holes shown is the same as that ultimately used for the middle and top tiers.

Below: Take a look at my basic wormery design plans.

Suggested Construction Materials

In order to replicate my wormery design, you will need:

• some containers. I used black plastic square(ish) garden planters that measured
  • 320mm long/wide (upper edges)
  • 320mm high
  • 250mm long/wide (lower edges)
• a tap (garden centres should sell replacement water-butt taps)
• a drill with both large and small drill bits
• smaller plant-pot or other object to place inside the base to raise the level at which the middle tier sits
• mesh material
• some sort of lid (if the containers don't come with one)
• newspaper (most of which should be shredded)
• water
• manure
• compostable food waste
• worms - of course

Fun with Drills and Sharp Blades

After planning precisely how your containers will fit together, work out where you need to place your air holes (middle and top tiers), and drill these will the smaller drill bit. you're aiming for a size through which the worms won't be able to easily escape. you will also need to drill worm holes in the base of the middle and top tiers (use the larger drill bit).

Below: These are the black plastic planters I used. This image shows two planters, showing what they look like before they are attacked with hole making devices.

These planters are fairly sturdy black plastic, and I was confident they would maintain rigidity with the number of holes I planned to drill.

After identifying (randomly) which planter was to be my base, I measured and drew on the location of the tap hole, and used a sharp craft knife to carefully (do this very slowly to avoid error) cut out a round hole. The hole you cut should be a perfect circle with a diameter equal to the part of the tap that goes through the hole - yes, this is rocket science!

The height of my tap measured 80mm in height. The hole in the planter for the tap needs to be sufficiently far enough up from the bottom so that the planter can sit on a flat surface without interfering with the tap. My original plan indicated that I would place the tap 100mm from the floor level, though I revised this to be closer to 50mm. As I plan to place my wormery on the edge of a raised bed the tap will have sufficient gap beneath it for me to pour off into a bucket.

Please take into consideration how you will collect your 'worm juice' when planning the tap position. Note also that the higher your tap, the more worm juice your container needs to collect before you can pour any off. In a worst case scenario you can always detach your base tier to pour out 'worm juice' without needing a tap at all.

Above: tap has been fitted into a cut hole in the base tier.

Below: note that the tap is high enough so as not to interfere with the floor - useful if you like a stable wormery on a flat surface.

Below: This tier (middle or top) shows the three lines of air holes, and even shows the badly erased pencil marks that aced as guidelines (a little bit of water or natural weathering will clean these marks away). Your wormery is a functional device, but that's no reason that it shouldn't look nice. You can drill sufficient air holes randomly around the top, or you can measure each hole to the millimetre. Air holes should be small, and ideally the worms shouldn't be able to get through them.

Below: A close-up of middle/top tier air holes. Note that perfect measurement of air hole positioning is no guarantee that when it comes to drilling you'll get the holes spot on.

Below: Food waste is added to the top tier, and worms are supposed to be able to move freely between the top and middle tiers. This means, as they are interchangeable, that the top and middle tiers need to have holes in their bases to allow the free movement of worms. These holes are intended for worm travel, so the more the merrier. Note again the non-random placement of holes for purely aesthetic purposes.

Drilling holes can leave plastic burrs on the inside of your containers. It is worth taking a moment with a craft knife to cut these away. We wouldn't want our worms injuring themselves on sharp edges!

Below: The base tier needs something inside it upon which the middle tier sits so as to keep it raised (at least if you are using nesting containers that would otherwise stack too tightly together). As this ceramic plant-pot was on sale for 99 pence it seemed like a bargain to both act as a support, and also to provide sufficient weight to the base to keep it stable.

Below: Compare the size of the ceramic plant-pot and the black plastic planter.

Below: As the middle tier will have holes in the base, I was worried about worms falling into the base tier. I made a 'net' out of some garden mesh to sit between the base and middle tiers to catch any worms that decide to go exploring in the wrong direction, this will hopefully stop them drowning in their own juices. Note: if this catches worms, they may be able to make their own way back into the middle planter, but it is worth checking, now and then, and rescuing any stranded worms.

Bottom Up

It makes sense to build your wormery from the bottom, so I took the base tier and placed the up-turned plant-pot into it.

Below: Plant-pot inside the base tier.

Below: Plant-pot inside the base tier showing the inside of the tap fitting. Note that the circumference of the plant-pot rim sits snugly in the bottom of the planter. As I purchased these at the same time I was able to ensure that it would fit. The inner part of the tap fitting almost interferes with the plant-pot, so bear this in mind when factoring in the best position of the tap.

Next I placed my worm catching net into the base tier, sitting on top of the plant-pot. The net was easy to make by folding in the corners of a square piece of mesh and fastening the corners together with some sandwich bag ties.

Below: Showing the placement of the net inside the base tier.

The next step is to place the middle tier to sit on top of the net. One way to ensure a good fit is to turn the middle tier upside down, fix the net over the base, and then place this down carefully into the base tier to sit on the up-turned plant-pot.

Below: Showing how the net, in the base tier, fits to the bottom of the middle tier.

Below: Placing the 'netted' middle tier into the base tier.

Below: Final fitting and placement of middle tier inside base tier.

Below: Note the air holes of the middle tier are clearly visible above the rim of the base tier.

Below: Proof that I have more than just the two tiers. Note the middle and top tiers are identical and fully interchangeable.

The wormery needs a lid, this should fit across the top of the top tier. I found this rubber outdoor mat on sale in the gardening section of a DIY shop. The pattern of squares on the top of the mat happens to fit flush with the rim of the planters (the inner 16 squares sit inside the rim, and the outer 20 squares sit outside the rim).

Below: This mat is quite heavy and so not only provides protection from rain and nosy birds, but also weight to aid stability.

Below: Showing how the 'lid' fits.

Getting your hands dirty

Get all remaining materials together in one place, and get ready to dirty your hands.

Below: Here we see some water (in a watering can) and a local, free, unread newspaper.

Below: If making one wormery isn't awesome enough, I made two at the same time. I'm not greedy, one of these is for a friend. Making several wormeries at a time is a great way to spread the cost of materials.

Below: This is farmyard manure, if you hadn't realised. No extra points for working out which DIY shop I purchased most of my materials at.

Below: Worms don't like to read, so most of the newspaper will need to be shredded. Here's a bag I made earlier.

Below: They may not look like it, but these are worms. I purchased these, 1kg per wormery, from a reputable online seller of worms.

Constructing the Wormery

Below: I took a few sheets of unshredded newspaper and tore them to fit inside the base of the middle tier.

Below: Using a watering can I poured on just enough water to wet the newspaper. This will cover over the large holes and (hopefully) prevent worms falling through from the middle to bottom tier.

Below: While I was watering-can crazy, I took the opportunity to pour water onto the shredded newspaper. It needs to about as wet as a half-drained sponge - a phrase that doesn't really mean much. Use enough water to wet all the paper, and if you use an old plastic bag with holes the excess water will drain away. This wet shredded newspaper is going to be a component of the worm bedding.

Below: This is a handful of farmyard manure, I did say we'd be getting our hands dirty.

Below: Put manure into the middle tier until you are halfway up to the air holes. Make sure that the manure isn't compacted into lumps, loosen it in the bag with a trowel, or break it apart by hand when adding to your wormery.

Below: Then add wet shredded newspaper until you are almost, but not quite, up to the air holes.

Below: Mix the newspaper and manure together.

Below: You can't really do this properly without getting your hands in there and really mixing it up. This manure and wet shredded newspaper mix is the bedding material for your worms.

Below: Add a little more manure on top - you should not yet have reached the lowest level of air holes.

Below: Finally it is time to open up your bag of worms. For a wormery of the size shown here I used 1kg of worms.

Below: Carefully transfer your worms from the bag into the middle tier, on top of the wonderful worm bed that you've made.

Below: Extreme close-up of wriggling worms.

Below: Try to spread the worms out a little bit, they are squishy so be careful.

Below: Worms like the dark, so add a little more manure on top of them. You should now be up to the lowest level of air holes. Note that as we are about to put the top tier right on top of the middle tier, this extra layer of manure stops any potential worm crushing.

Below: Sprinkle a little water on top of the manure and worms, just to make sure they're moist. Not too much, we don't want to drown them!

Below: Drop Carefully place, your top tier onto/into your middle tier.

Below: You might just about be able to see some of the worm bedding/manure through the holes of the top tier.

Below: This is a bucket of food scraps. Worms supposedly aren't too happy with citrus fruits nor the fleshy parts of onion and garlic. The picky eaters also prefer their food in small chunks. In addition avoid meat, fish, cheese, and rotting/mouldy food waste.

Below: Tip the food waste into the top tier. Keep adding food waste every few days. Over time this food waste will be turned into compost.

Below: Put the lid on.

Below: Transfer to a sheltered part of the garden, out of direct sun, and where the wormery won't be tipped over by a strong gust of wind. I have contemplated drilling a hole in the rim of the base tier and using a cable-tie to secure to a sturdy stalk of the nearby shrub.

Cycling through top and middle tiers

When the top tier fills with compost the worms will have migrated up into the top tier. At this point empty the middle tier's contents onto your garden (keep an eye out for stow-away worms trying to escape, re-capture them add add them into the top tier). The top tier now becomes the middle tier, and the freshly emptied tier becomes the top tier.

Over time, and as the composting process is carried out, liquid composting by-products collect in the lower/base tier, from which they can be collected and used on your garden as a liquid fertiliser. This 'worm juice', as some call it, is quite concentrated and should be diluted with water at a ratio of approximately 1:10. Keep a close eye that this liquid doesn't fill up the base tier and soak into the middle tier. If liquids do not gather as quickly and in the quantities that you wish, or your tap position is too high to drain off the liquid, feel free to add your diluting water directly to the base tier from which you can then pour off liquid fertiliser that is ready for use on your garden.

Costing

The following are the prices for the materials I used to construct one wormery.

• 3 planters £10.00
• Ceramic plant-pot £0.99
• Tap £3.98
• Green mesh £0.95
• Rubber tile/mat £5.99
• Farmyard manure £1.50 (1/4 of a bag that cost £5.99)
• 1kg worms + postage £23.50
• TOTAL £46.91

Note that you can save quite a bit on materials by reusing materials that you may have around the house. It's also a good idea to club together with friends to purchase worms as they are cheaper per gram in larger quantities, and you can split shipping charges.

Recovering Costs

The worms will supposedly double their number in 2 months, given sufficient room, and will maintain a suitable population level for their accommodation. If you have several friends wanting to make a wormery, and some of them are prepared to wait a few months, you can share half your worms with a friend for suitable financial repayment. In theory from 2 kg of worms and sufficient patience (2 months), 4 friends could each get 1kg of worms for approx £10. Alternatively you could sell half your worms on ebay every few months.