Building a vermicomposter – composting can be so easy

Building a wormery: Someone is holding soil full of worms in both hands.
Worms turn organic waste into valuable fertiliser – build a worm compost bin and see how compost is made!
  • Difficulty
    easy
  • Cost
    20-30 €
  • Duration
    3 h

Introduction

Sustainability and the circular economy are all the rage. A worm farm fits perfectly into this concept, even if you have an organic waste bin at home. After all, it has to be emptied and the contents taken to the landfill.

 

With a homemade vermicomposter, you not only produce first-class fertiliser, but also improve your CO2 footprint. If you have plenty of space, you can also build your own compost bin in the garden instead of – or in addition to – your DIY wormery.  

 

This article provides simple building instructions for an earthworm box and the necessary background knowledge. Further information can also be found in our article all about compost.

You need

Let's go – step by step: Building a vermicomposter

This worm farm is inexpensive to build and can be completed in just a few hours.

Of course, you must pay attention to occupational safety at all times to protect yourself and your health. In our overview of safety precautions for DIY, you will find the most important tips.

Do you already know our 18-volt system? This includes countless devices for a wide variety of applications. The special thing about it is that you can use all the tools in the 18-volt system with the same battery over and over again. Simply remove the battery, plug it into another tool in the system and continue with the next step.

Step14

Make a sketch and cut the panels to size

Building a worm box: schematic representation of a worm box with dimensions

This is how your finished DIY wormery will look – the construction couldn’t be simpler.

You need:

Our crate should have external dimensions of 60 x 40 x 40 cm (W x H x D). Accordingly, you will need four large panels for the front, back, base and lid and two small ones for the side walls.

 

Most DIY composters want to stay as close to nature as possible and favour local wood, such as spruce. However, a worm box made from untreated wood is unlikely to last very long, as it is always a little damp inside. A possible good alternative – also in terms of sustainability – is to use waterproof screen-printing plates for your DIY wormery.

 

Cut all the panels with a jigsaw to size. If you have a circular saw on hand, it will be quicker. Sand all edges by hand with the sanding block or with the multi-sander. Take a look at our video tutorials for jigsaws and video tutorials for sanders and our sanding guide if you need more information on selecting or using the tools.

Step24

Screw the parts together

You need:

With the cordless drill driver, first pre-drill the base plate and side walls of your vermicomposter and then screw them together.

Tip
Watching the worms at work
Fancy a bit of environmental education? The worm farm is even more fun – and not just for the kids – if you build a side wall from "hobby glass" (polystyrene) instead of wood. Interesting insights are guaranteed. But also think about a device for darkening the pane when not in use.
Step34

Attach the wire mesh

You need:

Insert a grid in the centre of the worm box to separate the two halves of the box. Galvanised aviary wire, for example, is suitable. Select the mesh size so that the worms can get through easily, but not so large that the humus falls through.

 

You can staple the wire with the tacker directly to the inside of the walls. However, it is better to build a wooden frame for it, then you won't injure yourself so easily on the wire. Screw on a guide rail for the frame so that you can remove the grid from the box if necessary.

 

Because you can expect water to collect at the bottom of the worm farm from time to time, you should lay down wax paper. Let it protrude upwards by about 2 cm all round and staple it down.

Step44

Attach the cover

You need:

Finally, screw the hinges and the handle to the lid and attach it to the box. The lid should not close too tightly so that some air can always circulate. If necessary, you can regulate the air supply with small blocks that you stick under the lid. Take care not to fill the wormery too high so that the worms cannot escape.

 

That's it! Do you need more ideas about waste? Learn how to make a DIY bin shed or how to dispose of autumn leaves correctly. Perhaps you are particularly interested in the topic of sustainability? We have lots of practical DIY upcycling ideas to share.

Planning & background knowledge: Building and operating a vermicomposter

A worming compost box is quick to build, but you need a little background knowledge to use it properly. We provide this here and answer some frequently asked questions.

What is a vermicomposter?

Worms have the ability to turn rubbish into treasures. If you don't have a garden for a compost heap but don't want to simply throw away your organic waste, you can build your own wormery. The worms and various microorganisms decompose your organic waste. This quickly produces excellent worm or vermicompost, which you can use as fertiliser or potting soil.

How is a DIY wormery constructed?

A worm bin is inexpensive and easy to maintain with a little knowledge and experience. There are two main construction principles for such a vermicomposter: either it consists of two chambers in one box or of several (usually two to three) boxes stacked on top of each other with open transitions in between. In our building instructions, we have opted for a worm bin with two chambers.

Which materials are suitable for DIY wormery?

Worm boxes can be made of plastic or wood. Wood is the natural building material, but plastic has the great advantage of being unharmed by moisture. Worm gardens in a wooden box therefore need a little more attention and care.

 

It must always be ensured that moisture can diffuse outwards through the wood and that no water from the composting process collects at the bottom of the wormery. Conversely, this also means that you cannot use a wooden box to make worm tea, which is very popular.

Where should I put a vermicomposter?

Because the composting process comes to a standstill at low temperatures and the worms cannot withstand frost or direct sunlight, you should place the worm farm indoors or at least in the cellar or a frost-free garden shed.

 

If you decide to put it outside, perhaps during the summer, make sure you don't put any meat, cooked vegetables or leftover bread in the box. Otherwise, you may attract rats or other animals! And don't forget to protect your crate from rain and sun.

What is the difference between a wormery and a Bokashi bucket?

A worm bin is not the same as a Bokashi bucket. Although both transform kitchen waste into valuable plant soil through chemical processes, the difference is a bit like the difference between mouldy cheese and sauerkraut.

 

While composting takes place in a worm farm (i.e., decomposition with the help of oxygen and other substances), fermentation takes place in a Bokashi bucket. A fermentation process is set in motion in an airtight container using lactic acid bacteria and yeasts (known as Effective Microorganisms or EM). Incidentally, this is also how sauerkraut is produced, which is why the Bokashi bucket often smells slightly similar, while the worm bin smells of damp forest soil.

How do I start a DIY wormery?

To start a vermicomposter successfully, there are certain points to consider. Firstly, your worms need somewhere to live. To do this, build a worm box (e.g., from wood) as described in the step-by-step instructions.

 

The next steps are as follows:

 

Prepare the underlay

As soon as the worm box is ready, fill one of the chambers. You will need the second one later for harvesting, see below. Firstly, prepare a first layer of bedding. This can be newspaper or cardboard. It contains carbon, which is important for the worms. Tear or cut the material into strips so that it forms a loose nest.

 

Worms breathe by exchanging gases through their moist skin, so spray the padding lightly with water using a spray bottle. It should be damp, but not soaked.

 

Fill with kitchen waste

Then comes the organic waste. Practically anything plant-based is suitable, such as vegetable, fruit or eggshells, coffee grounds (not too much) and leftover tomatoes, onions and so on.

 

Put a thin layer of these ingredients on the bedding material, then moistened paper again and possibly some soil. Add another layer of food scraps on top and finally, more bedding.

 

Fill your worm bin about three quarters full. The layering ensures faster decomposition. Meat, oils or dairy products should not be placed in the worm farm as they attract flies and maggots. Ideally, various types of waste should be placed in roughly equal proportions.

 

Settle worms

Now it's time to welcome the main players: the worms. There are around 4,000 different species of earthworms in the world, but only six are suitable for composting.

 

One of these is by far the most popular: Eisenia fetida, the compost worm (also known as the manure worm or red worm). This species is the least sensitive, eats diligently and multiplies more than most other worms.

 

To get started, you will need several hundred specimens, which are commercially available. Carefully lift the top layer of bedding and pour in the worms. Then cover with bedding again.

 

Feed worms regularly

Feed the worms a cup or two of leftover food every few days. Make a small hole with your hand, put the kitchen waste in and cover it with bedding again. Observe the progress of the composting process. You will soon find the right amount. Too much organic waste is just as unsuitable as too little. Give the worm composter time. It will take a few weeks before the humus is ready.

 

Harvest worm compost

Harvested worm compost is dark and crumbly and smells earthy. To harvest, first fill organic waste into the second chamber (i.e., on the other side of the separating grid) using the same procedure as described above. Then wait a day or two until the worms have migrated from the old compost to the tasty fresh food.

 

You can use the compost from the first chamber for your houseplants, your self-made raised bed, or for the DIY herb garden on the balcony. Maybe you still have some wood left over from building boxes. Then how about also building decorative garden signs?

FAQ: How do I use the vermicomposter correctly?

Would you like to make a wormery and still have lots of questions? Here are the most important answers:

 

  • What is the best temperature for a worm bin? Ideally between 15 and 25 degrees Celsius. It should never be below 5 degrees, and well above 30 degrees would not be good for long periods.
  • What is the right worm food? A healthy mixture of nitrogen (i.e., all plant components) and cellulose (e.g., paper, cardboard, wood chips).
  • How moist should the contents of the worm bin be? About the same as a squeezed-out sponge. You can easily test this with the squeeze test: take a little material from the worm box and squeeze it firmly in your hand. If a little water comes out between your fingers without dripping down, the moisture level is ideal.
  • How do you ensure sufficient ventilation? The design of your wooden crate with a loose-fitting lid already provides ventilation. You can also drill a few holes in the top of the side walls.
  • What is the best pH value? The environment must not be too acidic for the worms, they feel most comfortable at a neutral pH value. Do you notice an acrid ammonia odour? Then your worm bin is over-acidified. You should counteract this with minerals (e.g., lime, rock flour).
  • What are nematodes? These nematodes, also known as eelworms, are only a few millimetres in size and are found in many species. They also include pests that attack plants. For vermicomposting, it is good to know that the nematode genus Heterorhabditis eats mosquito larvae. So, if your worm bin is infested with fungus gnats, for example, it can help to spread these nematodes.
  • What is worm tea? Worm tea is excess liquid that can be produced during composting. This is actually not a bad thing, as you can use it as an energy drink for your plants. However, worm tea is less desirable in the context of a worm bin. After all, you have to be able to transport it out of the box somehow. It is therefore better to regulate the moisture balance so that the humus is moist but there is no brown broth at the bottom. There are other methods for obtaining worm tea.
  • What do ants in the worm box mean? It is probably too dry in the worm box. Too much sweet fruit such as peaches or apples can also attract ants. The same applies here: if the humidity is right, ants should not pose a challenge.

 

Are you interested in everything that creeps and crawls? And do you have the urge to make even more? Then take a look at our creative DIY ideas for animals – including birds and insects. For example, you can build an insect hotel or a bird feeder with just one tool, or try your hand a building a bat box. 

 

Have cats at home? How about making a cat scratching post or a trying out our 10 ideas for making your own cat bed?

How much does a wormery cost?

When considering the financial aspects of a worm bin or vermicomposter, distinction must be made between the manufacturing and operating costs.

 

How much it costs to make a worm farm depends of course on its size and the material used. You can expect to pay around 20-30 EUR for an average worm bin. If you have some old wooden slats lying around, you can build your own vermicomposter for free.

 

This is far below the costs for ready-made wooden boxes on the Internet. There you can find models for over 400 EUR.

 

Worms are a cost factor that should not be underestimated. For a DIY wormery with 500 worms – the minimum number you need to start with – it costs between 25 and 35 Euros, which is practically as much as the worm bin itself. And even with the best care for your squirmy helpers, you may have to buy some more.