The worm bin - composting on your own balcony

Recycle your kitchen, as Lara und Felix do

“In this way, everyone can contribute a small part to the formation of sustainable soil.”

You don’t necessarily need a garden to make your own compost. With a so-called “worm bin”, you can also live sustainability on a small scale: Kitchen waste that would otherwise end up in the residual waste can be turned into valuable humus in this way.

What is a worm bin?

The worm bin is divided into two chambers. In one chamber, compost worms (Eisenia fetida) are settled in a suitable substrate. The second chamber remains empty at first. The compost worms can be fed regularly with kitchen waste and paper. Once the first chamber is full, the second chamber can be filled. The worms then migrate there on their own, so that the humus soil in the first chamber can be harvested without any problems. 

Ready-made worm bins can be easily ordered on the internet. If you have some manual skills and want to do it yourself, you can also easily build your own worm bin.

How to build a worm bin?

Building instructions

All you need are wooden boards and roof battens from a Do-It-Yourself store (a kind of hardware store), some rabbit wire, hinges and screws. The boards are used to make a cuboid box, and the lid can be attached using the hinges. Use roof battens and rabbit wire to make a grid that divides the box into two chambers in the middle. If you want the worm bin to withstand the weather better, it is a good idea to seal it from the outside with a wood oil. Your local Do-It-Yourself store will be happy to advise you on this. Now the compost worms can move into their new home!

Colonisation of the worm bin 

The most important thing for your own small compost is, of course, the compost worms. These can be obtained from various suppliers on the internet. Some traders also offer feeding soil that contains valuable minerals and microorganisms. These can positively influence the microclimate in the worm bin and accelerate the composting process. However, whether one decides to use this substrate is up to each person. The compost can also thrive without it.

Before placing the compost worms in the worm bin, it should be lined with some newspaper or cardboard. The cellulose contained in the paper ensures that the soil is loose and well aerated. Then fill in about 20 cm of fertiliser-free soil. Now the compost worms can be placed in the box. As they are very shy of light, they will quickly retreat into the soil.

The first feeding can take place immediately. After moving in, the compost worms will tolerate about a handful of fruit and vegetable peelings, cardboard and coffee grounds. Fish and meat waste, citrus fruits and spicy vegetables such as onions and chilli do not belong in the box. Egg shells can be put in the compost, but they do not decompose very well and are therefore also rather unsuitable.

The worms need water, just like humans!

There should be sufficient humidity in the box, regular spraying with water can help. In summer, make sure that the substrate does not dry out. If you wish, you can also cover the substrate with a hemp mat or an old jute bag. After an acclimatisation period of a few months, during which the worms are slowly fed, almost all kitchen waste can disappear into the home compost. In this way, everyone can contribute a small part to the formation of sustainable soil.

About Lara und Felix

We, Felix and Lara, have been living together in a cosy city flat in Aachen for some time. We are both studying physics and biology at RWTH Aachen University. We try to organise our everyday life as sustainably as possible. Since many herbs and vegetables already thrive on our balcony, having our own compost was an ideal addition for us.