Granny Trude  Little Superheroes in the Soil

Oma Trude kompostiert © Illustration: Celine Buldun

Granny Trude loves plants, so she makes good use of her garden compost heap, especially in spring. But composting works inside too, even in a small urban apartment – with the indispensable aid of… some little worms with a big appetite for organic waste! 

My Dears,

I recently told you about my efforts to grow oyster mushrooms. You’ll be happy to hear that the mushroom-growing kit I ordered worked like a charm, and my first harvest tasted delicious, very aromatic and fresh. And it’s so fascinating to watch these natural wonders grow.

Composting without a garden or balcony

I don’t know these days whether it’s still all right to laugh, celebrate or even enjoy things while people around us are suffering, especially in Ukraine. But we still have to live our everyday lives – which, in my case, includes telling you all about my latest discoveries in matters of sustainability. So here we go: 

As so often happens, it all started harmlessly enough with some chitchat. A fellow I used to work with mentioned “worm bins” in passing and said he knew plenty of city dwellers who use this small-scale form of composting.

A worm bin? Composting on the balcony or in the home? If who know me, you’ll know that this immediately piqued my curiosity, even though I’ve always had an ordinary compost heap in one corner of my garden. Finding out about worm bins was a piece of cake. There are plenty of sites on the Internet and plenty of mail-order worm suppliers. Miri, my granddaughter in Hamburg, recent told me about her successful vermi-composting project: she set up a worm bin at home to teach her kids about nature. Which is a terrific learning experience for Ava and David! 

What’s a worm composter?

A worm composter is basically a mini-compost heap with lots of worms in it. It obtains the same results as a big garden compost heap, only it’s a special box made of wood or plastic for people who don’t have a garden. Actually, you don’t even need a terrace or balcony, especially since worms don’t like it too hot or too cold. Their preferred temperature range is between 18 and 25 degrees Celsius. So you can even keep them indoors, e.g. in a pantry. 

Even in such a tiny space, the worms will make short work of your kitchen scraps and other organic waste and break it down into good humus. Once they’ve eaten their way through and digested it, they excrete what’s known as “vermicast” or “castings”, an excellent humus that your plants – indoors and out – will love. This nutrient-rich soil is also known to gardeners as “black gold”: add just five or ten percent to your soil and it’ll go a long way towards helping your plants grow and thrive.

If you’re slightly disgusted by worms, use gloves: you’re going to have to get your hands dirty anyway to produce good humus. I’ll explain how later.
By the way, don’t worry about worms escaping to other parts of your home. They apparently stay where their food is: in the bin – which has a lid besides. 

How does it work?

Worm bins come in various forms and use various methods, though the main principle is always the same. Some are made up of a single box in which everything takes place. Some have several boxes stacked one on top of the other. At any rate, you have to help the creepy-crawlies move from the bottom to the top (or from left to right), from the harvest-ready humus to the new “worm chow” or feeding area, which has yet to decompose to form humus. For a better idea of what I mean, check out a video about the composting process on the web. 

I found a description on a worm bin supplier’s website that I’d like to share with you: it might clear up some questions. Other suppliers are likely to have slightly different recommendations, but this will give you an idea of how the process works:
  1. You’ve got yourself a worm bin with all the necessary accessories. Now take some shredded cardboard and soak it in water. 
  2. Mix the softened cardboard into the bedding supplied for the worms.
  3. Put the mix in the worm bin and place the worms from the well-sealed bag on top of the mixed bedding.
  4. A coconut mat is also included. Since the worms feed on the matting over time, you’ll have to replenish it every now and then.
  5. After leaving your worms alone for 72 hours without opening the lid and poking around inside, put some coffee grounds and chopped-up kitchen scraps under the coco mat for them to feed on.
  6. Repeat this feeding every day.
  7. After a few days, check to see whether any “worm tea” has seeped down to the bottom of the bin, which you’ll need to drain. This liquid is another product of the decomposition of the organic waste via the worms’ digestive process, and it’s said to be a terrific fertilizer (diluted to a 10% solution).
  8. After four to six months, when the worms have multiplied, place a fitted, perforated box over the earthworms and their earthy habitat. From now on, put your organic waste in there to keep feeding them.
  9. The worms will crawl up to the top of the soil inside the new box to reach the food.
  10. Once they’ve reached the top, remove the worm humus by placing the whole bin, with the worms and organic waste inside it, on a large surface and scooping out the humus. 
And then the whole process starts all over again. According to the worm bin manufacturer, it takes only six months to obtain 5 kg of worm humus from 50 kg of organic waste.

Why...

... make your own humus? Well, for one thing, because it’s humus of excellent quality and you won’t need to buy any fertilizer, which would have to be produced somewhere and transported from there. What’s more, your organic waste doesn’t need to be transported from your home to a composting or biofermentation plant. That saves CO2 emissions at the composting plant as well as those caused by trucking. Which means you’re making a small but important contribution to protecting the environment and combatting climate change. And, in the process, learning a thing or two about how things work in nature.

Favourite food

Worms eat half their body weight per day. So 1 kg of worms will devour ½ kg of organic waste in a single day. Every day you should feed them cellulose (shredded cardboard, paper) and organic waste chopped up into pieces about 5 cm long. Different types of worms prefer different foods. And once a month, you should add a special mix of minerals to keep the soil pH in the neutral range. 

A mix of the three most commonly used worms (see worm facts below) is ideal for composting purposes because the first two types consume a lot of fresh organic waste, while the European nightcrawler (Eisenia hortensis) prefers loamy potting soil, cardboard and paper. Some folks actually report having more space in their paper bin again thanks to their worms. Incredible! Almost sounds like a joke, but it might well mean the recycling truck doesn’t need to come round as often anymore.

Worm facts and figures

You don’t need to know these interesting facts in order to compost, but they’ll definitely grow your understanding of worms, I promise you that:
  • There are over 3,000 different species of earthworms around the world, about 50 of which dwell in our climes. 
  • Worms are active around the clock and don’t sleep. The earthworm is called Regenwurm in German, from the verb sich regen (to move, to stir) and not from the noun Regen (rain). 
  • The vibration of raindrops draws worms to the surface because it’s the same frequency as the digging of one of the worm’s main predators, the mole. So the worms are crawling away from the mole, so to speak.
  • Worms can break down heavy metals in the soil.
  • Worms slurp their food (since they have no teeth) and only eat dead plant matter, never living plants.
  • We distinguish between dew worms, which are larger, and compost worms, which are smaller. Dew worms are the earthworms you find in meadows and gardens.
  • The redworm (Eisenia fetida, aka manure worm, tiger worm etc.) is the best known and most common composting worm. It grows to 6–10 cm long and 3–6 mm thick. A redworm is fully grown and sexually mature after 60 days.
  • Eisenia andrei is similar to the redworm (Eisenia fetida) and equally widespread. 
  • The third in the troika of creepy-crawlies most commonly used for composting is the European nightcrawler (Eisenia hortensis) aka European red worm. It can grow up to 10–17 cm long and 1 cm thick. It takes longer to sexually mature (about 100 to 150 days) and on the whole breeds less quickly.
Well, have I piqued your curiosity? And don’t worry: if for some reason it doesn’t work out for you, just leave your worms on the nearest compost heap. Hopefully, you’ll find one nearby, even if you live in the city.

Environmentally yours, 
Granny Trude