What Is Vermicomposting?
Vermicomposting is the process of using worms — specifically red wigglers (Eisenia fetida) — to convert organic kitchen waste into a highly concentrated, nutrient-rich compost called worm castings (or vermicast). Unlike traditional outdoor composting, vermicomposting can be done indoors, produces results in weeks, and creates one of the most potent soil amendments available.
For people without gardens, those in flats or small homes, or anyone who wants faster results, a worm bin is an ideal solution.
Why Red Wigglers?
Not all worms are equal when it comes to composting. Garden earthworms burrow deep into soil and aren't suited to confined conditions. Red wigglers, by contrast:
- Live naturally in decaying organic matter, not mineral soil
- Thrive in the temperature range of a typical home (15–25°C)
- Are prolific eaters — they can consume roughly half their body weight in food per day
- Reproduce quickly, building population to match food supply
Setting Up Your Worm Bin
Choosing a Bin
You can buy purpose-made worm bins (often tiered systems that make harvesting easy) or make your own from a plastic storage box. Key requirements:
- Opaque material (worms avoid light)
- Drainage holes at the bottom to prevent waterlogging
- Ventilation holes at the sides or lid for airflow
- A tray underneath to catch liquid ("worm tea" — an excellent liquid fertiliser when diluted)
A bin of around 30–40 litres is sufficient for a small household.
Bedding Material
Before adding worms, fill the bin with damp bedding material — this is their habitat and initial food source. Good options include:
- Shredded cardboard (most worm composters' go-to choice)
- Torn newspaper (avoid glossy pages)
- Coconut coir (sold in compressed blocks)
- Dried leaves
Moisten the bedding until it feels like a wrung-out sponge — damp but not dripping. Fill the bin about halfway.
Adding Worms
Start with around 500g of red wigglers. Source them from a reputable supplier, another worm composter, or sometimes from fishing bait shops (ensure they are the correct species). Place them on top of the bedding and leave the lid off briefly — their aversion to light will encourage them to burrow in. They will adjust to their new environment within a few days.
What to Feed Your Worms
Red wigglers will eat most fruit and vegetable scraps, but there are important guidelines:
| Excellent Worm Foods | Feed Sparingly | Avoid Entirely |
|---|---|---|
| Fruit and vegetable scraps | Citrus peels (acidity) | Meat and fish |
| Coffee grounds and paper filters | Onions and garlic | Dairy products |
| Crushed eggshells | Spicy foods | Oily or cooked foods |
| Shredded paper and cardboard | Starchy foods in bulk | Pet waste |
| Tea bags (paper only) | Glossy or treated paper |
Chop or tear food into small pieces to speed up processing. Bury food scraps under bedding rather than leaving them on the surface — this prevents fruit flies and odours.
Maintaining Your Bin
- Moisture: The bin should remain moist. If it dries out, sprinkle with water. If too wet, add dry bedding.
- Feeding frequency: Feed every 2–3 days when starting. Observe your worms — if food is piling up, slow down; if the surface is clear, you can add more.
- Temperature: Keep between 15–25°C. Avoid placing near radiators or in direct sunlight. In winter, insulate the bin if kept outdoors.
- Bedding top-ups: Add a thin layer of fresh bedding occasionally to maintain structure and balance moisture.
Harvesting Worm Castings
After 2–3 months, the bin will start filling with dark, earthy castings. The simplest harvesting method:
- Move all contents to one side of the bin.
- Add fresh bedding and food to the empty side.
- Over 2–3 weeks, worms will migrate to the new food source.
- Harvest the casting-rich side — it will be largely worm-free by then.
Worm castings can be mixed into potting compost, used as a top dressing for houseplants, or dug into garden beds. The diluted liquid collected below (worm leachate) makes an excellent liquid feed — dilute 1:10 with water before applying to plants.
A Low-Effort, High-Return System
Once established, a worm bin is remarkably self-managing. A healthy bin barely smells, produces no mess, and converts scraps into one of the finest soil amendments available — all from organisms that ask only for darkness, moisture, and something to eat.