The Worm Species Used in Vermicomposting
Not all earthworms are suitable for vermicomposting. The common garden earthworm (Lumbricus terrestris) lives deep in mineral soil and does not thrive in a confined bin. Vermicomposting relies on epigeic species — worms that live and feed in organic surface material rather than mineral soil.
The primary species used worldwide is the red wiggler (Eisenia fetida), also called the tiger worm or dung worm. It tolerates a wide range of temperatures, reproduces rapidly and processes organic material efficiently. A related species, Eisenia andrei, is sometimes used alongside it. Both are available from suppliers in Poland, typically through online retailers or garden centres specialising in organic cultivation.
Sourcing Worms in Poland
Eisenia fetida can be found in Poland through online platforms such as Allegro, where sellers list them as "dżdżownice kompostowe" or "robaki kompostowe". Some fishing supply shops also stock them as bait worms. A starting population of 500 g to 1 kg of worms is typically sufficient for a household bin of 40×60 cm.
Bin Design and Setup
A vermicomposting bin can be as simple as a food-grade plastic container with drilled ventilation holes, or a purpose-built stacked tray system. The bin must:
- Exclude light — worms are photophobic and retreat from exposed surfaces
- Allow drainage — excess moisture must escape to prevent anaerobic conditions
- Provide ventilation — small holes on the sides and lid allow gas exchange
- Be opaque — any transparent containers should be wrapped or painted
Size Recommendations
A standard starting bin for a household of two to four people is approximately 40 cm × 60 cm × 30 cm deep. At this size, a healthy worm population can process roughly 0.5 kg of kitchen waste per week. Worm populations self-regulate to the available food and space — a larger bin does not necessarily require more worms to start.
Bedding
Worms need a moist, aerated bedding material to live in. Suitable bedding options include:
- Damp torn cardboard or newspaper — the most accessible option for Polish households
- Coir (coconut fibre) — available in compressed blocks at garden centres
- Shredded dry autumn leaves
- Peat-free potting compost mixed with cardboard
Bedding should be moistened to the wrung-out sponge standard — saturated bedding creates anaerobic conditions. Fill the bin to about 60% capacity with damp bedding, then place the worms on top. They will work their way down within a few hours.
Finished vermicast after sifting to remove unprocessed material and worms. Photo: Wikimedia Commons.
Feeding the Worms
Worms process food from the surface downward. Add food in relatively thin layers — around 2–5 cm per feeding — and bury it slightly under the bedding surface to reduce odour and fruit fly attraction. Feed frequency depends on the size of the population and the volume of waste.
Suitable Kitchen Scraps
- Vegetable peelings — courgette, carrot, potato, capsicum
- Fruit scraps — apple cores, banana skins, orange peel in moderate quantities
- Coffee grounds (a popular addition — worms consume them readily)
- Tea bags (paper-based only, not nylon mesh)
- Egg shells — crushed finely, they help regulate bin pH and provide grit
- Stale bread in small amounts
- Cooked plain rice or pasta in modest quantities
What to Avoid
- Meat, fish and dairy — create odours and attract pests
- Heavily spiced food — garlic and chilli in large quantities can be problematic
- Salty or pickled foods
- Glossy paper
- Fats and oils
Temperature and Polish Winter Conditions
Red wigglers function best between 15°C and 25°C. Activity slows below 10°C and stops near freezing. In a heated Polish apartment, this presents no difficulty — indoor temperatures during winter typically remain within the functional range. For outdoor or balcony bins, supplementary insulation with old blankets or newspaper wrapping is needed once temperatures drop below 10°C at night.
In Polish conditions, the most practical location is under a kitchen sink, in a utility room, or on an insulated balcony between March and November. The bin produces minimal odour when managed correctly and requires no external power source.
pH Management
Vermicomposting bins tend toward acidity over time as organic acids accumulate during decomposition. Adding crushed egg shells or a small amount of agricultural lime periodically helps maintain a pH between 6.0 and 7.0, which is optimal for red wiggler activity. A basic soil pH test kit can be used to check bin conditions if problems arise.
Harvesting Vermicast
After two to three months, the lower section of the bin will contain finished vermicast. Several harvesting methods are used:
Migration Method
Stop adding food to one half of the bin and add fresh food and bedding to the other half. Over two to three weeks, the majority of worms migrate toward the fresh food. The worm-free section can then be harvested.
Light Exposure Method
Tip the entire bin contents onto a tarp in indirect outdoor light. Worms will move away from light, forming concentrated clusters in the centre of each mound. Finished compost from the outer layers can be removed and the worms returned to the bin with fresh bedding.
Using Finished Vermicast
Vermicast can be used as a potting mix amendment (10–20% by volume), worked into garden beds before planting, or diluted in water to create a liquid fertiliser. It is particularly valued for seedling propagation due to its fine texture and microbial diversity.