Compost factory : A keyhole garden for composting with wormsMake your worms survive danish cold winter outdoor.

  • Earthworms: Eisenia foetida (Red Wigglers) (price:389DKK) (free compost in Copenhagen)
  • Stones, Gravel (found in the site)
  • Metallic bin
  • Tapaulin and geotextile
  • Plastic tube and pot
  • Soil (poor in nutriments)
  • Organic waste, paper and cardboard

Step-by-step construction instructions

    1. We have flattened and compacted the soil and marked two circles: R=22,5cm (that is the size of the bin) and R=90cm.
    2. We constructed the wall around 50cm height in a keyhole shape.
    3. We ajusted the level of the ground in order to allow a one way runoff of the water.
    4. We posed the tapaulin and tested the runoff. We conected the tube at the lowest point and opened a hole to the tapaulin.
    5. We tested the runoff of the water towards the exterior of the keyhole in a pot.
    6. We filled 2-3cm with gravel and flattened.
    7. We posed the geotextile and filled with the soil. We added offen some gravel in the periphery to fill the holes of the wall.
    8. Rest to do: put organic waste, cardboard, paper and plant the keyhole garden!
Step 2: Keyhole wall

Step 3 - 6. Plastic at the bottom to collect worm tea

Step 7: Filling the walls with soil. Yellow bucket is there to collect worm tea

Finished construction, before filling with soil


    • Mi-september: Construction and worms installation
    • January: One month frost (-8°C outside temperature), two weeks snow. The surface layers of compost and soil were frozen (thikness of ice around 10cm) but positive temperatures (around 1°C) deeper inside the compost bin.
    • Early March:Adult worms in the compost bin have survived the danish winter!
      • IMG_0398.JPGIMG_0402.JPGIMG_0390.JPG


  • Lina
  • Philippo
  • Steen
  • Sofien