Katie Irwin shows us how to make a productive worm farm from repurposed bits and pieces you can find around your home or from second-hand sources.

Did you know that 21 million tonnes of solid waste goes into landfill in Australia each year, with 40% of that being organic waste?

When dropped in landfill, organic matter decomposes anaerobically (without oxygen) which produces carbon dioxide and methane (both greenhouse gases), contributing to global warming. There is also landfill leakage into water ways and ground water, and the destruction of animal habitat for landfill sites.

Got waste? Get worms!

Composting your own organic waste with a worm farm reduces your reliance on landfill and creates super fertiliser for your garden. Worms break down food scraps into worm castings, a nutrient-dense soil perfect for adding to gardens or growing seedlings in. Another product of worms, worm tea, can be used as a supercharged fertiliser for plants.

Just $79 in materials

For this DIY demonstration we sourced everything for our bathtub worm farm from our garden shed, Gumtree and Facebook Marketplace. You can really make a worm farm container out of almost anything – get creative with you what you have and just apply the same principles.

Here are our building materials, which cost a total of just $79:

  • Bath tub ($40 on FB Marketplace)
  • Chicken wire (free from shed)
  • Drainage rocks ($8 20kg bag from Bunnings)
  • Shade cloth (free from shed)
  • Hay/shredded paper (free from chook pen/newspaper from local café)
  • Compost/soil/manure (from compost bin/manure $2 on side of road)
  • 2 x hessian bags ($4 from Gumtree)
  • Worms (1000 worms for $25 from Gumtree)
  • Door (free from FB Marketplace)
  • Chairs to act as a stand (free from shed)

The build

Essentially you want to create a relatively weather-proof and predator-safe enclosure with good drainage for your worms.

  1. Firstly, we placed our bath tub on some old chairs we had in the shed. You could build a stand for the bathtub out of an old pallet – which would look a lot nicer – but we wanted to use what we had.
  2. Start by covering the plug hole/drainage holes with some chicken wire.
  3. Cover the bottom layer of the bath with drainage rocks. Cover the rocks with a sheet of shade cloth or similar so that you don’t lose any worms into the rocks or down the drain hole.
  4. Make a cosy bed for your worms on top of the shade cloth with shredded paper.
  5. Layer with compost, soil or manure and add your happy worms.
  6. A bucket underneath the drainage hole catches the worm tea.

Maintenance

Water your worms gently with a watering can. Your worm farm should be damp like a wrung-out sponge, but not too much water so as to drown them. We then covered the soil with hessian bags (reused coffee bean bags) to keep the temperature stable.

To keep the chickens and possums out we covered the whole bath with an internal door we picked up for free on Facebook.

Feeding your worms

We feed our worms:

  • most fruit and vegetable food scraps
  • tea leaves
  • coffee grounds
  • egg shells
  • newspaper
  • pet hair.

We do not feed them:

  • dairy
  • meat
  • pet poo
  • citrus
  • onion
  • chilli & garlic.

Allow your worms to settle in for a few days before feeding them. We blend up food scraps for our worms so that they are easier to digest. Worms do not have teeth, so you will find they can consume a lot more if their food is blended up for them.

Over the first few weeks you will get to know how much your worms can eat. You don’t want food to rot before they get to eat it as this will attract other animals and will release greenhouse gases (which we’re trying to avoid!).

Because the bath tub is so large, I feed them on one side of the tub only. Gradually, the castings will build up on that side of the bath tub.  When you’re ready to harvest your castings, start feeding the worms at the other end of the bath tub. They will migrate down, allowing you to harvest the casting from the other end. Worm castings are perfect for growing seedlings in or adding to vegetable patches.

The worm tea should be be diluted with water before being used as a liquid fertiliser. Suggested dilution ratios vary a lot – do some research online to help find what works for you.

Hungry worms? List on ShareWaste

Once your worm farm is established, I highly recommend listing it on ShareWaste – a brilliant app where people can connect with you and bring their food waste to your house. This is a fabulous way to give back to the environment and your community, whilst supporting those who don’t have composting facilities…yet.