This is the third blog post in a three-part series which covers three different composting systems.
To recap, there are three main ways you can compost your waste:
· Composting bin
· Worm farm
Each system operates differently. In my last post on the subject of composting, I focussed on Bokashi. In this post, I will explain how a worm farm works.
In a worm farm, composting worms such as tiger worms or red worms eat through a mixture of food scraps, garden waste, waste paper and cardboard to produce worm castings (composted material) and liquid fertiliser, known as worm tea. Both the castings and the worm tea are excellent fertilisers and are therefore great for the garden.
Types of worm farms
There are two types of worm farms: stacked worm farms and continuous flow worm farms.
Stacked worm farms are divided into different layers. They usually consist of (i) a sump, which collects the liquids; and (ii) frames, usually two, which are stacked on top of each other as the worm farm fills up. To use a stacked worm farm, place the sump on a stand with a bucket underneath the tap to catch the liquids. Keep the tap open to allow the worm farm to drain. Place a frame on top of the sump. Fill this first frame with moist bedding and add your worms. Feed a small amount of food to your worms. Cover with wet carpet, paper or cardboard. Over the next 6 months incrementally increase the food you feed your worms to build their population. When your first frame of worms is full add another frame on top. The worms will move to the upper frame and will feed on the fresh food placed there. When this top frame is nearly full you can harvest the castings from the frame below. Take away the lower frame and place the top frame directly on the sump. Use the contents from the full frame on your garden or pot plants. Rinse and store this empty frame until your worm farm is ready to take another top frame.
Continuous flow worm farms are generally a single vessel with a large open cavity that houses the worms. It is secured at the base to hold the castings in place but still allows air to circulate and liquids to drain through. You simply feed on the surface and harvest from an opening at the base. To use a continuous flow worm farm, fill the bottom quarter of the cavity with moist bedding and add your worms. Feed a small amount of food to your worm farm. Cover with wet carpet, paper or cardboard. Over the next 6 months incrementally increase the food you feed your worms to build up their population. Once the cavity is approximately two thirds full of worm castings you can start to harvest the compost through the opening at the base. The majority of worms will remain in the upper areas to feed on the available food. The castings will be quite compacted so they should be free of worms. The liquids will drain through naturally and can be caught in a bucket placed under the body of the worm farm for use as Worm Tea.
How to set up a worm farm
Choose a cool, shady site sheltered from the sun. Carports or sheltered porches are ideal. Use a layer of bedding first, for example hay, coconut fibre, shredded cardboard or paper. Bedding should be damp and porous. Add some worms. 1000 worms (250g) are fine. 2000 worms are even better. Worms can eat their own weight each day so don’t over feed them. For example, for 250g of worms, give them about 200g of food. Worms need air but not light so cover food scraps with damp carpet, newspaper or cardboard to provide a moist dark environment.
What to feed your worms
As for a composting bin, aim for a ratio of 30% green waste and 70% brown waste. To recap, green waste is normally soft, fresh and moist. Examples of green waste include food waste, grinds and tea bags, egg shells and fresh green lawn clippings. Brown waste is normally dry and brittle. It can therefore take a long time to break down. Examples of brown waste include dry leaves, paper, cardboard, vacuum dust, egg trays and twigs. Don’t add any of the following: spicy food, chilli, onion, garlic, meat, milk products, bread, pasta, cooked or processed food, citrus or acidic foods, oils and liquids such as soup.
Increasing your worm population
Add food scraps regularly, ideally every 1 – 2 days. Cut up the food you feed your worms. Make sure the pieces are smaller than a golf ball. Start with small amounts and slowly increase the food you give them over the first 6 months. The population of worms will increase to match this and will reach a point where they can eat through all the food waste you can give them very quickly.
Harvesting worm castings
Worms feed at the top so harvest the casting from below. It is ready when the contents look like dark fine compost and few worms can be seen. Spread the castings around your garden beds. Castings may be liquefied by adding one part castings to ten parts water and stir well.
Harvesting worm tea
Always let the liquid drain off freely into a separate bucket. If your worm farm has a tap, leave it open. Worm Tea should be diluted to the colour of weak black tea (1:10). Apply every 2-4 weeks around plant roots as a nutritious fertiliser.
This post was based on information provided on the Compost Collective’s website. For a comprehensive guide on how to set up and look after a worm farm, visit https://compostcollective.org.nz/worm-farming/
The Auckland City Council runs a 2 hour workshop that offers you a basic introduction to the three different types of composting systems covered in this blog. After attending the workshop, you will be entitled to a $40 discount voucher which you can use towards the purchase of any of the three composting systems covered in the course.
The workshops take place in a variety of locations and are held regularly. For more information, visit the following webpage: https://compostcollective.org.nz/