The main type of worm used for worm farming is called the tiger worm (Eisenia fetida), amongst other common names, and it is one of the best types for this purpose because they naturally live in shallow decomposing organic matter, have high appetites, and breed easily. The technical term for worm farming is vermicomposting, and the fertile worm castings are sometimes referred to as vermicompost. Often people use the term “vermiculture” to mean worm farming, but technically it refers to just the breeding and raising of worms, whereas “vermicomposting” means the use of worms to process organic matter.
Worm farming can be done on a range of scales, from the compact indoor Tumbleweed Cube to the low-maintenance in-ground Worm Buffet, to the multi-layered Worm Café up to large-scale projects tackling industrial organic waste. Many businesses and institutions produce large amounts of food waste and unrecyclabe paper waste that can be transformed into valuable worm castings. Local government can also process food waste, green waste from gardens, and even sewage sludge using large-scale worm farms. There are many different businesses working in this area now, using a range of methods depending on the scale and type of waste. Some companies offer large contained units that can be installed on-site as a kind of giant worm farm.
Worms appear to be very simple creatures, but their anatomy and behaviour is more complex than it seems. Charles Darwin held a lifelong fascination with worms, studying them for decades, and revealing much about their lives. His final book, published in 1881, was titled The formation of vegetable mould, through the actions of earthworms, with observations on their habits, but is often just called “Darwin’s worm book”. Darwin talks about the anatomy of the worm and how they digest organic matter. Worms have a digestive system extending along their entire body, and they consume organic matter with the help of digestive proteins as well as tiny mineral particles in their gizzards and intestines. They also have glands that secrete calcium to regulate their body and stomach pH levels. Darwin observed worms himself in partnership often with his children over many years and corresponded with people from around the world about their behaviour. Many kids love having a worm farm to this day, and benefit from seeing how they can make a difference to issues such as climate change, waste disposal and growing their own food.
Showing genuine interest and curiosity about the nature and behaviour of worms, Darwin discusses their sensory abilities, intelligence, and importance for soil health. He writes about various experiments he did, including giving worms different plants and seeing which they prefer or avoid. In one test he gave the worms a range of different vegetable leaves, including celery, cabbage, wild cherry, and carrot, and found they much preferred the latter two. He also gave them different aromatic herb leaves, such as sage, thyme, and mint, which they avoided except for the mint, which was “very slightly nibbled.”
In later parts of the book, Darwin brings together observations and experiments about how worms move soil and their effect on soil health. He writes at length about the sheer volume of soil that worms process through their bodies, showing how great the impact of such a small creature is. Darwin’s fascinating book can be accessed on the internet by putting the title into your favourite search engine.
If worm farming has caught your attention as a home composting method, there are several important things to learn from Darwin’s work and the modern experiences of this powerful environmental tool. Firstly, the finer the materials are when they are added to your worm farm, the easier and quicker the worms can break them down. Secondly, the amount of food you give them needs to be matched to the size of the worm population. If your worm farm becomes smelly or mouldy, chances are you are adding more food than they can eat at one time, paving the way for unwanted organisms to step in and create problems. Thirdly, worms need air to breathe, so it is important to make sure the food you add is not too wet. Adding some shredded corrugated cardboard or paper, chopped straw or similar will stop things getting out of control for your wormy friends.
A wonderful benefit of worm farming is the way it recycles your household organics to create one of the best-balanced organic fertilisers on the planet. Tapping off the liquid from creates an instantaneous boost to your plants when it is diluted down to the colour of weak tea, while the solid castings provide a relatively slow release biologically based fertiliser that not only feeds your plants but keeps them healthy through the beneficial microbes that they introduce around the plant roots. Finally, worm farms help build up the carbon rich humus levels in the soil, helping to stop carbon emissions, while encouraging rapid plant growth that extracts carbon dioxide form the air. Win/win/win. Happy worm farming!