‘Vermes’ is Latin for worms, therefore, vermicomposting is the processing of organic materials through specific types of worms to produce a high quality soil conditioner. In other words, composting with worms. It is an on-site recycling system, taking food waste and making it into plant food, which in turn feeds the plant to produce more food!

The worm composting process

Worms don’t actually eat the food waste, as such, but they thrive on the micro-organisms that grow on the decaying organic material.

All earthworms have a grinding gizzard that processes material into fine particles. During this process, important plant nutrients like phosphorous, potassium and calcium are converted through microbial action into forms that are more soluble and available to plants.

Some species of earthworm can consume organic residues very quickly, and these are the red worm (Lumbricus rubellus) and the tiger worm, (Eisenia fetida). The red and tiger worms suitable for vermicomposting work best at temperatures between 15 and 25 degrees C, with a moisture content of between 70% and 90%. These worms generally don’t survive in the relatively cold South Island soil, but will live happily in a suitable insulated container. Worms will adjust their populations according to available resources of food, air, water and space.

Worm composting in an enclosed container simply copies what happens in nature, with you providing the food, air and water in the right ratios to keep the worms happy.

You can feed all kitchen scraps to the worms, as well as hand towels, tissues and food-contaminated papers. Some advantages of worm composting are that it is easy to do, can be done inside or out, takes little space and is educational and fun for children!

Environmental benefits of vermicomposting

• Turns organic wastes into a finely divided plant growth media with excellent porosity, aeration and water holding capacity.
• The ‘castings’ produced by worms contain nitrogen, phosphorous and calcium in a form that is readily acceptable by plants for uptake. Worm castings, compared to same volume of typical soil, has 5 times the nitrate; 7 times the phosphorous; 3 times the exchangeable magnesium; 11 times the potash and 1.5 times the calcium.

How to make a happy house for worms

Worms are living creatures with their own needs. It is important to create and maintain a healthy environment for them to live and work in. If you supply the right ingredients for a happy home, the worms will respond by making you the best compost possible.

• Choose a container, - a wooden box, dresser drawer, or commercial bins available from hardware stores.
• Make sure the bin is aerated – with plenty of holes to allow air in.
• Make a ‘bed’ for the worms, out of moist, shredded newspaper and a handful of soil.
• Add worms. Start with at least 500 grams for a family of four. Contact the Council to find out where to get them. The population will grow according to the amount of food available.
• Feed regularly. Bury the food or make sure you have a moist sacking, carpet piece or similar cover to reduce vinegar flies.
• It usually takes at least 3 months to fill, and the worms work on the waste all the time.
• Keep the cover moist, and it will also help keep the bin dark for the worms.
• Harvest the vermicast when the bin is full, and use the same worms to start the process again.

Image from The Compost Collective

Hints to help

• The larger the surface area of food, the more quickly it will decompose. Chop or 'whiz' food if you like
• Before harvesting your compost, stop feeding worms for a week or two, then add an onion mesh bag or similar with food scraps in it to one corner of your compost. The worms will quickly move to where the food is. Remove bag with worms and put in a covered bucket (keep dark) while you deal with the vermicompost.
• Tip the bin out onto a big sheet of plastic or onto a concrete floor. The worms will go down away from the light. Carefully remove top layers of compost. Return worms from bucket and plastic to worm farm and start again.
• Use all food waste, including egg shells – these provide much needed grist for the gizzard.
• Keep the bin moist but not wet, warm but not hot, fed but not overfed!

Troubleshooting

• Unpleasant smell: A correctly functioning worm bin should not smell. Increase the air holes, and gently stir the contents of your bin to introduce air. Stop adding food until most of what is available has been eaten.
• Too wet: Check that the drainage holes do not become blocked. Add shredded paper to absorb moisture. Make sure that there is plenty of air circulating the bin.
• Fruit flies: These are more of a nuisance than anything. Discourage by burying the food in the bin, or ensure that you have a good, weighty cover of wet carpet or similar. Do not overload bin.

Other composting techniques

Check out our other pages for more information on home composting and commercial composting.

Resources

Check out The Compost Collective for more information on worm farming and other forms of composting.