Earthworms ?! Frequently asked questions about vermicomposting

Article written by Sara Silva, founder of the project No Footprint Nomads.


What is vermicomposting?


It is the process of transforming food scraps into nutritious fertilizer with the help of earthworms. Vermicomposting has many advantages:

– reduces the amount of garbage in the dumps,

– avoids the bad smell of decomposing garbage,

– produces a rich and free fertilizer,

– helps plants to grow,

– improves the composition and structure of the soil.


Can I use any kind of worm?


Unfortunately not. Although there are many species of earthworms worldwide, only seven are suitable for vermicomposting. The most used species is Eisenia Fetida, or Californian red worm. Lumbricus terrestris or earthworm can also be used.


Where to buy the worms?


You can buy directly from producers, such as O Minhocário, or from distributors, such as EcoGrowing.


How many worms do I need?


North Carolina State University solid waste specialist, Rhonda Sherman, recommends approximately 5 kg of earthworms for an area of ​​1 m². Californian red earthworms consume half their weight in nutrients daily, that is, if you produce 2 kg of waste per day, the ideal amount is twice the weight in earthworms – 4 kg. To calculate how many leftovers you produce daily, follow the steps below:

– place the kitchen scraps produced in one day in a bag and weigh it,

make sure you only select the scraps that can be fed to the worms,

– repeat the step above for one week.4,

– what you produce in a week is the average of the seven days.

Buying 4 kg of earthworms can be expensive, so you can start with less and let them reproduce. It takes longer, of course, but it is a more economical solution.



How to build a vermicomposting system?


Although you can buy on the internet, the composting bin can be made at home with inexpensive materials. A set of buckets with a lid or storage boxes are a few options. The important thing is that the containers are dark (the worms are sensitive to light) and are clean. The size of the system depends on the amount of waste produced: 1 kg of food waste requires an area of ​​61 cm x 30.5 cm and 25 cm in height.


You need three similar containers, stacked on top of each other with the lid on top. The next step is to ensure aeration and drainage. Drill some holes in the bottom container to drain the liquid and place a tray for collection. Drill the sides of the top container, next to the lid, for ventilation (avoid drilling the lid as it can lead to moisture loss). Place the vermicompost in an airy place, away from direct sunlight.


How should I feed the worms?


Earthworms feed mainly on vegetable and fruit scraps, pasta, bread crumbs, finely ground eggshells, coffee grounds, and tea leaves. You must also add other materials, such as paper and cardboard or dry straw, but not everything is good for their diet. You should avoid feeding them the following:

– meat, fish, and seafood,

– oils or fried foods,

– citrus fruit,

– non-organic materials (plastic, metal, glass),

– animal and human excrement,



Earthworms also need certain levels of humidity (about 80%) that can be maintained with the addition of moistened newsprint or more liquid kitchen scraps.


The compost bin stinks. What should I do?


The possible causes for the vermicompostor’s bad smell are the following:

– too much food: if there is too much food, it begins to decompose (do not feed the worms for a week),

– non-compostable materials: remove these materials from the compost bin and keep a container in the kitchen where you save the kitchen scraps before feeding them to the earthworms,

– exposed remains: cover them with at least 5 cm of wet newsprint strips,

– too much moisture: add dry newsprint or cardboard and leave the composter exposed to the sun without the lid for a while,

– little aeration: drill more holes in the sides of the top container.


There are flies around the compost bin. What should I do?


Flies are a sign that the remains are exposed or that there is too much food. Cover the remains with dry material, as indicated above. Avoid feeding the worms until the food scraps disappear almost completely.


How long does it take to produce compost?


The formation of vermicompost depends on several factors, so it is difficult to say exactly when it will be ready for collection. It is estimated to be between 3 to 6 months. Vermicompost is nothing more than the product of the digestion of organic matter by earthworms and resembles soil.


I’m going on vacation. What do I do to keep the worms alive?


There is no problem going on vacation and leaving the composter unattended for 3 to 4 weeks. Before you leave, add a little more food and make sure the humidity is adequate.


What to do with the liquid and the compost?


The liquid that accumulates in the tray at the bottom of the vermicomposting unit is the result of drainage and contains pathogens harmful to plants. It should not be used in the garden, except to kill weeds. You can make compost “tea", a liquid obtained from solid compost. This liquid can be sprayed onto plant leaves and acts as a fertilizer.


The solid compost is ready to be used directly on your garden plants. Just add it to the soil.




Sherman, R. (2018). 2. Composting. Retrieved 30, September, 2020, from

Vermicompostagem. (2016, December). Retrieved September 30, 2020, from

How Many Composting Worms Do I Need? (2019). Retrieved September 30, 2020, from

Vermicompostagem Perguntas e Respostas. (2013, January). Retrieved September 30, 2020, from

Jen Fong, & Hewitt, P. (1996). Worm Composting Basics. Retrieved September 30, 2020, from

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