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Composting at home with worms

Worm Humus is a superfood for your plants. You make it at home on the balcony or in the garden, taking advantage of the food scraps from the kitchen and from the pruning of the garden, without flies or bad smells

Earthworms have been very important in the history; they were prized by the Romans, sacred to the Egyptians, and defined by Aristotle as the intestines of the earth. Nowadays we known about 4,400 types of earthworms, but only about 6 of those are used for organic waste degradation.

The Californian earthworm (Eisenia foetida) is the earthworm used in vermiculture. It is the most suitable for reasons of breeding, reproduction, feeding and adaptability to captivity. Strangely, the red worm, also called Californian, is from Europe.

The worms must be protected from sunlight and predators; birds, shrews, mice, planarians, scolopendras (they are poisonous) and fire ants.

The earthworm live up to 16 years, the adults weigh 1g (0.03 oz) and reach 10cm (aprox 4 inch) in length. They have 5 hearts, 6 pairs of kidneys, 182 excretory tubes, and one worm produces about 10,000 worms per year.



The best way to make earthworm humus is outdoors, in terraces of up to 3 m. long, 1 m. wide and about 40 cm. high, covered from rain and excessive sun to better control temperature and humidity. Once done you add a first layer of 20 cm. of straw, shredded cardboard, remains of dry pruning ... elements that carry carbon. The second layer should be 10 cm and contain nitrogen: kitchen scraps or manure. Repeat as many layers as the worms need and avoid wet food on the surface. 

There are many vermicomposters on the market to have in the city that usually include several levels to better manage waste. 

In both cases, the production of humus produces leachates, waters of a brown color with a high amount of nutrients that we can return to the vermicompost when there is a lack of water or use them diluted to water your plants. 

The compost is ready when there are no worms inhabiting it, it is dark brown, porous, has a homogeneous texture and smells like dense, humid forest soil. Good humus has a neutral pH and the ability to retain water. To easily collect the humus, we put its new food in a mesh bag and leave it on the surface where the worms that we want to remove are found. With some time they will move towards the new food and leave the humus, where they no longer have food. Then we ccollect the humus and restart the cycle. 


Control factors

The main factors to avoid bad smells and insects are: temperature, humidity, oxygen, carbon and nitrogen.

We control the temperature and humidity with shading and watering, the oxygen removing and aerating and the carbon and nitrogen by balancing the feeding.

Here are more details:

  • Temperature: ideal from 19 to 20 °C (66 to 68 ºF) but they develop perfectly between 18 and 25 °C (64 to 77 ºF).
  • Humidity: optimal is between 70 and 80%. More than 85% worms stop producing hummus and at less than 55% they die. Squeeze a handful of hummus with your hand, if 8 or 10 drops come out humidity is aprox 80%. Ants appear in the lack of humidity, so water the compost or add wet food. When the decomposition slows down or stops, it may be due to a lack of moisture.
  • Oxygen: Decomposition needs oxygen. If there is not good aeration, the compost gives off a rotten smell that can attract insects. If the food looks shiny and sticky, it's time to stir. To reduce humidity we add chopped paper or cardboard, straw, twigs, dry leaves... then we gently stir to redistribute oxygen and release gases produced by fermentation. 
  • C/N ratio: The carbon - nitrogen ratio should be from 25: 1 to 40: 1 (depending on the source), it is a huge difference ... But we observe that the food of the worms is composed of a large part of carbon (paper, dry leaves, straw ...) and a small part of nitrogen (kitchen scraps, manure...). The imbalance is shown so that:
    • If there is a lot of carbon, carbon dioxide is generated, the compost cools and decomposition slows down . Earthworms can live in a high carbon environment. (too much paper, dry leaves, straw ...)
    • If there is a lot of nitrogen, ammonia is produced, which generates bad odors, flies appear and the temperature of the compost increases. A very high level of ammonia in the substrate is toxic to worms. (too much kitchen scraps, manure ...)
  • pH: The optimum pH of worms is between 6.5 and 7.5 although they can support pH of 5 to 8.4. Some foods, like coffee, eggshell and pine sawdust, can change the pH of the compost, so use them knowing what you're doing. You can measure the pH of our compost with the test strips sold in the pharmacy.
  • Salinity: Too much salt inhibits the reproduction of worms and can kill them, so avoid feeding them with very salty items or previously washing them with water to remove excess salt. I guess the spiciness irritates them too. 

You can perectly keep worms without being an expert on the carbon / nitrogen ratio.

Tend to maintain the proportions that we already commented, take the precaution of adding straw, paper, cardboard ... and stir gently if it begins to smell strange or attract insects. Especially at the beginning, it is recomended to take a look at the tables that indicate the carbon / nitrogen ratio of each food to get a general idea.



Earthworms absorb soil with the mouth but they feed on the decaying matter in it. They ingest almost all of their own weight in soil daily and excrete more than half of what they eat in the form of hummus. During this process they enrich the earth with macronutrients such as nitrogen, phosphorus, potassium, magnesium and calcium and micronutrients in small quantities such as boron, zinc, iron, manganese and copper.

Earthworms mineralize the earth by providing all kinds of mineral nutrients that are very easily absorbed by plants.

This process of humification (formation of humus) that the worm does with the organic matter in a few hours of digestion, could take several years to be done in a soil without worms.

They need a healthy environment so that they can decompose as quickly and healthily as possible. The food you feed them should be:

  • Decomposed: The more decomposed the better, since the worms feed on semi-decomposed matter, but they really doesn't matter so much if you throw them the food almost without decomposing. Very fresh foods can make fermentations that release heat and increase the temperature of the vermicomposer, which should be as close as possible to 20ºC. (68 ºF)
  • Chopped : Chopped foods decompose more quickly, so that they will produce humus faster. Food in peaces also provides the space and aeration necessary for the worms to move between them, breathe comfortably and to promote drainage of the excess of water. But if you have a large compost bin, they will continue to humidify even if you don't chop their food. 
  • Humid: It is necessary to maintain a pleasant humidity for them so that they can breathe (they breathe through the skin). To achieve this you can water or add the food moistened in water. When adding food cover the most humid components on the surface, such as fruits, with cardboard, straw, paper... to avoid flies.  
  • Little by little: You have to add the food little by little, one layer at a time, not very thick and checking that the layer that is going to be covered is partially decomposed, since if we overfeed the worms they will leave food without decomposing and that decreases the quality of our humus.



Earthworm foods are divided into two large groups, depending on whether they provide nitrogen or carbon:

  • Fruits, vegetables and desalted algae: provide nitrogen and moisture.
  • Paper, cardboard, straw, pruning waste and litter: they provide carbon and reduce moisture. 

There are also foods that are toxic to worms and others of which we must add with caution.

The lists are not fixed, we may be interested in composting some of these things, in fact everything can be done. But we must know the consequences of adding one element and another to know how to balance them, otherwise it can be dangerous for the worms or decreases the humus quality.


As with us but in tiny bodies, contamination with heavy and toxic metals alter the vital functions of the worms, such as reproduction and growth. In addition, these components are not filtered by the worms, so they will pass into the humus and from there to the garden or area fertilized with it. Whenever you can, avoid:

  • Paintings on paper and cardboard.
  • All non-organic .
  • Manure from animals treated with dewormers .
  • Pruning remains treated with phytosanitary products .

Do not add

  • Inorganic and chemical , obviously. 
  • Oilsporridges and purees create problems of humidity and anaerobic fermentation (putrefaction).
  • Proteins: Meats, fish, eggs and milk produce putrefaction, bad odors, attract mice, ants, insects and can poison worms.
  • Carnivore or omnivore manure and diseased plants can transmit pathogens to the humus and from the humus to the garden.
  • Flours and cereals usually generate fungi and rice attracts insects that can be harmful to worms or to the garden.
  • Pesticides, insecticides, glues and dyes from wood, paper, cardboard, manure and pruning; they transmit chemicals to the humus and from the humus to the garden.
  • Eggshell whole or in pieces, they can be sharp elements for worms and they make better use of them when ground.
  • Fresh manure releases ammonia, acidifies the substrate and makes the worms sick to death. You have to compost it before.

Add with caution

  • Fresh food, green grass, coffee grounds, ashes, sawdust, ground eggshell, onions, garlic, citrus fruits, vinegars, salt and spices are components that create changes in the environment, for example they modulate the pH, and each of them must be known before adding to the worms.
  • Bones, nut shells and bottle corks take a long time to decompose and must be added crushed.
  • Seeds, if they do not decompose will germinate in the area fertilized with the humus.
  • Fresh oak and holm oak leaves as they contain less than 1% nitrogen, are not attractive to earthworms.
  • Walnut and chestnut leaves have resins and tannins that are harmful to worms.
  • Hair fibers break down easily and help oxygenate.


Life is reading at the window while it rains together with your beautiful plant.

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El Campichuelo English

El Campichuelo is a place in which an experiential way of life is practiced. We experience through the sensations that offer us the contact with nature and the exploration of ourselves. It may be a different path than the one you know, even so we invite you to be a participant.

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