1. How vermicomposting works :

Vermicomposting is a process for the bio-oxidation and stabilization of organic matter through the combined action of micro-organisms and earthworms. The resulting compost, known as vermicompost, does not require the thermophilic phase characteristic of composting. The high quality of this compost is due in particular to its excellent granular structure.

It’s a natural, odorless aerobic process that’s very different from conventional composting. Earthworms (compost worms)

ingest organic waste and then excrete dark, odorless, fertile manure. Worm manure is a ready-to-use soil improver that can be applied in large quantities, since its nutrients are released at a rate suitable for growing plants.

To produce high-quality vermicompost, you need a good selection of earthworms. Epigeic worms, such as Eisenia Fetida (red worm or manure worm), are best suited to ingesting organic waste. This category of worms lives on the soil surface and in decomposing organic matter.

Worms thus condition the microbiology of the substrate, since their intestines contain the same bacterial species as in the environment in which they develop. The number of micro-organisms found in their intestines and excreta is two to three times higher than that found in the surrounding substrate.

2. Example of windrow vermicomposting :

The vermicomposting process described below consists of the following steps:

Mixing materials: the best feed for composting worms is animal and food waste, as well as green, fresh, nitrogen-rich, pre-composted plant waste, to facilitate digestion by the earthworms. The mixture used is composed of 1/3 digestate, 1/3 bovine manure and 1/3 sawdust. The materials were mixed using a horizontal rotating drum.

Pre-composting: 3-week maturation of the organic matter mixture, making it more digestible for earthworms.

During the pre-composting process, the thermophilic phase

induces an exothermic reaction within the windrow. The temperature at the heart of the windrow can then reach 60°C to 80°C.

Windrow vermicomposting: the mixture of organic matter is

windrowed for the vermicomposting phase inside a ventilated shed, on a concrete slab. Two types of heat-tolerant Eisenia Foetida worms were used.

Introducing earthworms into a compost heap helps to mix materials, aerate the heap and accelerate decomposition.

Worm density is around 150 worms per liter of organic matter. The mixture of fresh organic matter is added, in layers a few centimetres thick, to the top of the windrow. In this way, the earthworms move upwards, from one layer to the next, while ingesting the fresh material. It takes about a week for the worms to migrate from the finished vermicompost to the fresh organic matter. The added organic matter has a density of between 350 and 650 kg/m3. Earthworms ingest around 75% of their body weight daily (0.15 g of material for an individual weighing 0.2 g).

The windrows are watered by hand, to maintain the right level of humidity, and covered with plastic sheeting to keep the worms protected from light. The worms have photosensitive cells on their skin that cause pain and paralysis when exposed to light, with the exception of blue light.

Vermicompost recovery and drying: the worms are recovered from the top of the windrow and the vermicompost from the bottom. The final sieving performed by a worm harvester ensures that no worms remain in the vermicompost. The resulting vermicompost is air-dried in a shed sheltered from the rain. A two-week nitrification process takes place, during which the ammonium is transformed into nitrates, a form in which it can be assimilated by plants.