Compost'In indoor terracotta worm composter

Compost worms are most active between 15 and 25 °C, in material that is damp but never waterlogged, and they need plenty of oxygen. Below 5 °C or above 30 °C, the worms risk dying, which rules out a windowsill in full sun, the vicinity of an oven or radiator, and a balcony in winter. They also shun vibration, so avoid standing the bin on a washing machine or against a fridge. A temperate kitchen, a pantry or a corner of a room out of direct light suits them perfectly, and you keep the composter right beside the chopping board.

Add your raw or cooked peelings, provided they contain no sauce or dressing, as well as coffee grounds, split-open tea bags, crushed eggshells, mushroom peelings and faded flowers. Cut the peelings into small pieces, as the finer the material, the faster it breaks down. Keep meat, fish, pasta, bread and brioche, oil, milk, citrus fruit, and walnut and rhubarb leaves out of the pot. Do not store your fruit peelings in a bucket before adding them either: fermentation attracts fruit flies, whereas if you add them straight away and cover them with sawdust, they go unnoticed.

A worm composter starts slowly, because the worm colony must first multiply according to the food available. Allow about 6 months before harvesting a first batch of compost. Once the worms occupy the whole ring, the cycle shortens to 3 months, and to 2 months if you add a compost activator once the pot is full, which speeds up decomposition by about 30% for a month. Without worms, composting remains purely bacterial and takes about twelve months. The compost is ready when you find almost no worms in it, a sign that decomposition has run its course. While you are away, a pause of 3 to 4 weeks without any feeding causes no problem for the colony.

Composting does not rely on worms alone: bacteria, fungi and small detritivores break down the organic matter alongside them. The batch of compost worms supplies, with the adults, the young and the eggs, the soil microfauna that gets the composter started. It is therefore normal to spot woodlice, millipedes or a few fruit flies when you lift the lid, as each of these creatures helps to break the material down. Their presence shows that decomposition is under way; only fruit flies call for action when they become numerous, and a handful of sawdust that dries out the surface will reduce their numbers.

The vermicompost you obtain looks like very fine potting compost. Mix it with about two thirds soil or potting compost for repotting, seedlings, planters and houseplants, and ideally use it within 6 months of harvesting. If you run an aquaponic system, it also makes a good nursery medium: seedlings raised in a mix enriched with vermicompost set off with a well-developed root ball when you transplant them into the grow beds. The compost itself must never be poured into the fish water, and the vermiponics guide explains how worms can live directly in a grow bed filled with grow medium.

At 26 cm in diameter and 22 cm high, the composter fits on a corner of a worktop, and it weighs 5.5 kg empty: so choose its position before filling it. Its 8-litre ring handles the peelings of a household of one to two people. If your household grows, a second composting ring stacks on top of the first, doubles the volume to 16 litres and then handles three to four people; its height then reaches about 37 cm, which is worth checking under wall cupboards. The lid and the sawdust reservoir serve both tiers.

The Compost'In arrives in three terracotta pieces, the lid, the sawdust reservoir and the 8-litre composting ring, together with an instruction booklet that gives the full list of accepted waste. These pieces are shaped by a German ceramics company, less than 200 km from Haguenau, in Alsace, where the composter was designed; the clay then develops a patina over time, so that each piece takes on a colour of its own. For a year's worth of deposits, the annual accessories pack includes two bags of coarse sawdust and two bags of activator, with or without worms depending on the version you choose.