What is a Worm Compost Bin?

A worm compost bin is a compost maker used to create vermicompost in small-scale vermiculture operations. Earthworms in the bin process degradable waste matter and transform it into nutrient-rich compost that can be used to nurture garden plants. Organic compost is an effective and environmentally friendly reuse of decomposable waste matter.

Composting bins and compost tumblers are ideal for apartment dwellers and people with limited garden space. Compost tumblers usually have a plastic or metal compost mixer drum that rotates to speed up the compost making. Composting bins come in different types, shapes and sizes, and are typically made of wood, plastic, rubber or metal. They can either be purchased ready-made, or various old containers can be used as compost bins.

Ventilation holes are drilled at the bottom and at the sides of the worm compost bin to ensure sufficient oxygen supply and to allow for wastewater drainage. The bin is placed on stacked bricks to protect it from pest incursions, and a tray is placed underneath to catch the water waste. This water can be reused to moisten the bedding in the bin.

The bin is filled to about a third of its size with bedding material like straw, shredded paper, moist squeezed paper, sawdust, dry leaves or cardboard pieces. It is a good idea to stir the bedding to create air pockets for the worms to breath in and burrow in easily, and add a handful of soil as grit to aid earthworm digestion. The soil and the bedding are moistened with water before the earthworms are added. Earthworms are obtained from different sources like gardens, farms, nursery mail order suppliers and fish bait shops. Of the many earthworm varieties, Eisenia fetida or Red Wrigglers and Lumbricus rubellus or Driftworms are commonly used in vermiculture.

A light is focused on the bin to encourage the earthworms to burrow into the bedding, and then it is time to add biodegradable materials like vegetable matter, egg shells, food waste, fruit rinds, tea bags and coffee grounds. Dairy products and meats are not recommended as earthworms don't seem to favor these much. The waste is inserted into different sections of the bedding at different times, and covered up with more bedding to deter pests like fruit flies. Cut grass, weeds, decomposed cow manure, or goat droppings and urine are often added as compost activators. A compost activator helps balance the carbon and nitrogen content in the bin and speeds up the composting process.

The worm compost bin is covered with a lid or a burlap sack and placed in shade. A temperature of 50 to 77 degrees Fahrenheit (10 to 25 degrees Celsius) is ideal for the earthworms to do their work. Periodic checks should be made to ensure that the bedding is sufficiently moist. Earthworms cannot survive in dry bedding and can even drown if it is over-watered.

Normally, the worm compost bin should not stink; it should have an earthy smell, particularly after the earthworms begin their work. A stink indicates that the waste is too wet and this can be remedied by either removing the wet waste or adding dry leaves to the bin. The compost is typically ready to be used after about three or four months.

The compost is then sifted free from the earthworms and their eggs. It is leached in water to make compost tea or mixed with equal amounts of potting soil to add to garden plants. The earthworms and their eggs are returned to the worm compost bin with fresh bedding and waste to restart the compost making process.