A worm factory is a multilayered compost bin that is designed to efficiently harness the power of worms to make nutrient-rich compost for your garden (or for whatever else you might want to use nutrient-rich compost for). Compost produced by worms is particularly good for gardening, helping your plants flourish.

Worm factories are built like dressers, with the bottom drawer housing the rich, ready-to-use compost.

Here’s how they work: Let’s say you just bought a new worm factory – who wants to deal with a used worm factory? – and, just to make this a more pleasant hypothetical, let’s say you bought the worm factory on sale. First, you would remove the bottom tray and fill it with the compost you accumulate throughout the day – things like leftovers and rotted food. According to some advertisements, worm farms can even process things like junk mail and cardboard.

After the tray is loaded, add several worms to it. The worms will go to work on the waste, slowly converting it into nutrient-rich compost as they digest whatever you threw in there. The worm factory not only produces worm castings (also known as vermicast, worm humus, or worm manure), but also a liquid nutrient called leachate. The leachate is formed by moisture trickling through the worm factory. The liquid collects nutrients as it trickles downward, and the final product is collected in a separate tray.

Once the bottom tray is full and crawling with worms, add another tray of compost to the factory. Once the worms exhaust the original food source in the bottom tray, they will migrate upward, starting the process all over in the tray above. Not only are worms creating more compost this way, they are also removing themselves from the tray that has the ready-to-use compost in it.

There are a variety of different worm-factory models made by a variety of different companies. Which factory you choose will depend on how much organic waste you want to convert into nutrient-rich compost. You may also be influenced by aesthetics: some worm factories are black, some are red; some are tall with many shelves, others are short with only a shelf or two. However, they all serve the same function: to efficiently convert unprocessed compost into nutrient-rich compost for your garden.

Amazon offers a well-reviewed Worm Farm for sale here:

Worm Factory 360 WF360G Worm Composter – Green