Worm composting turns kitchen scraps into finished compost in a contained bin using red wiggler worms

Worm composting, also called vermicomposting, uses a specific type of worm—usually red wigglers—to break down food waste and paper in a bin you keep indoors or outdoors. The worms eat the scraps and produce castings (their waste), which is rich, dark compost ready for gardens or houseplants in about three to six months. Unlike traditional composting, worm bins take up minimal space, produce no smell when managed correctly, and work year-round in most climates.

The process is straightforward: you build or buy a bin, add bedding and worms, feed them regularly, and harvest the finished compost when it's ready. The main difference from other composting methods is that worms do the work instead of bacteria and heat, and you control the environment more tightly because the worms need specific conditions to survive.

Key Takeaways

  • Red wiggler worms are the standard choice for home worm composting because they thrive in bins and reproduce quickly.
  • A worm bin needs drainage holes, air holes, and bedding made from shredded newspaper or cardboard to keep worms moist and comfortable.
  • Feed worms fruit and vegetable scraps, coffee grounds, and crushed eggshells—never meat, dairy, oils, or pet waste.
  • Finished compost is ready to harvest when the bin is mostly dark, crumbly material and the original bedding is no longer visible.
  • Worm bins work best in temperatures between 55°F and 77°F, so keep them in a basement, garage, or shaded outdoor spot during summer.

Choosing and setting up your worm bin

You can buy a ready-made worm bin or build one from a plastic storage container. A 10-gallon plastic bin works for a household of one or two people; larger households do better with a 20-gallon bin or a stacked system. The bin must have drainage holes in the bottom (at least four, each about the size of a pencil) and air holes near the top and sides (roughly 20 to 30 small holes). If you use a plastic bin without holes, drill them yourself using a power drill or a heated nail.

Place a tray or plate under the bin to catch liquid that drains out—this liquid, called worm tea, can be diluted with water and used on plants. Line the bottom of the bin with newspaper or cardboard to prevent worms from escaping through the drainage holes while still allowing water through. Fill the bin halfway with bedding: shredded newspaper, cardboard, or a mix of both. Dampen the bedding until it feels like a wrung-out sponge—wet enough to hold together but not dripping. Fluff the bedding with your hands to create air pockets.

Adding worms and their first meal

Order red wiggler worms online or buy them from a local garden center or bait shop. You need roughly one pound of worms (about 1,000 worms) per household member, though you can start with half a pound and let the population grow. When the worms arrive, open the container and let them rest in a dark place for a few hours before adding them to the bin. Gently place them on top of the bedding and let them burrow down on their own—do not bury them.

Wait three to five days before feeding them. During this time, the worms adjust to the bin and begin eating the bedding. When you're ready to feed them, bury a small amount of food scraps—about a handful—under the bedding in one corner of the bin. Bury it rather than leaving it on top so you avoid attracting fruit flies and mold. The worms will find the food and eat it over the next week or two. Do not add more food until the previous batch is mostly gone.

What to feed worms and what to avoid

Worms eat fruit and vegetable scraps, coffee grounds with filters, crushed eggshells, and shredded newspaper or cardboard. Chop large pieces into smaller chunks so they break down faster. Avoid meat, fish, bones, dairy products, oils, fats, pet waste, diseased plants, and glossy or colored paper. These items either attract pests, create odors, or harm the worms. Do not add onions, garlic, or citrus in large amounts—small quantities are fine, but too much can irritate the worms.

Feed worms on a schedule based on how fast they eat the previous batch. In a new bin with a small population, this might be once every two to three weeks. As the worm population grows and the bin fills, you may feed weekly or more often. The key is to watch the bin: if food is still visible and uneaten after two weeks, you are feeding too much. If the worms seem to finish everything in a few days and the bin looks empty, you can increase the amount or frequency slightly.

Maintaining moisture, temperature, and air

Worms need moisture to breathe and move through the soil, but too much water causes rot and odor. Check the bin weekly by squeezing a handful of bedding: it should feel damp but not soggy. If it's too dry, spray it lightly with water from a spray bottle. If it's too wet, add dry shredded newspaper or cardboard and stir gently to increase air flow. A properly maintained bin should smell earthy, like forest soil—never sour or ammonia-like.

Temperature matters more than many people realize. Red wigglers slow down and stop eating below 55°F and become stressed above 77°F. In winter, keep the bin in a basement, garage, or insulated shed. In summer, move it to a shaded spot or wrap it with a blanket to keep it cool. If your home is very warm, you may need to reduce feeding or add extra bedding to help the bin stay cool. Worms can survive brief temperature swings, but prolonged heat or cold will kill them.

Air flow prevents the bin from becoming anaerobic (oxygen-starved), which causes bad smells and kills worms. The air holes you drilled should be enough, but you can also stir the top few inches of bedding gently once a month to add oxygen. Do not stir too deep or too often—you'll disturb the worms and break apart their cocoons (the small, lemon-shaped egg cases where baby worms develop).

Recognizing and fixing common problems

A sour or ammonia smell means the bin is too wet or has too much food. Stop feeding for two weeks, add dry bedding, and stir gently. Fruit flies appear when food is left on top of the bedding or the bin is too wet. Always bury food scraps, and if flies are already present, cover the top of the bin with a damp cloth or newspaper to block them. Mold is normal and harmless—worms eat it—but excessive white or fuzzy mold suggests the bin is too wet.

If worms are trying to escape by crawling up the sides or out through drainage holes, the bin is either too wet, too dry, too hot, or has too much food. Check all four conditions and adjust. Worms will not leave a healthy bin. If the population seems to be shrinking, you may be overfeeding, underfeeding, or keeping the bin at the wrong temperature. Reduce feeding, check moisture and temperature, and give the bin a few weeks to recover.

Harvesting finished compost

Finished compost is ready to harvest when the bin is mostly dark, crumbly material and you can no longer see the original bedding or food scraps. This usually takes three to six months, depending on how often you feed and the size of your worm population. The compost should smell earthy and look like dark soil.

To harvest, push all the material to one side of the bin and add fresh bedding and food to the empty side. Over the next two to four weeks, the worms will migrate to the new side to eat. Once they've moved, scoop out the finished compost from the old side and use it in gardens or potted plants. You can also harvest by removing the entire contents of the bin onto a tarp, letting it sit in sunlight for a few hours, and then hand-sorting the worms back into the bin with fresh bedding. This method is slower but ensures you don't accidentally throw away any worms.

Frequently Asked Questions

Can I keep a worm bin in my apartment?

Yes. A properly maintained worm bin produces no smell and takes up as much space as a small storage container. Keep it in a closet, under the sink, or in a corner of a basement or garage. The key is managing moisture and not overfeeding so odors don't develop.

How long does it take to get usable compost?

Three to six months is typical for a new bin. The timeline depends on how many worms you start with, how often you feed, and the temperature. A larger population and warmer conditions speed things up. You can harvest a small amount of compost after two months if the bin is mostly finished material.

What happens to the worms when I harvest the compost?

You separate the worms from the finished compost and return them to the bin with fresh bedding. The worms stay alive and continue composting. If you harvest by moving worms to a fresh side of the bin, they migrate on their own and you straightforward scoop out the old compost.

Can I use garden soil or potting mix instead of shredded paper for bedding?

No. Worms need light, fluffy bedding that holds moisture but allows air flow. Garden soil compacts and restricts oxygen. Shredded newspaper and cardboard are the standard choice because they provide the right texture and break down slowly enough to last several months.

What do I do with the liquid that drains from the bin?

This worm tea is nutrient-rich and can be diluted with water (one part worm tea to ten parts water) and used on houseplants or garden plants. Do not use it undiluted, as it may be too strong. If the bin is draining a lot of liquid, the bedding is too wet—add dry newspaper and stir gently.