Do worm farms smell?

By Teresa J. Frith

worm bins

These days a lot of people have started keeping worm farms, and keep their worms in what’s called worm bins.

Worms are great for composting and are very eco-friendly, as the worm castings (worm poop) are used for fertilizing gardens, other plants and lawns. But a big question being asked by many is “Do worm farms smell?”

If you keep your worm bin outside, odors may not be a big issue, however, if you keep it indoors, you likely have some concerns on possible bad odors.

The answer to “Do worm farms smell?” is that a properly maintained bin ought to have an earthy, sweet soil smell.

It shouldn’t stink at all, and if it does, it could be caused by the following issues:

  • Adding too much food—One reason for a bad smell is rotting food scraps if you are feeding your worms too much. Worms should be able to digest the food within a few days and you don’t have to feed them every day, about once to twice a week is fine.
  • Feeding the wrong kind of foods – Another reason for bad smells is if you are giving your worms the wrong kind of food scraps. You should never use things like meat, citrus, onions, oils, fats, dairy or cruciferous veggies like broccoli or cabbage. The bin is too moist – Although worms need moisture, if you add too much water it can cause the worms to drown. Then you could be smelling dead worms. (We solved this with the Worm Bucket kit - it has built in drainage so worms can never drown in our system.)
  • Dead worms cause a rotten rancid kind of odor. Or, the bedding in the bin could be rotting due to too much moisture. Be sure the bin has drainage holes and you don’t add so much bedding that it causes puddles to form outside the box.
  • Not enough aeration – Be sure to keep the bedding fluffed up and loose so enough air is getting to your worms, and they have room to burrow around in the bin. Add new shredded newspaper or other bedding as needed and remove dirty, soggy or smelly bedding regularly.
  • Abundance of aerobic bacteria – This type of microorganisms perform decomposition of raw materials, which in turn becomes compost. However, if there are too many of them it can cause a sour, vinegary, ammonia type of odor. If this is the problem, you likely need new bedding. You can try fixing it via mixing in some shredded cardboard, wood chips, straw or hay to your existing bedding. This should absorb the smell in time, but it may take a week or so to go away.
organic garden

All in all, worm farms are a great method of producing your own fertilizer for your garden, lawn or other plants. As long as you properly maintain it by not feeding the worms too much or feeding the wrong foods, don’t let the bedding get too moist or too tightly bunched up, and make sure there is proper drainage, your bin should not smell like anything other than fresh, earthy soil.