WORMbag Worm Composter

Set up the WORMbag out of the rain and sun, away from extreme heat and freezing temperatures, on a flat, level surface. Your home, a garage, an office, a classroom, and especially a basement or cellar, where temperature and humidity stay stable, are all good spots. Choose its location before filling it. Once active and full, the WORMbag worm composter is heavy and must be moved carefully, by at least two people, so its structure doesn't get bent out of shape.

All our tips: Where to put your worm composter: kitchen, basement, garage, utility room...

Sturdy and backed by a 2-year warranty, the WORMbag works even better with a few accessories. Our Eisenia composting worms are sold separately, and the instructions recommend starting with 8.8 oz to 1.1 lb (250–500 g). For the starter bedding, mix cardboard with our additive-free 9 L coconut fiber block or our natural fiber substrate, designed specifically for getting started. An XXL hemp mat, which you can cut to the shape of the bag, keeps moisture in at the top of the WORMbag, and our mini mixing rake aerates the surface without getting your hands dirty. When you're away, consider WormFood.

Fill about 1/5 of the WORMbag with moist bedding, such as rehydrated coconut coir mixed with cardboard or paper, to a depth of 7.9–9.8 in (20–25 cm). Make sure the drawstring at the bottom is pulled tight, close the bag, and wait 12 hours before adding the worms. The instructions recommend starting with 8.8 oz to 1.1 lb (250–500 g) of composting worms, sold separately. You can go up to 4.4 lb (2 kg) to compost faster, but a smaller population is safer when you're just getting started. Garden earthworms won't work in the WORMbag worm composter: you need composting worms.

All our tips: How to start your worm composter, step by step

With the WORMbag, start small: wait 3 days after adding the worms, then add thin layers of food scraps. With 8.8 oz (250 g) of worms, add no more than about 14 oz (400 g) of scraps every 3 days; with 1.1 lb (500 g) of worms, add about 1.8 lb (800 g). Watch how quickly the scraps disappear before adding more. The population grows during months 2 through 4, and you can then feed more often. Cut the scraps into small pieces and cover them with cardboard or paper. If the temperature rises inside the WORMbag, there's often too much food, so pause feeding for a while.

Your first harvest from the WORMbag comes after about 6 months, from the bottom of the bag. Undo the clips and Velcro flaps on the lower section, place a shallow container under the WORMbag, then gradually loosen the drawstring: the vermicompost drops out and is easy to collect, with a little scraping if needed. Stop as soon as you reach a layer with worms in it, then pull the drawstring tight again. If your harvest contains a lot of worms, the compost isn't ready yet: put it back on top and wait at least a month.

All our tips: How and when to harvest vermicompost and compost tea