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Airflow in Composting Worm Bins

worm composting airflowComposting worms need oxygen, but how much airflow do their bins need? While starting a worm bin is quite simple, the reasons for the bin design are more complicated. All worm bins need air holes, proper drainage, and suitable bedding. Without a proper design, a worm bin becomes a coffin for sick worms. And the smell! Thus, using a standard worm bin design is important to composting success. If you want to turn kitchen scraps into valuable fertilizer, find out about airflow in composting worm bins.

How Worms Breathe

Humans breathe through the mouth and nose, and into the lungs. Worms breathe through their skin. Oxygen diffuses from the air through the skin. Worms do not have lungs. So long as they have access to enough air and moist skins, they will breathe easily.

Worms make tunnels by eating their way through organic matter and soil. The tunnels allow air to flow. Tunneling also digs up the soil and makes it fluffier. Fluffier material has more airflow than compact material. Releasing European Night Crawlers (Super Reds) into the garden helps break up the soil, adds tiny air pockets and tunnels, and provides worm fertilizer.

Be careful when you place a bag of composting worms into a worm bin or the garden. You might be tempted to dig a hole, empty the worm bag, and cover it with soil or bedding. However, the worms will be deprived of oxygen if you do this. Some of them might not make it! Best to place them gently on the surface. They will dig their way down. Worms will move away from light, so sunlight or shining a light on them will encourage them to dig down quickly.

In the wild, a heavy rain saturates the soil and starts to fill up the worms’ tunnels. The worms cannot get enough air, so they crawl onto the surface. This is a perfect feeding time for birds and other worm-eating critters!

The worm bin is a small environment and as such, its lid protects it from rain. The worm bin needs to be maintained properly to keep the worms productive. Deprive them of oxygen and the worms will suffocate.

Good Worm Bin Design

A good worm bin generally has these attributes:

  • A lid to keep out the rain and discourage predators
  • Drainage holes at the bottom
  • Air holes in the sides
  • Room to fit enough bedding so the worms can move around
  • Empty space above the bedding for air and to let the bedding/fertilizer mix get bigger

Worm bins for composting can be made from wood, plastic, old pallets, mesh wire, or cement blocks. See our video about making a worm bin from a tote.

The best type of worm composter is made from trays stacked one above another. Start with one tray for the bedding, worms, and scraps. When this tray is full, add another tray of bedding. Feed only in the top tray. The worms will migrate up, leaving perfect fertilizer in the lower trays. In this way, you can compost without the effort of separating worms from bedding. Uncle Jim’s Worm Farm carries several styles of tray-based worm bins.

Air Exchange

Airflow is needed in the worm bin. Just like us, worms generate carbon dioxide as part of their breathing process. They release CO2 out through their skins using diffusion. This carbon dioxide needs to go somewhere. If it builds up, it will deprive the worms of oxygen. So if you make your own worm bin, be sure to have plenty of air holes. A worm bin that you buy should already have sufficient air flow. Good air goes in, and bad air goes out.

In this context, diffusion means that chemicals move from an area of high concentration to lower concentration. Oxygen is more concentrated in the air than in the worm. Therefore, the oxygen spontaneously moves from the air, through the worm’s skin, into the worm. If the worm’s skin needs to be moist for this to work. Carbon dioxide waste is more concentrated in the worm than in the air. The CO2 naturally diffuses into the air.

When Things Go Wrong

You will know something is wrong if the worm bin has a foul odor. A healthy worm composting bin should have an “earthy” smell. If something stinks, you might not have enough air holes. It’s possible that the drainage holes are blocked, or there is something else wrong. Consult our worm bin odor guide if this comes up.

Treat your worms like living creatures – because they are living and breathing! These humble creatures will happily turn your kitchen scraps and garden waste into valuable fertilizer. Uncle Jim recommends Red Worms for composting, and European Night Crawlers for composting, fishing, and releasing into the garden. See our selection of convenient composting bins.

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