Surviving Winter: How to Keep Your Worm Bin Warm

• Unless you're using a tropical species of worm, your composting worms, such as Red Wigglers, will survive down to freezing temperatures. If they do freeze, their cocoons should survive and hatch when things warm up.
• If your composting efforts slow down in winter, it may be worth not investing too much into keeping your worms warm so they slow down with you.
• There are several promising solutions to help keep worms warm, including insulation, thermal mass, transplanting heat, drying out the material, strategic overfeeding, relocation, and heaters.

Insulation

By keeping the worm bin surrounded by insulative material, such as straw, fall leaves, other dry carbon rich organic matter, or even actual insulation such as an insulation blanket, you will mitigate how much the cold reaches the bin, and how much internal heat escapes.

Another great insulator is the earth itself. If your system can be partially submerged, this could help with insulation.

Adding Thermal Mass

The larger your bin is, the more easily it can hold onto its own heat. I have seen compost piles about 1-2 yards large be able to survive a cold Utah winter without the worms dying.

Transplanting Heat via Water

This is probably not sustainable in many cases, but it is possible to bury jugs of warm water into the worm bin. This will transfer heat from the jug into the worm environment, and you can remove the jug and refill it with warm water as desired.

Allow the Material to Dry Out

As fathers across the world love to say, "it's not the heat that gets you, its the humidity!" Just as humid weather makes the cold feel that much colder, it is the same with worms. Water is a very effective conductor of thermal energy. The more wet the worm's environment is, the quicker thermal energy will be transferred to, or lost from, the pile. If you allow the environment to dry out a bit more than normal, it will help buffer temperature extremes.

✨Strategic✨ Overfeeding of Nitrogen Rich Foods

Bacteria and Fungi create heat as they reproduce and grow. Typically you don't want to add so much food that the bin begins to hot compost, but a risky method to keep your worms warm during winter would be to induce a slow and steady thermophilic effect in your compost pile.

Coffee grounds are great at creating heat as they are nitrogen rich and have a lot of surface area. You can get them pretty easily from coffee shops around you and add to your worm bin to help heat it up.

Definitely go slow and steady with this one.

Relocation & Worm Storage

If you have a solid worm population going and want to keep them active through winter, maybe its worth considering moving them into the garage, or a warmer part of your home. Your worms will thank you!

If it is not feasible to move all of your worms inside, consider taking a small portion of your worm colony and bringing just them inside. Take good care of them, encourage growth and reproduction, and if your outdoor colony is wiped out during winter you can use this colony to re-introduce worms to your outdoor system.

Space Heaters and Seedling Mats

This would not be feasible for a outdoor bin, but you could just use a space heater to keep the bin warm, or if it could fit on a seed heating mat you could use one of those.