Straw Bale Worm Composting

Worms are industrious, tireless workers. Did you know worms never sleep?  They eat our garbage and turn it into productive soil. Worms can be kept in a small bin with no odor in an apartment or small space. They are part of the solution to our collective nature deficit disorder.  It’s no wonder that Charles Darwin spent almost 40 years of his life learning from worms. They are super amazing creatures.

One of the schools I taught gardening at this summer had set up a straw bale worm composting system in the spring. By the end of the school year, they were separating all their worm-friendly lunch scraps and adding them to the bin, all but eliminating the compostable waste component going to the landfill.

They set it up something like this. First went in a layer of bedding (carbon) that consisted of dried leaves, shredded paper, shredded cardboard and some loose straw. This layer contained little or no nitrogen as you don’t want the layer to heat up in advance of the worms arrival. Red worms will not survive if the pile is above 95˚C or hotter. About 12 inches of bedding is a good place to start. Wet the bedding with a hose. Make sure you have adequate drainage. Worms need to stay moist because they break down oxygen from the water and breathe it in through their skin. But, too much water will drown the worms.

After two or three days, when you are sure the pile is cool, introduce your worms. The ones they used at the school are the same ones I have in my home worm bin, Eisenia fetida, or red wigglers as they are commonly called. These worms thrive in piles of rotting vegetation and are ideal to stay in your worm bin working their way through the decaying matter. The school added around a pound of worms to the bin to start.

Begin feeding the worm your waste slowly at first, two- three days a week for the first couple of months. Dig a hole in the bedding and deposit your food scraps, then cover over the hole. Worms will increase their populations depending on the level of waste in the bin. Within a couple months, you can feed them everyday. And make sure to continue to water the top of the worm bin as needed.

Do not turn the compost in the worm bin. Turning compost invigorates bacteria and may make the pile too hot for the worms to survive.

Foods you should not put in your worm bin are meat, cheese, any dairy, garlic, onions, anything salty or covered in a sauce. Also avoid citrus peels. Citrus has an essential oil in its peel that is used as a natural insecticide and can be harmful to the worms.

To harvest the worm castings in this system, you should begin by adding the kitchen waste on one side. When you are completed with the one side, work toward the other. The worms will migrate accordingly and you can dig out the castings on the other side.

A rule of thumb in worm composting is to keep your bale at least two parts carbon (brown stuff like straw or dirt) to one part nitrogen (green stuff like grass clippings or kitchen waste). Too much green will make your pile anaerobic- slimy and smelly. Too much carbon will have no negative consequences. The carbon bedding serves as a home to the worms, but is also part of their diet. Keeping the layer of brown on top of the green waste will greatly reduce the chances of being visited by rodents and other pests interested in grabbing a quick bite to eat.

I’ve seen some posts online that show that you can continue with the straw bale system into the winter months if it is covered properly. I think this is pretty cool, but have no first hand experience with it.

For my personal compost, I use the Worm Factory 5-Tray Worm Composter kept indoors during the colder months. And by the way, I love the worm factory. It is so easy, the worms migrate from one tray to the next leaving behind their castings for you in a lower tray. The casting tray can easily be emptied into your garden and you have an empty tray to add to to the top to begin the process again.

Happy Worm Farming!!


  • Joel Bruneski

    I use this type of compost/worm pile at home ending up with bales stacked about three high by the end. I like this system because I have plenty of hay available and after a couple years it get’s added to the pile itself. Also, if the pile does heat up at all the worms can move into the bales to escape.

  • Joel Bruneski

    **please add to previous comment of mine, same day.**
    It also helps insulate from the cold in the winter. We can drop down to -30 cel in the winter and I still end up with worms in the spring.

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