In our quest to live more sustainably, composting with worms (vermi-composting) is one thing we can easily do that supports our efforts in a number of ways. This article will touch on some of the basic concepts of vermi-composting. If you are not already a worm composter, then we hope this will encourage you to try it out.
Besides converting food and garden scraps into nutrient-rich compost, vermi-composting also supports local agriculture by keeping the food-nutrient cycle local. A healthy soil microbiome supports plant vitality and immunity to disease and pests. The vast numbers and diversity of microorganisms in worm compost contributes sizably to the microbial populations of our garden soil or potting mix. Disposing your food wastes in the trash and sending it to the landfill as garbage contributes to global warming, because the decomposing food generates the greenhouse gas, methane.
Of the many thousands of species of worms, two species, the Red Wiggler (Eisenia fetida) and Redworms (Lumbricus rubellus) have become popular for home composting. Both species serve as voracious decomposers in the natural world, and both also thrive in bins with dense populations.
There are numerous styles of bins. The most common for home use are either the ones with stackable tiers or plastic tote bins that have been modified to house the worms. Because liquid (leachate) tends to accumulate at the bottom of plastic bins and become anaerobic (smelly), my preference for this type of bin is one with a reservoir to collect and drain away the leachate.
With both of these types of bins, the worms need to be separated from the castings. More on this shortly. There are some self-separating bin designs that make the task much simpler, especially for larger volumes. I am using a horizontal migration bin now that I am happy with. The composting is done in one chamber that is separated from a second chamber with a 1/4” mesh screen. The second chamber is separated from a third, also with a screen. Once the first chamber is full, bedding and food are then added to the second chamber, the worms will migrate through the screen to the food. Same strategy for the third chamber. When the worms have fully migrated to the third chamber, the process is repeated in the other direction.
To create a successful bin, it is useful to mimic their natural environment as much as possible. It will be necessary to keep a source of bedding material on hand to provide a residence for the worms, and into which you can bury your food scraps. Many worm keepers use shredded newsprint, but for health and safety reasons, I am a purist, preferring to use a mixture of more naturally occurring materials. Plus, I think it serves a higher purpose to recycle the paper products on behalf of trees.
To make my bedding, I mix together leaf or straw mulch, coffee chaff from a nearby coffee roaster, spent coffee grounds, and some active plant compost or composted animal manure. If you can locate a source of llama, alpaca, or rabbit manure, these can be used without pre-composting, and are favored by the worms.
Worms will eat just about any food that will decompose, but they have their preferences. Avoid feeding them spicy foods such as onions or hot peppers. Also avoid meat, fish, and dairy. Please keep in mind as well, that worms have small mouths, so larger scraps such as broccoli stalks will linger for a long time. The organisms in the bin are helping to break down the food scraps into smaller bits. It is considered to be good feeding practice to mix the food beneath the bedding. Some worm keepers will rotate their way around be bin, feeding in a different area each time. Avoid clumps or globs of food which can become smelly, anaerobic pockets.
If you are using a tote bin for worm composting, once full, you will need to separate the worms from the castings. The easiest method I have found for this is the “light avoidance” method. Worms are sensitive to light. If you empty any amount of the bin contents onto a tray or sorting table, the exposed worms will burrow back into that pile. You can then remove any of the surface layer of castings until you begin to expose worms again. The newly exposed worms will then burrow further into the pile. Repeat this process until you have removed all the castings. The worms will have clumped together making it handy to gather and to restart your freshly emptied bin.
Castings are potent and do not need to be used full strength. Roughly 20% castings will be sufficient in your soil mix. Or top-dress your house plants and water the castings into the plant. The castings can be made into a steeped tea for watering house plants, or a specially brewed tea for generating larger volumes for larger areas.
Besides the practical results of generating your own fertilizer for your home or community, worm composting offers a window into the diversity and function of intact healthy ecosystems. I find it fascinating to observe the variety of species that reside in the bin and the way they interact with each other to generate a hugely useful by-product simply in exchange for our stewardship.
Ben Goldberg has been playing in the dirt since he was a kid, and has been keeping worms and making worm bins in various sizes and shapes since 1995. He enjoys presenting interactive worm composting workshops, which are informative and fun. Ben lives and works in the Pioneer Valley farming region of western Massachusetts along with some of the most productive soil in the world. For questions and to learn more contact Ben at firstname.lastname@example.org.