New vermicomposters worry that their two-week old bin isn't producing castings and that they may be doing it wrong. Things look fine and smell fine, but the worms aren't “destroying” the food like we think they should.
If most beginners think of vermicomposting the way I did, then they think of a worm bin like salad with distinct ingredients each serving a distinct purpose with vermicomposting seen as a linear process where worms eat waste and then poop out worm castings.
And once there are enough worm castings, you simply harvest them by separating the castings from the rest of the bin.
End of story.
But a far better analogy for vermicomposting is that of a soup.
Yes, you certainly start with distinct ingredients like bedding, food, and the worms of course, but what you’re actually doing is creating a soup or a stew using a much more circular process that builds upon itself.
And what you end up with is a brew of bedding, food, and worms, but also worm castings, microbes, plant growth hormone, humus and other organic matter that didn’t exist when you started your bin.
Note: This article is part of a “Vermicomposting 101” series of posts aimed at helping the beginning vermicomposter. The read other “VC101” articles on how to start a worm bin, how to choose worm food, how to maintain moisture, and the differences between composting and vermicomposting, please visit the Vermicomposting 101 section of this site!“
How the Vermicompost “Soup” Is Forming
In a nutshell, here is a decent beginner-level description of what is happening in your bin.
Your carbon-rich bedding and nitrogen-rich bedding are both breaking down, but at different rates. In this regard, it’s helpful to think of bedding as simply a different kind of food.
What is helping to decompose this material? Microbes…..normally bacteria in a new worm bin.
In the decomposition process, more and more of the surface area of the organic material is being exposed to oxygen and to microbes. In response, the microbe population, aka the number of mouths feeding on the food waste, expands.
An increased microbe population results in increased surface area, more food is now available for our microbes, which multiply in response to a food source that can sustain them. This further accelerates the decomposition in our worm bin.
This is what happens in an actual hot composting pile as the mesophiles, or mesophilic microbes, do most of the decomposing in the beginning before giving way to heat loving thermophilic microbes or thermophiles.
But because a properly-maintained worm bin is fed in small quantities (often thin layers), the thermophiles can never bloom because the organic waste is not piled deep enough to trap the heat needed to keep those heat-loving microbes happy.
Now you’ll notice that we haven’t even started talking about worms yet.
Enter the Worms
By the time that the worms are entering the picture, there should be a thriving microbe population which is why I recommend taking plenty of time to prepare a worm bin before you introduce worms. And what the worms are actually consuming are microbes that they are hoovering up off the surface of the decomposing waste. Yes, a little food itself enters the worms’ mouths but their main food is the microbes.
As these microbes travel through the worms’ digestive system and are exposed to the flora in the worms’ gut, their populations continue expand and condense, ultimately forming a bacterial mucus around the digested organic matter that will exit the worm in the form of worm castings.
Give what we know about microbes – that they consume organic matter and are themselves consumed by worms – what effect do you suppose these worm castings have on organic matter?
The castings themselves will promote the decay of organic matter and itself become food for the worms.
Yes, the worms eat their own poop!
And it’s glorious, not awful like when your cat does it.
Assuming the temperature, moisture, and pH remain within acceptable ranges, this virtuous cycle will continue until there is no organic matter left for the microbes to consume. When the microbes run out of food, their population will begin to decline.
This is why if you plan to harvest worm castings and store them for several weeks or months, it’s a good idea to add an organic food source like leaf mold or some other organic material for the microbes to munch on.
But the lack of a visible food source doesn’t mean the microbes are already starving. Plenty of anecdotal evidence exists of microbe populations continuing to thrive well after a worm castings harvest, even in less-than-optimal storage conditions.
Back to the Soup Vs. Salad Analogy
The time it takes you to make a salad equals the time it takes you to throw the ingredients together.
But a soup will take longer as the ingredients all need time (and normally heat of course) to interact with one another to create a concoction via more slowly-developing chemical and physical changes.
This is why a new worm bin owner is disappointed that their 2-week old worm bin isn’t breaking food down quickly enough. That bin is still a salad. Even with good conditions, there haven’t been enough of these cycles to produce a rocking and rolling ecosystem.
Wrapping It Up: Is Your Bin a Soup or a Salad?
There is no magic point at which your bin turns from salad to soup. And I would even argue that in less-than-optimal conditions, your bin may become a salad on top of the soup below as the microbes and worms are in survival mode more than thrive mode. But this new material will be better absorbed into the soup because of the community of microbes below.
Well I hope this has been helpful, especially for you beginners who may be initially discouraged by the lack of apparent progress in your bins. Again….if things look fine, smell fine, and your worms aren't trying to escape en masse from your worm bin, things probably are just fine!
Let me know if you think your bin is a soup or a salad, or if you think I'm smoking crack by even making this comparison!