Make Worm Compost From Kitchen Scraps

Ready to up your compost game? Start a worm bin to convert your leftovers and organic materials into worm compost (and grow tasty treats for your chickens).

by John Moody
PHOTO: Morozov Alexey/Shutterstock

Long before I had land, I had two uncommon things for an apartment-dwelling city slicker: earth boxes and a worm bin. I moved the boxes around the common areas of the apartment complex so I could grow something despite the lack of land, and I hid the worms in the building’s shared basement area. Early in the morning or late at night, I would sneak down to feed my silent friends, hoping none of my neighbors would be so offended as to report me to the landlord.

When my family moved to land, I kept both. The earth boxes became a convenient way to grow certain herbs and move them from summer to winter housing. My small original worm bin, though, was insufficient for our larger land and family. It was time to upgrade. I spent almost a year looking at options, including old wooden shipping boxes, 55-gallon barrels and other such reusable industrial discards.

Then one day I realized I had my new worm bin sitting right in front of me: some old intermediate bulk container totes. These IBC totes are durable, movable, affordable and just about the perfect size for my purposes. I cut the top from one of these containers and began my next, much larger stage of making vermicompost and low-cost chicken food.

Why Worm Compost?

For numerous reasons, worm compost is worth the small bit of extra effort beyond regular compost. First, worm compost is superior. Numerous studies, such as “Earthworm Castings as Plant Growth Media” by Rhonda Sherman, an extension solid waste specialist at North Carolina State University, show that worm compost provides improved germination and growth rates, protection from various pests and diseases, and other benefits beyond those of regular compost. This is partly because worm castings contain hormones and other plant-promoting compounds that even well-made regular compost lacks.

Second, worm compost is generally a cool compost; it doesn’t rely on various types of bacteria that produce large amounts of heat to break down waste into compost. Hot (thermophilic) composting has many benefits, but it also causes the loss of certain key nutrients, especially nitrogen.

Worm compost is generally considered a superior fertilizer, as the nutrients are turned into a “slow release” form as the worms work their way through the various materials you feed them. The final composition of your compost is determined by what you feed the worms, allowing you to tailor your compost to your soil and plant needs.

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What Worms Need

You might ask: “Why an IBC tote?” It’s all about providing what worms need. First, worms need a relatively stable environment in terms of temperature and moisture. A common reason people run into problems worm composting is that their bins are too small. Small bins—from 5 to 20 or so gallons—are more difficult to manage. They get too hot or too cold, too wet or too dry. In them, it’s easy to overfeed, creating issues with pests or smells. Then can also go thermophilic if too much material is added, upsetting the worms.

IBC totes—which hold about 250 to 300 gallons—have eliminated almost all the problems we had with smaller bins. Indeed, it has been more than four years since we had any problems. (The last involved mice taking up residence in one bin; we solved this by adding a pair of cats to our outdoor animal mix!)

The size of the totes helps ensure that things stay within a suitable temperature range. Even when our state reached an unheard of minus-30 degrees Fahrenheit for three consecutive nights—so cold that even our water and septic froze solid—our worms survived just fine in our dirt-floored, unheated barn in their snug little IBC totes.

IBCs don’t dry out as easily as smaller bins and are less prone to becoming waterlogged. Note, overwatering is another common issue with worm bins; it can cause the bin to go anaerobic (lacking oxygen), which creates noxious smells and other issues.

If you are unsure whether your bin is at a proper moisture level, use the hand test. Take a handful of material from the bin and squeeze it. No more than a few drops of water should fall out, and your hand should feel moist. If more water runs out, the bin is too wet and you might need to add some dry matter. If no moisture forms in your hand, it’s too dry, and it’s time to lightly water.

A larger bin lets you feed more material at a time and less often. This way, you disturb and work the bins less frequently, which is better for you and the worms. Often, we will go two weeks or more without providing any care to the bins, only to come back and find the worms are still moving right along making beautiful compost and more worm babies. Asked what my favorite farm animal is, my response is always “worms.” You really can’t beat something that thrives on neglect.

Worms do, however, need food and bedding. Worms aren’t overly picky about food; our general guideline for beginners is no animal products or overly fragrant foods (citrus, raw onions, garlic and so on). The former can attract lots of pests; the latter are disliked by the worms and sometimes resistant to decomposition, slowing down your bin.

Bedding provides the worms a place to hang out and reproduce after a long day of turning various waste streams into high-quality compost. Many options are available—peat moss, leaf mold and more. We use coir-dehydrated, shredded coconut husk, as well as no- to low-ink cardboard and similar cellulose materials (such as the noninked part of paper egg cartons and flats). The cardboard also serves as good insulation and light blocking along the outer edge of the totes.

Worms are most akin to chickens when it comes to eating: They grind their food down. So, just like chickens, worms need grit. For a small bin, you can often provide all the grit they need via eggshells.

In the past, we would toss our shells on a cheap metal cookie sheet and dry them in the oven with the residual heat from cooking. Once they were dry, we would collect them in a bucket until it was about half full, then we’d smash them to small pieces. Once a week or so, we would dump shells into a bin that needed additional grit. Now that we have so many bins to feed, grit is the only other thing we purchase. We use agricultural lime and oyster shell, adding a couple of big handfuls each week.

Drawbacks to IBC Totes

The surface-area-to-depth ratio isn’t ideal for worm compost. A shallower, larger bin would be better. Everything we have seen over the years that is shaped more suitably, however, is also four to 10 times the cost.

Second, because the bins are lofted for drainage and already fairly tall by themselves, the height factor can be an issue for some people. For us, these two drawbacks are more than offset by the durability, low cost and other benefits of the totes.

For the depth issue, we know that a tote will never get more than two-thirds full, lest the bottom layers compact and create other issues. The extra space is very useful during cold spells or in colder climates, as we can fill it with appropriate insulation—usually 4 to 6 inches of straw with an old blanket on top—if needed during exceptionally cold stretches.

Where to Get Worms

We use two types of worms: red wigglers as well as less common (but much larger) night crawlers. Both have performed well in our bins. If you plan to sell worms for fishing bait, night crawlers are much larger. We haven’t had success competing with the crazy-low pricing on them in our area, so while we have a bin or two with night crawlers, we don’t plan to expand their numbers.

If you can, get worms directly from someone actively making worm compost. You can order worms online or purchase a bucket of worms with bedding/bin mix and all the other material and microbes when you purchase directly from an active worm farmer. When we sell starter colonies, people get everything—the microbes, worm eggs, old timers and babies along with food, bedding and more—an entire ecosystem custom built for worms.

Some new worm farmers have trouble with worms rejecting their new homes. Why? Because it doesn’t smell or feel like what they’ve known. In these cases, you end up putting a light bulb over them for a number of days to keep the worms from leaving. Instead, why not just relocate a portion of their home and have a much higher success rate when you start?

an example of a worm compost bin

Location, Location, Location

IBC tote worm bins don’t need much, but a few things are crucial. First, they need to be out of sunlight, wind and rain. We keep ours in various unused sections of our barn. Any covered, relatively sheltered space will do.

Second, they need a slight pitch toward the drain to ensure that excess moisture naturally moves down and out. To accomplish this, and to provide sufficient space for a 5-gallon “catch” bucket to sit under the drain, we use cinder blocks and pallets to loft and slightly angle the totes.

Custom Compost

Another benefit of worm compost: You can customize the final product based on the inputs to create exactly what you need for your plants or soil conditions. Because we now have five to seven totes in production at any given time, we choose a particular tote for a particular purpose, such as more organic matter and less fertility and minerals.

If you need a great deal of phosphorus and potassium, you can feed a great deal of banana peels and other K- and P-rich foodstuffs. Because the worms need grit, by choosing grit of different mineral compositions—grit is generally mostly calcium and magnesium— you can adjust the calcium:magnesium ratio of the compost, such as by using dolomitic or calcitic lime. You can see how worms would let you easily tailor your compost to your plant and soil needs with just a few minutes of research and number-crunching to alter your inputs to ensure a particular final product.

Compost Calculations

As a general rule, worm compost should be no more than 10 to 15 percent of a mixture. At this rate, you get all the benefits—increased growth and yields, disease protection and more—without risking some of the possible drawbacks.

The main issue with worm compost is similar to too much of any compost: overstimulation of plant growth leading to plant health problems. More is not always better, even if your soil is somewhat poor. It’s best to give your plants a small amount to start—again, roughly 10 to 15 percent of the soil mix—and if more fertility is needed, side-dress the plants every few weeks during the season. While the nutrients in worm castings are a perfect, plant friendly, slow-release fertilizer, the hormones and microbes get right to work, and too much at once will cause problems.


Sidebar: Collecting the Compost

A common question we get is how to collect worm compost. If you have multiple bins, you can have finished compost available when you need it, without interrupting the compost creation process. Note that with the new FDA Food Safety Modernization Act, feeding a worm bin and harvesting finished castings soon after is no longer allowed.

For personal use, this is not as issue, but if you sell produce and are subject to the FSMA or if you sell worm compost, you need to navigate the rules regarding compost safety. Read the current NOP rules, which are what FSMA uses for vermicompost (a summary is available, too).

Generally, we build up our main worm bins starting in July through November, so that by the time we hit winter, they are nearing their peak volume and thus optimal thermal mass to get through winter. From January on, we don’t feed these three to four bins, instead letting them finish for use in spring transplants and sales. We stop feeding one to two bins much earlier—in late September—for castings we will use in our spring starts that get going in January and February.

To collect castings, we made a simple compost screener that sits on top of our garden cart. With smaller hardware cloth, you can even save the worm eggs from making it through the sifting process, but we haven’t found that necessary. Instead, we stick with 1⁄4-by-1⁄4. To save the worms, after sifting we let the garden cart sit for a few hours or more in a moderately sunny spot. The worms crawl down to the bottom valleys, and we can pull the finished, relatively worm-free castings from the top.

Remember at the beginning of the article when I mentioned worm composting makes low-cost chicken food? If your bins are doing well, you can collect worms consistently for your chickens. You can do this as you harvest compost, keeping a portion of the worms separate to give to your flock, or you can also break into into the bins just to get at the worms. Coming in at 60 to 70 percent protein, it doesn’t take many worms to make a big difference in a laying hen’s diet! Since the most expensive part of animal feed is the protein faction, a small flock can see a substantial feed cost reduction if you feed them just half an ounce to an ounce of worms per chicken per day and opt for a lower-cost, lower-protein feed ration.

This story originally appeared in the March/April 2019 issue of Hobby Farms magazine.

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