4 Step-By-Step Vermiculture Systems

By Rhonda Sherman

Let’s take a look at the major types of vermi-systems that worm farmers are using to grow earthworms and produce vermicast. I’ll start with the simplest — a windrow — and then cover pits, bins and continuous flow-through bins. For more details on how to harvest vermicast from various systems, refer to The Worm Farmer’s Handbook.


Windrows are linear piles containing bedding and feedstocks that will eventually reach heights of 24 to 30 inches (61-76 cm). They are typically 4 to 8 feet (1.2-2.4 m) wide and however long the space allows. Many people living in milder climates, such as the West Coast of the United States, have established outdoor windrows for vermicast production, though windrows can also be set up inside large buildings.

A front-end loader, skid steer, shovel, or pitchfork can be used to make a windrow. Simply spread a 6- to 8-inch-deep (15-20 cm) layer of bedding of the desired width and length on bare ground and add 1 pound (0.5 kg) of Eisenia fetida earthworms per square foot (0.09 m2) of surface area. It’s important to smother vegetation first so grass and weeds don’t grow into the windrow, which would interfere with harvest. Since composting earthworms do not burrow, you don’t have to worry about them migrating out of the windrow into the soil. After the worms have settled into the bedding, apply feedstock in a layer 1 to 1½ inches (2.5-3.8 cm) deep, and wait until the feed has been consumed before adding more.

During cold weather, 3 to 4 inches (7.6-10.2 cm) of feedstock may be applied to the top of the windrow to help keep the worms warm. Although many worm growers have success with outdoor windrows, some folks report problems with excess moisture, anaerobic areas and predators such as moles and birds. Vermicomposting in windrows is a slow process that can take up to 12 months to produce finished vermicast.

The Wedge System

Some people use a variation on windrows called the wedge system. As with normal windrows, this vermi-system can be used either outdoors or inside a structure.

Those using the wedge system maximize space by applying feedstock in layers at a 45-degree angle against a finished windrow. Worms in the windrow will eventually migrate to the fresh feed. Keep adding layers of feedstock until the second pile reaches the depth of the first windrow, and then start a new wedge windrow. The worms will keep moving laterally through the windrows toward the new food. After three or four months, each wedge windrow can be harvested.

A wedge can be created from a pile instead of a windrow. For example, at Arizona Worm Farm, Zach Brooks starts a wedge by creating a 3-cubic-foot (0.08 m3) pile of pre-composted food waste, horse manure, mulch and shredded cardboard at the corner of two low walls. He adds 10 pounds (4.5 kg) of worms to the pile. Once a week thereafter he adds 1 inch (2.5 cm) of the same pre-compost to the outer slope of the pile. He also adds a light layer of mulch over the compost because it helps keep the wedge cooler and makes the vermicast more fungal dominant.

This inexpensive vermicomposting shed was constructed of concrete blocks, shade cloth, tree limbs and yagua leaves in the Dominican Republic.

It takes four months for the wedge to “grow” 1 foot (30 cm) in length. When the wedge reaches 6 to 7 feet (1.-2.1 m) long, Brooks starts harvesting the wedge from the back end. Two hundred pounds (91 kg) total of feedstock is added to one wedge, and they harvest 100 pounds (45 kg) of vermicast. When I talked to Brooks, the ambient temperature was 105°F (41°C), but in the center of his wedges the temperature was in the high 70s (about 25°C).

Pits or Trenches

Pits, or trenches, have been used for decades. As with other vermicomposting systems, you lay down moist bedding, add worms and apply thin layers of the feedstock on top. People like pits for vermicomposting because they are simple holes in the ground — no construction required. The earthen sides provide insulation against both hot and cold weather. Some people choose to line their pits with cement blocks. However, raising earthworms in pits can strain your back from bending over so often. Another disadvantage is that pits can be flooded by heavy rains.

A successful trench model was established in North Carolina in the early 2000s. A hog manure vermicomposter named Tom Christenberry was having trouble with his continuous flow-through bins overheating, so he created a trench system that allowed the ground to help moderate excessively cold or hot temperatures. Inside a pole barn he dug five trenches 4 feet wide by 200 feet long by 21 inches deep (1.2 × 61.0 × 0.5 m). Between the trenches were hard-packed dirt and gravel lanes that would support a tractor.

Inside the shed in the Dominican Republic, worm beds lined with concrete blocks are on each side, with empty space in between for carrying out earthworm husbandry tasks.

To feed the worms, he drove a tractor straddling the top of a trench. The tractor pulled a manure spreader that was calibrated to deposit hog manure into the trench, and a worker would then use a rake to evenly spread the manure 1 inch (2.5 cm) deep across it. He carried out this feeding process weekly using raw hog manure that had been flushed out of a barn and run through a solids separator.

Before you commit to setting up a pit system, ask yourself whether you will be able to handle all of the bending that it will require to apply feedstock, check the worms and bed conditions and harvest the vermicast. I used to think I could work with pit systems, but I now realize that I couldn’t deal with getting on my knees, bending over and reaching down into the pit on a regular basis.


Worm bins are a type of containment system that can be built, purchased, or repurposed. They are set up like the previous systems described — with moist bedding on the bottom, worms added on top and then feedstock applied in thin layers on top of the bedding.

To make worm bins, worm growers often repurpose discarded items, including refrigerators, livestock tanks, tubs, barrels, wooden or plastic boxes, mortar trays, plastic buckets, washing machine tubs, and other containers. If such containers have solid bottoms or sides, drill holes for drainage and airflow.

Earthworm beds and bins can be built by hand from a variety of materials, such as lumber, plywood, concrete or cinder blocks, fiberglass, structural clay tile, poured concrete, or bricks. Wood is one of the most popular materials, but raw wood may decompose within 4 to 10 years, depending on the climate and other factors, so many folks will cover it with plastic or coat it with raw linseed oil. Avoid using redwood, cedar, or other aromatic woods to construct the bins; they contain tannic acid and resinous saps that are damaging to earthworms.

Photo A

Here are two different styles of concrete-block worm bins: one at Camden Street Learning Garden in Raleigh, North Carolina (A), and the other at a farm in the Dominican Republic (B).

Photo B

Worm farmers throughout the world build concrete-block bins, often on bare ground. They are inexpensive, easy to obtain and won’t rot. Concrete also provides more insulation than plywood, so it will keep your worm bed warmer in the winter and cooler in the summer.

Remember that birds love to eat worms, so if your bins aren’t lidded you should use netting to keep out avian predators. Always keep direct sunlight off the worms, too, by either locating the bins in a well-shaded area, placing them under a roof, or covering them with lids.

The worms in my Worm Barn at the Compost Learning Lab live in two MacroBins. These containers are manufactured by a company called Macro Plastics to store and transport vegetables. When I first saw one, I immediately thought, This would make a good worm bin! and decided I had to acquire some.

The MacroBin is constructed of impact-grade copolymers and has smooth surfaces and ventilation slots on every side, as well as the bottom. It is approximately 45 inches long, 48 inches wide, and 34 inches high on the outside (1.1 × 1.2 × 0.9 m). The inside of the bin is approximately 41 inches by 45 inches by 29 inches (1.0 × 1.1 × 0.7 m). It can accommodate 1,300 pounds (590 kg) of materials and can be lifted by a forklift from any side.

The MacroBin costs about $230, with discounted rates for bulk purchases. I wasn’t aware of anyone else using these agricultural bulk containers as worm bins until I saw 10 of them set up for vermicomposting while touring a composting site in San Diego.

Garry Lipscomb and Bill Corey, the owners of NewSoil Vermiculture LLC in Durham, North Carolina, made bins out of plastic 55-gallon (210 L) drums for the commercial operation in the basement of their home.

Many worm farmers repurpose plastic IBC totes (intermediate bulk containers) to make worm bins. They are large tanks used to store and transport 275 to 330 gallons (1,040-1,250 L) of liquid or bulk materials. IBC totes cost less than $150 new, with versions housed within metal cages available for approximately $100 more. These tanks are being repurposed for a variety of uses, so it’s pretty easy to acquire them used at a lower price.

Editor’s Note: This excerpt was also published in the February 2020 issue of Acres U.S.A. magazine.

The Worm Farmer's Handbook
The Worm Farmer’s Handbook by Rhonda Sherman

This excerpt is adapted from Rhonda Sherman’s book The Worm Farmer’s Handbook: Mid- to Large-Scale Vermicomposting for Farms, Businesses, Municipalities, Schools, and Institutions (Chelsea Green, 2018) and is printed with permission from the publisher. It is available from Acres U.S.A. at acresusa.com or by calling 800-355-5313.

How to Build a Worm Humus Container

By Helmut Schimmel

Editor’s Note: This is an excerpt from the book Compost Revolution by Helmut Schimmel. You can buy this book, and more like it, at the Acres U.S.A. bookstore.

My first worm container resembled a small cold frame that was partially submerged in the ground and covered with a black sheet. It only produced modest worm humus yields. When evaluating my attempts up to that point and the experience I had collected, I decided to build a relatively stable and sufficiently large worm humus container that would take a minimal amount of effort but would also be suitable for use over the winter in outdoor conditions. I was aware that the size and design are already subject to certain important requirements to ensure successful vermicomposting.

Examples of important factors include

  • the highest possible ratio of volume to exterior surface area
  • prevention of cold air entering through the sides in winter and
  • protection against drying in summer and against animals that might eat the compost.

Migration box according to the two-chamber principle

Used corrugated plastic sheets from a greenhouse complex seemed like a good choice for building the new housing for my underground coworkers. I set up four sheets, about one meter in height, in a circle with a radius of approximately one meter and embedded them into the ground, with two of them opposite from each other embedded in concrete. I attached the other two sheets between them to the parts of the first two sheets that they overlapped using screws in a way that allows them to be removed, which is important for removing the compost.

I excavated the circle of soil within the container to a depth of about twenty centimeters. Then I lined it with finely-meshed chicken wire (to keep out moles), which I embedded in concrete along with the stationary corrugated plastic sheets at the sides. I stuck a strong wooden stake directly in the middle of the circular area with a round wooden board as a cover on top. It serves as a support for covering material to protect against rain, direct sunshine, frost, cold, and snow. I call the container a “worm silo” rather than a “worm compost pile.” It works according to the two-chamber principle, with the exception that the border between the “chambers” does not physically exist.

I decided against a container with two separate chambers, which you can read about in all the publications on the topic of “earthworm migration boxes.” Building a migration box of this type requires significant expenses. An interior partition is made out of perforated bricks, and the ground is also covered with them. It must be possible for worms to travel through the wall, so it is usually made up of hollow bricks that are laid such that worms can crawl through them. From my own experience, I can say that I do not need any such partition.

The finished worm humus is made up of solid, cohesive crumbs of soil that form a stable layer. Removing the outer sheet from the worm silo allows me to easily remove the finished humus while the other half, with the worms, remains in place. Why would I need an additional partition?

Scetch of finished humus container
Schematic depiction of how my worm humus container is constructed

Building these internal partitions is usually expensive and leads to “traffic” (in this case, worm traffic) being impeded. Earthworms love freedom and reject confinement. I guarantee my brandlings “freedom of movement” between east and west. As “nightcrawlers,” they make it out of even enclosed spaces and are present in the surrounding areas if there is sufficient moisture, and not just in the summer. Although my container functions without an internal partition, it does rely on the same principle by steering activity in the worm silo in a certain direction, i.e. luring the worms from one side to the other. A pitchfork can be employed if needed. A few weeks before it is time to collect and remove the finished worm humus from one of the sides, the remaining worms are moved to the other side along with the upper layer of food. The side that is going to be cleared out is kept increasingly dry (pre-drying the worm humus), which causes the worms to migrate to the nearby fresh food on their own. When I remove the humified soil, I orient myself by the markings on the side. It couldn’t be simpler.

Preparing the final product

I think the size of my container is well suited to my 350 square meter community garden plot. The surface of my worm silo takes up at least three and a half square meters of ground area. Every year, I empty half of it.

I use part of the mature humus immediately, without sifting it, to improve the soil quality in my garden. I spread the other half over a tarp and let it dry in the air until it can be sifted. The Optimus Society strongly stresses this sifting process as it produces an especially pure and high-quality end product. They recommend using a particularly fine sieve (two millimeters).

Going to all this effort makes the preparation laborious and expensive. The dried and sifted worm humus has a long shelf life and can be stored without any issues.

In total, I produce more than 1.5 cubic meters (about one metric ton in weight) of worm humus per year. This is enough to make me completely self-sufficient. The next year, the vermicompost in the second chamber is ready for use. As soon as one half has been completely emptied out, it is immediately replaced with new seeded material. Then the worms can go back to feeding from both sides.

Next up: Chapter 8: Worm Keeping in Winter

About the Author of Compost Revolution

Helmut Schimmel is a longtime authority on the care and reproduction of earthworms and the production of valuable worm humus. His coworkers in this venture belong to Eisenia fetida—earthworms which are indispensable in the humus economy. Expert gardener and horticulturist Helmut Schimmel draws from his great wealth of knowledge acquired over decades of study and practice to yield this single, definitive book on the practice.

Harness The Power of Earthworms

By Paul Reed Hepperly, Ph.D.

When moist, practically all soils from tundra to lowland tropics support the activity of earthworms. Largely unseen, earthworms are a diverse, powerful workforce with the capacity to transform soil into fertile ground.

Found in 27 families, more than 700 genera and greater than 7,000 species, earthworms vary from about 1 inch to 2 yards long. Their living mass outweighs all other animal life forms in global soils. Although we may view earthworms as being both prolific and productive, do we fully appreciate our human capability to favor their beneficial efforts as allies allowing farms and gardens to flourish? I think not.

Earthworms’ powerful activities include promoting favorable soil structure, increasing biological diversity, improving soil function, balancing nutrients needed by plants and animals and optimizing living soil.


In commercial vermicompost, earthworm production is favored by a brief compost cycle to produce earthworm diet. Because earthworms derive their nutrition from fungi, bacteria, protozoa and nematodes, their lives and those of teeming masses of microorganisms and microbes are closely interlinked. Trained as a plant pathologist, I marvel at the unseen microscopic realm and its power to transform. Scientists have found that microbes break down plant and animal debris. This process promotes the nutrition and health of earthworms, microbes, soil and everything that depends on the soil.

handful of worms
Earthworms not only play productive roles in sustainable agriculture, but they have enormous capacity to help mitigate our elevated atmospheric greenhouse gas content by reducing carbon and nitrogen gas.

As earthworms turn and churn, they function as effective premier plant residue shredders. Their work helps liberate plant nutrients into the digestive tract by microbe activity while the earthworms themselves are favored.

We are asked by some great thinkers to ponder on the earthworm and its significance. Charles Darwin referred to earthworms as “the intestines of the soil.” Rudolf Steiner, originator of biodynamic agriculture, referred to them as the “stomach of the earth.”

Earth Motor

Earthworms play a critical role in improving and enriching soil. Through their tunnel networks they create air channels, optimizing aeration and providing conduits for watering the soil. By allowing water and air to channel through the soil they promote rooting. Roots and plant residue feed the rich microflora that feeds the worms. Worms feed the earth that nourishes the plants. This is a productive interdependent life cycle. The ability to maximize water percolation also minimizes runoff, and reduced runoff greatly reduces soil erosion.

earthworm anatomy
Earthworm Anatomy: Diagram shows the position and morphology of the calcium glands of the earthworm.

Together earthworms and microbes are the great digestive fermenters. They join together in shared shredding/digesting. As digestion results from joint effort, insoluble plant materials are solubilized. In the alimentary tract, what was waste is consolidated into value-added packets known as castings.

Earthworm castings are an ideal organic amendment/fertilizer with greatly increased nutrient solubility compared to the organic materials they originated from. Castings are particularly rich in phosphorus which stimulates seedling and root growth and extension.

Unlike most synthetic fertilizers, they are well balanced in macronutrients, secondary and micronutrients. The humic substances in earthworm castings support the foundational physiological processes of plants such as photosynthesis and respiration. Their growth regulation properties include the ability to stimulate defensive reactions in plants, allowing them to deal with stress and adapt to difficult conditions.

Scientists have compared the earthworm tunnel system to a motor with pistons — the muscular earthworms are the piston drivers of the soil pump. Plant materials fuel the living soil machine with microbial-aided decomposition working together with the worms deriving their energy through the plant remains.

The earthworms drive plant material into the ground, infusing life into the whole system.

No Everyday Compost

micronutrient composition

In a strict sense, worm castings are not vermicompost at all. They are really earthworm manure. Unlike many other animal manures, however, casting are not laden with toxic ammonia. Earthworm castings are rich in organic nitrogen. This critical difference gives unique advantages over other animal manures. Earthworm castings are also distinctive in being rich in carbon and calcium.

Calcium, carbon and nitrate constitute a trifecta. They avoid the ammonia toxicity and salt issues common in ammonia-rich manures and fertilizers. Because of the organic nature and low ammonia, earthworm castings can be used in close proximity to seedlings without plant toxicity.

Besides calcium, red earthworm castings are exceedingly rich in iron. Copious calcium excretion is critical to the metabolism and digestion of earthworms, and earthworms can be greatly restricted in acid soils. Where soils are high in alkalinity, the ability of plants which originally adapted to more acid environments, show inability to absorb and utilize iron. This results in plants yellowing due to iron deficiency or chlorosis. The organic, chelated form of iron from castings is ideal for such situations because they are readily soluble and rich in iron.

Humic materials from the earthworm microbial combo are champion chelators. Earthworm castings have a 6.9 pH, neither highly acid nor alkaline. This neutral, slightly acid pH is friendly to both earthworms and most plants they depend upon.

Besides the castings, the earthworm ejects granules akin to miniature lime stones. The fine structure of earthworm granules is both beautiful and well organized. Like castings these granule outputs are dispersed into the soil, where they act to benefit soil fertility, biology and structure.

In its composition, the earthworm granule is mostly mineral. Although calcium is its biggest component it usually features a silica center clear in electron micrographic analysis. The granule is a rich source of a diverse variety of micronutrients. Under the scanning microscope, these little gems resemble mineral snowflakes.

An abundant earthworm population will produce about a ton of these per acre every year under good conditions. As such, the earthworm-tilled soil becomes limed with calcium carbonate quartz granules besides being enriched with a critical spectrum of major, secondary and micronutrients.

These granules take carbon dioxide that was in our atmosphere as greenhouse gas and trap it as insoluble carbonate. The little lime stones neutralize the soil, preventing it from becoming overly acidic. Calcium also serves as a mortar for cementing soil aggregates together, conserving both carbon and soil structure.

Earthworms On the Farm

In upstate New York, longtime organic farmers Klaas and Mary Howell Martens were asked to review my work on worms. Upon reviewing this article, they urged me to go beyond the living soil machine metaphor.

They asked me to stress the cycling and mineralization capacity of earthworms. On their farm, in their personal witness, they testify to cover crops of over 3 tons of fall dry matter residue being cleaned up by early spring by the worms. They were amazed when they analyzed the soil that same spring. The soil analysis showed 360 pounds of N, 40 pounds of phosphate and 160 pounds of potash per acre available, more than sufficient for an optimum maize crop. This was without any application of synthetic chemical fertilizer.

Relying on the legumes and worms to till and feed, Klaas reported, “Earthworm recycling and mineralization occurs sometimes overnight. I have seen large clumps of leaves fall from my spreader in the spring and days later I went back and nothing was there. Yet, upon looking closer at the soil surface it was covered with worm castings … amazing.”

A Deadly Trio

In conventionally farmed and tilled fields it is common to find few or no active earthworms. Toxicity of pesticides commonly used in the field crops, the destruction of their habitat by excessive tilling, and acidity and toxicity of fertilizers constitute a deadly trinity for earthworms. When appropriate worm environment is produced all of these constraints are eliminated and the need for synthetic fertilizer is reduced or eliminated.

Soil acidity is the mortal enemy of earthworms, and the use of ammoniated fertilizers and tillage can largely stymie their beneficial natural soil-building potential. Earthworms are well known as premier bio-indicator organisms, revealing soil potential and overall environmental health.

In a mechanized agriculture vast mines of calcium carbonate rock are crushed into fine powders and transported to depots and then to farms where massive spreader trucks lime the fields.

Can we be more thoughtful in promoting natural earthworm populations? Yes, let us begin as farmers and gardeners by identifying acidic, low calcium soils and spread lime to remediate this common condition. Let us also incorporate manure, compost, cover crops, rotation and other sustainable practices.

Synthetic nitrogen fertilizer is directly toxic due to ammonia content and indirectly by its effect on acidifying the soil. When fertility is largely based on ammonia, the absorption of the ammonium ion causes the plant to release hydrogen ions to maintain electro-neutrality. This causes an acid release that first invades the root zone and continues to expand into the soil profile itself.

Earthworms promote a natural liming and are favored by liming. Calcium, I believe, is used by the earthworm to lime the soil as they themselves are sensitive to heavy metals, such as aluminum, which abound in soil. When these are soluble as in an acid environment, they are deadly, but when acidity is buffered they are harmless.

The only nutrients available to plants are those that become soluble. Carbon is the primary element in earthworm castings. This high carbon content demonstrates the organic nature of this amendment and organic nature is key for solubility of difficult-to-dissolve minerals. Tests show copper, manganese and zinc have water solubility of 15 percent or less without humic substances. On the other hand, when using organic chelation with soluble organic material, water solubility increases to over 85 percent, more than five times solubility in water alone. Fulvic and humic acids are champion organic chelators.

Carbon & Calcium

Professor Albrecht was a well-known proponent of the role of calcium. He envisioned calcium as the key to unlocking soil fertility. After carbon, calcium is second in abundance in earthworm castings. Unlike synthetic amendments that do not address secondary nutrients, earthworm castings do just that. Castings have abundant nutrients in balanced rations.

Calcium provides a key not only to structure and nutritional aspects for the plant but also acts as mortar in the formation of soil structure or aggregation. It helps granulate or aggregate the particles and stabilizes them from erosive force by its cementing action, which helps water and nutrients flow through the soil system. When earthworms build their soil profiles, they need mortar to be master builders.

Since the 1980s more and more research has shown calcium has some amazing capabilities. In humans, calcium is involved in the structure and function of our bones. As calcium granulates and coagulates soil aggregates, the serum calcium is critical in this defensive blood clotting in animals and humans. As calcium is lost in membranes the defensive reactions of plants are triggered. When calcium is low in plant cell walls and membranes, they become very susceptible to soft rot by fungi and bacteria.

Too Good to Cast Off

composition of earth worm

Turned, high-temperature compost is well documented as an excellent organic input. Yet, the value of earthworm castings is less recognized and cooler in temperature and impact. In this respect, castings not only have excellent value, but exceed those present in turned hot compost — in the total and range of macronutrients, secondary and micronutrients, they beat the turned hot compost hands down.

Hot composts can pasteurize the substrate yet the beneficial microbes need a cooler ambient temperature, which is found in the earthworm environment. In the story of Old John Henry, the mythic miner challenged the mining machine and died trying to defeat it. Our subterranean earthworm hero “John Henry Earthworm” meets the challenge of tilling soil and liming it. However, he is not beaten by the machine. In fact, the biological force of earthworms can prevail over the machine in this contest when the emphasis is on the potential of that force and they stay healthy and alive.

Global Opportunities

Many of us in the center parts of North America are spoiled by being blessed with wonderful, comparatively young prairie soils founded on limestone parent materials. These soils may have fewer concerns about acid soil infertility compared to the vast majority of tropical soils in the developing nations. This tropical problem can be found in rich red clay soils in the southeast United States.

biomass of biological components

Few peoples in Central and South America, Africa and tropical Southeast Asia are so well blessed as we, the people from the North American maize and soybean belt.

Tropical areas are notably plagued by possessing the majority of soils which are old, degraded and suffer from acidity, toxicity and deficiencies.

Consider that even commercial North American farmers using synthetic fertilizer typically add up to 1 ton of lime each corn crop to neutralize their heavy ammonia dependence and use. There is much untapped value in earthworms and they make sense in a wide range of areas, both tropical and temperate. An agriculture which will flourish for millennia will need to take earthworms into account not only as the prime soil health bio-indicators but also as the master engineer and builders of the soil machine.

Certain areas in the eastern half of the United States, tropical South America, Africa and Southeast Asia are dominated by acid, infertile soils.

The use of synthetic ammoniated fertilizers will worsen this all-too-common condition. Fortunately, nutrients from earthworms are ideal based on nitrate nitrogen form and its liming effect based on calcium in the worms’ metabolism. In addition, in countries throughout the world there is no shortage of limestone for agricultural use.

Many organic farmers have noticed slow initial nutrient release response from organic amendment. This can constrain high yields because of the low solubility of nitrogen and other critical nutrients. This is avoided with the earthworm castings, which are rich in soluble nitrogen as nitrate and soluble phosphorus for pop-up growth needs. They have

available humates from soil organic matter and complete secondary and micronutrients to overcome an array of issues. The best point is that their nitrogen as nitrate does not acidify the soil as common ammoniated synthetic nitrogen does.

While synthetic fertilizers are classified based on nitrogen, phosphate potassium salt contents alone, this reliance can easily lead to nutritional gaps in the supplies of essential secondary and micronutrients which are not considered. More importantly their use and dependence does not avoid soil acidity issues over the long term but rather will generate them.

In contrast, the worm castings provide a full complement of essential micronutrients playing critical roles in plant health and the secondary nutrients essential to plants and animals.

Because these are needed in relatively small quantities, and organic products have better solubility and retention characteristics, these can be utilized efficiently and economically with better environmental and energetic footprints. When the best natural production systems are used, earthworms are favored and do not need continual application and reapplication.

While the earthworm casting has significant nitrogen, it is in nitrate rather than ammonium form. Nitrate, when absorbed by plants, causes release of hydroxyl ions, working together with the calcium carbonate granules to lime the soil, not to acidify it. One negative nitrate in the plant, leads to one negative hydroxyl out of the plant. This conservation of charges results in liming the root zone or rhizosphere. This in turn helps the rhizosphere and earthworm to create favorable environments for the plants and themselves in the virtuous cycle. This working together is especially important for the problematic, acid, infertile soils in the majority of struggling areas in the global tropics.

Our tropical agricultural resource is our ace in the hole in globally regenerating the world environment and reversing greenhouse gas issues.

Research shows not only can worm castings stimulate yields over that of an optimum rate of synthetic fertilizer inputs but indeed exceed them substantially. This is related to not having the high salt index of synthetic fertilizer and being a complete nutrition. We have shown that castings have primary, secondary and micronutrients at ideal levels. Humic materials, that are produced by the microbial and worm tag team, are able to stimulate plants as growth regulators at parts per million dosages.

Finally, the rich microbial population has been associated with pathogenic fungi and bacteria suppression. In addition they possess the ability to stimulate the signal active defensive actions of plants to insect pests and adverse environmental conditions.

After seven years working with worms, I have come to the conclusion that my earth-changing ability is exceedingly small compared to my underground friends, the earthworms. For this reason I ask us to transform our intention in regards to the unseen and unheralded worm that works tirelessly and constantly for our benefit and that of the environment. Give them a chance and they will reward you with their endless, tireless efforts.

This article appeared in the June 2015 issue of Acres U.S.A.

Paul Reed Hepperly, Ph.D., scientist, consultant, educator and advisor, previously served as the research director for Rodale Institute, 2002-2009. His son Reed Paul Hepperly is CEO of Hepperly Enterprises, a premium compost supplier and developer of tropical root crops in Mayaguez, Puerto Rico. Paul resides in Tennessee.

The Best Worm-Friendly Worm Bin for Composting

By Bill Palmisano

Composting with worms produces a consistently superior product called vermicompost, which contains high counts of beneficial soil micro-organisms.

Harvesting the finished vermicompost from most worm bins presents a problem, though: one either stops feeding a significant part of the bin to take it out of production, encouraging the worms to vacate the area to be harvested, or the worms have to be physically separated from the finished compost.

The Continuous-Flow Worm Bin

Continuous-flow worm bins are designed to provide a continuous output of finished vermicompost without disturbing the worms or taking any part of the bin out of production. This design makes it much easier to harvest the finished compost. Most continuous-flow designs have a winch-powered knife that cuts a slice of finished compost from the bottom of the bin about 2’ above the ground.

There is a passive self-harvesting non-mechanical continuous-flow design that is simple to use, though. This elegant design is used at the Open Alternative School (OAS), a public elementary school in the Santa Barbara Unified School District in California. The bins are fed with food scraps, paper and cardboard. They produce rich compost that is then used in the school’s large organic garden. This design can also be adapted to compost animal manure.

Continuous-flow worm bin construction
A 4’x8′ continuous-flow worm bin in construction at OAS.

Continuous-flow boxes receive air from the top and bottom of the pile. This provides the aerobic conditions that worms need in order to thrive. This design makes it difficult for anaerobic (low/no-oxygen) conditions to develop. Excess water cannot collect at the bottom of the box to become anaerobic because excess water drains through the ropes. The finished compost also drops through the spaces between the ropes and falls to the ground for collection.

In my experience, students are universally fascinated by the incredible variety and vibrancy of the organisms found in a healthy worm bin. Schools can provide a steady supply of feed materials for bedding such as uneaten food, kitchen waste, paper and cardboard. Students watch as the worms facilitate the decomposition of food to produce vermicompost.

The worm bins at OAS provide a tremendous volume of nutrient-boosting vermicompost that is full of soil organisms. The compost inoculates the soil and ensures the success of the school’s garden and orchard. The only downside we’ve found to the use of vermicompost is that tomato seeds sometimes sprout out of it; these are easy to identify and weed out, though.

The two worm bins at OAS that process food waste are located in a shady 60-year-old redwood lath house. The bins have a total surface area of 90 square feet. This is enough to process more than 50 gallons of food waste a week.

worm bin for composting
A finished continuous-flow worm bin

A thin layer of food waste is spread on the surface of the box and covered with shredded office paper, torn newspaper and/or sliced, pre-wetted cardboard. Microbes begin and worms finish the digestion of the food and paper, producing dark, humus-rich vermicompost. The boxes are raised about 18” to 24” inches off the ground. The bottom of the box is made of closely spaced parallel ropes, through which the finished compost falls down to the floor. When enough compost has accumulated, it is simply raked out and used in the garden or bagged up for fundraising sales.

This worm bin design was discovered in the late 1990s in an article in the now-defunct Worm Digest. An organization called Berkeley Worms originally constructed two dozen 4’x8’ continuous-flow worm bins at the Berkeley Transfer Station that were made out of recycled lumber, using rope as the bottom layer of the boxes.

How to make a continuous-flow worm bin
Ropes through the middle of the worm bin

These were used for about five years until the wooden frames rotted and the boxes began to fall apart. The current design replaces the wood with a steel frame. The bottom of the box is now polypropylene rope strung parallel at 2” intervals across a galvanized or epoxy-painted steel frame.

The first steel-framed bin we constructed has been making vermicompost for 17 years and shows little sign of wear or decomposition (except for the lids, which wear out and need to be replaced every few years).

The 2” x 12” wooden sides that contain the worms, food waste, paper, cardboard and compost sit directly on top of the steel frame on which the ropes are strung. The box lids are made of 1⁄2” exterior plywood, with a stiffening lumber frame screwed to the plywood’s perimeter that fits snugly to the 2” x 12” wooden sides in order to exclude rodents.

All About Compost Worms

The worms used in our bins (Eisenia fetida) are known as redworms, manure worms, litter worms or red wigglers. They are not earthworms. In their natural habitat, Eisenia fetida do not build tunnels in the mineral soil like earthworms. They remain in the upper litter layer, where they help decompose plant and animal detritus.

Food decomposition in a worm bin begins when microbes start to grow on the surface of the food waste, paper, or cardboard. Worms slither along the surface and use their mouths to suck up this microbial growth. The microbial food passes through the worm’s pharynx and esophagus to the crop, where is it is temporarily stored. It then moves to the worm’s gizzard, where strong muscles, aided by small pieces of sand, crush the microbes and release their internal juices. This soupy mix passes to the worm’s intestines, where the gut extracts the nutrients the worm needs and the remainder is processed and then excreted as worm castings.

Worms require wetter composting conditions than the optimal 50% moisture level of a thermophilic (hot) compost pile. Worms demand aerobic (presence of oxygen) conditions and 80% or greater moisture in order to properly diffuse oxygen through their skin.

Managing Worm Bin Temperature

Redworms are the only vermiculturing beast I’ve worked with, and they have very specific environmental parameters. I stress the need for high-moisture conditions and the requirement for an oxygen-rich environment. They also demand a specific temperature range: under 40°F (4.4°C) or over 90°F (32.2°C) and they start to die off. They don’t work very fast until the temperature is above 60°F (15.5°C) and seem the most active at about 80°F (26.7°C). Keeping an active worm box warm in all but the coldest temperatures is possible because of the metabolic heat produced by the active decomposition. Lids must be kept closed tightly when it is cold.

In very cold conditions the box needs insulation to keep the temperature at an acceptable level; a seed tray heating mat can be placed in the box if it is extremely cold. One must keep feeding the worms as necessary. It can be a challenge, however, to keep them cool in hot weather.

Food waste is a high-nitrogen feed source and will heat up when decomposing—protein and calorie-dense foods more so than whole fruits and vegetables. Monitoring the box temperature with a thermometer is helpful in warm conditions. Adding food to a box that is over 80°F can lead to catastrophe when the ambient temperature is already warm.

It is disheartening to open the lid of an overheated worm box and smell the unmistakably putrid odor of dead worms. However, there are strategies to deal with the heat. Do not feed the worms if the box temperature is over 80°F. Provide shade from the sun for the bin in hot weather. If a shady location is not available, stapling a layer of Tyvek (a weather-durable, white, moisture barrier ) to the lid and sun-exposed sides of the bin will provide some protection from solar heating.

It is also important to feed the worms thinner layers of food. Another hot-weather strategy is to feed in shallow rows or piles with larger “fallow” areas adjacent for the worms to escape into if the food areas get too hot. Also helpful is adding more carbon bedding waste: straw, shredded paper and/or wetted cardboard.

One can increase air circulation by propping the lid open or leaving an air vent space between removable lids (but beware of rodents). Or one can use a fan to blow air over the surface of the bin.

Air circulation in hot weather is key. Evaporating water can cool the contents of the bin. Remember to add water to keep the moisture level up. Hot air temperatures coupled with high humidity are the most challenging of conditions. In extreme cases, ice can be dumped on the surface of a bin that is overheating. In hot and muggy conditions, wetted corrugated cardboard may be the dominant feed source to prevent overheating.

How to Keep Your Worm Bin Pest-Free

The entire worm bin needs to be sealed off from rodents and other animals. The warm, cornucopia environs of a worm bin are irresistible to rats and mice. Removing a mouse or rat nest from your bin can be a daunting project, so it is extremely important to prevent them from getting in.

In our design, the plywood lids have a lumber-frame lip that overlaps the top of the box with less than a 1/4” gap. 1/4” hardware cloth encloses the compost collection space under the box.

I use 1/4” because I have found that small mice are able to squeeze through the 1/2” hardware cloth. For harvesting, 1/2” plywood panels slide up and down in snug channels formed by 2” x 2” lumber, the channel lumber being screwed to the bin’s support posts (no hardware cloth needed here).

The complete exclusion of animals from your bin must include some type of paving that the bin rests on. Access doors and hardware cloth must remain in flush contact with the pavement. It is a good idea to periodically inspect for digging, gnawing, or access points on the bin’s exterior (including the lids). Act promptly if you see signs of rodents digging inside the box. They usually leave evidence of their visits with round holes, tunnels and debris piles on the surface of the box’s contents. Look for access areas around the exterior of the bin and seal the entry spot as soon as possible with hardware cloth, lumber or bricks. In my experience there is usually a week or two following the initial feeding visits by a rodent before the subsequent building of a permanent rodent nest inside the bin.

Another benefit of having a paved surface under the bin is that it makes harvesting the finished compost easier. Simply rake it out! However, you don’t want to let it pile up for too long. I have never had any finished compost get smelly and anaerobic, but if it builds up for more than a year I have seen it produce a mild, very short-lived odor when finally harvested.

If there is a perennial vine, shrub or tree nearby you may need to guard against root invasion of your finished product. I once built a bin on an asphalt driveway adjacent to a cape honeysuckle vine. The compost built up for a few months, and when I went to rake it out my rake stuck in the compost and would not move. The entire pile of compost under the ropes was permeated with fibrous roots that had entered the finished compost from cracks in the asphalt. I rebuilt the bin in a slightly different location with two layers of thick, matted root-blocking weed cloth covered with concrete pavers on top of the asphalt.

Bedding Materials

Cut-up cardboard produce boxes make excellent bedding and covering material; be sure to slice them into strips for faster breakdown and water penetration. Waxed produce boxes cannot be recycled, but can be given to worms. The waxes are food grade and do compost, plus they feed fungus, which is a desirable organism in your compost.

I once had the chore of moving a large worm bin that had been in production for six years. Disassembly was the only option because it could not fit through the door intact. I was stunned by the amount of plastic and aluminum foil debris that had accumulated on the ropes at the bottom of the box, even though I had been careful to pick the trash out of the food waste that I fed into it. Of note were plastic ghosts from paper cups and plates. Most paper cups have plastic film bonded to the paper, as do some paper plates.

Try tearing paper cups and plates before putting them in the worm box. If they tear cleanly and easily, they do not have a plastic coating. Also, compostable cutlery and compostable plastic containers are anything but compostable in a worm bin. Remember to remove plastic tape from cardboard boxes.

Vermicompost is pathogen-free. Our school district is very leery of garden composting because of the possibility of contamination with pathogens when not done properly. However, they have no problem with vermicompost, because all pathogens that traverse the worm’s gut are destroyed, as are all pathogens that come in contact with the secretions on a worm’s skin. Between the worms’ gut and skin there is no chance for a pathogen to survive the vermicomposting process, so worm boxes are the ideal partners for school food-waste composting.

In conclusion, this particular worm bin design is slightly more complicated to build than a standard worm bin, but the generous output of compost, large worm populations and ease of harvesting more than make up for it.

Editor’s Note: This article appeared in the March 2018 issue of Acres U.S.A.