Making a worm bin

Why buy an expensive worm farm, when you can set up a perfectly good stacking system wormery, for less than half the price of buying in a fancy branded worm farm from a dealer? You won’t even need to be much of a handyman, nor use expensive materials to produce a neat unit that will look good and function well.

Page Index

  • The Principle of the Stacked Bin Worm Farm
  • Choosing Your Bins
  • Instructions for Creating Your DIY Worm Composter
  • The Sump
  • The Composting Bins
  • Setting it Up
  • Starting Production
  • Worm Terms Dictionary

The Principle of the Stacked Bin Worm Farm

Traditional methods of vermiculture have their place, but today’s suburban worm farmer wants a composting system that takes up minimal space, looks good and is clean and convenient to use. The home worm farmer, or amateur vermiculturalist can use suitable modern products and a better understanding of the habits and requirements of the compost worms in the worm bins to design a system that is both convenient to handle and efficient in the usage of materials and manpower.

An inexpensive DIY worm farm

The principle of the stacked bin worm composter is that, unlike the drab earthworms, who dig deep, our red compost worms always migrate upwards, towards the food, leaving their castings to fall below them. We use this information about red worms to our advantage. Generally the idea is to build up a multiple stacking system of connected worm bins or trays that are slightly tapered to allow the bins to nest, one within the other. Worm castings (the compost) are collected in the lower bins and worm food (kitchen or garden scraps) is consumed in the upper levels of the wormery. When a lower bin is nearly full of castings it is emptied and rotated to the top and so on.

Choosing Your Bins

The size and number of the nesting bins is variable, depending on the desired scale of the operation. Common plastic storage bins, sold for general household use at hardware stores, supermarkets and camping goods outlets are quite suitable for making your worm farm. Usually the sides are not vertical, but slightly tapered for convenient stacking on the retailer’s shelves – this suits us, as it allows for partial nesting of bins . A lid would be required for the top bin. Worms hate light – so don’t get opaque bins. Heavy black bins are good. The plastic storage containers are not expensive and come in a variety of sizes. For a small scale composting set-up, for processing kitchen waste, three containers of about 45 litre (ten gallon) each would be adequate. For processing a greater amount of waste such as from large gardens or stables, bigger bins with more tiers can be set up, just as easily.

Instructions for Creating Your DIY Worm Composter

Cross sectional diagram of Three Bin Composter.

The Sump

The lower sump bin is configured differently from the upper bins and would be prepared first. Its function is to collect excess fluid leachate, called worm tea, or compost tea.

  • The sump may be fitted with a 3/8 inch (15mm) barrel tap, through a small hole drilled in the base for conveniently draining out the excess fluid (the worm tea) that will accumulate there. This tap is not essential, but would avoid the otherwise potentially messy job of having to tip the worm tea out by rotating the bin.

  • If you do decide to put in the tap, make sure it seals well in the hole, by providing good washers and lock nuts.

The Composting Bins

The two upper bins will actually hold the worms. They are to be identical and are prepared as follows : –

  • Drill a pattern of ¼ inch (6mm) holes across the entire base of each container for drainage and to allow for ventilation and the upward migration of the compost worms, these holes should be regularly spaced at approx two inches (50mm) centres apart in either direction.
  • For further aeration, drill a row of ¼ inch (6mm) holes at two inch (50mm) centres, in a continuous line around the walls of each of the bins. This line of holes would be about four inches (100mm) below the top rim of the bin.
  • It is not essential to drill holes in the lid, which is closed tightly over the upper bin. as you should get enough air through the sides.

Setting It Up

After preparing your bins, you first set up the lower (sump) bin on bricks or blocks, allowing enough space to tap off the fluid from beneath it. Choose a shady location for the worm farm (in a shed or garage, if you are subject to frosts).

  • The second and third bins are “nested” within each other and dropped into the sump bin. To maintain a working space for the worms, and for accumulation of compost, you need a few spacers or packers of about six to eight inches height, between the two upper bins and some smaller packers of about four inches in the lower (sump) bin. You can use wood blocks or sealed food jars for packers.
  • The packers also prevent the tapered worm bins from jamming together and cause a gap between the bins, which improves ventilation.
  • To prevent “nasty bugs” from squeezing in between the bins, you should close (caulk) the small gap between them with strips of shade cloth, or mosquito netting.

Starting Production

Now you are ready to go into production : –

  • Set up your worms in the top bin with a good (damp) fibrous bedding such as coconut coir, (or just shredded newspaper), put in a little compost and a handful or two of damp soil with the worms and after a few days you will be ready to start feeding in your kitchen scraps. Cover the food with more bedding material to discourage pests and keep the lid closed.
  • Make sure the worm farm is never allowed to dry out, by sprinkling water over the bedding periodically, if there is not already enough moisture coming from the food scraps.
  • When the top bin has been fully productive for a while, the worms will multiply and compost will be start accumulating from the worm castings. When the quantity of compost is meaningful, stop putting feed into this bin and swap over the upper two bins by putting bin No 2 to the top of the stack, with bin No 1 now in the middle.
  • Set up this new top bin with clean bedding, a small amount of the old castings and immediately start feeding your kitchen scraps into it. Over a few days, the worms will naturally migrate upwards towards the new food source, leaving the lower bin with only a few stragglers and it should be ready for the harvesting of your compost within about three weeks after the swap.

  • To get at any specific layer, to add food, bedding or to remove the vermicompost, just lift off all the overlying worm bins, one by one until the desired level is exposed for examination and then replace them in the same order. They will not be too heavy – but don’t try lifting more than one layer at a time, unless you have a good chiropractor!

All you need to do is to keep repeating the process of alternating the top two bins on a regular basis, taking out the compost, whenever it accumulates, and tapping off the worm tea from time to time. This vermitea, is a very valuable product as it is a highly concentrated liquid fertilizer that can be diluted for immediate use on your garden.

Further useful information can be seen about making a low budget worm farm at an ezine article, written by us: making a low budget worm farm.

Composting with worms (vermicomposting) is a great way to cycle your kitchen scraps and yard waste back into the ‘circle of life’. When compared to your average compost pile, there is much less physical labor involved (frequent mixing not necessary), the process produces results sooner, and can even be done indoors or in confined spaces. When such bins are regularly maintained, following some basic rules, there will be very little-to-no odor. Similar “worm tower” systems exist, but they cost no less than $80-100 and don’t hold much material.

With just a few plastic storage bins/totes, a bit of window screen material, some metal mesh (hardware cloth), some wood, a few screws and some rivets, you can make a space-efficient powerhouse of a composter that can handle all of your kitchen scraps for under $50 (not including the cost of worms).

About vermicompost:

In home-vermicomposting systems, red wiggler worms (Eisenia fetida) are the most commonly used species in temperate climates as they will tolerate confinement and a relatively wide range of temperatures, but are still highly productive eating machines – they will process about half their body weight in kitchen scraps every day! One can find red wigglers for sale in many places, including online (check out: https://unclejimswormfarm.com/).

Vermicast/castings (worm poo) in the bins & leachate (liquid worm waste and condensed liquids) collected in the bottom of the base bin/tray can be used as a soil amendment and wide-spectrum natural fertilizer which is significantly more nutrient-dense than traditional aerobically-produced compost. If *fresh*, and from a reasonably well-maintained set of worm bins, vermicast and the accompanying leachate are also a potent source of beneficial microorganisms with the power to breathe life back into dead soils! That is why worm castings are sometimes called “black gold”! The big bags of castings available at the local garden supply store are a waste of money compared to what one can make at home – store-bought castings sitting around in non-ideal conditions for any amount of time practically guarantees that much of the nutrients have degraded, and that the majority of the accompanying microbial population have died off.

Most of the castings that I harvest from my bins are used to make “worm tea” – a biologically-rich and readily bioavailable organic fertilizer. I will cover the fabrication and usage of an actively-aerated tea-brewing system in a later Instructable…

Design basics:

In stacking tower-style systems, small plastic trays with perforated bottoms stack on top of a solid-bottomed base, with a vented lid on top of the stack of trays. Starting with one of the perforated trays nested above the base, worms are added to the tray along with food and bedding (diet-balancing high-Carbon material such as shredded paper), and more food scraps and bedding are piled in successive layers until the heap of worms/food/bedding is high enough to contact the underside of the next tray above. At this point, all fresh material is added to this upper tray. The worms will eventually finish processing the food in the lower tray(s), and thanks to the perforations in the tray bottoms, the worms are free to migrate upwards in search of fresh food, or downwards in search of suitable mating conditions. The stacking arrangement also allows the most fully-processed tray (the lowest) to be removed for vermicast harvesting, and returned empty to the top of the stack continuing the process indefinitely. Most worm composters have air vents in both the lid and in the base to keep the compost oxygenated, and often feature a means with which to empty any collected leachate from the base.

About this build:

I built this set of worm bins at TechShop Menlo Park in early 2013, documented it as well as I could (at the time, there were little-to-no Instructables detailing such a build and its use), and over three and a half years later they (and the worms) are still performing wonderfully! In that time, I have brewed hundreds of gallons of worm tea from harvested castings, and my gardens are doing quite well!

This design is based on the following plans for the “Oregon Soil Corporation Reactor Jr.”.

Note that the following linked file is not consistently available online:

The upper bins each hold a large number of worms, the resulting vermicompost, and food scraps in various states of decomposition/consumption. The base bin is constructed differently than the upper bins, as the purpose of the base bin is to collect leachate and facilitate air movement into the upper bins.

The design linked above is a good start, but I decided to make a few adjustments/improvements. After inspecting the shape of these storage bins, drilling all those holes high on the sides of the upper bins seemed unnecessary as the adjacent nesting bins would cover the holes, preventing air from passing through while still allowing foreign insects to enter the top bin with ease. Additionally, drilling even several times the recommended number of holes throughout each bottom of the upper bins may still enable the formation of potentially dangerous pockets of anaerobic bacteria. Drilling a sufficient quantity of holes in the bottoms, to ensure that the contents stay aerated on their own, would significantly weaken the bins, aside from being highly tedious work. Here, I’ve used sections of hardware cloth riveted over the floor of the upper bins, allowing much more oxygen to permeate the composting material, and allowing the worms a minimally-impeded passage between bins. Don’t worry, the rough metal mesh doesn’t cut up the worm’s bodies – when they run into something hard/scratchy, they just wiggle backward and alter course!

Composting worms speeds up the composting process. New worm bin owners tend to make mistakes. Once you get the hang of vermicomposting, you will love it! Reducing trash, saving the earth, and creating free fertilizer makes worm composting worthwhile. Your household might even adopt the worms as members of the family! Watch out for these five common mistakes.

Mistake #1: Overfeeding

Enthusiastic worm bin owners toss every available scrap into the bin. The worms cannot keep up. The bin starts to smell terrible!

In theory, worms can eat their weight in scraps per day. However, that number might be lower, depending on air temperature and other factors. A fool-proof method is to feed them every 2 to 3 days. Be conservative in the quantity. Soon, you will get a feeling for how much food they can handle. They should start eating one feeding before you add another. An entire feeding should be completely gone in 1 to 2 weeks.

Mistake #2: Wrong Foods

Worms need a healthy diet in small pieces. Whole cabbages and watermelon rind halves will take too long to break down. Processed food, meat scraps, salty snacks, spicy foods, oily sauces, yogurt, pineapple, and bushels of tomatoes can spoil the bin. Most non-food items are also bad ideas.

The ideal diet for composting worms is non-acidic fruit and vegetable scraps. Grains, bread, coffee grounds, tea bags, and pasta are also fair game. Aged grass clippings, hair, and herbivore animal manure are compostable. Add shredded black-ink newsprint in moderation. Torn or shredded brown corrugated cardboard is acceptable. Clean, crushed eggshells add grit and calcium. All items should be small. Larger items should be cut up or run through a food processor. Smaller pieces break down faster. This reduces odor and discourages pests.

Mistake #3: Too Wet or Too Dry Composting Bedding

The over-enthusiastic worm bin owner pours gallons of water on their worms. The negligent owner lets the bin dry out. Too wet, and the bin becomes stinky and the worms might drown. Too dry, and the worms dehydrate, cannot breathe, and can’t tunnel effectively.
The easiest way to check worm bin moisture levels is by picking up a handful. Squeeze it. If water comes out, it’s too wet. Worm bin bedding should have the feeling of a wrung-out sponge.

See our instructions for drying out a wet worm bin. Also find out how to keep the bin moist.

Mistake #4: Forget to Harvest Worm Castings

Avid gardeners eagerly look forward to removing finished compost from their worm bin. Fresh “black gold” is the best organic fertilizer to make plants grow. Gardeners mark the days until the worm castings are ready for harvesting.

However, non-gardeners typically focus on reducing trash and odor. For them, the worm castings are a side-effect. Their worm bin eventually fills up with worm castings. Adding more trays or getting a larger bin puts off the inevitable.

Harvesting finished compost means separating worm castings from the worms. You will leave bedding behind for the worms to live in. Using a screen should only take 30 to 60 minutes. Making mounds takes a day, mostly waiting time. Tray-based composting bins might only take 10 minutes.

Compost can be harvested:

  • at the start and end of the growing season
  • whenever it is getting full
  • as needed, if the worms have been in the bin for at least three months and there are extra worm castings inside

If you have more “black gold” than you need, donate it to a local gardening project or neighbor.

Mistake #5: Too Hot or Too Cold

Just like people, composting worms have an ideal temperature range. The worm bin and bedding help regulate the temperature. When the air temperature is below 54 degrees Fahrenheit, worms slow down. Below freezing, they can die. Above 84 degrees can cook the worms.

Do you live in a climate that has temperature extremes? See our tips for keeping composting worms cool in summer and warm in winter. Bin location is the primary issue. You can mitigate some of the temperature hazards using ice, bin blankets, insulation, relocation, and moisture regulation.

At Uncle Jim’s Worm Farm, we offer expert information about managing your vermicomposting bin. Peruse our blog, check out our product descriptions, and read our Frequently Asked Questions. We are the #1 supplier of composting worms in the USA.

When it comes to vermicomposting, worms deserve all the credit. These tiny creatures, which have been around for thousands of years, eat our food scraps and transform otherwise wasted resources into a nutrient-rich fertilizer that replenishes the soil.

Longtime worm enthusiast and SSRC diversion coordinator, Sean Barton, recently led two sessions of a DIY vermicomposting class as part of MSU’s 14th annual Grandparents University (GPU). Barton and a handful of SSRC student employees guided Spartan alumni and their grandchildren through the construction of upcycled worm composting towers, made exclusively of discarded kitty litter buckets collected in our material recovery facility (MRF). The buckets were converted into a habitat for the red wigglers (Eisenia fetida) by drilling holes for ventilation and migration, and adding shredded paper from our MRF. Once the towers were built, participants had the opportunity to take home a half-pound of worms, or about 400 red wigglers, in their new vermicompost bins.

Under the right conditions, these composting superheroes can consume their weight in food scraps every day, which is a pretty valuable skill considering Americans toss an average of one pound of food per person per day. When we don’t compost, our food scraps accumulate in the landfill and release methane gas (a potent greenhouse gas) as it decomposes in the garbage pile’s anaerobic conditions. Reducing our food waste by portioning our meals better, coupled with composting, is a tangible way to help fight climate change.

“I watched grow as a child, and I knew that was wrong,” said Sean. When he discovered the power of worms to slow that growing trash mound, he got down to business. For seven years, Sean and his wife lived without a garbage can, relying instead on MSU’s Recycling Drop-Off Center and his wiggler colony. “I think a lot of people like the idea of composting and it’s a way you can be the change,” said Sean. “Vermicomposting is something you can do in a residence hall or studio apartment. There’s no smell.”

Being sustainable doesn’t have to stink!

Continue your eco journey with our DIY Vermicomposting Tower Tutorial, below. This step-by-step guide is based on the bucket system created by Sean Barton.

HOW TO MAKE YOUR OWN VERICOMPOST BUCKET TOWER

What you’ll need:

  • 3 kitty-litter (or similar) buckets
  • power drill
  • 3/8th-inch drill bit
  • 1/16-inch drill bit
  • worms
  • bedding (shredded paper or straw)

#1. Using the thicker bit, drill eight or more holes in the bottom of TWO buckets. The worms will crawl through these holes to reach the food waste.

#2. With the smaller drill bit, create ventilation holes on the sides of the same buckets that have bottom holes. Make sure you drill the holes above where the buckets sit in each other when stacked. On our buckets, this meant drilling above the handle.

#3. Put the worms and bedding in a bucket with bottom holes — this will be the top of your vermicompost tower. Stack your buckets so that the one without holes on the bottom is the base of the stack (it will catch any worms or debris that fall through the other two). From bottom to top, the order is: no-hole bucket, empty bucket with bottom holes, worm bucket with bottom holes.

#4. You may want a lid for your tower to keep critters or children from getting into your worms. Conveniently, the kitty litter buckets come with lids! Simply drill holes with the small bit into one lid. Voila.

HOW TO VERMICOMPOST WITH YOUR TOWER

Over time, add food scraps to the top bucket until it is about half full. Then, switch the top bucket with the middle bucket (the new order from bottom to top will now be: no-holes, worms, empty). Add some bedding to the empty bucket and begin adding food scraps. Once the worms have eaten the food in the middle bucket, they will make their way through the holes into the top bucket. Thus, you will have fresh compost in the middle bucket, free from worms and ready for your garden! At this point, you can start the process over again, moving your worms to the middle bucket once it’s about half-full of food.

Bedding options

  • Straw, shredded newspaper, paper tubes, cardboard

Food

  • Always: fruits, vegetables, coffee grounds, bread, rice and other cooked grains, crushed eggshells
  • Okay in moderation: Garlic, onion, citrus fruits
  • Never: Meat, bones, dairy products, oils

Trouble Shooting

  • Odor: Add more bedding
  • Worms on outside of bin: Add more food
  • Fruit Flies: Keep lid on or add mesh screen to top bucket

Lastly, don’t forget to thank your worms each time you deliver your scraps… after all, they are doing all the work!

Bedding

  • Dry Bedding Material
    (use a combination of one or more dry bedding ingredients listed below)
    • Brown leaves/straw
    • Shredded paper or newsprint (avoid glossy paper)
    • Egg cartons /coffee trays
  • 2 Tablespoons – crushed eggshells or agricultural lime
  • 1 litre of soil (ordinary garden soil)

Steps to Prepare Bedding

  1. Fill worm bin with dry bedding material. (leaves, shredded paper, etc.)
  2. Add water (approximately 2-3 litres) and mix contents.
  3. Bedding should be the consistency of a wet sponge.
  4. Pour off any excess water. (Worm bin should be ½ full of wet material)
  5. Add more dry bedding or water as required.
  6. Add crushed eggshells/limestone and soil.
  7. Add the worms.

Adding the Worms to the bin
*Note: To ensure your worm bin is fully ventilated, drill at least 10-20 – 3/16″ holes in your bin.
Water should be left out overnight prior to preparing bedding.
This will insure any chlorine evaporates and will bring water to room temperature.
Do not use water from a water softener – the salt will burn your worms.

Important: Be sure to add the worms to the composter under direct light.

Simply place the worms on top of bedding. Their natural photophobic tendencies will force the worms into the bedding to a darker, more comfortable environment. Allow the worms to settle into bedding overnight. Start feeding the next day.

As most worm bins have air holes in the bottom, the worm bin should be raised off the ground. A tray should also be placed under the worm bin to catch any excess liquid. If liquid is dripping out of the bottom, this is an indication the worm bin is too wet. Simply pull back bin contents, and add dry bedding on the bottom to absorb the excess liquid.

Feeding the Worms

As the worms do not like to be disturbed, it is best to feed the worms 1-2 times per week rather than daily. Worms eat about half their weight daily. If feeding twice a week, add 1.5 – 2 lbs. each time. If a lot of food scraps are left over from previous feeding wait a day or two prior to adding additional food.

Bury food a couple of inches under the bedding. Bury the food in a different location each time. Be sure to cover food with bedding. Fruit flies are attracted to exposed food. Sprinkle a handful or so of crushed eggshells on top of bedding about once a week. Eggshells counter the acidity in food scraps. Do not over feed the worms!

Add additional bedding (eg. leaves, straw, shredded paper, etc.) when it is difficult to bury food scraps. Also helps absorb excess moisture if bedding becomes too wet. Worms generate heat and produce liquid, therefore, condensation will form on the lid.

Worm Food

Fruit/vegetable peels Coffee grounds/filters Plant cuttings
Tea bags Crushed eggshells Brown paper towels
Cooked pasta & rice (no sauce) Egg cartons/coffee trays Breads/cereals/grains
Leaves/grass clippings Beard clippings Beans
Manure (horse, cow, rabbit) Sawdust (from untreated wood)

Worms do not have teeth, they have a gizzard and use the soil to process their food. Your worms will be eternally grateful if you chop the organic material into small pieces. The smaller the pieces, the greater the surface area to rot. The worms can process the organic matter more rapidly. They adore the pulp from juicers.

Do not include: meat & dairy products or pet waste.

Location of Bin

Store worm bin in cool, preferably dark place. Worms can live in 5° C – 30° C (40° – 90° F) temperature, ideal temperature 15° C – 21° C (60° – 70°F).
Do not allow worm bin to freeze.

The Harvest

Harvest the worms when bedding has almost all been consumed (or turned into beautiful black castings) (4-6 months). Do not feed the worms for one-two weeks prior to harvesting. Allow the worms to finish their job. If any bedding or organic material is remaining, simply set aside and add with new bedding. There are several methods for harvesting.

Dump and Sort
Under bright lighting, empty composter contents onto a plastic sheet. Separate into pyramid shaped piles. Wait 10-15 minutes. Worms are very photosensitive, so to avoid the light, the worms will crawl to the bottom of the piles. Remove the top portion of each pile. Repeat this process until only the worms are remaining. Add the worms to fresh bedding and start vermicomposting process over again. Mix nutrient rich castings in gardens and houseplants.

Side to Side (If you are not comfortable handling the worms you may want to try this method of harvest.)
Feed the worms on one side of the bin for a number of weeks. This will force the worms to migrate to that side of the bin. Once the worms have moved over to the food source, remove the castings from the vacated quadrant. Replace the castings with fresh bedding (see bedding preparation above). Wait a week or two then repeat the process in the opposite direction, herding the worms into the new bedding.

If you encounter any problems or have any questions, please do not hesitate to contact us.

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