Guide to Composting with Worms
Red Worms of the species Eisenia foetida and Eisenia Andrea are one of the best choices of worms for home vermicomposting. Red worms are shallow-dwelling creatures that feed on decomposing organic matter, and adapt easily to living on household food or plant waste in the confines of a worm bin. Red worms, also referred to as red wigglers will consume their weight in food every two days, rapidly transforming your table scraps vegetable and yard waste into nutrient rich compost. Red Worms are not common soil dwelling worms but are more enticed to moist manure and mature compost heaps.
To maintain a healthy vermicomposting system your composting worms will need a temperate shelter, plenty of air, water, bedding materials and food.
- A container with a depth between 12” to 18” inches is ideal as Red Worms are shallow-dwelling creatures that primarily feed near the surface.
- Plastic storage totes are popular options for do it yourselfers. Be sure that your container is sturdy and easy to lift once full of bedding, compost and worms.
- Your container should have roughly one square foot of surface area per pound of food waste produced per week. A common storage tote will provide roughly 3 square feet of surface area and be capable of processing 3-4 lbs of food waste per week.
- To prevent excessive moisture from building up in the bottom of plastic bins you will need to provide drainage. One option is to drill drainage holes in a plastic tote and place that container in another container, which will act as a catch basin for excessive moisture.
- Use a 1/8” - 1/4” drill bit, and drill a series of holes along the sides and in the bottom of the container. This will provide proper drainage and allow for a larger surface area of oxygen to contact the compost. The inner tote can then be placed on bricks, wooden blocks, PVC feet... inside of a second storage tote to capture excess liquid known as compost leachate.
Red Worms are hardy creatures and can tolerate a wide range of temperatures from 110°F to near freezing, however this is not recommended.
- Temperatures between 65°F-80°F are ideal for active decomposition.
- Colder temps slow decomposition.
- Excessive heat can harm worms.
- In colder months worm bins should be elevated off of concrete floors as floor temperatures can fluctuate greatly and affect the rate of decomposition.
Choosing a stable temperate climate is your best option when choosing a good location for your worm bin.Worm bins can be kept inside or outside year round.
- Basements are excellent locations (warm, dark, temperate and moderately dry).
- Worm bins can be kept in a kitchen where waste materials are produced.
- Worm bins can be kept in sheds, garages, on patios, balconies, or in the garden.
- Outdoors, bins should be sheltered from sunlight and rain.
- Even small amounts of summer sunshine can cause overheating.
- If temperatures drop below 40 degrees F, bins should be moved indoors, or well insulated.
Oxygen is necessary for the worms and the millions of oxygen breathing aerobic organisms that are a part of a healthy vermicomposting system. Worms absorb oxygen into their bloodstream thru their entire skin surface and release carbon dioxide.
- A large surface area will provide more oxygen helping to maintain aerobic conditions.
- Keeping the lid off of your bin will provide sufficiently ventilation and ensure a large surface area for gas exchange.
Compact food deposits or overly soggy bedding materials can be void of oxygen, and produce anaerobic conditions.
- Anaerobic conditions will produce foul smelling odors and gasses such as ammonia, rotten eggs (sulphur smell), or rotting garbage.
- Anaerobic conditions should be addressed immediately by either turning, adding fresh bedding or removing the foul smelling materials. This will help to convert anaerobic condition to a healthy oxygen rich aerobic environment.
Worms are comprised of a high percentage of water making the moisture content crucial for both worms and active bacteria.
- 60% - 90% moisture content is recommended.
- Bedding materials should be pre-moistened like a wet sponge before adding to composting bins.
- Worm bins can be loosely covered to conserve moisture. A loose fitting lid with air holes (optional), a dark sheet or burlap placed on top of the bed can work as a cover.
- A solid lid is necessary for outdoor bins to keep out unwanted scavengers and excessive rain.
- Shredded newspaper and cardboard are a good choice for bedding materials.
- Shredded paper and cardboard provides little nutrition for your worms, but are a good source of carbon.
- Shredding all paper and cardboard into 2” or smaller pieces is best for a rapid decomposition.
- Soaking paper or cardboard prior to shredding will make it easier and also keep paper dust down.
- Many newspaper throughout the country and locally are printed with soy and vegetable based inks.
- Most black ink in newsprint is carbon black and should pose no risk to your worms.
- Avoid highly colored and glossy print, as they are likely to contain heavy metals, which may pose a health risk to worms.
- White office paper will take longer for the ecosystem to process.
Leaves, leaf mold and straw
- Choose leaves that breakdown quickly such as Poplar, Maple and Box elder.
Oak leaves contain high tannins that could be harmful in concentrations.
- Oak leaves should be allowed to compost for several months prior to use.
- Pine needles are not recommended as they contain acids that can be harmful to your worms and take a long time to decompose.
- Introducing leaves, leaf molds, and spent straw can also introduce other organisms and possibly unwanted pests to your worm bins.
- For faster decomposition, shred or chop materials as fine as possible.
Coconut Coir Fiber: (#1 choice)
- Coco-coir is the most widely recommended bedding material for use in home vermicomposting systems.
- Coco coir fiber is generally pH neutral.
- Coir holds 8 to 10 times its volume in water
- Created from coconut hulls, coir fiber is a renewable resource produced throughout the South Pacific in India, Sri Lanka, and Indonesia.
- Though coco-coir requires lengthy transportation it offers a renewable alternative to peat and can also be blended for potting mixes or amending soils.
- Coir is generally leached of salt by allowing the coconut hulls to sit through 2 - 3 monsoon seasons.
- Peat is a suitable bedding material for vermicomposting.
- Peat is inexpensive and can be found at many garden centers.
- Peat is very acidic and will need to be pH adjusted with lime or ash to reach a near neutral level prior to using with your worms.
- Peat is a non-renewable, mined, resource.
- Peat is sterile and needs to be inoculated with compost or compost tea prior to use.
Green manures, wild herb wastes, gasses and clovers:
- Lawn clippings; clovers; wild herb wastes such as Comfrey, Yarrow, Nettle, Lambs Quarter, Dandelion, and Plantains, can provide a nutritional boost for your finished compost.
- Green manures can generate heat if used fresh or in high concentrations.
- Dry green manures materials and shred prior to use.
- Use in moderation and monitor temperatures for best results.
Manure and animal wastes:
- Horse, Cow, Rabbit, Goat, Alpaca, and Llama are some of the more preferred animal manures used in vermicomposting systems. Rabbit, Alpaca, Goat and Llama manure is considered 'cold', as they “generally” do not generate a great deal of heat.
- Manures can be used in your worm composting system as a bedding material and a food source with excellent nutritional benefits.
- Mix manures with 50% paper.
- If used fresh, most manure will generate heat.
- Pre-composted or aged 6 months to prevent heat build up.
- Chicken manure is very “hot” and not recommended for your worms.
- Hot composting methods can be used to kill undesirable seeds, and to prevent potential human pathogens in manure.
- Manure from animals treated for parasitic worms or with antibiotics may pose a health risk to worms.
- Use no more than 25% wood chips as bedding materials in confined vermicomposting systems.
- Hardwood chips can be used to create bulk and add air space throughout the bedding.
- Wood chips may take years to fully decompose, but will provide food and shelter for fungal growth.
- Wood chips should be allowed to mature for several months prior to use.
Grit is used in the gizzard of worms and aids in digestion, but should make-up no more than 5% of the bedding materials.
Sand or Soil:
- Soil from a productive garden or a mature compost heap will provide sufficient grit and help to inoculate your bin with native microorganisms
- River sand, beach sand or Aragonite; a finely ground mollusk shell flour that is a high calcium all can be used as a form of grit for worms.
Eggshells (#1 choice)
- Eggshells are a preferred source of grit for your worms as they contain a high concentration of Calcium Carbonate and they are very inexpensive.
- Pulverizing eggshells in a blender or coffee grinder will break them down to an adequate size for your worms.
Rock Dusts; Glacial Rock Powder, Rock Phosphate, Granite dust or Rock Flours:
Rock Dusts contain many trace minerals and are an excellent source of grit for worms.
- AZOMITE is a mined volcanic deposit that provides grit and contains a broad spectrum of over 70 minerals and trace elements. This is an amazing product that is highly recommended. AZOMITE posses a negative charge and attracts positively charged odor molecules, which can be used as an odor control or an absorbent for chemical contamination.
- Powered lime in the form of calcium carbonate can also serve as a source of grit. Worms use calcium to maintain proper health and for reproduction.
- Do not use hydrated forms of lime, as this can harm your worms.
- Lime will add trace minerals, but will also have an effect on the pH of your bedding materials.
- This forceful pH adjustment is not necessary and can pose a damaging effect to some of the beneficial microbes by limiting the natural diversity of the beneficial life present.
Notes on Bedding Materials:
A wide variety of bedding materials can be used in vercomposting, providing a diverse array of nutrients for your worms to transform into rich compost and castings. It’s a good idea to prepare your bedding materials in advance and keep a supply on hand as needed.
* It is very important to moisten dry bedding materials before placing worms into their new home. Start at about 60% moisture content, as it is easier to add more water than take it away. Make the bedding materials damp, but not dripping wet, the bedding materials should feel like a wrung-out sponge. Grab a handful and squeeze it tight, you should be able to extract a few drops of water.
If your bedding materials become too saturated, add some dry shredded paper to absorb the excess moisture. Plastic bins tend to accumulate excess moisture on the bottom. Standing liquid may promote anaerobic conditions, which are not good for your worms. Wooden bins “breathe” better, but will tend to dry-out faster than plastic bins.
What is a good ratio of bedding materials?
A 50-50 blend of shredded paper and coco-coir with a light dusting of grit is a great starting point for bedding materials. Another option would be to incorporate 25% shredded paper, 25% shredded leaves, 25% coco-coir, 25% manure or mature compost along with a light dusting of grit.
When starting a new worm bed, it may take several weeks for microbial populations to grow large enough to breakdown food waste for the worms. Preparing your bedding materials several weeks in advance will help ensure a highly active environment prior to introducing worms.
Adding one cup of cornmeal, oat or wheat flour to your bedding will help to increase the microbial activity within the materials. One way to encourage faster decomposition is to inoculate your bin with worm castings or another mature form of compost. Place a small amount on the bottom of the bin and blend a few cups with your bedding materials. This will help inoculate the new bedding materials with active organisms as a starter, much like yeast to a batch of bread. This can also be achieved with the use of compost teas. This pre inoculation will reduce the transitional stress associated with starting a new worm bin.
Red Worms will generally eat half of their weight in food each day; yet have been identified to eat up to their weight daily. When worms are introduced to a new bed, be cautious not to over feed your worms. Overfeeding is one of the most common mistakes made by those new to vermicomposting.
- Worms actually rely on bacteria to digest their food. Bacteria, fungi, and a variety of macro and microorganisms are responsible for breaking down organic materials into worm-sized food
- Add food in small portions at first as it may take days or even weeks for the microbial life to process food into useable matter for your worms. I cannot emphasize this enough.
- The finer the materials of food the faster the worms will process the materials into compost.
- Freezing food waste will help to breakdown materials by opening up the cells of the food. Once thawed the food will be soft and more accessible to the worms.
- Fruit and vegetable waste: Avoid citrus as it can be too acidic and attracts several types of insects. Also avoid fruit treated with herbicides and pesticides.
- Tea Bags: remove strings and staples
- Coffee grounds and filters:
- Dry and shredded yard wastes, wild herbs:
- Manure: these act as a great source of food and bedding material.
What not to feed to worms?
- Dairy products
- Fatty or oily foods
- Onions (they stink)
Notes on Feeding Worms:
When you feed your worms, bury the foot 2”-3" beneath the surface. This is important to avoid fly and odor problems. Pull aside some of the bedding, add the food in a 2” layer, and cover with bedding. Bury food in different locations in the bin each time you make a deposit. The worms will travel to find the newly added foods. After a month or so you should be able to add more bedding in order to accommodate more food waste. Remember that “odors” are sign that too little oxygen is reaching part of or all of the composting system. If you find an area that stinks, where food waste and/or bedding are very wet or compacted, you’ll want to mix in more fresh bedding and reduce your feeding in the future. If you have the correct ratio of surface area to worms to food scraps, there is little to do, other than adding food and monitoring conditions.
How can I fatten-up my worms?
Feeding worms good organic vegetable scraps and quality-bedding materials is your best option. However, if you wish to fatten your worms in a hurry, the recipe bellow will serve you well.
Worm Feed Recipe
- 5 parts chicken layer pellets or chick starter
- 2 parts wheat or rice bran
- 2 parts alfalfa meal
- 1 part whole-wheat flour
- 1 part agricultural lime
- 1 part powdered milk
Bran flakes provide carbon, trace minerals and vitamins. Wheat flour, alfalfa meal and powdered milk are good sources of protein and contain vitamins B, C, E and K; calcium; and trace minerals.
Who Else Lives in the Worm Bin?
There are endless numbers of organisms at work in a worm bin. All these creatures, large and small, are a part of the composting ecosystem. These critters work hard at decomposing what you feed your worm bin (their ecosystem). The worms rely on this food web to breakdown the larger particles of organic matter into digestible sizes. With a good source of food and comfortable conditions your worm bin is universe full of life.
Worm bin community:
- Nematodes (predatory, bacterial and fungi feeders)
- Soil Mites (these are not the type that attack your plants)
- Feather-winged Beetles
- Isopods such as; Sow Bugs and Pill Bugs
- Rove Beetles
After feeding your bin for three months or longer you will have produced a dark, mature, vermicompost. The contents of your worm bin will have substantially decreased in size, and there should be little or no original bedding or food visible. The mature compost will be coffee brown to black with excellent humus like structure. It is important to separate the worms from the finished compost; otherwise worms will begin to re-ingest their waste and can become sick. Your finished compost should contain about 70% castings and will smell earthy and sweet. If your compost possesses any strong odors it still needs time to mature. Stop feeding your bin about two weeks prior to harvesting.
One harvesting option is to move the finished compost to one side of the bin; add new bedding; add some of the vermicompost as an inoculant; place fresh food waste in this area of the bin. A piece of cardboard can also work to hold back the finished compost so you may fill the other side with fresh materials. Once the new half is full of new bedding materials remove the cardboard. The worms will gradually migrate to the fresh food and bedding, leaving the mature vermicompost for the taking.
Another option is to empty all or part of the contents of the bin onto a large plastic surface and expose to indirect sunlight or a bright lamp. Worms are sensitive to light and this will encourage the worms to retreat beneath the surface. In a few minutes you can begin to remove the top layer of vermicompost now free of worms. As you remove the top few inches of compost the worms will again retreat lower and lower as they are exposed to light. This slow process works well as the worms will ball together as their space is limited.
When you’re finished, place the remaining worms and compost remnants into fresh bedding. Keep a watchful eye out for the tiny, lemon-shaped worm cocoons, as this is a source of future generations. These cocoons can be placed into fresh bedding awaiting their hatching. Mix as much of the finished compost into with new bedding as a starter. Store the remaining mature compost in plastic bags or containers until ready for use. Your finished compost can be further screened to remove some of the larger bedding materials but is not necessary. A household colander/ strainer works well as a hand held sieve.