Many people associate worm composting with converting rich waste materials, like fruit and veggie scraps, into beautiful worm castings - but, a very important part of vermicomposting success involves establishing, and maintaining a safe worm habitat.
The main category of materials needed to make that happen are what we commonly refer to as “bedding”.
The term bedding refers to high-carbon (high C:N) materials that provide structure, hold moisture, and balance the N-rich food materials being added to a vermicomposting system. When used as a cover material (something we highly recommend), they can also serve a very important role in moisture-retention and pest prevention.
There are a lot of high-carbon materials out there, but it’s always important to keep in mind that not all of them are created equal!
Similar to living materials, we feel it is valuable to classify a bedding as either “primary” or “secondary”, based on its overall habitat potential.
These are the C-rich materials that offer: 1) good water-holding capacity, and 2) good airflow. Even if they are used as a sole bedding material, they should work quite well. Some examples include shredded cardboard and “scrunched” paper (see description further down), and coco coir. Although coir is not bulky in the same way as shredded cardboard, the fibrous nature of the material does actually support air flow quite well. Given that it is a natural material, with excellent water-holding capacity, we feel it should be considered a primary bedding.
These are the C-rich materials that are still great for vermicomposting, but aren’t ideal as the sole habitat material. They will: 1) have good water-holding capacity (but limited air flow) OR, 2) support good airflow (but have limited water-holding capacity), OR 3) offer neither of these, but can still be a valuable carbon to add to your system. Some examples include straw (air-flow), shredded leaves (air-flow), and hemp tow (it offers decent moisture-holding, and air flow - but is not as good as the primary materials mentioned).
NOTE: Intact fall leaves can be a great material to add to worm composting systems (ideally, larger systems), but they don’t hold moisture very well, and they also tend to stick together when wet - impeding airflow (and proper moisture cycling) - so, they should always be combined with at least 2 or 3 other habitat materials.
Do keep in mind that - like just about everything in vermicomposting - there are always going to be some gray areas when it comes to bedding classification, so don’t get too caught up in over-analyzing your different options.
Bottom-line, the absolute best way to avoid all bedding concerns, is simply to use a diversity of materials. We recommend combining at least 2-3 - especially complimentary - bedding materials, so you end up with a habitat that holds moisture and supports good airflow.
The only other missing link at this point is the importance of your habitat also being microbially-active.
This can easily be achieved via the use of living materials, but the use of microbial sprays, such as dilute EM solution, or compost teas/extracts can be a good alternative (or enhancement if combined).
Speaking of living materials, some may wonder…
Are primary living materials even better than primary bedding?
In some cases, absolutely! There are indeed primary LMs that can provide all the benefits we look for in an amazing worm habitat (moisture-holding, airflow, and microbes). A prime example would be something like aged, bedded horse manure, but it certainly isn’t the only option.
Straw/hay, cardboard, leaf litter, even wood chips/mulches, can all be amazing living materials for your vermicomposting systems too, as long as they’ve been allowed to rot for a while (how long will depend on the material).
Notice that we’re basically just talking about rotten, C-rich “bedding” here?
So, if you do happen to have any of these materials available (or you have the patience to make some), be sure to put them to good use in your systems!
In a typical worm composting system, bedding (and other habitat materials) should make up at least 70% of the total volume. This highlights one of the great advantages of vermicomposting - you don’t need to worry about the carbon:nitrogen (C:N) ratio nearly as much as you do with regular composting. As long as some rich materials (“greens”/”foods”) are getting added, and warm, damp, aerobic conditions are maintained, the worms - and other organisms - are going to work through those high-carbon wastes over time.
A bedding mix we often recommend is 40% shredded cardboard, 40% rinsed coco coir, and 20% hemp tow. This type of mix could be further enhanced with any form of primary living material, such as aged, bedded manures, rotten straw/hay, rotten leaves, or really rotten wood chips.
Don’t get too hung up on the exact proportions, just be sure that safe habitat materials make up 70% to 80% of your total system volume, and provide the 3 key things that are required: 1) Moisture-retention, 2) Airflow, and 3) Microbes.
Different Bedding Options - In More Detail
This is one of the best bedding options available, especially for small to medium-sized systems. It tends to be readily available - and helps to boost both air flow and moisture retention. The best types of cardboard to use are corrugated cardboard and egg carton (or drink tray) cardboard. Avoid the use of any glossy, coloured cardboard (e.g. cereal boxes etc), since these can contain heavy metals and other unwanted chemicals. Whether you add it damp or dry will depend on where in the system you add it, and what other materials are being added with it. Down at the very bottom of a system and up at the very top, dry shredded cardboard can help with moisture management, whereas in the main worm composting zone, it is best for the cardboard to be damp (at least by the time the worms are added), unless you are also adding other materials that are already very wet (e.g. fruit/veggie slurries).
Shredded White Paper / Newsprint
These are bedding materials very often recommended for vermicomposting. In moderation they can be ok, but we generally recommend steering clear of them as much as possible. Office paper and newsprint can both contain a lot of chemicals and, when shredded, they can also mat together, impeding airflow and moisture cycling in the system.
We feel a better paper option is...
This is an under-the-radar approach we hit on a number of years ago that has proven to be a great way to add paper to a worm bin without impeding air flow. As the name implies, the idea is to scrunch up the paper into small balls or mini "logs" before adding them to your system. Brown kraft paper is likely the best choice, but any unbleached paper should work well. NOTE: Due to the bulkiness of scrunched paper, we recommend using it further down in your systems, rather than as a cover bedding. For this reason, this is often a bedding you can add dry.
This is a fluffy, fibrous bedding material made from the outer husks of coconuts. It has the advantage of being an all natural, sustainably-sourced material (it’s basically just coconut husk "waste"), with excellent water-holding capacity. Although the particles are quite small, the fibrous structure of coir helps to support more airflow than other small-particle bedding options like peat moss (which we don't recommend, for multiple reasons). As such, we feel it is an excellent choice for small to medium sized worm bins, especially during your initial set-up (as touched on above, a bedding mix with 40% shredded cardboard, 40% coco coir and 20% hemp tow can work very well). Something to keep in mind with coir is that it can have elevated salt levels (which can be very harmful for the worms), so it’s a good idea to rinse it before use. An easy way to do this is to line a 5 gallon bucket or other larger container with a fine mesh net and then rinse the rehydrated coco coir with water and squeeze out the excess water. Alternatively, even an old pillow case could perform a similar function - just make sure the coir is wrung out to the point of being damp, not wet.
This byproduct of the hemp fiber production process is a great (secondary) bedding option that not a lot of people talk about. Like coir, it is an all-natural, sustainably sourced "waste" product - but unlike coir, there is a large supply produced here in Canada. It has somewhat similar properties to chopped up straw, but is more fluffy in nature - helping to improve its water holding capacity - and it actually breaks down more quickly than many other types of bedding, making it a great choice for smaller systems.
This refers to the dead, dried stalks of cereal plants such as wheat, oats and barley. It is commonly used for livestock bedding, but can also be a great bedding for vermicomposting systems - especially larger systems. As a secondary bedding that supports good air flow but tends not to hold moisture well, it should always be combined with other bedding for best results. In smaller systems, straw can work especially well as a cover material, but as it breaks down it can provide great structure and increased water-holding capacity.
Many (non farming types) mistakenly assume this is basically the same thing as straw. While it does have some similarities - and can be used in some of the same ways in vermicomposting - it's important to realize it is quite a bit richer in nutrition, putting it somewhere between a food and a bedding. In larger, outdoor systems, it can be used more freely (in a similar manner to straw) - but in smaller worm bins we recommend using it a bit more sparingly. Likely the best use for hay in a typical worm bin is as a cover material, where it provides the same protective advantages of straw, but with the added perk of turning into more of a quality food source for the worms as it breaks down.
In many regions of the world, deciduous trees offer us an incredible, free bounty of organic matter for our composting systems. Layered with other materials in larger systems, intact leaves can work just fine as-is, but in smaller systems they often mat together, impeding air flow, and can take a long time to break down. For a more optimized approach - we recommend shredding them up. This can be done with various leaf vacuums and yard waste shredders, or simply by running a mulching mower over them (just keep in mind that the last option will leave you with more grass clippings mixed in, so it should be treated more like a food material). Even shredded leaves should be considered a secondary bedding, best mixed with other materials - including some with better moisture-holding capacity.NOTE: make sure your shredded leaves are added to your systems damp (but not wet, since the excess moisture will drain down and potentially pool in the bottom), otherwise they will be much slower to breakdown and can create other issues.
Wood Chips & Mulches
It is rare to see bulky, woody wastes recommended as vermicomposting bedding, since they usually have very little water-holding capacity, and can take a very long time to break down. We generally don't recommend using these materials in smaller systems - unless they've been allowed to rot for a long time (making them more of a living material) - but they can be great for air flow and drainage in larger outdoor systems, and can be screened out later for use as a high quality "vermi-mulch", or recycled back through other systems as a valuable living material. NOTE: some caution is warranted when working with chips and mulches made from coniferous trees - especially certain types, such as cedar - since they contain potent oils, which can impede the composting process. We recommend sticking with hardwood materials, as much as possible.
Once again, this isn't a material typically recommended as a worm bin bedding. It is slow to break down, doesn't support good air flow, and often isn't even great for moisture retention. That being said, we recommend not completely writing it off, especially if you have access to a large (untreated) supply of it - and even better if it has been allowed to sit and rot outdoors for quite a while! Another similar product potentially worth considering is hardwood stove pellets. These can soak up and hold a lot of moisture, leaving you with a fluffy, moist bedding that is surprisingly similar to coco coir. Still, we feel it’s important to use sawdusts in moderation, and to always make sure they are mixed in really well, with a variety of other habitat materials.
Another type of “bedding” that can be beneficial in a worm bin is some form of worm blanket. These are placed at the top of a system (ideally, along with a layer of loose cover bedding), and offer additional moisture-retention and protection against pests. The material used to make the blanket will influence its durability and benefits. Heavier jute and coir worm blankets will last longer, but will likely have less habitat-enhancement or long term food value than a hemp blanket (which breaks down, and ends up integrated into the habitat, more quickly).
Other Habitat Amendments
No habitat discussion would be complete without a look at the topic of amendments. None of these are mandatory, but they are worth considering for further enhancement of the process and end products.
Rock Dusts and Buffers
Various mineral-based powders can be a valuable addition to a vermicomposting system, helping to keep pH balanced, providing the worms with grit (to aid digestion), and contributing a variety of micronutrients. Our own pH Buffer Grit mix combines glacial rock dust with oyster shell flour.
Crushed Egg Shells
Often thought of as "food waste", egg shells are another buffering amendment that can contribute minerals and grit to a vermicomposting system, especially when ground up really finely. Just keep in mind that larger fragments can take a very long time to break down, so, unless you are able to reduce your shells to a fine powder, you will likely end up with some in your finished castings (but they will continue to break down over time in your gardens).
BioChar is a carbon-rich and charcoal-like substance produced through the process of pyrolysis, the burning of organic material in a low oxygen environment. It can improve the habitat quality in a vermicomposting system by exponentially increasing the available surface area for microbial colonization. BioChar can provide additional odour control, also helping to keep the worms better protected against harmful gasses such as ammonia. Passing BioChar through composting systems is an excellent way to activate it, and make the finished compost even more valuable as a soil amendment.
Adding Bedding to a Vermicomposting System
There are two key ways we recommend adding bedding (and other habitat materials) to your systems when setting them up: 1) layering, or 2) prepared habitat mixtures. Which one you choose can depend on the system being used, as well as your personal preferences and goals.
This is a great strategy in cases where you want to keep things simple - especially when you are aiming to take a more passive approach. The basic idea is that you will add alternating bedding (and other material) layers all the way up through your system. We recommend always starting and ending with a loose, primary bedding like shredded cardboard. The cover bedding layer should be nice and thick - and we also recommend the use of worm blankets (like our hemp blankets) for even more moisture retention and protection from pests.
It’s also important to make sure your layers are well-moistened. You can either do this with each material in a separate container before it is layered in, or you can simply spray down each layer (really well) as they are added (or use a watering can, in the case of larger, outdoor systems).
TIP: Using a dilute EM spray or some form of compost tea/extract, instead of water, can be a great way to inoculate your bedding materials while moistening them. This is especially helpful in cases where you don’t have good access to living materials. (If you are using our Bokashi Living EM concentrate, you can dilute at a rate of 8:1 (non-chlorinated water-to-EM), or 80:1 for better value).
NOTE: the infographic above offers just one potential layering set-up (for non-stacking systems). The different combinations are virtually endless, and the best approach usually involves using materials you have good access to. Also note, if you do use garden soil as a living material, make sure it is a rich, lightweight loamy soil, not heavy mineral soil (e.g. high sand or clay contents), since these can impede air flow and cause other issues.
Prepared Habitat Mixtures
This is a somewhat more “optimized” approach, where you are creating your main habitat mix (best done in a separate container) before setting the system up. In this case, we recommend thinking in terms of a “3-zone” approach, where the bottom and top levels (“false bottom” and “cover bedding”) are loose, primary bedding materials - often added dry - and the main habitat zone mix - best added damp - is sandwiched in between them.
Aim for your bottom and cover zones to take up about ½ the total habitat volume (combined), and for the main zone to take up about ½. The upper and lower zones will gradually be integrated into the “worm zone” over time, but initially they provide a valuable protective role.
To prepare your middle (worm) zone mix we recommend adding your different components to a good sized tub or tray (we love black plastic, mortar mixing trays, but a larger plastic tub can work well too). Don’t worry about making “too much”. If anything, there are great advantages to ending up with lots of leftover habitat material! This can be stored in some sort of plastic tub or similar container with air holes. It will continue to slowly break down over time, essentially turning into a highly valuable (“primary”) living habitat material.
Great materials for your loose cover bedding include shredded corrugated cardboard, hand ripped egg carton cardboard and straw. You can kick things up a notch by also adding a hemp worm blanket in your cover zone. Keep in mind, these cover materials will gradually get integrated into the main worm zone (and fully broken down) over time, so it’s a good idea to keep your loose bedding layer topped up and to replace your hemp blanket (if you use one) as needed.
When setting up a new system, it’s also important to include some food for the worms! Add a small quantity of fast-to-breakdown fruit and/or veggie scraps, such as apple cores, banana peels, melon, cucumber or lettuce (and other leafy greens) underneath your cover bedding.
- Bedding refers to high-carbon materials that provide structure, hold moisture, and balance the N-rich foods in a vermicomposting system. They are extremely important habitat materials, but can also serve a key protective role when added to soak up excess moisture, or used as cover materials over the main worm composting zone.
- Bedding and other safe habitat materials should make up most of your system volume (70-80%), and you should use a diversity of materials that compliment each other, based on the water-holding capacity, and air flow support.
- Primary bedding materials are the ones that hold water well, and are also bulky enough to support air flow. (e.g. Shredded cardboard, coir)
- Secondary bedding either holds moisture well, or supports good airflow, or is simply a high-carbon material that can improve habitat quality. (e.g. straw, shredded leaves)
- Another important habitat requirement is a rich microbial population - this is where living materials can help. Primary living materials (e.g. aged, bedded horse manure, rotten straw) can often be highly-valuable “all-in-one” habitat materials, but we still recommend mixing them with other materials to achieve even more habitat diversity.
- Layering of bedding, and other materials, offers a simple-but-effective way to get a system set up. It’s especially well suited for larger, outdoor systems.
- Prepared habitat mixes offer a more “optimized” approach. They should be sandwiched in between upper and lower bedding layers, and should take up at least ½ of the total system volume. This approach tends to be better suited for small to medium sized systems.
- Aside from bedding (and other habitat materials), it is also important to add a small quantity of fast-to-breakdown fruit and/or veggie scraps - such as apple cores, banana peels, melon, cucumber or lettuce (and other leafy greens) - when setting up a new system. Remember to always keep food deposits buried under your cover bedding.
- It is important to add new bedding to your system periodically, since the worms (and other organisms) will gradually consume these materials over time. It is also important to add new bedding (either dry or moist, depending on moisture levels in the system) any time you remove castings or worm-rich material from an active system.