A worm bin is probably the easiest way to start a home compost – especially if you’re short on space. A 15-20 litre bucket can make an excellent home for red wigglers and can be stored under the sink, allowing for the composting to be done inside, year round. When managed properly, your worm bin will not smell and pests will not be an issue. And your co-residents may not even know it’s there…
So what sort of things should be added to a worm bin?
1. Browns
A worm bin starts with a material that is often referred to as “bedding”, or “browns”. Note that it doesn’t actually have to be brown in colour, rather it’s a material that is relatively high in carbon, an element that ALL living forms use to produce energy. Often, the brown materials also provides structure, drainage, and moisture absorbency – all critical aspects of keeping a healthy bin.
Here are a few ideas for brown material.
- Shredded cardboard, or mixed paper
Try to avoid the glossy flyers and anything that might contain plastic (like tape, wrapping, liners, etc.) - Dried leaves
I always save my yard leaves and use them through the winter. I prefer using my own so that I know the leaves are clean and free of other garbage, including waste materials from vehicles, which can get into bags of leaves that were collected on the street. - Wood chips, straw, wood chips or other woody types of material
These are all excellent sources of carbon but they take longer to break down in a worm bin. - Peat, coco coir, or even used potting soil
There are a number of soilless mediums that can be used for bedding. I have one worm bin that gets all my used potting soil and the finished compost is nicer than the original soil!
2. Greens
Green materials are typically thought to be the worm food, and can include most of your fruit and vegetable scraps, with a few exceptions. Like the brown, your greens don’t actually have to be green in colour – rather, these are foods that contain more nitrogen, which help living forms build DNA and grow. The moisture content of these “green” foods can be rather high, so be careful to not add too much, and balance that moisture with ongoing additions of fresh bedding. I generally aim for equal amount of brown and green by volume, and more browns can’t hurt. If you are planning to feed your bin and notice that there are still some green materials remaining from the last feeding, then reduce the amount – eventually you get a good feel for this.
Here are a few ideas for green material:
- Fruit scraps
My worms love banana peels, avocado rinds, and melon. Peels and cores are an excellent feedstock – just chop any of the larger pieces to make them easier for the worms to consume. - Veggie scraps
Typically vegetable matter will contain slightly more nitrogen than fruits. Veggies also contain a wide variety of micronutrients, enzymes, and growth hormones – all of which are great additions to a worm’s diet and eventually will be passed on to plants, in the finished compost. - Used Coffee/Tea Grounds
I think worms like coffee as much as humans. Just make sure not to overdo it as coffee grounds can contribute to a dry bin. Tea is also nice addition to the bin and can add a variety of herbs that might not be in your food scraps. Note that some tea bags contain plastic or metal, which is better removed before putting in the bin.
3. Grit
Grit is an inorganic material that does not break down like food scraps, and is necessary for worms to properly digest the other foods.
Here are some good sources of grit:
- Fine Sand
Collected from the beach or a playground, or purchased in the hardware store. - Egg shells, Oyster Shells
In a finely ground form, seashells can work as a grit and are also an excellent source of calcium. - Topsoil
Go outside and grab a handful of dirt from the garden. Topsoil contains a mixture of sand, silt, and clay as well as a variety of naturally occurring organisms, which may benefit you worm bin. Just make sure you don’t put too much topsoil in the worm bin because the extra clay can make difficult for the worms to move through.
4. Moisture
The proper amount of water is critical to a healthy worm bin. Red wigglers like an environment that is about 70% moisture. Not soaking wet: if you squeeze a handful of the mix, you should see only a few drips. Also note that food scraps will contain more water than you might think, so monitor the bin and adjust accordingly. If excess water is pooling at the bottom ogf your bin, then the mix is too wet and you can add more bedding to balance the moisture.
5. Air
Maybe this one is obvious but worm compost can get pretty wet and heavy, and block air flow. Check the mixture in your bin to ensure the bin contents are not too mucky and dense. The mixture of worm castings, bedding, and food should remain somewhat loose and mixable by hand.
What to avoid?
There are somethings that just don’t work that well in a worm bin, and so are better left out.
- Meats, Dairy, Oils
Technically red wigglers can process a small amount of meat and dairy products but the high amounts of oils can be hard on their digestion. As with other oily products like salad dressings and cooking oil. - Citrus, Garlic, Onions
Red wigglers will eat these eventually but they just don’t seem that excited about them. - Salts
Salts used in cooking and processed foods can slow down your worm bin too, if added regularly or in large amounts.
What about breads?
Breads can be added to your worm bin but you may find that it creates unwanted mold. The mold is not harmful to worms though, and eventually the worms will eat it up. Same goes for moldy fruit or vegetables.
What about sugar?
Do red wigglers like cake as much as humans? Yes, they do. And like humans, sometimes too much sugar can be a bad thing, creating too much activity and then crashing after. So just add sugar in moderation – like on worm birthdays, Halloween, and Valentine’s Day.
What about seeds?
Worms can process seeds if they have been ground into a flour but otherwise, the seeds can pass through the worm digestive tract and remain viable. Keep that in mind if you are considering adding yard clippings and other plant material.
What about animal manure?
Worm bins can thrive on a balanced amount of manure from herbivorous animals, like that produced by cattle, sheep, and horses. But animal manures introduce another layer of complexity, with respect to the management of pathogens. Also, some manures are a bit too rich for the worm bin and can cause excessive heating in the bin. As for pet manure, better to just avoid it as the faces of animals like cats and dogs can contain harmful pathogens.
Conclusion
Most households contain all the materials needed for maintaining a healthy worm bin. Take a look around and ask your neighbours for supplies if you are short – they might enjoy participating in your composting project.
As with food use, it’s helpful to ask questions about available materials. For example, does this feedstock contain more or less carbon and nitrogen? Is there any chance that the feedstock has been contaminated? Likely, you will learn what your bin needs at any given time and your worm population might have preferences. You can tell if a bin is healthy by using your senses: it should smell earthy, it should look like the worms are busy, without too much water and condensation, and it should feel loose and break apart when turned.