What is compost?
While there are various ways to compost, to make it simple we’ll compare traditional compost and vermicompost methods. Composting and vermicomposting both break organic waste down into smaller bits of organic matter, but the way the two processes work is where they differ.
Composting
Traditional composting uses high temperatures to fire up microbes into munching away on food waste and turning it into smaller bits of organic material. The high temperatures also ensure that any pathogens or weed seeds are destroyed.
Vermicomposting
Vermicomposting, on the other hand, uses a different snacker: earthworms. In vermicompost bins, worms feast on food waste and turn it into “casts” or worm manure. Passing through the worm’s gut helps deactivate any harmful bacteria.
Why vermicomposting is important
The greatest global benefit to vermicomposting (or sustainable waste removal of any sort!) is that you can divert material from going to the landfill.
Food in a landfill breaks down anaerobically, or without oxygen present. This breakdown process tends to produce methane, a very potent greenhouse gas (over 25 times more potent than carbon dioxide). Vermicomposting and composting does the opposite. When you vermicompost, worms break down food waste and other material in an aerobic, or oxygen-rich environment (aka the worm bin). This helps reduce the amount of material entering our already overloaded landfills, and helps reduce emissions.
Benefits of vermicomposting
There are several additional benefits to having a worm compost bin:
- Feeding yourself turns into feeding your plants. Your food scraps become food for your worms, and the worm casts become food for your plants. Worm casts are super nutrient-dense and provide a slow-release food source for your plants. The soil gets a boost. Worm casts promote healthy soil by increasing organic matter and stimulating microbial activity.
- Vermicomposting can be done indoors. Worm bins allow for indoor composting, which can’t be done with traditional composting methods.
- You get a quick turnaround. Vermicomposting is usually quicker than traditional composting. Worms can eat up to their weight in food per day!
- You learn more about yourself. When you start saving your food waste to feed your worms, you learn a lot about your eating and food waste-generating habits. Use this as an opportunity to audit your household’s waste, and challenge yourself to use what you have on hand before heading to the grocery store to buy more.
How to vermicompost
Audit your food waste
Track how much food waste you generate for 2-3 weeks. This will help you determine how many worms you need to process your scraps.
Select a container
This can be wood, plastic, or metal - just make sure it has a lid, has air and drainage holes (and something to catch any excess moisture that might drip out), is easy to move and manage, but large enough to handle your food waste stream.
Choose a location
You’ll want to put your worm bin somewhere dark and cool (55-75F), that is easy for you to access, but not easy for pests or pets to get into. Under a kitchen sink, in the laundry room, or in an interior garage are all great options.
Add bedding
Bedding helps absorb moisture and add air pockets. Shredded newspaper, brown paper, or cardboard fluff up nicely in a worm bin. Moisten the bedding to the point where it feels like a wrung-out sponge: not too wet, not too dry, but juuuuust right.
Introduce your worms to their new home
But first - make sure you get the right worms. The worms you find in your yard are not necessarily the ones you want - many eat and burrow differently than worms you’d want in a worm bin, and you might accidentally grab and spread invasive species like jumping worms. Red wigglers (Eisenia fetida or Eisenia andrei) are the best option for compost worms. The amount of worms you need will depend on how much food waste you normally have, but plan on about 1 lb of worms per 1 lb of scraps.
Feed your worms
Worms can eat fruit and veggie scraps, crushed egg shells, tea leaves, coffee grounds, and bread. Really, most plant-based kitchen scraps are fine to feed your worms, but you do want to avoid meat, dairy, oil, salty foods, pet waste, raw onion or garlic, and large amounts of citrus. Make sure to bury scraps under the bedding to avoid flies or odors.
Sunday Tip:
If you notice a ton of moisture dripping out of your bin (especially if that moisture is smelly or stinky) your bin is too wet. Add some more bedding and stop feeding until you notice the dripping stops.
How to harvest worm casts
Worm casts can be collected and added to soil or potting mix to feed your plants. After the worms have about 3-6 months to eat and produce casts, there are a couple of ways you can harvest the worm casts from your indoor vermicomposting bin. Before harvesting, you’ll want to stop feeding your worms for 2-3 weeks, to ensure you don’t accidentally harvest any undigested food waste.
Side-by-side method
- Shift bin material (bedding, food, and worms) to one side of the bin, leaving half the bin empty.
- Add fresh bedding and a few food scraps to the empty side of the bin.
- Over a week or two, worms will migrate to the “fresh” side, leaving the “old” side worm-free and ready for harvest.
Top-down method
- Move the bin to a bright area, and harvest the top ⅓ of the material from the bin.
- Give the earthworms time to burrow down, then harvest the next ⅓ of the material.
- The remaining ⅓ will contain most of your worms, and can be left behind. Add fresh bedding and food to start fresh!
Dump and sort method
- Dump all your bin material out onto a tarp laid out in a bright area.
- Pile the material up and let it sit for about 30 minutes, so the worms can burrow to the bottom of the pile.
- Harvest the material on top ⅔ of the pile, and return the bottom ⅓ (and your worms!) to a cleaned and freshly prepared bin.
How to use worm casts
- New container planting: mix a 1:4 ratio based on your container size (¼ vermicompost and ¾ potting mix)
- New garden bed: mix vermicompost into the top 4 inches of soil
- Indoor plants: sprinkle ½ inch of vermicompost on top of soil
- Garden plants: sprinkle 1 inch of vermicompost on top of soil
Tips for vermicomposting at home
Escaping worms
Sometimes, worms will try to escape the bin. This is normal, especially when you first introduce the worms to their new home, but if you still have rogue worms after a week or so, check your bin. First, make sure the bin’s lid is on securely and there isn’t a constant bright light nearby. Move the bin to a darker location, if necessary.
If lighting isn’t the issue, check the moisture. Worms need moisture to maintain that slimy layer on their skin - that’s what allows them to breathe (earthworms don’t have lungs - instead, they breathe as air passes through that mucous layer). Too much moisture can suffocate them, but too little moisture can dry them out. Add additional bedding or stop feeding for a week if things are too wet, or mist the bedding if things are on the dry side. Remember, bedding should feel like a rung-out sponge.
Mites
Mites can sometimes show up in worm bins, particularly if you add too much food at once, the bin gets too wet, or if there is a lot of acidic food (citrus, tomatoes, etc.) added. Stop feeding for a few days and add some additional bedding to soak up any excess moisture until the mites disappear.
Odor
A happy worm bin shouldn’t smell. If you start noticing some funky odors, plug your nose and start investigating. Make sure no meat, oil, or dairy products were accidentally added, and remove anything that might have snuck in. Make sure all the food is buried under bedding and add more bedding if you see exposed food or if the bin is too wet. Sometimes, if too much food is added at once, it may also start to rot (and smell) before the worms can eat it all - reduce the amount of food you add at each feeding - or, buy some more worms!
Cited Sources
Composting with Worms. Oregon State University.
Importance of Methane. US Environmental Protection Agency.
Indoor Worm Composting or Vermicomposting
Vermicomposting. Utah State University.
Vermicomposting - Composting with Worms. University of Nebraska-Lincoln.
