Indoor worm composting is a great way to expand your composting system. You may ask, “what is worm composting? And how does it differ from regular composting?” After all, aren’t worms involved in regular composting? Don’t most outdoor compost piles have lots and lots of earthworms all throughout?
- Worm composting uses different kinds of worms than the earthworms in your usual compost pile
- Worm composting can be done indoors
- Worm composting is typically done in a much smaller, enclosed container
- The most common ingredients in worm composting are different than what is used in outdoor compost piles
- Worm composting is easy to do year-round.
There are a number of considerations when setting up and operating a worm composting environment. Below are the most important components to include. But before getting into that, why do it in the first place? First, it is a great way to recycle food scraps. Also, worm castings are extremely nutrient-rich, and plants just love it! And, it is a great way for kids to learn about worms, composting, and other gardening topics.
First of all, you can’t just go out to the garden and dig up some soil worms to create a worm compost bin. The types of worms used are not soil worms, but surface-dwelling worms. Specifically, there are two species of worms that are used: Eisenia foetida and Lumbricus rubellus. Both are commonly referred to as red worms, in the composting business.
The best way to get these worms is to buy them. You can purchase them online, or at a composting specialty store. Since compost stores are not very common, on-line is probably your best option. You can expect 2 pounds of worms to eat about 1 pound of food waste per day. This is probably the right amount for most families. Believe it or not, you can actually buy these from Amazon.com, which is great because the purchase is secured by Amazon. What’s more, they are a very competitive price for worms, at 22% off the retail price!
Environment - There are several components to the worm bin environment that you need to know if you are going to build your own system. It is actually not all that difficult to build your own system, though there are also a number of excellent ones on the market that you may want to purchase instead. If you build your own, you need to meet these requirements:
Darkness – Although these are “surface” worms, they still need to be in darkness. They are used to crawling just beneath the surface of the soil. Exposure to sunlight will quickly dry them out and kill them.
Warmth – The temperature needs to be between about 59-86 degrees F. This is one of the reasons why indoor worm composting is the best way to go. It is easy to control the temperature. Moisture. The environment needs to be wet, but not too wet. Just as with normal composting, too much moisture crowds out oxygen. Worms do need oxygen. The moisture should be too a level of a wrung out sponge.
Oxygen – Worms are tolerant of low oxygen, but not no oxygen. Also, they will work faster in an oxygen-rich environment. Good air flow will also ensure healthier worms and a better-quality end product.
Food – The worms primarily feed on microbes that feed on the food in the compost container. You can help the environment by chopping, blending, freezing or cooking the food materials. Use fruit and vegetable scraps and peels, pulverized egg shells, tea bags and coffee grounds. Avoid using meats, dairy products, oily food and grains. When you add the food bury it under some of the bedding material.
Bedding – As with regular compost, it is necessary to have a good C:N balance. The food scraps are usually nitrogen-rich material, so you need to include carbon-rich, absorbent materials for bedding. It is better to have too much, rather than too little bedding. Ideal sources of bedding are shredded cardboard (especially cardboard egg cartons), peat moss, shredded news print or shredded paper. You can also use shredded fall leaves and chopped up straw. These provide a long-term food source for the composting process. You will need to add new bedding over time, but not daily like with the food scraps. Fill the container about ¾ full with bedding, sprinkle with water to make it moist, bury the worms in the bedding, and then add food scraps daily, burying them into the bedding.
Container – You may choose a DIY, or a purchased container. If you do it yourself, a simple Rubbermaid tub, as from a department store or a dollar store should suffice. It is better to have a shallow container with large surface area, rather than a deep container. A bucket is no good. Remember, these are surface-dwelling worms, and they prefer to live in the top 6” of the soil. A container that is 24”x18”x8” is ideal.
There are a number of purchased systems that work great, and make things a little easier. If you do go this route, get a “flow-through” system, or “continuous flow” system. This allows you to put the compost in one end, and take out the compost from the other end. Again, this is something that is easier to get on-line, and Amazon.com has a number of different kinds, all highly rated, and many which are eligible for free shipping.
Harvesting the compost
With a purchased composter, harvesting the compost is a simple matter. The system is usually designed to separate the compost from the worms, bedding and food automatically. With a home-made version the process is a little more complicated, but still not too difficult.
As the worms convert bedding and food scraps into compost, you will need to add more bedding over time. When the bin is filled with mostly compost it is time to harvest. This usually takes 3-5 months. It is important to do this, not only for your benefit, but also because when the container is mostly compost it is unhealthy for the worms. Follow these steps to separate the compost from the worms and other materials in the container:
- Do not add any new food or bedding for two weeks
- After two weeks, push all contents to one side
- Put fresh bedding and food scraps in empty side
- Remove large pieces of undecomposed stuff from the compost and add to the side with the bedding.
- Over the next 2-3 weeks the worms will make their way over to the new bedding and food and the compost will be emptied.
- You can encourage migration by leaving the compost side of the bin uncovered. It will dry out and the worms will leave.
- Remove the compost and replace with fresh bedding and food.
- Sift through the compost and put any food scraps or worms you find back into the bin.
That’s it. If you prefer, you can do this more quickly by simply dumping out the contents of the container onto a tarp or large piece of plastic, and then separate out the worms and larger scraps by hand. However, if you are a little squeamish you may not want to do it this way. Also, this way is a little bit more of a shock to the worms.
Either way, once you have harvested the compost it is ready for use. Add it to flower beds or potting soil right away and enjoy the results!