How to start composting indoors
According to the EPA, food scraps and yard waste together make up more than 30% of what we discard. Composting keeps these materials out of landfills, where they release methane, a greenhouse gas, thereby reducing our carbon footprint.
Indoor composting is a convenient and inexpensive option for people who live in apartments or don’t have a lot of spare outdoor space. In addition, indoor compost bins have the advantage of not being subject to fluctuating external temperatures and rainfall, which can hamper decomposition. You can buy a bin at a local hardware or garden store and get set up quickly, producing compost in three to four months. If properly maintained, your bin will not attract pests or smell bad.
Best indoor composting methods
There are two basic ways to compost — vermicomposting (using worms) and aerobic composting. A study published in the Journal of the Science of Food and Agriculture found vermicompost to be higher in nutrients than traditional compost; however, both methods produce a compost rich in nitrogen, phosphorus and potassium. If you don’t like the idea of having worms inside your home, aerobic composting is a good alternative.
Vermicomposting
In vermicomposting, worms eat the waste in the bin then excrete castings (manure). These casings combine with other decayed organic matter to form vermicompost.
Aerobic composting
In aerobic composting, microbes in the soil layer of the compost bin break down the kitchen waste and brown materials and release nitrogen, phosphorus and potassium, producing compost.
Best containers for indoor composting
To get started, choose a container that fits in your storage space (anywhere the temperature doesn’t get too hot or too cold). You can buy worm composting bins, but it’s easy to make one using an opaque plastic storage bin or bucket. You can get them in a variety of sizes, depending on how much space you have and how much composting you expect to do. Per the U.S. Department of Agriculture, a bin that’s 1 x 2 x 3.5 feet will handle the kitchen waste from a family of six.
To ensure sufficient airflow (oxygen is essential for microorganisms and worms), drill 15-20 quarter-inch holes into the lid of your compost bin and 8-10 in the bottom for drainage. Cover the holes with fine nylon mesh to keep fruit flies out and the worms in. Place the bin upright on a tray that has at least 2-inch walls to catch any excess liquid. Empty the tray regularly but save the liquid “compost tea” and dilute it (one part tea to ten parts water) to create a nourishing spray for plants.
How to set up a compost bin
All composting uses three basic ingredients: brown materials (such as shredded paper and egg shells) which provide carbon; green materials (fruit and vegetable scraps) which provide nitrogen and water to break it all down. To develop compost successfully, the EPA recommends that you use an equal amount of browns to greens and alternate layers of organic materials of different-sized particles.
To get started, fill your container three-quarters full with damp bedding material (paper, cardboard, sawdust) and cover it with a thin layer of soil.
Follow the directions according to your system of choice.
Vermicomposting
If you’re vermicomposting, put your worms on top of the moist bedding layer. The EPA recommends one pound of red worms for an 18-gallon bin. Collect your scraps in a separate container and once a week, bury the scraps in the worm layer, then replace the bin lid. This type of compost doesn’t have to be turned since the worms aerate as they burrow.
Once vermicompost has replaced all the original material in your compost bin, you can push this to one side of the bin and add new bedding and soil to the empty side. The worms will move over to the new soil and you can scoop out the compost to use.
Aerobic composting
If you’re aerobic composting, bury the day’s compost-safe food scraps and other organic waste in the soil layer then replace the bin lid. Without the worms to aerate, this method requires turning the contents once a week to maximize oxygen distribution. After a few months, when the contents have fully converted to compost, you can remove the finished product for use and start over again.
What can you put in an indoor compost bin?
You can put most food scraps you would put into an outdoor bin in an indoor one. Fruit and vegetable scraps, eggshells, nutshells, coffee grounds and filters, tea bags, shredded paper and house plant trimmings are all good options. Cut or tear scraps into small pieces before adding them to your bin to speed up decomposition. You can also compost pet hair, although this may take longer to break down in an indoor bin.
It’s important not to put anything in your bin that will cause odors or attract flies or rodents. This includes meat, dairy, eggs or anything fatty. You may also want to avoid adding too many items like melon and squash, which are high in water content.
Tips for successful indoor composting
To ensure a balanced compost mixture, turn the contents of your aerobic compost bin regularly. This will break up dry or soggy clumps and encourage microbial activity. It can be helpful to keep a watering can and a bag full of shredded paper on hand to quickly address any imbalance in moisture levels.
Before adding new scraps, check that the previous addition has fully decomposed and be sure to bury the new waste or cover it with brown matter to avoid attracting fruit flies.
How to use your compost
Compost has a variety of indoor and outdoor uses. You can sprinkle it on your outdoor beds, planters and lawn as a conditioner. It can be added to indoor plant pots as food or mixed in with potting soil for repotting houseplants or establishing raised beds. Remember to save a couple of cups of compost per cycle to kick off your new batch.
Editor’s note: This piece was updated on March 29 to remove incorrect advice about lint composting.
Bryony Gilbey is a writer for BestReviews. BestReviews is a product review company with a singular mission: to help simplify your purchasing decisions and save you time and money.
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