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How to Compost Indoors—for the Urban Gardener
Monday, 14 March 2011 00:00  |  Written by Erica Mukherjee | Article

Compost Bucket photo by Steven DePoloYou don’t have to live at the end of a country road to enjoy the magic of watching things grow. From window boxes to community gardens, many city dwellers are becoming urban gardeners. If you want to start growing your own plants or expand on your current horticultural activities, indoor kitchen composting is an inexpensive and easy way to give your plants the eco-friendly nutrition they need. Here’s everything you need to know to begin composting indoors.

Composting Basics
No matter what method you use for your indoor composting, there are a few basic principles of composting that you should know. Traditional composting requires four raw materials: carbon, nitrogen, water and oxygen. Carbon is often called brown matter and includes paper, twigs and other dry waste products. Nitrogen is found in green matter—usually fruit and vegetable scraps, but also coffee grounds. Most of the time enough water is in the green matter to keep your compost moist, but you may have to add a bit from time to time. Oxygen is the easiest ingredient to add; it comes right out of the air. Why the need for oxygen? Well, traditional composting involves worms or bacteria and they need to breathe.

In a backyard, all you have to do is slop your green and brown matter together, mix it up and wait for nature to take its course. The compost heap needs to be turned every week or so to bring in oxygen, and watered if there isn’t enough rain. But otherwise it is a very low-maintenance way to create nutrient-rich soil. Indoors, the process is more complicated, but not horrendously so.

Indoor Composting
Moving the composting process indoors, especially into a small apartment, poses some additional challenges. For starters, compost, as it breaks down, can produce both liquid and an odor. Secondly, much composting takes place with the help of worms, something that people typically do not want in their apartments. Finally, setting aside the time and space necessary for composting may be a sacrifice for a time-strapped and space-deprived city dweller. However, the pleasure derived from creating new soil and not adding to already overflowing landfills usually compensates quite nicely.

There are two solutions to these problems. There is the option of purchasing an anaerobic kitchen composter that creates the soil you want with little muss or fuss. Or you may choose to go the traditional indoor composting route and tackle these issues in a green DIY fashion that involves some additional elbow grease but gets the job done.

Kitchen Composters
While traditional composting uses oxygen as one of its main ingredients, there are certain types of kitchen composters that use anaerobic—no oxygen—methods of fermentation to produce the same nutrient-rich compost.

With a kitchen composter, you start your composting process by laying down a mixture of a fermentation element, much like adding hops to beer. Then you start to put in your kitchen waste. This method produces not only compost, but also an organic liquid you can use like fertilizer.

Other kitchen composters work in the traditional, oxygen-based manner. They range from buckets with carbon filters to high-tech machines that handle most of the work. For instance, Nature Mill makes a composter that does all the aerating for you. You simply have to toss in your green matter and close the lid.

DIY Composting
For those of us who are a little more adventurous, great fulfillment can be had by making a composter from repurposed materials, in this case a five-gallon bucket or similarly sized plastic container. Punch a handful of holes around the lid of the container and another handful around the top edge. Then add a few more, three or four, at the bottom for drainage. Put your bin in some kind of tray; you shouldn’t have leaks, but better safe than sorry.

Start your composting by making a bed of dry matter out of shredded newspaper or something similar. Dampen this and place it at the bottom of your bucket. It should be about six inches deep. Then you need to add either worms or bacteria. The right type of bacteria is found in soil or grass clippings. This is a good option for people who don’t want worms in their apartments. Worms can be easily had, however, by ordering them online from places like the Worm Man’s Worm Farm.

After you add your bacteria or worms, cover them up with another shallow layer of damp brown matter. Then you can add any kitchen scraps or green matter that you have lying around. You’ll continue to add this matter over the course of your compost creation.

Put the lid on tightly. Keeping the lid on should prevent most smells from leaking out. Custom-made indoor compost pails have carbon filters that help to trap the smells.

Depending on your green matter, you should see your first batch of compost develop in one to four months. Take the lid off every couple of days to add new green matter and stir your mixture.

Once you have fresh, dry compost, you’ll have to get it out of the bucket. When you are using worms, this is tricky but not impossible. To get at your new compost, you’ll need to take the bucket to a well-lit place. Worms will automatically burrow down when exposed to light. This means that if you scoop off your new compost slowly from the top, it should be worm-free and ready to use. The worms, on the other hand, will still be waiting in the bucket for more green matter.

You can continue to compost indoors all year round. As you make more and more soil, you can use it on your house plants, sprinkle it on plants outside your building or donate it to a local community garden. If you don’t know where to donate it, just ask around at your local farmer’s market. There are always hungry plants that will appreciate your delicious compost.

Additional resources:
Composting 101: What You Need to Know to Start Now
Garbage, Worms and Me
'Take Me to the Box of Bugs!'—On Children, Composting and the Future of the Planet

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Comments (2)add
Written by EricaM , March 14, 2011
Thanks for the question. You can think of the liquid in your composter as an organic type of Miracle-Gro. Depending on its consistency, dilute it with a little water or pour it directly on your garden in small amounts.
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Written by Mary Lutz , March 14, 2011
Just one question left unanswered. Should we be dumping the liquids. I have a indoor composter with worms and a carbon filter. It has a lot of liquid. Should I drain it? If so in the drain or the garden?
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