How to Start Composting Indoors When You Have No Yard

How to Start Composting Indoors: Pick One of Three Methods

To start composting indoors, choose a method that matches your scraps, set up one container, and begin with small amounts. A worm bin is the usual first choice for an apartment: a lidded plastic bin, damp shredded paper, and one pound of red wigglers will process fruit and vegetable scraps under a sink. A bokashi bucket ferments almost all food waste, including meat and dairy, in about two weeks. If neither appeals, you can collect scraps and hand them to a drop-off program.

An ordinary compost heap is a poor fit indoors. It needs a pile of at least 3 x 3 x 3 feet to heat up, and a small open bin of rotting scraps in a kitchen draws flies. The three methods below are built for small, closed containers. If you do have a balcony or a few square feet outside, compare compost bins for a small yard as well.

What Goes In and What Stays Out

The list changes with the method, so check it before you buy anything.

Material	Worm bin	Bokashi bucket
Fruit and vegetable scraps	Yes	Yes
Coffee grounds and paper filters	Yes	Yes
Crushed eggshells, paper tea bags without staples	Yes	Yes
Citrus, onions, garlic	Avoid	Yes
Cooked food, meat, dairy, small bones	No	Yes
Greasy food	No	Not stated
Soups, sauces and other free liquids	No	Avoid
Pet waste	No	No, food waste only

Worms are the pickier eaters. The Environmental Protection Agency lists citrus fruits, odorous foods like onions and garlic, meat, dairy products, greasy foods, bones and pet waste as things to keep out of a worm bin. Washington State University Extension says bokashi takes almost all types of food waste, including cooked food, dairy, meat and even small bones, which suits a household that cooks a lot. Its one caution is to avoid adding soups, sauces or free liquids.

Chop large pieces before they go in. Smaller scraps break down faster in either system.

Start a Worm Bin, Step by Step

You can buy a worm bin or make one from two plastic storage bins. It should have a tight-fitting lid and be a dark color to keep out light.

1. Drill air holes around the upper sides of one bin, near the lid, and drainage holes in the bottom of the same bin. Set it inside the second bin.
2. Shred or tear non-glossy newspaper, office paper or cardboard. Soak it for 10 minutes, then wring it out so it feels like a moist sponge.
3. Fill the bin almost halfway with the damp bedding and add a handful of soil.
4. Add one pound of red wigglers (Eisenia fetida), which is about 1,000 worms. This is the species both the EPA and Oregon State name for bins.
5. Feed lightly. Start with about 1/4 to 1/2 pound of food scraps per pound of worms per week, and bury each feeding under the bedding.
6. Keep a 2-inch layer of fresh bedding over the worms and food at all times.

Bin size sets how much you can feed. Oregon State University Extension’s rule is 1 cubic foot of bin for each pound of kitchen waste per week, so a bin 1 foot deep, 1 foot wide and 2 feet long handles about 2 pounds a week. University of Maryland Extension describes a shallower tray, 21 inches by 15 inches and 5 to 8 inches deep, that takes 2 to 3 pounds a week. Weigh your scraps for a week before you choose. For ready-made options, see worm composting bins.

Put the bin somewhere that stays between 59°F and 77°F. Under a sink, in a closet or in a basement all work. Worms survive from 32°F to 95°F if they have at least four inches of bedding, but they slow down at the extremes, so an unheated balcony is a summer and winter risk in most climates.

Once the bin settles, feed two to three times a week and raise the amount as the worms multiply. They eat about 25 percent of their weight each day and can double their population in about 60 days. Expect a noticeable amount of dark castings after 6 to 8 weeks and a first harvest after three to six months.

Start a Bokashi Bucket

Bokashi is fermentation, and it runs without air. You need a bokashi bin, which is a sealed bucket that lets you drain off liquid, plus a bag of bokashi bran, which carries the bacteria and yeast.

1. Add a layer of food scraps.
2. Sprinkle a handful of bran on top.
3. Press the layer down to remove excess air, and seal the lid.
4. Repeat until the bucket is full. Drain the liquid every few days.
5. When the bucket is full, leave it sealed to ferment for about two weeks.

The contents will look much as they did going in. A healthy batch smells sour, tangy and pickled. A smell of sulfur, rot or ammonia is the sign of a batch gone wrong.

Fermented scraps are a halfway product and still need soil to finish. Gardeners bury them 8 to 12 inches deep in a bed. Without a yard, use what Washington State University Extension calls an urban alternative: fill a tote or bin with soil or finished compost, mix in the bokashi at 1 part bokashi to 3 parts soil, and let it sit for 3 to 6 weeks. Old potting mix from last summer’s containers is a good use for this, and reusing old potting soil covers how to prepare it. Wait 4 weeks or more before planting into a container that holds fresh bokashi.

Option Three: Collect and Drop Off

If you have no space for a bin, the EPA suggests a municipal or community composting program, which may collect food scraps or offer a site where you can drop them off. Your city’s waste department is the first place to ask.

At home you only need a closed container. The EPA suggests keeping scraps on the kitchen counter, under the sink, or in the fridge or freezer until you can take them out. Ask what the program accepts before you start saving scraps.

Fix Smells, Fruit Flies and a Stalled Bin

Overfeeding is the first thing to rule out. University of Maryland Extension notes that odors may arise if too many food scraps are added at one time, and a new bin’s 1 pound of worms eats only about a quarter pound of food a day.

• Sour or rotten smell in a worm bin. Add a 4-inch layer of dry bedding and stop feeding for two to three weeks.
• Fruit flies. Bury food beneath the bedding every time. Cut back on fruit peels or freeze them before adding them. A small cup of vinegar set in the bin attracts and drowns the adults.
• Uneaten food piling up. Oregon State’s advice for an overfed bin is to stop feeding and wait up to two weeks before feeding again.
• Bokashi that smells rotten. Add a generous layer of bran right away, compress the contents firmly to remove air, and drain the liquid daily.

If you later move to an outdoor bin, the balance shifts to dry browns and wet greens, with at least two to three times the volume of browns. The brown to green ratio explains that mix.

Using Compost When You Have No Garden Beds

Worm castings do not need to cure. They can be used immediately or stored. Maryland’s schedule is a harvest every 3 to 4 months: rake the compost to one side of the bin and add fresh bedding to the other side.

Without a garden, the uses are small but real. Oregon State suggests lightly topdressing houseplants with worm compost or blending it with potting soil, and Maryland caps it at no more than 1/4 of a potting mix by volume. Refresh balcony planters and window boxes at the start of the season, or follow soil for raised bed vegetables if a friend with a bed takes your surplus. Bokashi that has finished its 3 to 6 weeks in a soil tote can be used the same way as potting soil with compost in it.

Quick recap

• Pick by scraps: a worm bin for fruit and vegetable waste, bokashi for everything including meat and dairy, drop-off if you want no bin at all.
• A worm bin starts with damp shredded paper, a handful of soil and 1 pound of red wigglers, kept at 59°F to 77°F.
• Size the bin at 1 cubic foot per pound of kitchen waste per week, and feed lightly at first.
• Bokashi ferments for about two weeks, then needs 3 to 6 weeks mixed 1 to 3 with soil.
• For smells, add 4 inches of dry bedding and pause feeding for two to three weeks.