Water Cooler: How to start indoor composting

Apartment dwellers and anyone else without their own yard can sometimes feel left out of the Earth Day conversation when it touts all the benefits of growing food or landscaping with native plants in your outdoor space.

One way around this is to bring the outside in and start composting indoors. Turning your food waste into something useful is a satisfying process and allows you to reap the benefits of compost nutrients for houseplants, container gardens, indoor herb gardens and planter boxes.

Indoor composting actually has a few benefits over outdoor composting. The stable indoor temperatures allow the compost bin to thrive year-round rather than facing stagnant or high-maintenance periods. It is also completely protected from the elements such as heavy rains and direct sunlight, which can disrupt an outdoor compost pile.

There are two popular methods for indoor composting. Aerobic composting relies on soil microbes, whereas vemicomposting uses microbes and worms to turn organic material into compost. Both yield great results, but vermicomposting provides the advantage of more protection against soil pathogens, and it usually helps the soil retain more water.

There are tons of indoor composting bins on the markets these days, but you can use anything as simple as any lidded plastic container, a wood bin, or a metal or plastic garbage can. Choose whatever appeals to you and fits in the space you have available. Ideally it should be able to contain a week’s worth of food scraps. A one- or two-person household can usually use a 5- to 10-gallon container, but you can of course go smaller if needed.

The first step is drilling a grid of quarter-inch holes in the bottom and the lid, as well as a few around the rim of the container. This provides airflow to the compost. Place the bin on a tray so excess water has somewhere to drain . This liquid can actually be diluted in water to create a compost tea for feeding houseplants.

An indoor compost bin is composed of about three parts brown matter to one part green matter. Brown matter is carbon rich material such as newspaper shreds, torn cardboard, straw, dry leaves or dead plant clippings.

Green matter refers to the wet and nitrogen-rich items such as vegetable and fruit scraps, coffee grounds, pulverized egg shell and tea bags. Do not put any meat scraps, cooked scraps or fats in the compost. Slightly dampen the brown matter and use it to fill the compost bin to three-fourths full. Sprinkle a 3- to 4-inch layer of soil over it, and it is ready for food scraps.

Once the food scraps are added, use a small shovel or trowel to bury the day’s compostable material in the layer of soil. Put the lid on, and let the composting process begin.

If you choose to go the vermicomposting route, add 1 pound of red worms to the soil for every 3½ pounds of waste. Gather scraps in a separate container over the week, then bury them once a week in the soil and worm layer.

Aerobic composting requires oxygen, so you will have to manually turn the contents of the bin on a weekly basis. Vermicomposting does not require this. If the bin smells or seems too wet or dry, add more soil and dampened brown matter to balance the contents.

The contents will shrink as they decompose, but it may take a month or two to completely turn to compost. It is ready when it feels, smells and looks like rich, dark soil. Remove when complete, but leave a handful of finished compost in the bin for a microbial jump start for the next batch.