By Laura McKissack
Many gardeners have a compost pile or bin at home that serves to break down their yard waste and plant-based kitchen waste. For this type of compost to work, you need carbon (brown, dry material such as raked leaves), nitrogen (wet, green material like veggie scraps), water and oxygen. The right balance of these elements is necessary to ensure each component serves its purpose.
The ideal blend is about one part nitrogen to four parts carbon, and the pile should maintain the consistency of a damp sponge. A good example of this method is an old hardwood forest floor. Scrape aside the layers of accumulated leaves and you’ll find soil that’s rich, moist and dark in color from the years of composted leaves and other organic matter. Acceptable materials for your home compost pile are plant-based kitchen scraps (no meat or dairy), egg shells, unbleached paper products, coffee grounds and tea leaves, grass clippings and other yard waste.
An alternative to the pile method is composting using insects such as black soldier fly larvae, night crawlers or grubs. In warm and humid climates, black soldier fly larvae exist naturally in compost piles. The flies themselves live most of their lives out of sight in the trees, but the larvae can fully compost food scraps in 24 to 36 hours. Red wigglers (a type of earthworm) can be kept in a bin designed for a method of composting called vermicomposting. It’s difficult to get just right, but can be very effective. The result is a rich soil additive commonly referred to as worm castings, and a tea from the castings can also be poured from the bottom of the bin if there is adequate moisture.
Bokashi composting is another alternate form, and uses materials such as bran that have been inoculated with composting organisms called “effective microbes,” which ferment and accelerate the breakdown of the organic matter. The anaerobic (without oxygen) nature of this type of composting reduces the rotting odors typical of aerobic composting. And because the fermentation process happens without oxygen, meat and dairy products can be included in a Bokashi bin.
Kitchen scraps go into a bucket along with the inoculated material, and as they break down, about a cup of nutrient tea can be drained off every few days. When the bin is full and a thin layer of mold is present (indicating the fermentation is complete), it’s time to bury the contents. Dig a shallow trench in a fallow area and empty the bucket into the trench. Cover, and in two to four weeks, the organic matter will have fully broken down into rich soil. Both the nutrient tea and the pulp are immediately beneficial to all plants, including lawns. The tea adds microbial life to the soil and helps plants retain moisture.
The Bokashi method eliminates the need for adding yard waste, allows for composting a wider range of food scraps and, best of all, in the summer heat can be done primarily indoors. Patrick Van Haren, the founder and owner of Microbial Earth who sells Bokashi systems locally, has his bin on an enclosed back porch. According to Van Haren, the resulting compost is like “sauerkraut for the soil.” He likes to puree his scraps when possible in a Blendtec blender along with a little water to speed the process along and get more compost tea out of the bin.
The Bokashi method is ideal if your home doesn’t produce enough kitchen or yard waste to achieve the right balance for pile composting, but it doesn’t produce a large volume of new soil. Instead, it produces a nutrient-dense soil additive that builds the soil that is already there. It also saves the water needed to keep a compost pile moist during the dry, hot months and it reserves leaves and grass clippings so they can be used as mulch or simply left on the lawn where they will enrich the soil and help the lawn hold moisture. This method is a much quicker path from kitchen to compost, and preserves the greatest amount of nutrients that can be returned to your own garden. According to Van Haren, the liquid tea provides for 17 times more frequent cycling of nutrients (an exchange of organic and inorganic matter back into the production of living matter) than traditional composting, thereby building nutrient density in the foods grown in treated soil. And because oils, greases and animal tissues can be included, those things are removed from the sewage system, saving taxpayers money.
Whichever method is right for your home, consider starting a composting system this summer. You’ll have a great head start on the fall growing season and you’ll be contributing to the health and sustainability of your community and planet.
The Complete Compost Gardening Guide, by Barbara Pleasant and Deborah L. Martin. Lewis (Storey Publishing, LLC, 2008)
microbialearth.com (Be sure to watch the impressive demonstration of black soldier fly larvae destroying a whole fish in a few hours.)