From Garbage to Gardening Gold
American households apply 80 million tons of chemical fertilizers to lawns and gardens each year to keep them looking lush. Compost, on the other hand, adds nutrients to the soil naturally and reduces both the amount of yard and food waste that go into landfills—about 27 percent of all U.S. solid waste—and emissions of heat-trapping methane associated with that waste.
Compost also has several gardening advantages over manufactured fertilizers. First, it’s free (after a small investment in a bin). Second, it contains microorganisms that break down organic matter for use by plants, and provides a welcoming environment for earthworms and insects that aid decomposition. And perhaps most importantly, composting can help reduce global warming emissions and water pollution:
- Plants absorb carbon dioxide (CO2) as they grow and release it during decomposition. When plant matter is composted and added to garden soil, however, some of its carbon remains bound to minerals or in organic forms that break down into CO2 slowly, helping to keep carbon out of the atmosphere.
- Compost can reduce or eliminate the need for synthetic fertilizers, which require a lot of energy to manufacture and transport—a 40-pound bag of fertilizer contains the fossil fuel equivalent of three gallons of gasoline. In addition, the nitrogen in compost tends to stay in the soil, where it is available for use by plants, whereas the nitrogen in synthetic fertilizer can leak out of the soil if overused or improperly applied, polluting streams and groundwater.
- While composted waste does generate some methane (which traps 25 times more heat than CO2), turning it regularly exposes it to oxygen and thus reduces emissions compared with the same waste decomposing in a landfill.
Composting is relatively easy even if you have limited space and time, but the following guidelines will ensure the best results:
- Place your compost bin on level ground in a shaded area. If it has no bottom, choose a spot with good drainage.
- Alternate layers of carbon-rich “browns” (e.g., dried yard waste, straw, shredded newspaper) and nitrogen-rich “greens” (e.g., fresh yard waste, food scraps). You can even compost coffee grounds, dryer lint, and hair; see the Related Resources for lists of compostable items. An ideal carbon-to-nitrogen ratio is between 25:1 and 30:1, which typically can be achieved by adding one to two parts of “brown” material for every one part of “green” material. If the compost pile smells like ammonia, add more browns; if decomposition is slow, add more greens.
- Do not add pest-attracting meat and dairy products, slow-to-decompose greasy foods, and pathogen-containing pet waste. Avoid weeds that have gone to seed and vegetable seeds, which can survive the composting process and germinate in your garden. And, despite their labels, “compostable” plastic utensils and containers do not break down easily in home bins; instead, take them to a municipal composting facility if available.
- Keep compost moist and turn it about once a week to accelerate decomposition and create enough heat to kill pathogens and weed seeds. No-turn methods that use coarse materials like straw for aeration also work, but slow decomposition and increase methane emissions.
- When the compost is dark, crumbly, and earthy-smelling, work it into the soil or use as mulch.
