How to Start Composting

The U.S. Composting Council's 2015 International Compost Awareness Week reminds us that composting is one of the best ways to improve your soil and garden.

April 29, 2015

"Be loyal to your soil."

It's the mantra of the U.S. Composting Council's 15th celebration of International Compost Awareness Week (ICAW), and we couldn't agree more. Soil is the canvas on which growers—from the hobbyist gardener to the professional farmer—practice their art. And the best way to show some love to the dirt is by composting.


During this week, the U.S. Composting Council is hosting events across the country to spread the word that composting is necessary for anything that requires dirt—including food production, water conservation, and infrastructure development.

See what events are available in your area.

Not sure where to get started? Deborah Martin, former extension agent in the U.S. Department of Agriculture's urban gardening program, explains what you need to turn trash into black gold from her book Rodale's Basic Organic Gardening.

Compost is the best way to ensure good, healthy soil. By using compost, you are providing your plants with optimal nutrition naturally. By making it, you are keeping your organic refuse out of already-overburdened landfills. (About 75 percent of American household garbage is suitable for composting.) One to 2 inches of compost mixed into your garden beds your first year, followed by a ½- to 1-inch layer each year thereafter, will provide all the nourishment most flowers, fruits, and vegetables need. (Use the higher amounts in Southern regions or if you have sandy soil.)

More From Rodale News: The Beauty of Compost

Compost making involves controlling the natural process of decomposition to make it happen more quickly and with more predictable results. To make compost, you simply need to create optimal conditions for the breakdown of organic material: air + water + carbon + nitrogen = compost.

Air. Like most living things, the bacteria that decompose organic matter and the other creatures that make up the compost ecosystem, need air. Compost scientists say compost piles need porosity—the ability for air to move into the pile. Think of porosity in terms of fluffiness. A fluffy pile has plenty of spaces—or pores—for air to move about. A flat, matted pile of grass clippings, for example, does not. Occasionally turning your pile refluffs the material, moves new material into the center, and helps improve airflow into the pile.

Water. Compost microbes also need the right amount of water. Too much moisture reduces airflow, causes temperatures to fall, and can make the pile smell; too little water slows decomposition and prevents the pile from heating. Conventional wisdom says that compost should be about as moist as a wrung-out sponge.

Carbon ingredients. The microbes that break down organic matter use carbon as an energy source. Ingredients with a high percentage of carbon are usually dry and brown or yellow in color. The most common high-carbon ingredients are leaves, straw, and cornstalks. Sometimes people call these ingredients "browns."

Nitrogen ingredients. Microbes need nitrogen for the proteins that build their tiny bodies. Ingredients high in nitrogen are generally green, moist plant matter (such as fresh leaves) or an animal by-product (such as manure). These ingredients are often referred to as "greens," but in reality they can be green, brown, and all colors in between. Household kitchen scraps typically function as a nitrogen source in the compost pile.

C to N ratio. In order for a compost pile to decompose efficiently, you need to create the right ratio of carbon (C) to nitrogen (N), C to N. Piles with too much nitrogen tend to smell because the excess nitrogen converts into an ammonia gas. Carbon-rich piles break down slowly because there's not enough nitrogen for the microbe population to expand. An ideal compost pile should have a 30:1 C to N ratio. Grass clippings alone have about a 20:1 C to N ratio, so adding one part grass clippings or other green matter to two parts dead leaves or other browns will give you the right mix.

More From Rodale News: How Compost Turns Yard Waste Into Black Gold

How to Build a Compost Pile
Following are the fundamentals of compost making. There are many variations on the process, but at its heart, composting is simply a matter of combining organic materials and encouraging them to decompose.

Here's what you need:

• Carbon-rich "brown" materials, such as fall leaves, straw, dead flowers from your garden, and shredded newspaper or cardboard

• Nitrogen-rich "green" materials, such as grass clippings, plant-based kitchen waste (vegetable peelings and fruit rinds, but no meat scraps or dairy products), or barnyard animal manure (even though its color is usually brown, manure is full of nitrogen like the other "green" stuff). Do not use manure from carnivores, such as cats or dogs

• A shovelful or two of garden soil

• A site that's at least 3 feet long by 3 feet wide.

Here's what you do:

1. Start by spreading a layer that is several inches thick of coarse, dry brown stuff, such as straw or cornstalks or leaves, where you want to build the pile.

2. Top that with several inches of green stuff.

3. Add a thin layer of soil.

4. Add a layer of brown stuff.

5. Moisten the three layers.

6. Continue layering green stuff and brown stuff with a little soil mixed in until the pile is 3 feet high. Try to add stuff in a ratio of 3 parts brown to 1 part green. (If it takes a while before you have enough material to build the pile that high, don't worry. Just keep adding to the pile until it gets to at least 3 feet high.)

7. Every couple of weeks, use a garden fork or shovel to turn the pile, moving the stuff at the center of the pile to the outside and working the stuff on the outside to the center of the pile. Keep the pile moist, but not soggy. When you first turn the pile, you may see steam rising from it. This is a sign that the pile is heating up as a result of the materials in it decomposing. If you turn the pile every couple of weeks and keep it moist, you will begin to see earthworms throughout the pile, and the center of the pile will turn into black, crumbly, sweet-smelling "black gold." When you have enough finished compost in the pile to use in your garden, shovel out the finished compost and start your next pile with any material that hadn't fully decomposed in the previous one.

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You don't need a compost bin to make compost. You simply need a pile that is at least 3 × 3 × 3 feet. A pile this size will have enough mass to decompose without a bin. Many gardeners buy or build compost bins, however, because they keep the pile neat. Some are designed to make turning the compost easier or protect it from soaking rains. A bin may also be desirable to keep pets and wild animals from digging in the compost in search of tempting kitchen scraps, or for aesthetic reasons.

Pens made of wire fencing are good for stockpiling ingredients like dry leaves and grass clippings until they're needed in an active compost project, but the open sides let the outer materials get too dry for effective decomposition. Enclosed bins made of plastic or wood may become overly soggy without adequate ventilation and/or turning, but they're useful for keeping critters from raiding the compost pile.

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