Composting is one of the most direct and beneficial forms of recycling. You recycle garden waste, kitchen scraps, and autumn leaves into black gold, the dark, crumbly, nutrient-rich material called finished compost. Compost improves soil structure, making heavy clay drain better and helping sandy soil retain water and nutrients. It feeds beneficial soil organisms that defend plants against disease, buffers soil pH, can help bind and neutralize toxins like lead, and reduces erosion. Best of all, it costs nothing but time and a little effort. This guide covers why compost works, how to build a pile that heats up and finishes in weeks, alternative methods from worm bins to leaf mold, what materials to use and avoid, and how to put your finished compost to work.

Why Compost Works: Decomposition and the Soil Food Web

Compost is decomposed organic matter. Beneath the soil surface and in your compost pile, a microscopic and not-so-microscopic universe of organisms is at work breaking down dead plant and animal material into nutrients that living plants can use. Bacteria, fungi, earthworms, pill bugs, millipedes, and countless other decomposers consume once-living material, releasing heat as they metabolize organic compounds and transforming complex molecules into simpler ones that plants can absorb.

When you add compost to your garden, you're feeding this underground world. Finished compost brings organic matter, a spongy mass that holds both water and air, improving soil structure no matter whether your soil is heavy clay or loose sand. Compost also brings along the microbes and macro-organisms that make soil alive. Sandy soils get better water and nutrient retention. Clay soils get better drainage and aeration. Perennial and annual plantings alike benefit from the slow, steady release of nutrients as compost continues to break down in the soil, and the presence of this organic matter has been shown to suppress plant diseases, improve frost tolerance, and boost seed germination.

The Carbon-to-Nitrogen Balance

The heart of successful composting is understanding that decomposer organisms need both carbon and nitrogen to thrive. Carbon-rich materials, or "browns," are typically dry and brown in color: fallen leaves, straw, hay, dried grass clippings, corn stalks, peat moss, and woody materials. Nitrogen-rich materials, or "greens," are fresher and moist: grass clippings, kitchen vegetable scraps, coffee grounds, manure, weeds, and green plant debris.

For a compost pile to heat up and decompose rapidly (what gardeners call "hot" composting), you need roughly three parts carbon-rich material to one part nitrogen-rich material (a 30:1 carbon-to-nitrogen ratio by weight). This is not an exact formula; you need not measure precisely. Simply aim to layer approximately one part fresh, green, nitrogen-rich material with two to three parts dry, brown, carbon-rich material. For example, one part fresh grass clippings mixed with two to three parts fallen leaves makes a pile that will decompose quickly and heat up to 140 to 150 degrees F, hot enough to destroy many weed seeds and harmful pathogens.

If your pile has too much carbon (too many browns), decomposition will still occur, but much more slowly, and weed seeds and pathogens may survive. If you have too much nitrogen (too many greens), the pile will smell like ammonia. Simply add more carbon-rich brown materials to balance it out.

Building and Managing a Hot Pile

Location and Container

Start by choosing a convenient spot for your pile or bin. The location should be easily accessible so you'll bring materials to it regularly throughout the year. It helps if it's close to your kitchen (for scraps) and your garden (for finished compost). Select a shady location; sun will dry out the pile and slow decomposition. The ground should be level and well-drained. Within reach of a garden hose is ideal, as keeping the pile moist is important.

A container keeps your pile neat and contained. You can purchase a commercial compost bin (made of wood, plastic, or metal), a compost tumbler (a barrel on a stand that you turn to mix the contents), or make your own from simple materials. A homemade bin can be as simple as a circle of heavy-duty wire mesh (turkey wire, 2-inch by 4-inch mesh, about 3 feet high), fastened at the ends. A 9-foot length of 3-foot-high mesh makes a good bin when formed into a circle. Other options include wooden pallets nailed into a three-sided box, concrete blocks with snow fence sections, or chicken wire nailed to a frame of 2-by-4s. The bin should be at least 3 feet square and open or perforated for airflow. If you're using an open-bottom bin on soil, lay down galvanized wire hardware cloth first to prevent rodents from burrowing into the pile.

Building the Pile: The Layering Method

Once you have your location and container ready, pile materials in layers, like making a lasagna. This layering method ensures you mix carbon and nitrogen materials evenly.

  1. Start with a brown layer. Lay a 4- to 6-inch-thick layer of carbon-rich material on the bottom: dried leaves, straw, hay, shredded paper, peat moss, or wood chips. This base layer also allows air to flow up through the pile.

  2. Moisten the brown layer. Dampen it so it's moist but not soggy, like a wrung-out sponge. Moisture helps microbes break down material and speeds decomposition.

  3. Add a green layer. Lay a 2- to 4-inch-thick layer of nitrogen-rich material on top: fresh grass clippings, kitchen vegetable scraps, coffee grounds, or manure.

  4. Optionally, add a thin layer of soil. A shovelful of garden soil introduces microorganisms and earthworms that help decomposition.

  5. Repeat. Alternate layers of brown and green material until the pile is 3 to 5 feet high (or the bin is full). Moisten each layer before adding the next. If you don't have enough green materials on hand, add a cup or two of a high-nitrogen fertilizer such as alfalfa meal, blood meal, or cottonseed meal.

  6. Cover the pile. Once the pile is built, cover it with a lid or tarp to keep animals out, prevent wind from scattering material, and keep excess rain from making it too soggy (though you want it moist, not waterlogged).

Turning and Maintenance

As material decomposes, the center of the pile heats up. This is a sign that bacteria are actively breaking down organic matter. However, the heat doesn't extend evenly throughout the pile. After the center heats up and then cools down (typically a week or two to several weeks, depending on the time of year, size, and composition of the pile), turn the pile.

Turning the pile is simple: use a garden fork or shovel to move the cooler material on the outside of the pile to the center, and move the warmed material from the center to the outside. This mixes the pile, exposes new material to the most active decomposers, and reintroduces oxygen, which aerobic microbes need. Re-moisten the pile after turning if it has dried out. The pile should heat up again.

Keep turning the pile every week or two for faster composting. Even monthly turning works, though it takes longer. Turn the pile at least once or twice total. A stagnant pile takes a long time to finish and can smell terrible. If you have space and energy, maintaining two piles at once allows you to let one decompose while collecting materials in a second pile.

Troubleshooting

If your pile produces a foul, ammonia-like smell, you have too much nitrogen. Turn the pile to add oxygen and mix in some carbon-rich brown materials. If the pile smells sour or musty, the problem is too much moisture. Turn it, and the material's moisture level will help evaporate as you mix and aerate it.

If your pile doesn't heat up or decompose, check that you have adequate nitrogen (add fresh grass clippings or manure), sufficient moisture (it should be as damp as a wrung-out sponge), and good air circulation (turn it or check that your bin has adequate ventilation). Cold weather and rain slow decomposition, so expect faster results in warm, dry seasons. A compost pile cooks best if you turn it frequently and keep it moist but not waterlogged.

When Compost Is Finished

Finished compost looks like rich, dark, crumbly soil and smells earthy and pleasant. You should not be able to identify most of the original materials. Any remaining large sticks, leaves, or vegetables can be returned to a new pile. The time to reach this point varies from a few weeks to a few months, depending on the materials, moisture, temperature, and how often you turn the pile.

If you add materials to your pile a little at a time rather than all at once, don't worry. The pile won't heat up as dramatically and the process will take longer (often several months to a year), but you'll still end up with compost. This is sometimes called "cold" composting, and it works fine; the decomposition just proceeds more slowly.

Compost Bins and Systems

While a bare pile on the ground works, containers keep composting neater and often speed the process. Different systems suit different gardeners and spaces.

Traditional Bins

A stationary compost bin sitting on the ground is the most common method. Once you load the materials, you turn the pile within the bin or, if space allows, fork the materials into an adjacent empty bin. Commercial bins are available at most garden centers; homemade bins from wire, pallets, or lumber work just as well and cost less.

Compost Tumblers

These are barrel-shaped drums mounted on a stand. You load the barrel with brown and green materials, close the lid, and turn it with a hand crank or by rolling it. Tumblers make mixing easy, and the frequent turning speeds decomposition to as little as three weeks. The drawback is that barrels hold less material than a typical pile, so you may not get as much compost.

Worm Bins (Vermicomposting)

If you lack space or live where a traditional compost pile isn't feasible (apartment dwellers, urban gardeners, or anyone concerned about rodents or bears), worm composting offers an alternative. Red wrigglers (Eisenia fetida), not earthworms, are best suited to small-scale bin composting. They take little space, work indoors or outdoors, and when managed properly with the right balance of bedding (shredded newspaper) and organic matter (no meats, fats, or dairy), produce no odor.

To start a worm bin, you need a container about 1 to 2 feet deep with drainage holes and a tight-fitting lid (to keep pests out and maintain moisture). Bins under the kitchen sink, in a basement, garage, or other dark location work well. Add a layer of shredded newspaper or cardboard (the bedding), then add your worms. You can order a pound (about 1,000 worms) from online suppliers or get a handful from someone with an established bin. In a few square feet you can recycle kitchen waste and produce nutrient-dense worm castings.

Feed the bin with vegetable and fruit scraps, coffee grounds and filters, and teabags. Avoid meat, bones, fats, dairy products, oils, and glossy or coated paper. Start with equal portions of bedding and organic matter. Depending on where you live, you may need to bring worms indoors or insulate them with straw bales in winter; red worms in small, home-style bins don't survive freezing well.

Harvest worm castings as needed by separating out the worms, or do a complete reset and store the castings in buckets for later use while the worms go into new bedding. Use the castings directly in the garden, add them to planting holes, or brew them into compost tea (see below). The richness of worm compost makes it particularly valuable: research from Ohio State University found that plants grown in potting mix containing 20 to 40 percent vermicompost showed significantly less insect damage than those in plain potting soil, suggesting that the nutrient profile or chemical composition of worm-amended plants makes them less attractive to pests.

Leaf Mold

If you compost in a region with abundant fall leaves and prefer a simpler, slower method, leaf mold is an excellent option. It's ridiculously easy to make. In autumn, rake leaves into a pile at least 4 feet wide and 3 feet high, or contain them in a bin made of wire mesh fencing that's open on one side. Moisten the leaves as you pile them. For faster decomposition, mow over the leaves first to shred them, or sprinkle in dustings of a high-nitrogen fertilizer. Turn the pile occasionally and keep it moist.

Over about a year (or faster if you shred and turn), leaves decay into leaf mold, a dark, crumbly material. While leaf mold may not contain the nutrients of full compost, it's an excellent soil conditioner that improves texture, water retention, and provides habitat for beneficial earthworms and soil bacteria. Use it as mulch or work it into garden beds.

Composting Without a Pile

Not every gardener has space or desire for a traditional compost pile. Several alternatives exist.

Vermicomposting in Small Spaces

Worm bins, discussed above, are ideal for apartment dwellers, urban gardeners, or anyone who wants to compost indoors.

Leaf Mold (also covered above)

Suitable especially for rural gardeners with wildlife pressures. A pile of leaves composting in place holds no appeal for bears, raccoons, or skunks the way a pile with kitchen scraps does.

Trench Composting

Dig a trench or pit in your vegetable or flower garden, bury kitchen waste and chopped garden debris directly in the ground, and cover with soil. Over the following weeks and months, microorganisms break down the material underground, enriching the soil where plants' roots will grow. This method is especially useful if you lack space for an above-ground pile.

In-Place Mulching

Mow fallen leaves where they lie on the lawn. The tiny leaf pieces filter down between grass blades, decompose, and add nutrients and organic matter to the soil. Studies show this practice improves both soil and turf quality, and lawns green up faster the following spring. Use a mulching mower (or any power mower, though you may need multiple passes). Mow when leaves are dry, use a sharp blade, and set the height to 2.5 to 3 inches. This works best with light, regular mowing as leaves fall, so you're not dealing with a thick layer.

What to Compost

Materials That Compost Well

  • Vegetable and fruit scraps (peels, rinds, apple cores, coffee grounds, teabags)
  • Grass clippings (from untreated lawns; see caution below)
  • Fallen leaves
  • Finely chopped branches, twigs, and woody debris
  • Straw, hay, corn husks, corn stalks
  • Shredded paper and cardboard (no glossy or coated paper)
  • Garden plant debris and spent plants
  • Manure from herbivorous animals (horse, cow, chicken, sheep, rabbit)
  • Egg shells, hair, feathers, ground shells

Cautions and Items to Avoid

  • Meat, bones, and fish scraps (attract rodents and pests, create foul odors)
  • Grease, oils, fats, and dairy products (slow decomposition, attract pests)
  • Pet manure, cat litter, and dog waste (harbor pathogens harmful to humans)
  • Large amounts of sawdust or wood chips (extremely high carbon-to-nitrogen ratio; slow to decompose)
  • Diseased plants and perennial or seed-bearing weeds (can survive composting and spread problems)
  • Herbicide-treated grass clippings (persistent herbicides can survive composting and harm plants 200 days later; know your source)

Grass Clippings and Herbicide Residue

Grass clippings are excellent nitrogen-rich material for compost. However, herbicides used on lawns can persist. If you're collecting clippings from neighbors or public spaces, ask what herbicides have been applied. Newer products like aminocyclopyrachlor break down slowly and can remain active in compost for months or even after being applied to the garden, causing injury to vegetables and ornamentals. The safest approach: collect clippings only from lawns you know have not been treated with herbicides. If using commercially bagged compost, ask the supplier whether grass clippings were used and whether the source lawns were screened for chemical herbicides.

Fall Leaves

Leaves are a free, abundant source of carbon-rich material in autumn. Mow over leaves with your lawn mower to shred them before adding to the compost pile; this speeds decomposition. Alternatively, rake them into a separate leaf-mold pile and let them compost slowly over a year or more.

Coffee Grounds and Tea

Coffee grounds are a superior nitrogen source with an NPK ratio of about 2-0.3-0.2. They compost readily and add a pleasant smell. Tea leaves and teabags (remove staples) also compost well.

Manure

Animal manure is not glamorous, but it may be the most complete soil improver you can haul home. It adds organic matter, nutrients, boosts microbial activity, improves drainage in heavy soils, and improves moisture retention in sandy ones. The keys are knowing what kind you have, when to apply it, and how much to use.

Compost manure first or use aged manure. Fresh manure can carry pathogens such as E. coli and parasites. A hot compost pile that reaches 140 degrees F minimizes those hazards. If you must apply fresh manure, do it in fall before spring planting, or wait 120 days before harvesting leafy greens or root crops, and 90 days before harvesting aboveground fruiting crops.

Different animals have different manure characteristics. Cow manure is the all-purpose standby and most common bagged manure. Nutrients are low but moderately available. Chicken, bird, bat, and seabird manures are hot (quickly available, high in nitrogen and phosphorus) and can burn tender roots if used fresh; compost or dilute them before use. Sheep and goat manure is drier and richer in nitrogen and potassium than cow or horse manure, though it may carry weed seeds. Horse manure is often easiest to find locally, decent all-purpose product, but horses digest little of what they eat, so it's notoriously weedy; compost it hot. Worm castings are gentle enough to use fresh, though they're low in absolute nutrients; they're best thought of as a soil amendment. Rabbit and alpaca manure decompose readily. Avoid cat, dog, and pig manure entirely, as they harbor diseases that infect humans even after decomposition.

Shredding and Chopping

Smaller pieces decompose faster because they have more surface area for microorganisms to work on. Shredding leaves and woody material before adding them to the pile speeds the process. You can do this with a lawn mower run over leaves or branches, or with garden loppers, hedge clippers, or a chipper-shredder. A chipper-shredder is a worthwhile investment if you compost on a large scale and have lots of woody material. In a home compost situation, simply chopping materials with loppers or running a lawn mower over leaves is sufficient. If you use a chipper-shredder, observe all manufacturer safety precautions, wear eye and ear protection, and never investigate a jammed machine without first disconnecting the spark plug and waiting for all moving parts to stop.

Using Finished Compost in the Garden

Amount to Use

How much compost you use depends on your soil and gardening goals. As a general rule: apply about 40 pounds of composted manure per 100 square feet as a soil conditioner. Here are more specific guidelines.

  • New vegetable garden on poor soil: 4 to 5 inches of finished compost turned into the top 8 to 10 inches of soil.
  • Established vegetable or annual flower beds: 1 to 3 inches of finished compost added each spring.
  • Around trees and shrubs: 3 inches of compost spread around or beyond the drip line each spring.
  • Lawn top-dressing: 1/2 inch of compost raked in each fall.
  • Perennial beds: 1 to 2 inches as a mulch; no need to till it in (see research note below).
  • Container plants: up to one-quarter compost by volume mixed into potting soil.

Till or Not Till: Research from Perennial Beds

A common question is whether to till or dig compost into the soil or just spread it on the surface. Research from Washington State University tested this on perennial plantings. Researchers applied a 3-inch-thick layer of compost to test plots. Some plots were tilled to a depth of 7 inches, while others were left with the compost on the soil surface. After six years of measuring growth rates and fertility levels, researchers found that the difference in growth rates between tilled and untilled sites was minimal. Both treatments improved soil quality and leaf coloration. The tilled-in sites had slightly higher levels of carbon and nitrogen in the soil. The conclusion: gardeners shouldn't get too concerned about tilling in compost when applying it to perennial plantings. Simply spread a thin layer (1 to 2 inches) of finished compost over the soil around your perennials. As it continues to decompose, it will provide nutrients to plant roots. When perennial beds eventually need digging and dividing every 3 to 4 years, you can incorporate additional organic matter at that time.

Compost Tea

Finished compost can be steeped in water to make compost tea, which delivers soluble nutrients and beneficial microbes in liquid form. Compost tea offers the benefits of compost in a lighter-weight package, making it easier to apply to plants and soil than hauling finished compost.

Making Extract (Cold Steep)

The traditional method, used for thousands of years, is simple. Suspend a burlap sack filled with finished compost in a bucket or barrel of water and stir occasionally. After 3 to 7 days, strain the liquid through cheesecloth into another container. Use straight or diluted when watering plants. The longer the compost steeps and the more compost you use relative to water, the more concentrated the liquid.

Making Actively Aerated Tea

Brewing compost tea is a more active process. Add a food source such as molasses and add more air to the mixture. You extract nutrients from the compost and also grow a diverse population of beneficial soil microbes within 1 to 2 days. Adding the microbe-rich liquid to your soil boosts the number of beneficial organisms and provides many benefits, such as increasing the uptake of nutrients and protecting plants from disease.

To brew at home: Add 1 gallon of finished compost to a 5-gallon bucket. Next, add air and food. Attach air tubes from an aquarium pump and dangle them in the compost, keeping the pump outside the bucket. Add 1 ounce of molasses, fill the bucket with water, and stir. Turn on the pump and let the mixture percolate for 1 to 2 days. After brewing, strain the tea through cheesecloth into another bucket.

Using Compost Tea

Apply using a watering can or garden sprayer. If using a sprayer, filter the tea through a cloth mesh or cheesecloth bag to strain out any large pieces. On poor soil use straight; on fertile soil dilute one part tea to 10 parts water. Apply every two weeks. Rates vary depending on your gardening situation, but this gives a practical starting point.

Whether you make extract or actively brewed tea, it should smell sweet and earthy. If it smells foul, it may contain harmful microbes and shouldn't be used. For assurance, have your compost tested at a national lab that offers this service.

Finished Compost Tea Quality

For best results, use compost tea soon after making it. Aerobic microbes will die within 12 hours without continued aeration and a food source. The tea is most potent when freshly made.

Wrapping Up

Compost is one of the most direct and beneficial forms of recycling. Whether you build a hot pile that finishes in weeks, maintain a slower cold pile, start a worm bin, or simply mow leaves in place, you're recycling materials that would otherwise go to the landfill and transforming them into black gold for your garden. Gardens benefit from annual additions of compost: drainage improves, disease pressure drops, soil organisms thrive, and nutrient availability increases. The only cost is time and a little effort. Start with the method that fits your space and gardening style. Remember that no matter what approach you take, eventually everything rots.

Find more about composting styles in our companion article, What's Your Composting Personality? And for creative uses of those autumn leaves before they hit the compost pile, see Top 10 Things to Do with Fall Leaves.