Compost Basics: Recipes and Ratios

What is compost and how does it form?

Compost is the stable, dark, crumbly material left when microbes break down plant and animal residues under warm, moist, aerated conditions. The EPA and extension offices in North Carolina and New Hampshire all describe the same core needs: organic materials, moisture, air and time.

Heat from microbial activity speeds the process, but a cool pile also works if you are patient.

A well-run pile reaches a stage where the original scraps disappear and a uniform dark material remains. Learning to read that sequence is the main skill in composting.

What are browns and greens?

Browns are carbon-rich materials such as dry leaves, straw, shredded paper and wood chips. Greens are nitrogen-rich materials such as kitchen scraps, fresh grass clippings and garden trimmings. Microbes need both, and the balance sets how fast the pile works and whether it smells.

Extension guides give ratios, often expressed by volume or weight, but they vary by source and material. Treat any ratio as a starting point and adjust by what the pile tells you.

Wood chips and sawdust are very high in carbon and break down slowly, so use them in small amounts mixed with greens. Leaves vary by species, and some break down more slowly than others.

• Browns: leaves, straw, shredded paper
• Greens: kitchen scraps, fresh clippings
• Too many greens: smell and slime
• Too many browns: slow, dry pile

How do I build a pile step by step?

Choose a spot with drainage and some shade. Start with a coarse base layer for airflow, then alternate or mix browns and greens, chopping large pieces so they break down faster. Moisten as you go until the material feels like a wrung-out sponge.

A pile that is too small may not hold heat, and one that is too large may lack air. Guides often suggest a size range; check with your extension office for what suits your climate.

Use a bin or a simple pen if you need to keep animals out or keep the area tidy. A bin with a lid and fine mesh at the base helps with rodents. Check local rules, since some towns regulate bins and piles.

How do I manage moisture, air and temperature?

Turn or mix the pile periodically to add oxygen, especially if it smells or cools down. Add water if it is dry, and cover it in heavy rain so it does not become soggy. A compost thermometer lets you track heat if you want to, though many home composters work without one.

If you are composting materials that raise food-safety concerns, such as manure, follow specific guidance from your extension office rather than general home advice.

If a pile smells like ammonia, it likely needs more browns. If it smells like rot, it may need turning and drier material. Our guide on troubleshooting compost problems covers the common cases.

What should stay out of the pile?

Meat, bones, dairy and greasy foods attract pests and can cause odors. Pet waste and diseased plants carry pathogens or disease risk. Weeds with mature seed may survive in a cool pile. Treated lumber and glossy paper do not belong in compost for food gardens.

If you are unsure about a material, ask your extension office or local composting program before adding it.

If a material is not on any list you can find, leave it out until an expert confirms it is safe.

• Meat, dairy and grease
• Pet waste
• Diseased plants
• Seeding weeds in cool piles
• Treated wood

How do I know compost is finished?

Finished compost is dark, crumbly and smells earthy, and the original materials are no longer recognizable. The pile has cooled and does not reheat when turned. Some gardeners test it by sprouting seeds in a small sample.

Timelines vary widely, from a few months in an actively managed pile to a year or more in a passive one. Use finished compost as a soil amendment or mulch, and screen out lumps if needed.

Compost that is nearly finished but still lumpy can be used as mulch while the remaining pieces continue to break down.

How do I plan and budget for composting?

Costs are small: bins or materials for a frame, a pitchfork, a thermometer if you choose, and a water source. Collect browns in fall and store them for use through the year. Compare the cost of making compost with buying it, keeping in mind your time.

Record what you add, when you turn the pile and how it behaves. Notes help you adjust the balance and learn what works for your climate.

Choose a bin location close to the kitchen door and the garden so that the work of carrying material stays small.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.