Composting 101: Turn Kitchen Scraps into Garden Gold

What Is Compost and Why Does It Matter?

Compost is decomposed organic matter — the end product of bacteria, fungi, and other microorganisms breaking down plant material, food scraps, and yard waste into a dark, crumbly, nutrient-rich material that dramatically improves soil health.

Finished compost does something no synthetic fertilizer can: it feeds the living ecosystem in your soil. Healthy soil biology breaks down organic nutrients into forms plants can absorb, suppresses disease organisms, improves drainage in clay soils and water retention in sandy soils, and creates the porous structure that allows air and water to move freely to plant roots.

A single inch of finished compost worked into your garden beds each season is worth more to long-term productivity than any bag of synthetic fertilizer. It's also completely free — made from materials you'd otherwise throw away.

Browns vs. Greens: The Carbon-Nitrogen Balance

Successful composting comes down to balancing two types of organic material, traditionally called "browns" (carbon-rich) and "greens" (nitrogen-rich). Microorganisms need both to thrive and decompose material efficiently.

Browns (Carbon-Rich)	Greens (Nitrogen-Rich)
Dry leaves, straw	Vegetable and fruit scraps
Cardboard (no tape/ink)	Fresh grass clippings
Wood chips, sawdust (untreated)	Coffee grounds and filters
Paper bags, newspaper	Tea bags (compostable ones)
Corn stalks, dried plant material	Fresh garden trimmings
Egg cartons	Eggshells
Paper towels	Manure (chicken, cow, horse)

The Ideal Ratio

The classic recommendation is a 3:1 ratio of browns to greens by volume. In practice, most home composters err on the side of too many greens (kitchen scraps pile up) — if your pile smells bad or turns slimy, add more browns. If it's dry and not decomposing, add more greens and water.

What to Add (and What to Keep Out)

Safe to Compost

• All raw fruit and vegetable scraps
• Coffee grounds and paper filters
• Tea leaves and compostable tea bags
• Eggshells (crushed speeds decomposition)
• Lawn clippings (in thin layers to prevent matting)
• Fallen leaves (shred first if possible)
• Garden trimmings and spent plants
• Newspaper, cardboard (torn up, no tape or glossy ink)
• Straw and hay
• Wood ash (small amounts — raises pH)
• Herbivore manure (rabbit, horse, cow, chicken)

Keep These Out of the Pile

• Meat, fish, bones, dairy: Attract rodents and create foul odors
• Cooked food with oils or sauces: Same issues as above
• Dog or cat waste: Can contain pathogens harmful to humans
• Diseased plants: Most home compost piles don't get hot enough to kill pathogens — bag and dispose of diseased material
• Invasive weeds or plants that have gone to seed: Seeds survive cold composting and spread in your garden
• Treated wood products: Pressure-treated wood contains biocides
• Glossy paper or cardboard with heavy ink
• Coal ash (wood ash is fine; coal ash contains toxins)

Hot Composting: Fast Results

Hot composting is an active method that produces finished compost in as little as 4–8 weeks. It requires more attention and management but delivers fast results and reliably kills weed seeds and pathogens.

How It Works

When you build a pile with the right ratio of materials and adequate size (at least 3×3×3 feet — the minimum to retain heat), microbial activity generates enough heat to raise the pile's internal temperature to 130–160°F. At these temperatures, decomposition accelerates dramatically and weed seeds are destroyed.

The Hot Composting Process

1. Build a balanced pile: Layer browns and greens in a 3:1 ratio. The pile should be moist — like a wrung-out sponge.
2. Monitor temperature: A compost thermometer ($15–$25) lets you track when the pile heats up (usually 2–5 days after building).
3. Turn regularly: Turn the pile every 3–5 days when the center cools below 130°F. This reintroduces oxygen, which microbes need, and moves the outer material to the hot center.
4. Maintain moisture: If the pile is dry and dusty, add water. If it's soggy, add dry browns and turn to aerate.
5. Harvest: Compost is finished when it's dark, crumbly, earthy-smelling, and you can no longer identify original materials.

Cold Composting: Low-Effort Method

Cold composting (also called passive composting) requires almost no effort — you add materials over time and wait. The tradeoff is that it takes 6 months to 2 years to produce finished compost, and won't kill weed seeds or pathogens.

Despite the slow timeline, cold composting is the method most home gardeners use. Just keep a bin somewhere convenient, add kitchen and yard scraps regularly, and harvest finished compost from the bottom of the pile when needed.

Choosing a Compost Bin

• Open bin (wire or wood frame): Simple, well-ventilated, easy to turn. Best for active composters with space.
• Tumbler: Enclosed drum on a frame. Easier to turn, rodent-resistant, and tidier. Tends to dry out — monitor moisture.
• Enclosed plastic bin: Common in urban areas. Less ventilation can slow decomposition, but it's tidy and keeps wildlife out.
• DIY pallet bin: Four pallets wired together make an excellent, free compost bin. Size is ideal for hot composting.

Troubleshooting Common Problems

Problem	Likely Cause	Fix
Smells like ammonia	Too many greens (nitrogen excess)	Add more browns, turn pile
Smells like rotten eggs	Anaerobic conditions (too wet, too dense)	Add browns, turn to aerate, check drainage
Not heating up	Too dry, too many browns, pile too small	Add water and greens, make pile larger
Attracting flies	Uncovered food scraps	Bury scraps in center, cover with browns
Attracting rodents	Meat/dairy in pile, no cover	Remove problem materials, use enclosed bin
Taking forever	Cold composting, too dry, no turning	Chop materials smaller, add water, turn more often

Vermicomposting: Worms for Small Spaces

Vermicomposting uses red wiggler worms (Eisenia fetida) to convert kitchen scraps into worm castings — arguably the most nutrient-dense soil amendment available. A 2×2 foot worm bin under your kitchen sink can process several pounds of food waste per week and produce castings that outperform commercial fertilizers in plant trials.

Setting Up a Worm Bin

1. Get a plastic tote (10–20 gallons) with a lid. Drill 1/4-inch holes in the lid and sides for aeration.
2. Create bedding with shredded newspaper or cardboard, moistened until damp. Fill the bin about halfway.
3. Add 1 pound of red wiggler worms per square foot of bin surface. (Do not use earthworms — they won't thrive.)
4. Bury small amounts of food scraps in the bedding. Start with vegetable peels, coffee grounds, and crushed eggshells.
5. Keep the bin between 55–77°F. Avoid meat, dairy, citrus, onions, and oily foods.

Harvesting Castings

After 3–4 months, push completed compost to one side and add fresh food to the other. Worms migrate toward fresh food, allowing you to harvest the finished castings from the empty side. Mix a small amount into potting mix or side-dress plants — worm castings are concentrated, so a little goes a long way.

Using Compost to Amend Problem Soils

Compost is a universal soil amendment — it improves every soil type it's added to, which is a rare quality in gardening.

Clay Soil

Clay particles are tiny and pack tightly, creating drainage problems and compaction. Compost creates aggregates — larger clumps of particles — that open up pore space for air and water movement. Work 4–6 inches of compost into clay soil before planting and top-dress annually. Improvement takes 2–3 seasons but is dramatic.

Sandy Soil

Sandy soil drains too fast, carrying nutrients with it before roots can absorb them. Compost acts as a sponge, holding water and nutrients in the root zone. Apply 4–6 inches and incorporate; repeat annually to build organic matter content.

Compacted Soil

Compacted soil has had its pore spaces crushed by foot traffic, heavy equipment, or repeated tilling. Loosen it with a broadfork or garden fork, then work in generous amounts of compost. Stop walking on garden beds to prevent recompaction.

How to Use Finished Compost

As a Soil Amendment

Work 2–4 inches of finished compost into the top 8–10 inches of soil before planting. This is the most impactful use — it improves soil structure and provides a slow release of nutrients throughout the season.

As a Top Dressing (Mulch)

Apply 1–2 inches of compost around established plants. Rain and irrigation will carry nutrients down to the roots. This is also excellent for lawns — spread a thin layer in fall and rake in.

Compost Tea

Steep compost in water for 24–48 hours, then strain and use the liquid to water plants or spray on foliage. The liquid carries soluble nutrients and beneficial microorganisms. Best used fresh — don't store it.

In Potting Mix

Add up to 25% finished compost to potting mix for containers and raised beds. More than 25% can cause waterlogging in pots.

Frequently Asked Questions