Composting

Compost is the single highest-leverage input in a resilient food system. A well-run pile converts kitchen scraps and yard waste into finished amendment worth the equivalent of commercially bagged compost — and it does so indefinitely, from materials you already generate. For grid-down or supply-chain-disrupted scenarios, a working compost system means your soil fertility never depends on a store shelf.

This page covers hot composting step by step, cold composting, vermicomposting, and application rates for gardening and soil building.

The Carbon-to-Nitrogen Ratio

Microbes that decompose organic matter need carbon for energy and nitrogen for protein synthesis. The ideal ratio is 25:1 to 30:1 C:N by weight. In practice, this means roughly equal volumes of "browns" and "greens" — though exact volumes depend on material density. A pile that is nitrogen-heavy smells like ammonia; one that is carbon-heavy barely decomposes.

Browns (Carbon-Rich) — C:N Greater Than 40:1

Material	Approx. C:N Ratio
Dry straw	75:1
Shredded cardboard	350:1
Dry autumn leaves	60:1
Wood chips	400:1
Shredded newspaper	175:1
Untreated sawdust	500:1
Cornstalks	75:1

Greens (Nitrogen-Rich) — C:N Less Than 30:1

Material	Approx. C:N Ratio
Fresh grass clippings	20:1
Vegetable and fruit scraps	15:1
Coffee grounds	20:1
Chicken manure	7:1
Cow manure	20:1
Legume plant trimmings	15:1
Seaweed	10:1

Exclude These from Backyard Piles

Meat, fish, bones, and dairy — attract rodents, create persistent odors
Diseased plant material — unless pile reliably sustains 160°F (71°C)
Persistent weed seeds and invasive plants — unless hot composting with verified temperatures
Human or pet feces — pathogen risk without specialized thermophilic management
Treated lumber, glossy coated paper, or synthetic fabrics — contamination risk

Method 1: Hot Composting (4–8 Weeks)

Hot composting requires active management but finishes in 4–8 weeks and kills most weed seeds and pathogens. It demands a minimum pile size of 3×3×3 ft (0.9×0.9×0.9 m) to generate and retain sufficient heat. Smaller piles lose heat to the surface faster than microbes generate it.

Step 1 — Site Selection and Bin Setup

Choose a level spot with good drainage, and easy access for turning. A three-bin system built from lumber or free reclaimed pallets is inexpensive to build and maximizes workflow: Bin 1 = active pile building; Bin 2 = active hot phase turning; Bin 3 = curing and finished material. Each bin should be at least 3×3×3 ft (0.9 m³) internally. Total footprint for a three-bin system: roughly 9×3 ft (2.7×0.9 m).

A purchased plastic tumbler works for smaller households but is difficult to turn effectively and holds less volume.

Step 2 — Gather and Pre-Chop Materials

Collect enough browns and greens to fill a 3×3×3 ft (0.9 m³) pile in one session. Shred or chop materials to 2–3 inch (5–8 cm) pieces maximum. Finer particles give microbes more surface area, accelerating decomposition by 30–50% compared to whole leaves or large scraps.

Step 3 — Build the Initial Pile

Layer in the following order, repeating until the pile reaches at least 3 ft (0.9 m) tall:

Base layer — 4–6 in (10–15 cm): Coarse browns such as wood chips, straw, or shredded cardboard. This creates airflow from below and prevents the pile from sitting in water.
Nitrogen layer — 2–4 in (5–10 cm): Fresh kitchen scraps, grass clippings, or manure.
Carbon layer — 4–6 in (10–15 cm): Dry leaves, shredded paper, or straw.
Moisture check between layers: If dry materials dominate, water each layer. Target moisture: damp like a firmly wrung sponge. Squeeze a handful — a few drops should appear, not a stream.
Repeat nitrogen and carbon layers until pile reaches 3–4 ft (0.9–1.2 m) tall.
Inoculate the top: Sprinkle 1–2 in (2.5–5 cm) of finished compost or garden soil to introduce a starter population of decomposers.

Step 4 — Monitor Pile Temperature

Check temperature with a long-stem compost thermometer (20 in / 50 cm probe — inexpensive at garden centers) inserted into the center of the pile.

Temperature	Meaning	Action
Below 100°F (38°C) after 48 hours	Too dry, too small, or C:N off	Add water and nitrogen source; verify pile is 3×3×3 ft minimum
131–160°F (55–71°C)	Active thermophilic decomposition	Maintain; turn every 3–7 days
Above 160°F (71°C)	Overheating — microbial die-off begins	Turn immediately to cool the center
Dropping to near ambient after 2–3 weeks	Active phase ending or pile needs turning	Turn; add fresh nitrogen if adding to rebuild heat

Kill thresholds: 131°F (55°C) sustained for 3 consecutive days kills most human pathogens. Weed seeds require 140°F (60°C) for 5+ days. To ensure even treatment, turn the pile so outer cooler material moves to the hot center.

Step 5 — Turn the Pile

Turn every 3–7 days during the active hot phase:

Use a fork to move the outer cooler material to the center of the rebuilt pile.
Break up clumps; check moisture — re-wet dry sections.
If ammonia smell is strong, add more browns and mix thoroughly.
If pile smells sour or rotten, it has gone anaerobic — add dry browns aggressively and turn thoroughly to reintroduce oxygen.
Within 24–48 hours of a good turning, the center temperature should spike again.

Most hot piles require 3–5 turnings before activity slows and the pile no longer reheats after turning.

Step 6 — Curing Phase

When the pile no longer heats up after turning, move it to a curing area or bin. Cure for 2–4 additional weeks without turning. Curing allows secondary decomposers — fungi, actinomycetes, and worms — to finish breaking down complex compounds. Applying immature (still hot) compost can temporarily tie up soil nitrogen, leaving crops nitrogen-deficient for 2–4 weeks.

Step 7 — Assess Finished Compost

Finished compost passes all of these checks:

Dark brown to black, crumbly and uniform texture
Smells like forest soil or fresh earth — not sour, ammonia, or sewage
No recognizable food scraps, leaves, or plant material (small wood chips are acceptable)
Volume reduced by 50–70% from original pile
Temperature at or near ambient air temperature after curing

Field Note

In summer, a properly built 3×3×3 ft (0.9 m³) hot pile can produce workable compost in 28–35 days with diligent turning every 3 days. In winter, piles in cold climates effectively freeze below 40°F (4°C). If outdoor composting stalls, insulate the bin with straw bales, or switch to indoor vermicomposting during hard freezes. A worm bin under the kitchen sink handles daily food scraps at no cost and produces the richest amendment.

Method 2: Cold Composting (6–12 Months)

Cold composting is essentially passive decomposition. Add materials as they are available, maintain basic moisture, and wait. No temperature monitoring required. Weed seeds and some pathogens may survive. Finished product in 6–12 months, sometimes longer in cool climates.

Best for: households generating small volumes of waste, limited time availability, or very mild climates with long moist seasons.

Management: - Add materials in rough 1:1 brown/green layers as available - Keep pile covered to retain moisture in dry climates and exclude rain in wet climates - Check moisture monthly — water if the pile is dry and dusty, add browns if soggy - Turn once every 1–2 months to prevent total compaction - Harvest finished material by pulling from the bottom of the pile or bin where the oldest, most decomposed material accumulates

Method 3: Vermicomposting (Indoor, Year-Round)

Red wiggler worms (Eisenia fetida) process kitchen scraps into worm castings — one of the most nutrient-dense amendments available. Castings contain microbial populations 10–1,000 times higher than surrounding soil and are high in available nitrogen, phosphorus, and humic acids that improve soil water retention.

Setup cost: Affordable for a purchased stacking bin; free with drilled plastic totes or 5-gallon (19L) buckets.

Worm Bin Setup (Step by Step)

Bedding: Shred newspaper or cardboard into 1-inch (2.5 cm) strips. Moisten to "wrung sponge" moisture. Fill bin 2/3 full of bedding.
Worms: Start with 1 lb (0.45 kg) of red wigglers per pound of food waste generated weekly. Red wigglers are surface-dwelling composters, not the same as outdoor earthworms. Purchase from a worm farm at an affordable per-pound price.
Feeding: Bury food scraps under bedding in different areas of the bin, rotating locations. Covering scraps prevents fruit flies.
Feed freely: Vegetable scraps, fruit peels, coffee grounds, and tea bags. Feed sparingly: citrus in large amounts, onions, garlic, and spicy foods slow worm activity. Avoid meat and dairy.
Harvest (every 2–3 months): Drive worms to one side by adding fresh food only there for 2 weeks. Harvest castings from the other side.

One pound of red wigglers produces roughly 1 lb (0.45 kg) of castings per week at full activity.

Using Worm Castings

Top-dress beds at 1/4–1/2 in (6–12 mm) depth
Blend into potting mix at 10–20% by volume
Worm tea: steep 1 cup (240 ml) castings in a 5-gallon (19L) bucket of dechlorinated water for 24 hours with an aquarium pump aerating; dilute 1:5 with water; apply within 4 hours

Troubleshooting Reference

Symptom	Most Likely Cause	Fix
Strong ammonia smell	Excess nitrogen, too much manure or grass	Add browns; turn pile
Rotten egg or sulfur smell	Anaerobic — too wet or compacted	Turn thoroughly; add dry browns; check drainage
Pile not heating after build	Too dry, too small, or C:N too high	Water; add nitrogen source; verify 3×3×3 ft minimum
Attracting rodents or wildlife	Food scraps exposed on surface, or meat/dairy included	Bury scraps in center; use enclosed bin
Pile is slimy or waterlogged	Excess moisture	Add dry browns aggressively; improve drainage under bin
White fuzzy threads throughout	Beneficial fungal growth	No action needed; healthy decomposition

Application Rates

Application Type	Rate (Imperial)	Rate (Metric)	Timing
Annual vegetable beds	2–4 in per season	5–10 cm per season	Before planting
Establishing a new bed	4–6 in incorporated into top 12 in	10–15 cm into 30 cm	Once at establishment
Lawn top-dressing	1/4–1/2 in	6–12 mm	Early spring or fall
Potting mix amendment	20–30% by volume	20–30% by volume	At mix time
Transplant hole	1 cup (240 ml) per hole	240 ml per hole	At transplant

For container gardening, mix no more than 30% finished compost into potting mix — higher ratios can retain excess moisture and cause root rot in containers with limited drainage.

Compost Economics

A 3×3×3 ft (0.9 m³) hot pile produces approximately 0.5–1 cubic yard (0.4–0.75 m³) of finished compost per cycle. At 6 cycles per year (hot composting in warm climates), that is 3–6 cubic yards annually.

Commercial bagged compost runs from inexpensive per bag to moderate investment for bulk cubic-yard delivery. Annual equivalent value from a productive home composting system represents meaningful avoided amendment costs from household waste streams alone.

System costs range from free (three-bin from pallets) to affordable (plastic tumbler) to moderate investment (cedar three-bin system with hardware). All options pay back their cost within one growing season.

Practical Checklist

Identify browns and greens sources available at your location
Build or acquire a minimum 3×3×3 ft (0.9 m³) bin or pile space
Build first hot pile with layered browns and greens; check moisture before closing
Monitor temperature for the first 72 hours; turn if not heating
Turn every 3–7 days during active phase; record turning dates
Cure for 2–4 weeks after active phase ends before applying
Set up a vermicompost bin for indoor year-round kitchen waste