The Carbon:Nitrogen Ratio
Compost microorganisms need carbon and nitrogen in approximately a 25–30:1 C:N ratio. High-carbon (brown) materials: dried leaves (60:1), cardboard (350:1), straw (80:1). High-nitrogen (green) materials: kitchen scraps (15:1), fresh grass clippings (20:1), chicken manure (10:1). Practical mixing: alternate 2–3 parts browns by volume to 1 part greens. The most common mistake — all greens, no browns — produces a slimy, anaerobic, ammonia-reeking mess.
Hot Composting (Berkeley 18-Day Method)
Requirements: minimum 1 cubic yard pile, correct C:N ratio, moisture like a wrung-out sponge (50–60%), and frequent turning for aeration. Properly built piles reach 130–160°F within 24–48 hours — hot enough to kill weed seeds and pathogens. Turning schedule: every 2 days for 14 days, then cure 4 days without turning. Total: 18 days. Finished Berkeley compost is dark, sweet-smelling, and crumbly — completely unrecognizable as its inputs.
Manure Composting at Scale
Livestock manure is the highest-value compost amendment. Chicken manure (10:1 C:N) is the hottest and most nitrogen-rich — always compost before applying directly (will burn plants). Rabbit manure (the homesteader's secret weapon) is a "cold" manure that can be applied directly to gardens without composting — the only common manure that won't burn. Cattle and horse manure are excellent bulk materials but often full of weed seeds — hot composting at 140°F+ for 60–90 days kills most.