Sifeng | Reading time: 8 minutes
Composting is the most effective way to turn livestock manure from an environmental liability into a stable, valuable soil amendment. Done correctly, composting reduces manure volume by up to 50%, destroys pathogens and weed seeds through heat, eliminates obnoxious odors, and produces a marketable organic fertilizer. Done incorrectly, it produces ammonia loss, anaerobic rot, fly problems, and a product that burns crops instead of feeding them. This guide covers the science and practice of cow manure composting — carbon-to-nitrogen ratio, moisture, aeration, temperature, and maturity — so farm managers can produce quality compost consistently, at any scale.
Raw manure is difficult to handle and unpredictable in the field: it is heavy, high in moisture, sticky, and its nutrients are locked in forms that release unevenly. Composting solves these problems through aerobic microbial decomposition. The finished product is stable, uniform, and easier to store and spread — and unlike raw manure, it can be sold as a value-added product for horticultural and residential use. For farms under nutrient management regulations, selling composted manure off-farm is often the most cost-effective way to manage excess nutrients while staying compliant. Composting also gives better control of odors and flies than any other handling method, which matters for farms near residential areas.
Composting is a biological process, and like any biological process it needs a balanced diet. Two parameters control everything else:
Carbon-to-nitrogen (C:N) ratio. Microorganisms need carbon for energy and nitrogen for protein. The ideal C:N ratio for composting is 25–30:1, with an acceptable range of 20–40:1. Cow manure alone typically has a C:N ratio of 18–25:1 — nitrogen-rich and too wet to compost effectively on its own. It must be mixed with carbon-rich amendments:
Material | Typical C:N ratio |
Cow manure | 18–25:1 |
Poultry litter | 13–18:1 |
Straw | 40–100:1 |
Sawdust / wood chips | 100–500:1 |
Leaves | 30–80:1 |
Corn stalks | 60:1 |
As a general rule, add roughly 2–3 times the volume of carbon amendment for each volume of manure, then confirm with a lab analysis — the C:N ratio of manure varies with animal diet and bedding.
Moisture content. The optimum moisture range is 50–60% (acceptable 40–65%). Below 40%, the pile is too dry and decomposition stops; above 65%, pores fill with water, creating anaerobic conditions that cause rot and odors. The practical "fist test": squeeze a handful of material — it should clump together with a little water seeping between the fingers, without dripping. Fresh dairy manure at 70–80% moisture needs amendment or pre-drying before composting starts.
Composting is an aerobic process — the microbes need oxygen, and the pile must hold more than 5% oxygen to stay aerobic. Turning the pile is how oxygen is restored, and the frequency is a balance: too little turning starves the microbes; too much turning loses nitrogen through ammonia volatilization. Standard practice: turn the pile when the temperature rises too high or the pile compacts — typically every 2–5 days during active fermentation. For large volumes, windrow turners or tractor-mounted buckets do the job efficiently.
Temperature is both the sign the process is working and the mechanism that makes compost safe. The fermentation process moves through three phases:
Heating phase — temperature rises to 55°C within 1–3 days as microbes multiply.
Thermophilic phase — the pile must maintain 55–65°C for at least 3 days (ideally longer) to kill pathogens, parasites, and weed seeds. Turn when the pile exceeds 65–70°C, because higher temperatures kill the composting organisms themselves.
Cooling/maturation phase — temperature falls below 40°C as decomposition slows; the pile continues to cure for weeks to months.
For large dairy operations, the practical approach is windrow composting: rows 1.5–2.0 meters high and 3–5 meters wide, turned by a tractor-mounted windrow turner. Total time from fresh manure to finished compost is typically 4–8 months, plus 2–12 months of curing — though dewatering the manure first dramatically shortens this timeline.
Fresh manure's biggest composting problem is its moisture content. Dairy slurry is over 90% water, and wet manure does not compost — it rots. The single highest-leverage step is to mechanically dewater the manure before composting. A screw-extrusion solid-liquid separator reduces moisture from 75–80% down to 50–60%, producing a fluffy, crumbly solid that piles and aerates easily, plus a liquid fraction that can be stored and used for irrigation or further treatment. Sifeng's 9GY-40 screw extrusion solid-liquid separator and 9GY-ZG35 separator are built for exactly this role — producing the dewatered solid that enters the compost windrow at the correct moisture, cutting composting time and producing a better product. This dewatering step is also the foundation of the full manure-to-organic-fertilizer process described in our solid-liquid manure separator comparison.
Compost is mature when three indicators align:
Temperature — turning no longer produces a temperature rise; the pile stays at ambient temperature.
Appearance and odor — the material is dark brown, crumbly, soil-like, and has an earthy smell rather than a fecal or ammonia odor.
Organic matter — finished compost typically contains 30%+ organic matter.
Partially composted manure can still be spread in the fall, but it will not deliver the same benefits as fully cured material. For farms producing compost for sale, screening to remove impurities before bagging or shipping improves the product and the price.
Sifeng provides a complete manure handling system from cleaning collection to resource utilization — the equipment chain that supports large-scale composting programs. Beyond separators, the product range covers mechanical scrapers, sewage fine filters, and mattress recycling equipment, with more than 40 patents and thousands of ranches as long-term customers. Sifeng's team conducts on-site inspections to design "one plant, one solution" configurations that match the composting operation to the farm's actual manure volume and winter conditions — the same approach applied in its 5,000-head ranch manure treatment project and documented in the dairy farm manure management complete guide.
Sifeng is a Chinese manufacturer specializing in livestock and poultry manure handling equipment, with a complete system from cleaning collection through solid-liquid separation, bedding recovery, and resource utilization. The company holds over 40 national patents, including its independently developed 9GY and 11FFG series machines, and builds equipment from thick galvanized carbon steel with G80 high-strength lifting chains and imported control systems. A nationwide service network combined with online remote support ensures rapid response for farms of every scale.
Contact Sifeng with your herd size, manure volume, and winter conditions to receive a composting line configuration and equipment quote.
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