Cow Dung Organic Fertilizer Production Line

Why cattle farms process manure into fertilizer

A dairy cow produces more than 7 tonnes of manure a year, and beef cattle about 5–6 tonnes. Spread raw, cow dung heats up in the soil, uses up oxygen and can burn roots and seedlings. It also carries parasite eggs and pathogens, and it smells, especially in hot weather.

Dry cow dung contains about 10–20% crude protein, 1–3% crude fat, 20–30% nitrogen-free extract and 15–30% crude fibre. Composted properly, it loosens compacted soil and improves soil fertility, and it gives the farm a product to sell.

Two ways to set up the plant

• An open composting line with a turner, followed by crushing, screening and optional granulation. Investment is lower and the line is efficient, but some steps need operators.
• An enclosed aerobic fermentation tank. Material is loaded, aerated and composted inside the tank, and exhaust air passes through biological odour treatment. Renyuan's tanks range from 32 to 116 m³ of chamber volume.

Composting cow dung

Cow dung is wet, so moisture control comes first. Drain or air-dry the manure to below 85% moisture. Mix it with straw, sawdust or mushroom residue, with manure making up 80–90% of the mix. The composting mix should then be at 40–65% moisture.

To check moisture by hand, squeeze a handful firmly. Water should show between your fingers without dripping, and the lump should break apart when dropped. Too dry slows composting; too wet blocks air. If the mix is too wet, add straw, sawdust, mushroom residue or dry soil.

1. About 48 hours after piling, the temperature rises to 50–60 °C. By day 3 it can pass 65 °C.
2. Turn the pile at this high temperature. Composting normally shows two peaks above 65 °C, and turning twice is usually enough.
3. Keep the temperature within 55–65 °C and keep the pile aerated. Without enough air the pile turns anaerobic and starts to smell.
4. Composting is complete in about 7–12 days, depending on local temperature and how often the pile is turned. The material turns dark brown and cools to ambient temperature.

Ground windrows use a crawler turner. Composting pits or troughs use a trough turner.

Finishing: powder or granules

1. Screen the composted material. The fine fraction can be sold directly as powder fertilizer.
2. Send oversize lumps through a crusher and back to the screen.
3. Granulate the screened material.
4. Dry the granules to the required moisture. Smaller lines can omit this step.
5. Cool the granules so that they store well.
6. Lift the product to a finished-goods bin and bag it on an automatic weigher. Renyuan's reference layouts bag 3–6 bags per minute.

Sizing a cow dung line

Renyuan recommends a single line capacity of 1–10 t/h. A smaller line does not reach an economical scale, and a larger one makes raw material and product logistics harder. A 10,000 t/yr cow dung plant needs roughly 600–1,000 m² of floor area.

What to send us for a configuration

• Herd size, daily manure tonnage and how manure is collected
• Moisture of the manure as collected
• Bulking materials available locally (straw, sawdust, mushroom residue)
• Powder or granular product and planned annual output
• Whether the plant will be built on the farm site