Manure Composting Systems

Fermentation is where manure stops being a waste. Get the moisture, carbon ratio, airflow and turning frequency right and you get mature compost in 10–15 days; get them wrong and the same pile sits for two months and still smells.

Windrow, fermentation channel and in-vessel systems for every site and climate
Turners from small self-propelled machines to rail-mounted groove systems
Forced aeration and covered fermentation where odour or rainfall is a constraint

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At a glance

Fermentation time: 7–15 days thermophilic, plus maturation
Target temperature: 55–65 °C core for at least 3 consecutive days
Moisture: 50–60% at start, 25–30% at the end
Carbon to nitrogen ratio: 25–30:1 at start

What composting actually does to manure

Composting is controlled aerobic decomposition. Micro-organisms consume the readily degradable organic matter in manure, and in doing so they raise the temperature of the pile. Above 55 °C, pathogens, weed seeds and fly larvae are destroyed; the organic matter is converted into stable humus; the carbon-to-nitrogen ratio falls towards the 12–15:1 range typical of mature compost; and the smell disappears because the anaerobic pockets that generated hydrogen sulphide and ammonia no longer exist.

That process only works if four conditions are held simultaneously. There must be enough oxygen, which in practice means turning the pile or forcing air through it. Moisture must stay between 50% and 60%, because a dry pile stops working and a wet pile turns anaerobic. The carbon-to-nitrogen ratio must be near 25–30:1, which is why manure is almost always blended with straw, sawdust or rice hull. And the pile must be large enough to insulate itself: a heap smaller than about 1 m³ loses heat faster than the microbes generate it.

Getting these four right is the difference between compost in a fortnight and a smelly heap in six months. It is also the part of a manure fertilizer project where we see the widest variation between a plant that produces consistent, sellable product and one that produces a variable material that no distributor will commit to buying.

Four system types

Choose the system by site, climate, scale and how close the nearest neighbour is.

Open windrow composting

Long piles on a concrete pad, turned by a self-propelled or crawler turner. The lowest-cost system with the most flexibility, and the standard choice for farms with space and a dry climate.

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Fermentation channel (groove) composting

Three-walled channels with a rail-mounted groove turner. Saves roughly 40% of the floor area because piles can be deeper, and gives more consistent fermentation in wet climates.

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In-vessel fermentation

Closed tanks or tunnels with forced aeration and temperature control. Primary fermentation in 7–10 days regardless of weather, minimal odour and near-zero leachate — the right choice for poultry manure and urban sites.

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Vermicomposting

Earthworms convert pre-composted manure into vermicompost, a premium product for nurseries and horticulture. Slower and more labour-intensive, but it commands the highest price per tonne in many markets.

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Choosing between windrow, channel and in-vessel

	Open windrow	Fermentation channel	In-vessel
Fermentation time	10–15 days plus maturation	10–15 days	7–10 days
Floor area	Largest	About 40% less than windrow	Smallest
Climate dependence	High — rain and cold slow it down	Moderate; channels drain better	None
Odour control	Depends on management	Good	Best — exhaust can be filtered
Leachate	Needs a drained pad and a lagoon	Collected in the channel	Almost none
Capital cost	Lowest	Moderate	Highest
Best for	Farms with land and a dry climate	Wet climates, limited land	Poultry manure, urban sites, cold climates

Design rules for a composting system that works

Build the pad from reinforced concrete with a 1–2% slope and a collection drain. Leachate from a composting pad is a strong, high-nitrogen effluent and must be captured, not allowed to run into a watercourse.
Size windrows at 1.2–1.8 m high and 2–3 m wide. Smaller piles lose heat; larger piles compact at the base and go anaerobic.
Leave at least 1 m between windrows for turning, and plan the turning route so the turner never has to reverse into a blind corner.
Blend carbon material at roughly 3 parts manure to 1 part straw, rice hull or sawdust by volume. This is a starting point, not a rule — the correct ratio comes from the carbon and nitrogen analysis of your own materials.
Turn 2–3 times a day in the first week, then reduce to once every two to three days. Over-turning after the thermophilic phase wastes fuel and cools the pile without benefit.
Cover the fermentation area in wet climates. Rain falling on a working pile adds water you then have to remove, either by longer turning or in the dryer.
Record the core temperature daily. It is the cheapest and most reliable indicator you have that fermentation is proceeding correctly, and it also evidences pathogen reduction for registration.

When fermentation is finished

The standard test on a farm is simple: the pile no longer re-heats after turning, the core temperature has fallen to ambient, the material is dark brown to black, it crumbles rather than smears when squeezed, and it smells of forest floor rather than of ammonia or manure. Under favourable conditions that is reached in 20–30 days from building the pile; with forced aeration and good management, in 15–20.

For commercial fertilizer production we recommend going one step further and allowing a maturation period, sometimes called secondary composting. Immediately after the thermophilic phase the compost can still be phytotoxic — it contains organic acids and a high ammonia concentration that inhibit root growth. Two to four weeks of maturing, without forced aeration and with occasional turning, allows those compounds to break down. If you are selling to nurseries or into a market where a germination test is used, this stage is not optional.

Equipment gallery

Photographed in our Xingyang workshop and on customer sites. Watermark-free, no phone numbers.

Manure Composting Systems — Shunxin Composting Systems photo 1

Manure Composting Systems — Shunxin Composting Systems photo 2

Manure Composting Systems — Shunxin Composting Systems photo 3

Manure Composting Systems — Shunxin Composting Systems photo 4

Manure Composting Systems — Shunxin Composting Systems photo 5

Frequently asked questions

How long does it take to compost animal manure?

With a turner and correct moisture, the thermophilic phase takes about 10–15 days and the pile is then ready for a maturation period of two to four weeks. That gives usable compost in 20–30 days from building the pile. In-vessel fermentation shortens the primary phase to 7–10 days. A pile that has not been turned, or that was built too wet, can take three months and still be immature.

What moisture should a manure compost pile be?

50–60% at the start. The practical field test is the squeeze test: pick up a handful and squeeze it — it should feel like a wrung-out sponge, with a few drops of water visible but none running freely. Above 65% the pore spaces fill with water, air cannot penetrate and the pile turns anaerobic; below 40% microbial activity slows sharply.

Do I need to add anything to manure before composting?

Usually a carbon source, because manure is high in nitrogen and low in available carbon. Straw, rice hull, sawdust, chopped maize stalk or shredded green waste are all suitable, blended at roughly 3 parts manure to 1 part carbon material by volume. A fermentation inoculant can speed up the start of the process, and it is worth using on poultry and pig manure where the ammonia load is high.

How hot should a compost pile get?

The target is 55–65 °C in the core, held for at least three consecutive days. That is the temperature band in which pathogens and weed seeds are destroyed. Below 45 °C the process is too slow and pathogens survive; above 70 °C the microbial population itself is damaged and fermentation stalls, which is why monitoring and timely turning matter.

Can I compost manure in winter?

Yes, but the pile must be larger and the fermentation will be slower at the surface. The core of a well-built windrow of 1.5 m or more will keep working in freezing weather because the microbial heat generation is internal. In very cold climates, in-vessel fermentation or a covered channel is the better answer, because insulation and forced aeration remove the weather dependency entirely.