Manure removal and drying in poultry houses — belts and pits
Manure (droppings consisting of faeces and urine combined) accumulates in the house and decomposes, releasing ammonia — a pungent, harmful gas that damages the respiratory tracts of birds and people. An efficient manure removal system combined with belt drying reduces ammonia, improves air quality and supports flock health.
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Poultry manure is a mixture of faeces and urine — birds excrete both through a single opening (the cloaca). Fresh, healthy droppings have a distinct shape: dark grey with a white urate cap. As manure sits in the house, bacteria break down uric acid and proteins, releasing ammonia. Even at concentrations of around 20–25 ppm (parts per million), ammonia irritates the eyes and respiratory tracts of birds; at higher levels it causes respiratory disease, suppressed immunity and poorer production results.
Why does rapid manure removal make such a difference?
The less time manure sits in the house, the less ammonia is produced. Systems that remove manure several times a week (manure belts) maintain lower ammonia levels than those where manure sits for weeks (deep pit) or for an entire production cycle (litter systems). Manure moisture also matters — wet manure produces more ammonia than dry. That is why drying complements removal. For ventilation, which affects air and manure moisture, see the guide on poultry house ventilation — broilers.
What is belt drying of manure?
Belt drying means blowing air along manure belts via perforated pipes or nozzles. The airflow removes moisture from the manure before it is conveyed out of the house. Drier manure weighs less (cheaper to transport), releases less ammonia, has better structure as a fertiliser and resists re-wetting during storage. It is a simple measure that significantly improves air quality and fertiliser value.
Three main manure removal systems — how they work and how they differ
The choice of system depends on the housing type (cages, aviaries, litter floors), house size and budget. Below is a comparison of the three most common solutions.
Manure belts (belt conveyor)
The most popular system in cage and aviary layer houses and in some hatcheries. A horizontal belt of plastic or rubber runs under each tier of cages or aviary levels. Droppings fall onto the belt and remain until the conveyor is activated. Several times a week (or daily) the belt moves and drops the manure onto a cross conveyor that carries it outside to a trailer or covered store. Frequent emptying means low ammonia. Belts can be fitted with a drying system (air supply pipes). The downsides are installation cost and the need for regular belt maintenance.
Under-floor channels — deep pit
In this system a deep concrete or earthen channel lies beneath the slats or wire floor (below the cage tier). Manure falls freely into the channel and accumulates there for months — often for an entire production cycle or year. Removal is infrequent: every few months or annually, using specialist equipment (pump vehicle or front loader). The advantage is simplicity — no moving parts to service. The disadvantage is the long dwell time, which favours ammonia generation; without drying, ammonia levels can be high. Mainly used in cage layer houses in North America and increasingly rare in Europe.
Litter-based housing — manure mixed with bedding
In litter systems (broilers, turkeys, geese, floor-housed hens) birds move freely on a floor covered with wood shavings, straw, rice husks or other organic material. Manure mixes with the litter, is partly absorbed and broken down microbiologically. The litter is not removed during the production cycle — it accumulates for the full batch (several weeks). Litter and manure are removed only at the end of the cycle, when the house is cleaned and disinfected. The advantage is simplicity and good bird welfare (natural behaviours). The disadvantage is a high risk of ammonia spikes if the litter becomes wet or compacted — which is why litter management and ventilation are critical here. See the guide on cage, litter and aviary housing for a comparison.
How belt drying works and why it is worth doing
Belt drying means blowing air across manure on the belts before it is conveyed out. This simple measure delivers concrete benefits: less ammonia, lighter manure and better fertiliser.
What a belt drying system looks like
A perforated plastic pipe (or nozzle strip) is installed along each manure belt, and a fan forces air from outside or from the house through it. The airstream blows across the surface of the manure on the belt and removes moisture. The air can be heated (which gives better results in winter), but even unheated air improves the situation in warmer seasons. The longer the manure rests on the belt before removal, the more moisture can be extracted — but dwell time should still be limited because of ammonia production.
How much moisture can be removed from manure
Fresh poultry manure has a water content of around 70–80% by weight. Well-dried belt manure can reach 50–60% water or less — a significant difference. Less moisture means less ammonia (the reaction producing ammonia proceeds faster in wet conditions), cheaper transport and better fertiliser value (more nitrogen stays in a less volatile form). Actual results depend on air temperature and humidity in the house, airflow through the pipes and dwell time on the belt.
Belt drying and house air quality
Blowing air across the belts limits ammonia evaporation from the manure before it reaches the cross conveyor. This is especially important in multi-tier cage layer houses — without drying, manure on the lower belts would contaminate the house air for hours. The combination of frequent belt removal and drying gives the best air quality results of any available system.
What efficient manure removal and drying deliver
The effects are felt at several levels — from bird health, through production costs, to fertiliser value.
Lower ammonia and healthier birds
Ammonia irritates the respiratory tract, suppresses immunity and predisposes birds to disease — especially respiratory infections in layers and broilers. Lower ammonia (ideal: below 10 ppm, acceptable: below 20–25 ppm) means fewer disease outbreaks, lower medication use and better production results. Healthy lungs are also an important animal welfare indicator.
Fewer flies and rodents
Fresh, moist manure attracts flies — larvae develop in wet organic matter. Frequent removal breaks the fly life cycle and reduces populations. Dry manure that is quickly removed is also less attractive to rodents seeking food and shelter. For comprehensive pest control, see the guide on pest and wild bird control.
Lighter and cheaper to transport
Manure that has lost 20–30 percentage points of moisture on the belts is noticeably lighter than fresh manure. This directly reduces transport costs to a biogas plant, composting facility or field — fewer loads, less fuel, lower costs.
More valuable fertiliser with higher nitrogen content
Ammonia escaping from wet manure is lost nitrogen. Dry manure retains more nitrogen in a less volatile form — making it a richer organic fertiliser. Poultry manure is high in phosphorus, nitrogen and potassium; once dried and composted it is valued by arable farmers. Its application is regulated by the nitrate action programme — see nitrate action programme — farm fertiliser planning. For manure utilisation options, see poultry manure utilisation.
Better house humidity
High air and litter moisture creates conditions that favour fungal and bacterial disease. Rapid manure removal and drying reduce the moisture released into the house air by fermenting organic matter. This supports ventilation and makes it easier to maintain optimal humidity (typically 50–70% for layers and broilers).
Safer working conditions
High ammonia concentrations harm not only birds but also the people working in the house. Above 25 ppm, workers notice burning eyes and nose; prolonged exposure risks respiratory irritation. An efficient manure removal system protects the health of farmers and farm staff.
Common mistakes in manure management
A few typical mistakes that lead to rising ammonia, poorer flock health or economic losses.
Too infrequent belt emptying
Belts run only once a week or less frequently lose the main advantage of the system — limiting manure dwell time. Belt manufacturers and production advisors recommend emptying every 2–3 days, and daily in summer or at high stocking densities. Use an ammonia meter to calibrate the frequency to your house conditions.
No drying system or insufficient airflow
Installing a belt drying system but setting too low an airflow rate, or allowing nozzles to become blocked, gives poor results. Regularly check pipes and nozzles for blockages and match airflow to manure output and climate. In winter, lower outdoor temperatures slow drying — consider heating the supply air or increasing the flow rate.
Wet litter in floor housing — ignored
Wet, caked patches in the litter are an alarm signal: the most common causes are drinker leaks, excessive stocking density or poor ventilation. Fix the drinkers and check the ventilation. Remove wet patches and top up with dry material (shavings, straw). Ignoring wet patches leads to local ammonia spikes and footpad dermatitis within days.
Neglecting belt and conveyor maintenance
A torn belt, broken drive or blocked cross conveyor is a breakdown that can mean days without manure transport — causing rapid ammonia rise and flock stress. Lubricate bearings regularly, check belt tension and drives, and schedule maintenance before the peak production season.
Frequently asked questions about manure removal in poultry houses
What is poultry manure and why does it produce ammonia?add
Poultry manure is a mixture of faeces and urine excreted together through a single opening (the cloaca). It contains large amounts of nitrogen in the form of uric acid and urea. As the manure sits, bacteria break these compounds down and release ammonia — a pungent, colourless gas harmful to birds and people. The higher the temperature and humidity, the faster ammonia is produced. Rapid removal and drying are therefore the foundation of ammonia prevention.
How often should manure belts be emptied?add
The recommended frequency is every 2–3 days under normal conditions, and daily in summer or at high stocking densities. The best guide is the ammonia concentration in the house — if it exceeds 10–15 ppm, increase the emptying frequency or improve the drying system. An ammonia meter is an inexpensive tool that lets you manage the system based on real data.
What is the difference between a deep-pit system and manure belts?add
In a deep-pit system, manure falls below the slats and accumulates there for many weeks or months — removal is infrequent. Manure belts convey manure out of the house several times a week or daily. Belts with drying give lower ammonia levels but require more investment and servicing. A deep pit is simpler and cheaper to build but ammonia can be a problem without good ventilation.
Is poultry manure a good fertiliser?add
Yes — poultry manure is one of the richer organic fertilisers. It contains large amounts of nitrogen, phosphorus and potassium as well as micronutrients. Dried manure has higher fertiliser value (less nitrogen escapes as ammonia). However, its application must comply with the nitrate action programme regulations — for doses, timing and buffer zones see nitrate action programme — farm fertiliser planning.
Is belt drying economically worthwhile?add
In most cases, yes. Lower ammonia levels translate into better flock health and lower treatment costs. Lighter manure means lower transport costs. Dry manure fetches a better price or is easier to sell as fertiliser. Installation costs (pipes, fan, electricity) typically pay back within a few years, and the health benefits can be seen immediately. More on manure utilisation in the guide on poultry manure utilisation.
What should I do if the litter in my floor house is very wet?add
First, find the moisture source — most commonly drinker leaks, poor ventilation or excessive stocking density. Fix the drinkers and check the ventilation. Remove wet patches and top up with dry litter (shavings, straw). If the whole house has wet litter, increase ventilation and heating. Do not ignore wet litter — ammonia rises rapidly and footpad dermatitis can appear within days.
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