Solid contents in poultry manure
There are different types of equipments and storage methods used for manure handling depending upon the solid contents which is classified as solid, semi-solid or liquid.
- Solid – the manure solid content is greater than 20%. Broiler manure normally contains approx. 20-25% moisture compared with liquid manures from layers which is 70%. The use of bedding material further contributes to the solids of the manure. To produce solid manure, the liquid must be drained off and the manure dried or bedding added. Then the solid manure can be stacked.
- Semi – solids – contains 5% to 20% solids ( called as slurry)
- Liquid – contains less than 5% solids.
Most poultry operations have different housing and feeding facility, Houses for layer, broiler
Production may vary greatly in size, appearance and arrangement of facilities. There are two
Main types of confined poultry facilities: cage houses and floor houses. Varieties of manure handling systems for these facilities are described below:
(1) Cage House, Deep Pit Systems: The deep pit offers operational advantages over other systems. For example, a separate manure storage facility is not required. In this system, manure is allowed to drop into a 5 to 10 feet deep pit under the cages where the droppings undergo a natural composting drying process. This causes a biological degradation of the wastes and reduces the weight and volume of the manure. Manure is usually removed from the storage twice each year. The success of the pit depends on the extent to which excess water can be excluded. If the manure is wet, the composting process will not occur, resulting in odours, fly problems and the need for frequent cleanouts.
If properly operated, a deep pit may not require cleaning for one to three years depending on the depth of the pit. This is an easy system to manage and requires only a front-end loader and a conventional manure spreader to clean out the pit. The deep pit should be constructed of concrete and be completely sealed to prevent groundwater seepage into the pit and escape of contaminants into the environment. In cases where the water table is very high, construction of the deep pit cage house completely aboveground is recommended.
(2) Cage House, Shallow Pit Systems: This system uses a concrete pit 15 cm to 20 cm (6 to 8 inches) deep to collect the droppings from overhead cages. The manure is allowed to collect for a short time, preferably not more than one week, then it can be scraped into a holding facility with a dragline or tractor mounted scraper. In cases where cleaning on a weekly basis is not practical, the droppings may be allowed to “cone-up” under the cages. In this case, additional air circulation is recommended to dry the manure and reduce odours. Also, the droppings should be covered periodically with sawdust or shavings if the manure storage period is Greater than one week.
(3) Cage House, Liquid Systems: Shallow pit systems can be adapted for liquid Manure handling. In this case, manure is flushed frequently into a suitable liquid Manure holding tank outside the poultry building.
(4) Floor Houses, Litter System: Broilers are often raised on litter for at least part of their lives. Breeders and pullets are raised on litter in many cases. Any clean, absorbent material can be used for litter such as wood shavings, shredded paper products or sawdust if available. The litter should be dry and should not produce excessive amounts of dust. The floor should be covered with fresh litter material prior to the housing of each new flock of birds at a recommended depth of 4 to 8 cm (1.5 to 3 inches). The litter removed from the building must be stored in a suitable storage structure.
Manure from most types of poultry operations is handled and stored as a solid, mostly on the ground. Chicken broilers and broiler breeder flocks are raised in barns which utilize straw or wood shavings for bedding. The manure and bedding accumulates in the barn until it is periodically removed when the flock is replaced. Front end loaders are normally used to remove the manure from the barn and transfer it to the storage area. Regular cleaning of the barn is also important to a successful fly control program. Other fly control measures include removing wet feed during fly breeding season, disposing of dead birds and keeping manure storing areas dark. You can also store manure in enclosed structures, protect ventilation inlets with screens and regularly spray with approved insecticides.
Caged layer chicken and a limited number of breeder barns utilize manure collection and transfer systems which do not involve the use of any bedding material. The manure is in a liquid or semi-solid form and a variety of collection, transfer and storage systems are used. For example, some layer farms use conveyors to move the manure daily to an area in the barn where it is eventually moved to the storage.The components of the various systems for solid, semi-solid and liquid poultry manure are summarized in Table 3.
Manure Handling Systems for Various Types of Wastes
Semi solids / liquids
Front end loaders
Earth moving equipments
Vacuum tank wagons
Continuous flow gutters
Large diameter pipes
POULTRY HOUSING MANAGEMENT FOR ODOUR CONTROL
Very little odour is given off by fresh manure. Once the manure starts to decompose, odour
Production begins. Inside a poultry building, even small deposits of manure are a likely source of odour. Solid manure tends to form fewer odours than liquid manure. By keeping conditions dry, the production of odour is reduced. Good housekeeping is the best management method. While the control of odours within the barn may require additional time or expense, it is beneficial for the welfare of the poultry and the people working within the barn. Frequently, the conditions that contribute to odours also reduce productivity and can make the poultry more susceptible to disease. The following guidelines for poultry housing management are recommended:
! Collect and transfer manure from the barn to storage on a daily basis or every batch (usually every 6 to 7 weeks for broiler operations - layer operations vary) to reduce the production of odours from the building;
! Maintain watering systems to prevent water from being added needlessly to manure and bedding;
! Thoroughly clean and disinfect buildings between successive groups of poultry;
! Do not surpass recommended bird densities in poultry buildings; and
! Remove dust, clean ventilation fans and shafts. Keep dust levels low since odours are absorbed and carried in the air on dust particles.
Ventilation of farm buildings, in addition to controlling the temperature and humidity, also controls the production and build-up of poisonous and odorous gases. The following guidelines should be observed:
! Maintain maximum air flow through poultry buildings. This will assist to keep Conditions as dry as possible and will promote aerobic conditions so that fewer odours are produced. It is also effective in diluting odorous gases as they are released to the outside environment;
! Maintain and repair ventilation fans and ensure they have the appropriate capacity for the number of birds being housed in the building; and
! Assess local conditions such as the prevailing wind direction and velocity when considering poultry building ventilation.
The position, design and height of exhaust outlets affects the dilution of odourous gases outside ofpoultry buildings. In general, higher outlets provide greater dilution of exhaust gases. Options for ventilation design may be discussed with experts in the field. Exhaust gases from poultry buildings may be treated for odour control as part of the ventilation process. Treatment requires additional expenditure, but may be warranted in certain circumstances. For these methods to be effective they must be designed and installed correctly. Qualified professionals should be consulted.
PLANNING A MANURE STORAGE
A storage facility is a permanent structure or location designed and operated to contain manure in an environmentally sound manner for the period of time required to allow the manure to be used as an organic fertilizer. The design of the storage will depend upon:
! The location of the storage;
! The storage capacity required for the poultry operation;
! The characteristics of the manure (such as the amount of solids); and
! The methods of filling and emptying.
Although some design considerations are discussed, producers are advised to contact an agricultural engineer for complete design information. Manure storage structures must also provide the following:
! Flexibility for timing manure spreading;
! Sufficiently impervious to prevent leakage; and
! An appropriate level of odour control.
Groundwater and soil conditions must be evaluated to ensure that the site is suitable for the type of storage planned. For example, where the groundwater levels are near the bottom of the storage, do not use an earthen storage without a suitable liner
The site for the storage must provide the following:
! The storage must be located close enough to the barns to allow for convenient filling and still permit expansion of the facilities;
! It must be accessible by an all-weather road for field spreading equipment;
! If possible, it should be located out of sight of the road and dwellings;
! The storage must be located to avoid collecting surface and roof run-off; and
Install a groundwater controlling drain around the manure facility to prevent the entry of groundwater into both earthen or concrete storages. For earthen structures, this drainage prevents groundwater from entering the storage. Groundwater reduces storage capacity and weakens the manure sealing capacity by lowering the total solids content. For concrete structures, this drainage prevents frost heaving, reduces external groundwater pressure when the storage is empty and prevents water entry.
In order to minimize any risk of pollution, all manure storages are required to meet the minimum separation distances.
Manure storage requirements for poultry farms depend on:
! Management practices and facilities;
! The type and number of animals;
! The amount of water from spillage or from washing;
! The length of storage time needed;
! The amount of precipitation and/or groundwater added to storage contents;
! The amount of dilution water added;
! The amount of evaporation;
! The amount of bedding material used; and
The storage must have some reserve capacity to allow for the accumulation of solids and for precipitation. When the storage is ready for clean out it must have enough capacity to handle a major rainstorm without overflowing
It is important to estimate manure production rates accurately, especially for expensive covered concrete systems. An agricultural engineer should be contacted to assist in the evaluation of these systems. Overflow of the manure storage is a serious environmental concern and therefore is prohibited.
Livestock producers must construct sufficient storage capacity to eliminate the need for winter manure spreading.
This will also help to minimize the extra management time, labour time and equipment use associated with short term storage. It also provides flexibility in:
! Poor weather conditions;
! labor shortages; and
! Equipment breakdowns.
SOLID MANURE STOCKPILES
Solid manure containing larger amounts of bedding is often stored in stockpiles. These storages must:
! be constructed and managed to contain all seepage and runoff;
! be constructed to help divert away or contain runoff from surrounding areas (this has
the added benefit of minimizing manure volume);
! contain a concrete bucking wall to assist filling the bucket if emptying with a front
! provide access for unloading and haul out equipment; and
! depending on soil conditions, be constructed with a sloping concrete slab to prevent
seepage and facilitate collecting the liquid runoff which can then be collected for removal by vacuum tanker or transferred to a separate storage.
SEMI-SOLID MANURE STORAGE
Wet manure and liquid runoff can be contained by a storage consisting of earthen dykes in combination with a reinforced concrete wall. Seepage can also be controlled by a concrete slab, depending on soil conditions at the site. By sloping the slab to the corner opposite the entrance ramp, excess liquids can be removed by vacuum tanker or transferred to a separate storage.
Aramp entrance provides access for the front end loader or other removal equipment. This entrance ramp must be crowned to prevent surface water from the yard entering the storage.
LIQUID MANURE STORAGE
Poultry manure is sometimes stored as a liquid by adding dilution water to facilitate pumping. Liquid poultry manure can be stored in three types of storages:
! concrete tanks below ground;
! lined earthen storages; or
! concrete or steel tanks above ground.
All barns with a proposed system of manure wash down should ideally have a water meter to monitor the volume of water used.
(a) Concrete Tanks Below Ground
The two main benefits of concrete manure storage include:
! Reduced loss of valuable nutrients
! Odours are generally not released except when the manure is agitated before the storage is emptied. Concrete tanks are more costly than earthen storages, but because they are impermeable, they are suitable for use in areas having sandy soils. In areas with a high water table level, above ground storage tanks are preferable. There are also a number of synthetic materials designed for use in earthen storages that provide impermeable barriers without the high
costs of concrete storages. These are discussed under the section on earthen storages. Concrete tanks must be designed to withstand all earth, hydrostatic and live loads. In planning the design of the storage, carefully consider the following:
! How the manure is to be agitated (please note that minimizing agitation reduces odours produced during transfer);
! There must be sufficient access ports for the pump if the tank is to be covered;
! Liquid manure tanks connected to animal buildings must have gas traps or valves between them to prevent gases from entering the building;
! Openings must be covered with grills or covers (these covers must weigh at least 20 kilograms (44 pounds) so they cannot be removed by children or displaced by animals and be of sufficient design so they can not drop through the opening-permanently secure covers with a safety chain);
! Open tanks must be surrounded with a fence (at least 1.2 metres or 4 feet high except where the tank walls extend this distance above the adjacent ground level) to prevent accidental entry into the pit;
! Agitation is more effective when large tanks are divided into a series of compartments; and
MANURE STORAGE FOR ODOUR CONTROL
Most odour causing gases are formed when manure is in storage. In practice, most manure storage is anaerobic (meaning in the absence of oxygen). The anaerobic conditions promote odour production. These gases either escape from the storage to cause immediate problems or are released later during spreading. Fewer odours are produced by solid manure handling systems than by liquid systems. An undisturbed solid manure stack is self sealing so few odours are given off until the pile is disturbed. Covered storages are an effective way to minimize odour generation. Storage covers: (1) reduce occasionalmanureagitation caused by wind and rain; (2) reduce the movement of odourous airfrom storage areas to neighbouring residences; and (3) reduce the addition of water from rain and snow thereby also reducing the total volume of manure to be spread. While in most instances the cost may preclude covering storage areas, in certain circumstances this expense may be justified. When evaluating manure storages, consider the following guidelines to reduce the potential for nuisance odours:
! Provide additional storage volume for greater flexibility in the timing of manure application. This can reduce the likelihood of storage overflow and permit
application to coincide with the most appropriate timing and weather conditions;
! With solid and semi-solid manure management systems, separate the liquid and solid portions of manure in storage to reduce the promotion of anaerobic conditions;
! Avoid the addition of silage effluent and waste food products to the manure storage
reservoir. These combinations create strong odours; and
! Planting a buffer zone of trees around manure storage areas to reduce the movement of air over the manure surface, thereby lowering the amount of odour released. This has the added benefit of removing the storage from the sight of neighbors and improves the image of the farm by providing a pleasant, aesthetically pleasing appearance.
Treatment of manure before it enters long term storage avoids odour problems in storage and during spreading. Treatment systems must be designed to handle the manure volumes generated by the poultry operation. An improperly designed or managed treatment facility will prove unsatisfactory. Often treatment is performed in short-term storage so less expensive reservoirs can be used for the larger, long-term storage. Some treatment methods for odour control are listed in Appendix A. It is important to note these treatments are mostly used in rare cases when dealing with severe odour problems.