GB2073771A

GB2073771A - Poultry rearing process

Info

Publication number: GB2073771A
Application number: GB8011961A
Authority: GB
Original assignee: Marshall Newbridge Ltd D B
Current assignee: Marshall Newbridge Ltd D B
Priority date: 1980-04-11
Filing date: 1980-04-11
Publication date: 1981-10-21

Abstract

A poultry rearing process involves rearing the birds from day-old chicks and then, after removal of the mature birds, removing the poultry litter comprising the soiled shavings and chicken excrement and burning it, either freshly cleared or after storage under an aerobic fermentation conditions, to provide heat for rearing a subsequent batch of birds. The extraction of ash from the burner automatically and the ash is loaded into a skip for removal from site. The exhaust gas of combustion is cleansed by passing through a multi-cyclone dust separator and then through a water scrubber.

Description

SPECIFICATION Poultry rearing process The present invention relates to a poultry rearing process, and in particular to a process for rearing batches of poultry starting from very young birds.

In poultry rearing, for example in the batch rearing of chickens from day-old chicks, it has been known to prepare the broiler house for batch rearing by laying down a bed of wood shavings to provide a surface on which the day-old chicks can be placed. As the batch of chicks matures, the same base of wood shavings is left in the broiler house and by the time the batch of chickens has reached slaughtering age, anything from 40 to 70 days after the start of the rearing process, the wood shavings have become mixed with chicken droppings with the result that the moisture content has become relatively high, and the resulting manure can be used as an agricultural fertiliser.However, some of the costs recovered from this use of the poultry litter as a fertiliser has to be offset against the transportation and handling charges incurred as the poultry litter is passed from the specialist chicken breeder to the farmer requiring the fertiliser.

We now propose a poultry rearing process in which a batch of young birds is reared in a rearing location then, after removal of the mature birds from the rearing location, the poultry litter is itself removed and burned to provide heat for warming a subsequent batch of birds.

Advantageously the heat is transmitted from the burner to the rearing chamber, for example a broiler house, by using the heat of the burner to produce hot water under pressure, or steam, which can be transmitted to at least one heat exchange in the rearing chamber. The useful heat may then be transferred from the heat exchanger to the rearing chamber by way of forced draught of ventilation air over or through the heat exchanger.

The poultry litter, comprising a mixture of poultry excrement and wood shavings, may bestored before burning. Combustion may take place soon after clearing out of the rearing chamber, or the stored litter may be kept for at least three months, between removal from the rearing chamber and the time of subsequent burning, under conditions favourable to natural anaerobic fermentation in order to enable the moisture content to reduce to a more favourable value for combustion purposes.

In order that the present invention may be more readily understood, there now follows a description of two embodiments of a poultry rearing process in accordance with the present invention, given merely by way of example.

In each type of process, a broiler house capable of accommodating 36,000 chickens from the dayold chick stage is, after clearance of a previous batch of chickens for slaughtering, first provided with a bedding layer consisting of 6 to 8 tons of whitewood shavings. The day-old chicks are then introduced onto this bed.

The batch of chicks is reared to slaughtering weight, which is attained some 6 to 9 weeks later.

Once the chickens have reached slaughtering weight the entire batch is removed from the broiler house and the chicken litter, in this case the soiled wood shavings, is removed and conveyed to a silo.

The total weight of the chicken litter removed from the one broiler house has been found to be of the order of 50 tons.

In one embodiment of the process, the chicken litter is kept in the storage silo for at least three months, under conditions favourable to anaerobic fermentation, until the moisture content has attained a value of the order of 20 to 25% by weight. It has been found that the calorific value of a sample of chicken litter which has been obtained under these conditions and stored for one year can be 5,300 Btu./lbs. and the moisture content is 23% by weight. An acceptable calorific value and a sufficiently low moisture content can be attained in less than one year; for example a storage time of approximately six months is preferred.

After storage and anaerobic fermention, the chicken litter is found to have a friable consistency and to be capable of stoking automatically into a solid fuel burner from which the waste gases can be passed over a heat exchanger to generate hot water or even steam. The hot water or steam can then be pumped to the same broiler house from which the chicken litter has previously been cleared, thereby providing the necessary heat for a subsequent batch of birds.

It has been found that the above-described system is capable of maintaining a broiler house temperature at a value of the order of 900F at the start of rearing of each batch of birds, dropping gradually to a minimum value of 700F as the birds approach slaughtering weight.

The process described above is particularly useful in installations where there is a considerable number of broiler houses operating at staggered intervals, so that while one broiler house in the set has just had its day-old chicks introduced there will be other broiler houses at various different stages ranging from those which have just been cleared to those with nearly mature birds. In this way a substantially constant output of chicken litter will be available and equally there will be a substantially constant demand for heat.

In a second embodiment of the process, the litter is burned immediately or almost immediately (i.e. before any substantial fermentation has taken place). In this case the poultry litter is capable of combustion without difficulty in igniting it, although the litter is more readily handled by automatic stoking apparatus after it has been allowed to dry out at least partially, by fermentation. In this second embodiment any storage of the litter will be of relatively short duration, i.e. up to 3 months.

When the time comes for burning of the litter a batch of the litter is removed from the storage silo and transferred to a stoker supply silo from which it is automatically withdrawn and introduced into the burner.

By appropriate control of the various heat exchangers at the broiler house end of the heat transmission system with each of the above describedembodiments of process, it is possible to ensure that each broiler house is heated to the appropriate temperature suitable for the stage of maturity of the batch of birds in that broiler house.

The hot water or steam generated in the heat exchanger of the burner apparatus is pumped to appropriate ones of the broiler houses of the set and is there passed through a heat exchanger over which a forced air flow is generated in order to distribute the available heat to the atmosphere in the broiler house. The ventilation of the broiler house may either be a closed circuit in which all the air circulates by way of the heat exchanger, or may be on the open circuit principle in which fresh ventilation air is introduced over the heat exchanger, or thirdly a combination of closed circuit and fesh air ventilation may be employed.

Multi-stage heat exchange at the burner end of the heat transmission system may be used, if desired.

The exhaust gas leaving the heat exchanger at the burner end of the heat transmission system is subsequently passed through a dust separator, for example ajnulti-cyclone separator, in order to remove dust from the exhaust gas before discharge into the atmosphere.

It is preferable for the exhaust gas from which the dust has just been stripped in the separator then to be passed through a water scrubber to remove other unwanted fumes from the exhaust gas.

An automatically-operating mechanical ash removal system may be provided, to extract the ash from the burner, thereby avoiding choking of the burner.

The silo in which the anaerobic fermentation/storage of the poultry litter takes place may have a vent outlet provided with a cyclone separator for removal of particles from the vented gas.

The ash removing equipment may include a screw conveyor which loads the waste ash into a suitable container, for example a skip, for removal from site.

Although the preferred examples given above illustrate the process in terms of chicken rearing, other poultry may be reared by this process. Also, although the chicken litter is in this case based on whitewood shavings, any other starting material such as straw and shredded paper may instead be used.

Claims

1. A poultry rearing process in which a batch of young birds is reared in a rearing location then, after removal of the mature birds from the rearing location, the poultry litter is itself removed and burned to provide heat for warming a subsequent batch of birds.

2. A process according to claim 1, wherein before introduction of young birds to the rearing chamber the chamber is given a bed of combustible material to provide a base on which the birds can be reared, and then this combustible material forms a part of the litter which is subsequently stored and burned.

3. A process according to claim 1 or 2, wherein, before burning, the poultry litter is stored under fermentation conditions during which its moisture content reduces.

4. A process according to any one of the preceding claims, wherein the poultry litter is stored under conditions favourable to anaerobic fermentation.

5. A process according to claim 4, wherein the poultry litter is stored for at least three months before combustion.

6. A process according to claim 5, wherein the poultry litter is stored for from six months to a year before combustion.

7. A process according to claim 6, wherein the storage step lasts for approximately one year.

8. A process according to any one of claims 4 to 7, wherein the litter is stored for long enough to allow the moisture content to fall to a value in the range 20 to 25% by weight.

9. A process according to any one of the preceding claims, wherein the waste gas of combustion is passed through a heat exchanger to generate hot water under pressure, or steam, for transmission to the rearing location for a subsequent batch of birds.

10. A process according to claim 9, wherein the hot water or steam is pumped to at least one further heat exchanger at the rearing location, or at another rearing location, where the useful heat from the water or steam is extracted.

11. A process according to claim 10, in which extraction of the useful heat from the water or steam is achieved by a forced air flow over the further heat exchanger or exchangers of the rearing location(s).

12. A process according to claim 11 , wherein the ventilation of the rearing location is by way of a closed circulating system including the further heat exchanger.

13.-A process according to claim 11, wherein the ventilation of the rearing location is by way of a fresh air intake passed over the further heat exchanger.

14. A process according to claims 12 and 13, wherein the ventilation of the rearing location includes both a circulating current and a fresh air ventilation current, in order to control the moisture content in the rearing location to a desired value.

1 5. A process according to any one of the preceding claims, wherein ash is extracted continuously from the burner by way of an automatic ash extraction system.

1 6. A process according to claim 15, wherein the automatic ash extraction system is effective to load the waste ash into a container for removal from the site.

17. A process according to any one of the preceding claims, wherein the spent combustion air from the burner, after passing through a heat exchanger to remove the heat from the air, is passed to a dust separator.

18. A process according to claim 17, wherein the dust separator is a multi-cyclone separator.

1 9. A process according to claim 17 or 18, wherein the spent combustion gas is passed through a scrubber to remove unwanted fumes from the gas before discharge of the gas to atmosphere.

20. A poultry rearing process according to claim 1, and substantially as hereinbefore described.