Method and device for increasing the dry matter content of manure by storing stackable manure, in particular poultry manure

Abstract: For increasing the dry matter content of manure, in particular poulty manure, this manure is stored in at least one essentially closed, roofed chamber having cavity walls (2), of which the inner walls (2b) are gas-permeable. Stable air or outside air being admitted to the cavity. In this roofed chamber (1) a controlled amount of air is passed over the manure at least partly via the cavity (8). The mixture, produced in the chamber by heating, of essentially ammonia, smell and water vapour penetrates at least partly via the inner walls into the cavity (8) and is removed from the chamber with the ventilation air and is converted into liquid aqueous ammonia in a chemical scrubber (16). The pH is kept at a value lower than 6 by metered addition of acid. Condensed water formed by condensation on the uninsulated outer walls and fed into the cavity by dripping from the insulated sloping roof is drained therefrom.

Description: The invention relates to a method for increasing the dry matter content of manure by storing stackable manure, in particular poultry manure, which manure is stored in at least one essentially sealed, roofed chamber having cavity walls, of which the inner walls are gas-permeable, stable air or outside air being admitted to the cavity. Such a method is known from CH-A-121,822. Poultry manure is normally stored in a barn ventilated by the wind. During storage, the dry matter content increases considerably as a result of heating (to more than 70%), ammonia, smell and moisture which are blown into the environment being released. This is bad for the environment and can result in odour nuisance. The object of the method according to CH-A-121,822 is to promote the heating by supplying air and collect the liquid produced during the fermentation and drain it into a pit. In this process, it will only partly be possible to prevent the emission of ammonia and moisture into the environment since the gases which are harmful to the environment are not bound and converted. The object of the invention is to eliminate this drawback and to provide a method specified in the introduction with which the gases produced by heating in a relatively cheap, closed chamber with uninsulated walls are effectively removed and are subjected to a wash treatment in order to remove and convert substances harmful to the environment. According to the invention, the method mentioned in the introduction is characterized for this purpose in that, in the chamber mentioned, a controlled amount of ventilation air is passed over the manure at least partly via the cavity, in that a mixture of essentially ammonia smell and water vapour, produced in the chamber by heating, penetrates at least partly via the inner walls into the cavity and is removed from the chamber with said ventilation air and is converted into liquid aqueous ammonia in a chemical scrubber, the pH being kept at a value lower than 6 by metered addition of acid, and in that condensed water formed by condensation on the uninsulated outer walls and fed into the cavity by dripping from the uninsulated sloping roof is drained therefrom. By making use of cavity walls and using no insulated walls, the condensed moisture can be efficiently removed without attacking the structure of the building. The ventilation flow rate can be adjusted to the amount of manure supplied and the quality (dry matter content) of said manure. Depending on the dry matter content of the manure, the condensed water formed in, and fed into, the cavity could be sprayed at least partly over the stacked manure. The same applies to the ammonia-containing liquid of the scrubber. As a result of heating, the dry matter content increases owing to the evaporation of moisture and ammonia from, for example, about 45% to more than 70%. The filling of the chamber with manure does not normally take place all at once but in layers. If a poultry keeper were to work with a single manure storage chamber, a large amount of ammonia which would disappear into the environment via the open doors of the chamber would be released on removing the manure, and a considerable amount of ventilation would have to be carried out to be able to perform the operations. The capacity of the scrubber is not designed for such a large emission of ammonia. It is therefore preferable that a number of closed storage chambers are used in such a manner that, while the dry matter content can increase to more than 70% by heating in one or more filled chambers, one or more other chambers are being partly filled. The invention also relates to a device for carrying out the method according to the invention, comprising at least one essentially closed, roofed chamber having cavity walls, of which the inner walls are gas-permeable and means for admitting stable air or outside air to the cavity. The device is characterized by means for admitting a controlled amount of ventilation air into the space above the manure at least partly via the cavity, means for removing the mixture, produced by heating and collecting in the space above the manure, of essentially ammonia smell and water vapour, along with the ventilation air, to a chemical scrubber in order to convert ammonia into liquid aqueous ammonia, means for metering acid into the scrubber and means for draining the condensed water present in the cavity. The sloping, uninsulated roof of the chamber may have a drip edge for condensation above the cavity. Building materials and structural parts are chosen and treated in such a way that they are not attacked or hardly attacked by water vapour and gases originating from the manure. The invention will now be explained in greater detail by reference to the figures. Figure 1 shows a plan view of a device suitable for carrying out the method according to the invention. Figure 2 shows a section. The storage device shown for stackable manure comprises an essentially closed building 1 having cavity walls 2 and a sloping, uninsulated roof 3. The chamber is divided into two compartments 1a and 1b by a partition 4. To feed fresh stackable manure into the compartments, use is made of loading elevators 5a and 5b, which are supplied by a conveyor 6 which extends out of a poultry shed 7. The cavity walls comprise an uninsulated, impermeable outer wall 2a and a ventilating gas-permeable inner wall 2b, of which at least the lowermost section is adequately resistant to the pressure of a stack of manure. Via the cavity 8, ventilation air is fed into the chamber 1 by means of air supply lines 9a in a controlled manner. For each tonne of manure, the air supply is, for example, 50 to 200 m 3 per hour. The chosen amount of air per tonne of manure is dependent on the quality (dry matter content) of the manure. The manure is provided in layers, heating takes place in the manure, as a result of which water vapour and ammonia are released and these are fed out of the chamber via the ventilation outlet 9 together with the air removed. The consequence is that the dry matter content of the manure increases to more than 70%. This manure is used for environmentally friendly fertilization of soil. The hot gases produced during the heating penetrate into the cavity 8 partly via the inner wall 2b. Condensation of moisture takes place on the uninsulated outer wall 2a. The condensed water formed on the uninsulated sloping roof 3 can also be fed into the cavity 8 via drip edges 10. The contaminated condensed water in the cavity 8 is fed via channels 11 to a collecting pit 12 and can be sprayed over the stored manure by means of a pump 13, a line 14 and spray heads 15. As a result of this controlled treatment of condensation, no drainage, or a small amount of drainage, of the water contaminated with ammonia will be necessary. The heavily contaminated outlet gases are fed via the outlet 9 to a chemical scrubber 16 which serves to scrub ammonia out of the outlet gases. Said scrubber contains a column of packed material 17 having a spraying device 18 above it and a liquid collection tank 19 below it, which contains scrubbing liquid with, for example, dilute sulphuric acid. Scrubbing liquid can be conveyed from the tank 19 to a spraying device 18 by means of a circulating pump 20. The sprayed liquid trickles downwards through the column 17 in which process the gaseous ammonia is transferred to the liquid phase and flows back into the tank 19. In this process the following reactions take place: NH 3 (gas) ⇆ NH 3 (water) NH 3 (water)+H 2 O⇆NH 4 + + OH - NH 4 OH+H 2 SO 4 ⇆ NH 4 SO 4 +H 2 O It is advisable to site the chemical scrubber in a sealed insulated chamber in the shed. Siting the scrubber in the chamber heated by the manure will limit the formation of condensation in the scrubber (as small a drain as possible). If no acid is added, the pH will become too high. That is why the pH is measured with the aid of a pH electrode 21 and, for example, sulphuric acid can be added to the tank 19 from a tank 22 by means of a pump 23. The acid store and the acid pump 23 may be integrated in the chemical scrubber. Water may be added with the aid of a float regulating system. Occasionally the tank 19 is so contaminated that at least a part of it has to be drained and clean water has to be added. The chemical scrubber may be provided with an apparatus which measures the concentration of contaminants in the scrubbing water and automatically performs the partial drainage of scrubbing water. The concentrated drainage water could be sprayed over the stacked manure. Because the chamber is divided into compartments 1a and 1b, a manure filling can be allowed to compost completely in one compartment and the other compartment can be filled in the meantime. When manure is removed, little nuisance due to ammonia and water vapour will then be experienced. It may be advantageous, especially in winter, to preheat the ventilation air to be fed to the cavities of the walls of the building 1 with the aid of a heat exchanger 24 in the shed 6. The most important advantages of the method and device described are that the ammonia gas produced by heating is not emitted or hardly emitted into the environment, that the chamber in which heating takes place has uninsulated cavity walls and an uninsulated sloping roof and can therefore be comparatively cheap, and that condensation and drainage water collected can still be evaporated completely or partly via the heated manure in a low-emission manner.

Claims: Process for increasing the dry matter content of manure by storing stackable manure, in particular poultry manure, which manure is stored in at least one essentially closed, roofed chamber (1) having cavity walls (2), of which the inner walls (2b) are gas-permeable, stable or outside air being admitted to the cavity (8), characterized in that, in the chamber (1) mentioned, a controlled amount of ventilation air is passed over the manure at least partly via the cavity (8), in that a mixture of essentially ammonia, smell and water vapour, produced in the chamber by heating, penetrates at least partly via the inner walls (2b) into the cavity (8) and is removed from the chamber with said ventilation air and is converted into liquid aqueous ammonia in a chemical scrubber (16), the pH being kept at a value lower than 6 by metered addition of acid, and in that condensed water formed by condensation on the uninsulated outer walls (2a) and fed into the cavity (8) by dripping from the uninsulated sloping roof (3) is drained therefrom. Process according to claim 1, characterized in that the condensed water formed in, and fed into the cavity is at least partly sprayed over the stacked manure. Process according to claim 1 or 2, characterized in that the ammonia-containing liquid from the chemical scrubber (16) is sprayed over the stacked manure. Process according to one of the preceding claims, characterized in that a number of closed storage chambers (1) are used in such a way that, while the dry matter content increases as a result of heating to a value above 70% in one or more filled chambers, one or more other chambers (1) are being filled. Apparatus for carrying out the process according to claim 1, comprising at least one essentially closed, roofed chamber (1) having cavity walls (2), of which the inner walls (2b) are gas-permeable, and means for admitting stable or outside air to the cavity (8), characterized by means (9a) for admitting a controlled amount of ventilation air into the space above the manure at least partly via the cavity (8), means for removing the mixture of essentially ammonia, smell and water vapour, produced by heating and collecting in the space above the manure, along with the ventilation air, to a chemical scrubber (16) in order to convert ammonia into liquid aqueous ammonia, means for metering acid into the scrubber, and means (11) for draining the condensed water present in the cavity. Apparatus according to claim 5, characterized by means (13, 14, 15) for spraying condensed water formed in, or fed into, the cavity (8) at least partly over the manure. Apparatus according to one of claims 5 and 6, characterized by means for spraying the ammonia-containing liquid from the scrubber (16) over the manure.

Inventors: KROODSMA WILLEM, KROODSMA, WILLEM
Applicants: STICHTING INST MECH, STICHTING INSTITUUT VOOR MECHANISATIE ARBEID EN GEBOUWEN
Application year: 1993
Main classification: A01C3
IPC codes: A01C3, A01K31