Description

The invention relates to a method for processing manure and to a device for performing this method.

It is known that the production of manure in intensive cattle farming along industrial lines has assumed such proportions that the processing thereof involves great problems. The spreading of the manure over agricultural land has contributed to a large extent toward the acidification of the environment and has therefore meanwhile been subject to strict controls, while industrial processing of the manure in special processing plants entails high transport costs and logistic problems.

The invention therefore has for its object to pro¬ vide a manure processing system which overcomes the above drawbacks. This is achieved according to the invention by a manure processing method which is characterized by collec¬ ting the manure, separating it into at least one solid and one liquid fraction and making both fractions suitable for use as fertilizer or nutrient. The manure can thus be pro¬ cessed in simple manner and at small cost on or in the immediate vicinity of the cattle farm where it is produced. Preferably applied variants of the method accor¬ ding to the invention form the subject-matter of the sub dependent claims 2-6.

According to the invention a device for performing the above stated method is provided according to the inven¬ tion with means for collecting manure, first separating means placed in series with the collecting means for separa¬ ting the manure into at least one solid and one liquid fraction and posttreatment means placed in series with the first separating means for making the separated manure fractions suitable for further use. Such a device can be

constructed rapidly and at relatively low cost from simple commercially available components.

A number of preferred embodiments of the manure processing device according to the invention is described in the dependent claims 8-11.

The invention is now elucidated on the basis of a non-limiting embodiment, with reference being made to the annexed drawing, in which: fig. 1 is a block diagram showing the different steps of the processing method according to the invention, fig. 2 is a partly sectional schematic view sho¬ wing a layout of the different parts of the processing device in their mutual relation, fig. 3 is a detail view on enlarged scale of the collecting means of the processing device shown in fig. 2, fig. 4 shows a section along the line IV-IV in fig. 3, and fig. 5 is a detail view on enlarged scale of the first separating means of fig. 2. A method for processing manure according to the invention comprises the successive steps of collecting the manure M in collecting means 1 (fig. 1) , (optionally perio¬ dically) supplying the collected manure O to first separa¬ ting means 2, separating the manure therein into at least one solid fraction S and one liquid fraction L and making both fractions S,L suitable for use as fertilizer or nu¬ trient. Making the solid fraction S suitable for further use comprises composting thereof in composting means 3. The composted solid fraction can then be re-used as fertilizer F without harmful consequences for the environment.

After leaving the first separating means 2 the liquid fraction L is supplied, if necessary or desired via a filtration element or stripper 4, to a cleaning station 5. In this cleaning station, which is further supplied with air A, the liquid fraction is cleaned by bacteriological means. The air herein released is re-routed back into the cleaning process.

The cleaned liquid fraction CL is subsequently separated in second separating means 6 into water W and residual materials R. The latter may therein comprise for instance ammonia concentrate. The clean water can be stored in a storage tank 7, for instance a silo, or can be used again directly as irrigation liquid I.

In the embodiment shown the collecting means 1 (fig. 3) comprise in the embodiment shown a gutter 8 which is recessed into the floor 15 in a cattle shed and which is covered by a grid 9. The animals 10 stand with their rear end directed toward gutter 8 so that their excreta forming the M manure all directly therein. When the gutter 8 is sufficiently filled a flushing liquid under high pressure is sprayed from a number of nozzles 11 into the gutter 8, whereby the manure is flushed to a collection tank 12. Flushing of the gutter 8 can also take place periodically under the control of a control system, for instance flushing cycles of 2 minutes each with an interval of 10 minutes. It is of course also possible for the farmer to sprayer the gutter 8 empty with a portable high pressure spray when he notes that it is full. The clean water from the storage tank 7 can optionally be used as flushing liquid. The collection tank 12 is provided with a sensor 14, for example an ultra¬ sonic sensor, which generates a signal when the level 13 of the manure in the tank reaches a determined limit.

When this signal is received a diaphragm pump 16 (fig. 2) starts which pumps the manure via two non-return valves 17,18 to the first separating means 2. The latter comprise a centrifuge 19 (fig. 5) which is driven by a motor 20 with frequency control. Centrifuge 19 is provided with a stationary central supply pipe 21 through which the collec¬ ted manure O is sprayed via an inlet cone 22 into a for instance 8-spoke blade wheel 23. The manure is flung out of the blade wheel 23 against the conical side wall 24 of centrifuge 19. Arranged in side wall 24 are recesses covered with sieve gratings 25 through which the liquid fraction L of the manure is flung outside, while the solid fraction S sinks downward along the inside of the wall 24 under the

influence of gravity and finally leaves the centrifuge via a closing plate 26. In order to enable removal of all remnants of the solid fraction from the centrifuge this latter is further provided with a flushing conduit 32 from which flushing liquid is periodically sprayed under high pressure via the nozzles 33 against the inside of the centrifuge wall 24.

The solid fraction S, which when it leaves the centrifuge can still contain 20 to 60% by weight of water, is discharged via a conveyor belt 27 (fig. 2) to be compo¬ sted. The liquid fraction L is collected in a housing 28 arranged around centrifuge 19 and pumped by a second di¬ aphragm pump 29 via the filter or stripper unit 4 through two non-return valves 30,31 to the post-treatment means 5. The post-treatment means 5 comprise a bacteriolo¬ gical cleaning station in the form of a so-called clamp silo 34. Silo 34 is filled with a layer of straw 35 which is enclosed between two layers of so-called black sand 36. The liquid fraction L is pumped into silo 34 through a feed conduit 37. Air A is simultaneously admitted into silo 34 through a conduit 38. The liquid fraction L is cleaned by bacteria present in the filling 35,36 of silo 34. The clea¬ ned liquid seeps downward through the layers 35,36 into a layer of filter sand 40 and is finally collected in a con- duit 42 via a number of drain conduits 41. The air in silo 34, which is heated by the cleaning action of the bacteria, rises and collects in the upper part 43 of silo 34 below a cover sheeting 39. The hot air is drawn out of silo 34 by a fan 44 and blown back into the conduit 38. The cleaned liquid fraction CL collected in con¬ duit 42 is finally separated into water W and residual materials R in the second separating means 6, which can be formed by an ultracentrifuge or a second stripper. The clean water W is stored in a tank 7 until it is re-used, for instance for irrigation or flushing of the different parts of the processing device.

Because the method and device as described above can be applied simply in any manure producing enterprise, it

is no longer necessary to transport considerable quantities of manure over great distances for processing or for sprea¬ ding, whereby great savings are possible and the manure problem is considerably lessened. *****