Background Art Korean Patent No. 0156010 is related to a method for producing a type of fertilizer rich in calcium by the use of organic waste materials, in which a mehtod is described for producing it by minutely processing such organic waste comprising refuse of food stuffs, human and animal excretion, offal from butcheries, and trash of fisheries products, adjusting the waste's water content to 50% or thereabouts, throwing it in a treatment tank equipped with a steaming and evaporating system, adding thereto unslaked lime in the amount of about 30% to 50% of the waste, letting the mixture to react for 24 hours or more at least, leaving it alone for two or three days to settle down, and then taking it out and crushing in a grinder.

However, such a method as described above consists of two separate steps, one of minutely processing the organic waste and the other of getting it to react, whereby costing more in equipment and facility, and the pretreatment of the organic material takes at least 24 hours, incurring a longer time in the whole treatment of the organic

waste, while, because the unslaked lime mainly contains calcium, the product must be used in a mixture with other botanical fertilizers in case such other contents are also required, the rather costliness of unslaked lime posing another problem.

DISCLOSURE OF THE INVENTION To solve such problems as given above, the present invention, by way of using slaked dolomite of certain predetermined sizes, is to perform both the steps of crushing and reacting the organic waste simultaneously, and by way of maintaining the reaction temperature high, to reduce the time taken for treatment, while providing a calcium- and magnesium-containing compost with the use of organic waste and dolomite, excellent in quality of the end product and cheap in the cost of the raw materials also.

The method, of the present invention, is characterized in that it consists of a step of feeding such organic waste as refuse of agricultural and fisheries products and others from animal husbandry, slaughter houses, etc. along with human and animal excretion, and the sludge deposited in water purification plants or sewers on one hand and slaked dolomite on the other at the ratio of 3 : 1-2 2 : 1 into a mixer equipped with a stirrer and an outlet ; and a step of reacting the organic waste with the dolomite, stirring them with the stirrer, for about 1-2 hours.

The organic waste used in the present invention can include such waste containing plentiful organic matters as refuse, rubbish, trash, offal, scum, garbage, residual, etc. of various agricultural and fisheries products, food stuffs, and from animal husbandry, butcheries, human and animal excretion, sludge deposited in water-purification plants or sewers, etc. The waste of agricultural and fisheries products include waste of fruits, fishes, shellfish, etc. The waste of foodstuffs can include the leftover from restaurants or other eating establishments and waste of noodles, breads, etc. The waste from animal husbandry includes excretion of cattle. The waste from butcheries includes the waste produced at butcheries when beasts are slaughtered and when the carcasses

undergo treatment. By the sludge deposited at water-purification plants or in sewers are meant the deposits which contain little metal harmful to humans but contain much of various organic and mineral matters. The sludge may also contain what is deposited by waste water enriched with nutrients and the microbial sludge deposited in water-purification plants using microorganisms or activated charcoal or what is deposited in sewage flowing with water therefrom. All these sludge of such a variety, containing a great deal of various nutrients would be excellent fertilizers. However, in case of processing by way of a landfill, other materials cannot be processed therewith because the sludge has a relatively large volume on account of its 80-90% water content and because it exists as a suspension owning to its micro-particles.

At the step of inputting into the mixer, the slaked dolomite means dolomite, a mineral carbonate, duly slaked. It contains MgO by about 32-35 wt% and CaO by about 5-55 wt%. In the present invention it is preferable to choose and use rocks of such slaked dolomite of the size of 30-50mm in diameter. If rocks of the size of less than 30mm in diameter were used, hydrolysis of organic waste would not sufficiently take place, because the reaction would end in too short a time consequent upon their too large specific surfaces ; while rocks larger than 50mm in diameter were used it would not merely take too long a time for the reaction because of their too small specific surfaces but may cause the rocks to strike hard the inner walls of the mixer, possibly bringing about even a ruin of the mixer itself. The dolomite in the form of rocks gets pulverized in a process of stirring to be described below and performs crushing of the waste, thus necessitating no separate stage of the breaking of the waste.

In the step of inputting into the mixer, again, the quantity respectively of the organic waste and the slaked dolomite is preferred to be in the range of 3 : 1-2 : 1 in proportion. If the organic waste less than 2 : 1 is thrown in, viz. the slaked dolomite of more than 2 : 1 is input, the economics of the treatment will suffer, while an input of more than 3 : 1 may make it difficult to maintain the temperature required for the

hydrolysis of the organic waste and take more time for the reaction, degrading the productivity of the process. Also, the content of water in the product may prove higher than is desired, an unfavorable factor weakening its physical properties.

The mixer can be anything only if it has a stirring device and an outlet equipped in it. For instance, the one illustrated in Fig. 1 can very well be included. As is shown in Fig. 1, a mixer M is equipped in its central part with a shaft 3, which revolves around a bearing 10 by the power transmitted from a gear motor 2 and gets its revolving vibration absorbed by an anti-dust retainer 9 enwrapping said bearing 10 ; a fan 6, which is a device for forced blowing-in of the air, and an exhaust 5, outlet for the air, as well as an inlet 1, through which the raw material is fed, are each formed in the upper part ; and an outlet 16, opened or shut through a door which revolves on a pivot in the process of the opening and shutting of an oil-pressure opener-shutter 12, is formed in the lower part of said body of the mixer M.

It goes without saying that on the shaft 3, housed in the inside space of said mixer M, is fixed many a blade 4 along its body for stirring the raw material being fed through said inlet 1.

On said mixer M are also equipped a safety valve 8 opening or shutting according to the different pressures inside, a temperature sensor 7 to perceive the temperature inside, and a look-through window 13 to look over the inside of the mixer M ; and below said outlet 16 a conveyor 14 is fixed for conveyance of the products yielded during the process of stirring by said shaft 3 to other locations.

While the mixer performs its function of mixing the organic waste and the slaked dolomite and making the mixture into the forms of cake, it also performs such other functions of disposing the steam being generated during the reaction and the gas of high temperature and high pressure which is generated after the reaction also. The mixer

and all that is attached to it are preferably made of anti-acid and anti-alkali materials and had better be capable of resisting changes of temperature and pressure.

In the production of the compost of the present invention, said input organic waste and the slaked dolomite are reacted with each other, while getting stirred, for about 1- 2 hours, and are formed into the shape of cake.

In the above-said process of reaction, the stirring induces proper mixture of the organic waste and the slaked dolomite at the same time that it induces thorough, even distribution of each, and the speed of the stirring is so arranged that adequate physical grinding of each can take place inside the mixer.

Also in the above-said process of reaction, the reaction time is preferably in the range of about 1-2 hours. If the time is less than an hour the water content of the product may be too much and the hydrolysis of the organic waste may be left insufficient, while if it is more than two hours the hydrolysis may prove extreme so as not to bring forth material benefit of the reaction.

To ensure the safety of workers the product is taken out of the mixer when the temperature gets lower than 60° C and the water content is less than 30 wt%.

The magnesium-or calcium-containing compost let out of the mixer can be used after either natural or artificial drying or possibly as it is in consideration of such conditions as the kinds of crops, circumstances of the soil, time of application, etc.

Brief Description of Drawings Fig. 1 is an illustration in the rough of the construction of a mixer used in an embodiment example of the present invention.

Best Mode for Carrying out the Invention Below, the present invention is further described in detail through the embodiment examples, but it goes without saying that these examples, being ones given only for illustration, do by no means confine the present invention to them alone.

Example 1 This example was intended to see the effects of the present invention by the use of a mixer in Fig. 1, table waste, and slaked dolomite.

The food waste and slaked dolomite of an average size of 40 mm in diameter were input in the mixer through the inlet 1. The gear motor 2 was set in motion to turn the shaft 3, fitted with stirring blades, thus stirring and reacting the waste and dolomite for 1-2 hours. During the reaction the temperature was confirmed by the temperature sensor 7, and the state of reaction through the window 13. The steam issuing as the water content decreased during the reaction was let out through the exhaust 5, and the gas of high-temperature and high pressure inside the mixer after the reaction was blown away to an exhaust-treatment device (scrubber, not shown in the drawings) through the outlet 16 by the force of air blown in by the fan 6. The manufactured product was thrown down through the outlet 16 and made into compost in the form of cakes, after passage through the conveyor 14. The thus produced compost in the form of cakes can be dried either naturally or in a separate additional drying apparatus before application as fertilizer.

Throughout this embodiment example the table waste and slaked dolomite were kept at 150° C ~ 170° C, accompanied by a reaction of generating heat of high temperature. Also, the reaction continued in a state of strong alkali under the influence of the two constituents of the slaked dolomite, and phenomena of physical collision occurred as the lumps of dolomite of the average size of 40 mm in diameter underwent the process of pulverization.

Under the high temperature of 150° C-170° C and in a condition of strong alkali, the bonding of glucoside, peptide, ester, etc., of the natural high polymers got loosened and thus the table waste was converted into low polymers absorbable by plants and crops.

As has been described above, to the table waste a decrease of water content occurred in a reaction of hydration accompanying generation of heat, and it was converted into useful compost by hydrolysis in a condition of strong alkali and by physical grinding through pulverization of the slaked dolomite.

Example 2 The reaction was performed in a way exactly like Example 1, except that the table waste and slaked dolomite were used in different quantities. The results of the experiments are given in Table 1 below.

Table 1. Ratios of food waste and their results Ratios 1 : 1 2 : 1 4 : 1 5 : 1 (Food waste to slaked dolomite) _ _ Reaction Temperature (°C) 180-230 160-180 110-130 80-110 Reaction Time (Minutes) 40 60 80 120 240 240 Water after reaction (wt%) 20 or less 20-25 35-50 50 or more As can be seen in Table 1, the ratios of waste to dolomite input in the mixer were most preferably 2 : 1-3 : 1 in terms of wt%. If the organic waste was less than 2 : 1 in wt%, viz. if the more dolomite was used, the economics of the treatment were lowered, while in case the ratio was more than 3 : 1, it was found difficult to maintain the temperature required for the reaction, the reaction taking the more time and the yield decreasing. Also the water content of the product was higher than otherwise, a

factor for worsening its physical property.

The above examples 1 and 2 were of the cases where table waste and dolomite were used according to the present invention, and similar results were obtained in experiments with the other agricultural and fisheries waste, animal husbandry waste, slaughter house waste, human excretion, sludge deposited in water-purification plants and sewers, etc., although descriptions of these are omitted here.

According to the present invention it is possible, by the use of lumps of slaked dolomite of the size of 30 ~ 50mm in diameter, to ensure a successful performance of crushing and grinding of the organic waste while in the process of stirring it, requiring no separate additional process of pulverization.

Also according to the present invention, it is possible, by the use of slaked dolomite which causes the temperature during the reaction to rise to a relatively high level, to reduce the reaction time which formerly was at least 24 hours to only 1-2 hours.

Also according to the present invention it is possible, by the use of slaked dolomite which contains not merely calcium but also magnesium, to contribute to the betterment of soil as well as to supply elements which crops need indispensably and in a great amount at that.