Method of producing protein-rich forage or nitrogenous fertilizer from fowl droppings, swine dung, cow dung and the like

This invention relates to a method of producing protein-rich forage or nitrogenous fertilizer as a commercial product from fowl droppings, swine dung, cow dung and the like by charging said ordure into a heated animal, fish or vegetable oil, subjecting the mixture to a smooth dehydrating treatment under the two-step reduced pressure conditions starting initial by with a limited pressure reduction and later increasing the degree of pressure reduction, and thereafter squeezing oil out of the treated mixture to thereby produce said forage or fertilizer. Said method is conducive to the prevention of malodor pollution caused by said livestock excrements and can also eliminate the wasteful use of fuel required in the incineration treatments.

BRIEF SUMMARY OF THE INVENTION 
A vast amount of cost and extensive facilities have been required for the 
elimination of malodor generated in the course of treatment or disposal of 
fowl droppings, swine dung, cow dung and such, and even if the treatment 
could be performed without generating offensive smell, the treated ordure 
could find no effective way of utilization but has been merely burned or 
discarded. 
The present invention is designed to accomplish an odorless treatment of 
fowl droppings and the like under the specific reduced pressure conditions 
by making use of a heated animal or vegetable oil and to also recycle the 
treated ordure as a useful protein-rich forage or nitrogenous fertilizer. 
The methods of treating the animal waste by utilizing an oil are already 
disclosed in, for example, U.S. Pat. Nos. 1,766,032, 2,875,222, 3,288,825 
and 3,057,699, but the techniques shown in these patents aim to merely 
extract and recover oils from the animal waste and shed no light on the 
formulation of forgage or fertilizer from the treated animal waste. 
The present invention provides a method of producing forage or fertilizer 
as a commercial product from fowl droppings and such by using an oil, said 
method featuring effective dehydration of said ordure under the two-stage 
reduced pressure conditions and ensuing perfect oil expression.

DETAILED DESCRIPTION OF THE INVENTION 
An embodiment of the method according to this invention is described below. 
About 900 kg of an oil is fed into a cooker with a capacity of 
approximately 6.5 m.sup.3 and heated to a temperature range above 
90.degree. C. in which the gelatinous substance would not be dissolved in 
the oil but is thermally coagulated. Then about 3 tons of sludge-formed 
ordure with around 90% of water content is supplied into said cooker and 
heated under stirring. Then the material is subjected to two-stage reduced 
pressure dehydration, that is, in the first stage of about 30 minutes 
after feed of the material, dehydration is performed under a limited 
reduced pressure of 10-20 mmHg, and then in the second stage, the pressure 
in the cooker is further reduced to 740-750 mmHg. The material which has 
been dehydrated to a moisture content of about 6% by around 3 hours of 
said treatment is taken out of the cooker and compressed by a continuous 
compressor under a unit pressure of 7,000 pounds to form the oil-separated 
flat-shaped solids or cakes. The cakes have an oil content of about 8% and 
a moisture content of about 5% and can be put to use as a protein-rich 
forage with a protein content of about 70%. 
According to the method of this invention, although gelatinous substances 
and proteins are contained in the sludge, the temperature of the sludge 
would not be lowered by pressure reduction since said sludge is kept in a 
state allowing free evaporation of moisture by heated oil owing to the 
restricted pressure reduction during the initial stage, that is, during 
the period of about 30 minutes after feed of the material, and thus the 
animal oil or the like supplied is maintained at a temperature above 
90.degree. C. that inhibits the gelatinous substances and proteins from 
being dissolved in the oil, and when the sludge is supplied into the oil, 
the gelatinous substances and proteins in the sludge are instantaneously 
heated and coagulated and thus prevented from being dissolved and effusing 
into the oil. Also, the proteins in the sludge is thermally coagulated by 
the heated oil while the moisture is prevented from being emulsified with 
the gelatinous substances and proteins owing to thermal coagulation of 
said substances, thus creating a situation where the moisture is apt to 
evaporate. Then the pressure is further reduced to render the density of 
moisture smaller than that of the oil to cause displacement of moisture 
and oil and induce separation and evaporation of moisture, thereby 
effecting uniform heat-dehydration as well as uniformalization of thermal 
efficiency. Further, carbonization of protein, calcium, etc., is prevented 
by the reduction of the dehydration time, keeping the dehydration rate 
constant at around 6%, and then the oil is separated from the soilds 
(cakes) through the steps of centrifugation, continuous compression, etc., 
to thereby obtain a high-grade forage consisting principally of 
water-soluble protein or a high-grade nitrogenous fertilizer. 
The protein-rich forage obtained according to the method of this invention 
is then dehydrated into a fine powdery form, and in this case, since 
dehydration is performed under a limited reduced pressure condition in the 
initial phase of the dehydration treatment, the gelatinous substances and 
proteins are not dissolved and the three substances, that is, gelatinous 
substance, protein and water would not be entangled and integrated with 
each other, so that the whole material undergoes uniform dehydration in 
the pre-heated oil and therefore a uniform pressure can be applied in the 
oil separation step for powdering the mass, thus allowing obtainment of a 
high-grade protein-rich forage with no scattering of quality among the 
products. 
Further, since said three substances are not entangled with each other, 
moisture can be removed in an uncontaminated state and hence BOD and COD 
of the evaporated or released water is very low and causes no pollution 
problem.