Chemistry: fertilizers – Processes and products – Organic material-containing
Reexamination Certificate
1998-08-10
2001-03-27
Straub, Gary (Department: 1754)
Chemistry: fertilizers
Processes and products
Organic material-containing
C071S015000, C426S055000, C435S262000
Reexamination Certificate
active
06206945
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process of producing a high-nitrogen, high-phosphorus fertilizer from animal wastes as well as a product of this process. Specifically, it relates to a process for treatment of animal wastes wherein nitrogen and phosphorus are retained and parasites and pathogenic bacteria are destroyed.
2. Prior Art
Present methods of composting animal wastes, e.g., poultry litter and cattle manure, tend to release nitrogen in the form of ammonia and create nuisance odors. Conventional composting allows the survival of parasites and pathogenic bacteria. Moreover, phosphates tend to leach away into the ground during conventional composting owing to their high solubility in water.
U.S. Pat. No. 4,486,216 discloses a process wherein fecal waste is treated with a smectite clay and lime by fermentation with aerobic and anaerobic microorganisms. U.S. Pat. No. 4,997,572 discloses a process wherein wastewater treatment sludge or animal wastes are treated with quicklime, with the loss of ammonia. U.S. Pat. No. 5,466,273 provides a process wherein organic wastes are treated with sulfuric acid and anhydrous ammonia, steam is introduced, and dolomite, potash, urea, and phosphate rock are added.
SUMMARY OF THE INVENTION
The method of the present invention overcomes the drawbacks of conventional composting. According to the method of this invention, the waste is mixed with soft-burned dolomite (calcium magnesium carbonate that has been calcined at approximately 900° C.). While soft-burned dolomite is preferred, any source of magnesium oxide is acceptable. The presence of magnesium is critical because of the formation of ammonium magnesium phosphate in the process, as explained below.
Water is added to a mixture of animal waste and calcined dolomite, principally CaO and MgO, whereby the heat of hydration of these oxides to the respective hydroxides is liberated and the mixture heats up to above 100° C. The strong alkalinity (pH>12.5) and elevated temperature of the mixture destroy parasites and undesirable bacteria in the animal waste. Ammonia that is emitted by the hot alkaline mixture is absorbed in a separate vessel in a dilute acidic medium, e.g., acetic, citric, nitric, sulfuric, or phosphoric acid, acid potassium phosphate or any other acidic salts that form ammonium salts. The mixture is allowed to cool to ambient temperature.
The mixture is neutralized by the introduction of carbon dioxide gas, whereby the pH is lowered. The ammonium salt recovered during the earlier evolution of ammonia is added back into the mixture. An inoculum of bacteria, such as a suspension of natural guano, is added to the mixture. The mixture is incubated in a closed vessel, whereby the mixture becomes anaerobic. The mixture is allowed to release carbon dioxide, whereby the pH rises. The solids of the mixture are recovered by drying, or filtration followed by drying of the filtercake. Any filtrate, since it contains some N and P, may be combined with a subsequent batch to preserve N and P values.
The process of this invention preserves nitrogen and phosphorus from the original waste in the form of relatively water-insoluble ammonium magnesium phosphate, which provides slow release of N and P into the ground when the product is used as fertilizer.
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Lazell, E.W., “Hydrated Lime: History, Manufacture, Use in Plaster, Mortar, Concrete”, p21-22 Dec. 1915.
Malone Philip Garcin
Weiss, Jr. Charles Arthur
MacEvoy John
Straub Gary
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