The present invention relates to improving the results of anaerobic digestion of organic waste especially animal manure such as chicken manure by removing the grit in the waste. by digesting the waste in a slurry at a temperature of 50 degrees C. or more for a period of time sufficient for the grit to settle out of the slurry.

DETAILED DESCRIPTION OF THE INVENTION

DEFINITIONS

The terms “about” and “essentially” mean ±10 percent.

The term “comprising” is not intended to limit inventions to only claiming the present invention with such comprising language. Any invention using the term comprising could be separated into one or more claims using “consisting” or “consisting of” claim language and is so intended.

The drawings featured in the figures are for the purpose of illustrating certain convenient embodiments of the present invention, and are not to be considered as limitation thereto. Term “means” preceding a present participle of an operation indicates a desired function for which there is one or more embodiments, i.e., one or more methods, devices, or apparatuses for achieving the desired function and that one skilled in the art could select from these or their equivalent in view of the disclosure herein and use of the term “means” is not intended to be limiting.

As used herein the term “grit” refers to insoluble matter that exists within organic waste. This especially includes the solid material found in animal waste such as described above. The term “organic waste” refers to any of the waste type materials described above which would be used in an anaerobic digestion system and containing grit. In one embodiment the organic waste is animal manure. In another embodiment it is chicken manure.

As used herein the term “tank” refers to a tank designed for holding organic waste and mixing at an elevated temperature. The tank can be made of any material such as stainless steel and in one embodiment, the tank is insulated to better hold the elevated temperature. The tank is fitting on the interior with a mixing apparatus to keep the contents of the tank mixing during the process of the invention. One skilled in the art could choose an appropriate mixing apparatus. Since the grit needs to be removed and eventually ends up on the bottom of the tank after the process, the tank can be fitted with a pump to remove the grit or remaining slurry, or with a bottom drain such as conical area, to remove the grit by bleeding off the grit. The degritted slurry is transferred by pump into the anaerobic digester.

The tank or system is emptied, typically daily, for the second batch of hydrolysis.

The method of the present invention involves adding the organic waste such as animal manure (chicken manure) to the tank. Water is added to the tank to obtain a lower solids slurry mixture. In general one skilled in the art can obtain the optimum percentage of solids, and thus the proper amount of water based on the weight of the manure added by simple testing of the process. In one embodiment the percent solids is 8% to 12% on a weight/weight basis. In other embodiments it can be 12% or less solids and can in some circumstances be higher than 12%. In general, the degritter process takes about a day, however, it depends on the severity of grit.

The contents of the tank need to be kept at a temperature of at least about 50° C. during the method of the present invention and as such the tank must also be fitted with a device for heating the contents and holding at that temperature. The tank can also be insulated. The water and/or manure can be preheated to that temperature before addition to the tank or can be heated in the tank after addition. Both analog and digital temperature control devices are within the skill in the art. In one embodiment the temperature is kept within about 50 to about 60° C. for a period sufficient to settle out essentially all the grit from the slurry. The sufficient time as used herein will vary depending on the organic material and ambient conditions, the size of the tank, and the like, but in one embodiment the time is about 18 to 24 hours. One skilled in the art could readily determine the amount of time based on the teachings herein and with minimal experimentation.

Once the slurry is degritted, it can be delivered to an anaerobic digester for productivity of biogas and fertilizer. Also, it can be further digested in a novel secondary solid. SECONDARY SOLID-PHASE DIGESTION FOR BIOGAS SEMI-SOLID PRODUCTION of a patent application filed of even date herewith.

Now referring to the figures, the followingFIG. 1depicts an embodiment of the hydrolytic degritter system of the present invention. In this view insulated tank1is shown with slurry2which is made from the addition of water3and manure4from containers/pipelines/faucets etc. Once the proper low solids slurry is formed, it is heated or kept heated by heater5and then kept in a. state of constant missing using mixer6. In this embodiment an 8-12% solids content slurry is utilized.

FIG. 1shows the process with grit10settling out at the bottom of tank1. In reality, the solids would settle out after the process but is shown in this manner for convenience. In this embodiment grit10can be removed from tank1by bleeding the grit into container15. The grit10in container15can be washed and that washing returned to the tank. The tank slurry minus the grit is transferred7to an anaerobic digester for production of biogas and fertilized over a period of 5-10 days. Though one skilled in the art can determine optimum times.

FIG. 2shows the hydrolytic degritter in a system for digesting the manure into biogas and solid material slurry which can be used for fertilizer and other uses. The slurry material is transferred to the primary anaerobic digester11. The slurry is digested for about 5-10 days or as needed to produce biogas12and a solid slurry about 2-5% solids13. The solids13are delivered to a secondary solid phase digester14for further biogas production and a semi-solid slurry which can be utilized as fertilizer16and a leachate17.

Those skilled in the art to which the present invention pertains may make modifications resulting in other embodiments employing principles of the present invention without departing from its spirit or characteristics, particularly upon considering the foregoing teachings. Accordingly, the described embodiments are to be considered in all respects only as illustrative, and not restrictive, and the scope of the present invention is, therefore, indicated by the appended claims rather than by the foregoing description or drawings. consequently, while the present invention has been described with reference to particular embodiments, modifications of structure, sequence, materials and the like apparent to those skilled in the art still fall within the scope of the invention as claimed by the applicant.