Hydrolytic degritter

Abstract

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.

What is claimed is: 
     
         1 . A method of separating grit from organic waste comprising:
 a) adding raw organic waste to a tank fitted with a mixing apparatus;   b) adding water to the organic waste in the tank to obtain a slurry mixture;   c) maintaining the temperature of the slurry at a temperature of at least about 50° C. while mixing the contents of the tank with the mixing apparatus for a period sufficient for the grit to settle to the bottom of the tank and   d) separating the settled grit from the remaining slurry in the tank.   
     
     
         2 . The method according to  claim 1  wherein the temperature is maintained at about 50° C. to about 70° C. 
     
     
         3 . The method according to  claim 1  wherein the slurry has about 8% to 12% solids. 
     
     
         4 . The method according to  claim 1  wherein the contents are mixed and incubated for about 18 to 24 hours. 
     
     
         5 . The method according to  claim 1  wherein the grit is removed by at least one of pumping or bleeding off from the bottom of the tank. 
     
     
         6 . The method according to  claim 1  wherein after the grit is removed, the remaining mixture in the tank is pumped to an anaerobic digester for digestion. 
     
     
         7 . The method according to  claim 1  wherein the organic raw waste is raw animal manure. 
     
     
         8 . The method according to  claim 7  wherein the manure is chicken manure. 
     
     
         9 . A system for separating grit from a low solids raw organic waste slurry comprising:
 a) a tank equipped with a mixing apparatus and containing the slurry;   b) a device for removing grit that has settled to the bottom of the tank selected from the group comprising a pump or a device to bleed or remove the grit from the bottom of the tank; and   c) a device for maintaining the slurry at a temperature of at least about 50° C. for a period of time sufficient for the grit to settle out from the slurry.   
     
     
         10 . The system which further comprises a device for performing anaerobic digestion on the slurry in the tank after the grit is removed.