Three Stage, Multiple Phase Anaerobic Digestion System and Method

Abstract

A three stage, multiple phase anaerobic digestion system and method designed to separate the biological phases, optimize microbial activity in each phase, and significantly increase system reliability and energy production. The system physically separates the biological phases of anaerobic digestion based on particle size, particle density, and solubility of metabolic products. The system allows a complex multi-phased biological system to develop without the need for excessive control or operator intervention.

I claim: 
     
         1 . A system for the anaerobic digestion of a raw feedstock containing raw organic solids, said system comprising:
 a hydrolysis tank where partial hydrolysis of the feedstock takes place, wherein the pH of the feedstock in said hydrolysis tank has a pH of 5.5 to 6.5, wherein the temperature of said feedstock in said hydrolysis tank is maintained between 24° C. to 35° C., wherein after a predetermined period of time, supernatant is drawn off said hydrolysis tank, wherein carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) formed in said hydrolysis tank are collected;   an upflow fluidized bed reactor having a top and a bottom, said bottom for receiving the drawn off supernatant from said hydrolysis tank, said upflow fluidized bed reactor providing for hydrolysis and acidogenesis of said supernatant, wherein the pH of the supernatant in said upflow fluidized bed reactor has a pH of 5.5 to 6.5, wherein the temperature of said supernatant in said upflow fluidized bed reactor is maintained between 24° C. to 35° C., wherein said supernatant exits in said upflow fluidized bed reactor at said top as filtered supernatant, wherein carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) formed in said upflow fluidized bed reactor are collected;   a heating means, said heating means configured for heating said filtered supernatant to at least 30° C.;   a packed bed reactor where methanogenic bacteria create methane gas (CH 4 ), said packed bed reactor having an inlet end and an outlet end; and   a pH adjusting means, said pH adjusting means configured for adjusting the pH of the filtered supernatant to maintain a pH of 7.8 to 8.5 in said packed bed reactor;   wherein said filtered supernatant is transferred into said packed bed reactor at or adjacent said inlet end, wherein said packed bed reactor includes a biological filter media, wherein said carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) collected from said hydrolysis tank and said upflow fluidized bed reactor are injected into said filtered supernatant within said packed bed reactor, said filtered supernatant, said injected carbon dioxide (CO 2 ) and said injected hydrogen gas (H 2 ) for digestion by said methanogenic bacteria, said packed bed reactor having a discharge port through which filtered effluent is discharged from said packed bed reactor, wherein said methane gas produced in said packed bed reactor is drawn off and stored.   
     
     
         2 . The system of  claim 1 , wherein said packed bed reactor has an upper portion and a lower portion, said upper portion containing low angle anaerobic digester media, and said lower portion containing high angle anaerobic digester media, wherein said filtered supernatant flowing through said lower portion then through said upper portion. 
     
     
         3 . The system of  claim 2 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 30° to 38° C. 
     
     
         4 . The system of  claim 3 , wherein said collected carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) are injected into said filtered supernatant within said packed bed reactor at a location spaced from said inlet end of said reactor. 
     
     
         5 . The system of  claim 2 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 49° to 57° C. 
     
     
         6 . The system of  claim 5 , wherein said collected carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) gasses are injected into said filtered supernatant within said packed bed reactor at a location spaced from said inlet end of said reactor. 
     
     
         7 . The system of  claim 1 , wherein said collected carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) are injected into said filtered supernatant within said packed bed reactor at a location spaced from said inlet end of said reactor. 
     
     
         8 . The system of  claim 1 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 30° to 38° C. 
     
     
         9 . The system of  claim 1 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 49° to 57° C. 
     
     
         10 . The system of  claim 1 , wherein carbon dioxide and hydrogen gas formed in said hydrolysis tank are collected via a raw gas collection system. 
     
     
         11 . The system of  claim 10 , wherein said raw gas collection system fluidly connects said hydrolysis tank and said upflow fluidized bed reactor to said packed bed reactor. 
     
     
         12 . A system for the anaerobic digestion of a raw feedstock containing raw organic solids, said system comprising:
 a hydrolysis tank where partial hydrolysis of the feedstock takes place, wherein the pH of the feedstock in said hydrolysis tank has a pH of 5.5 to 6.5, wherein the temperature of said feedstock in said hydrolysis tank is maintained between 24° C. to 35° C., wherein after a predetermined period of time, supernatant is drawn off said hydrolysis tank, wherein carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) formed in said hydrolysis tank are collected;   an upflow fluidized bed reactor having a top and a bottom, said bottom for receiving the drawn off supernatant from said hydrolysis tank, said upflow fluidized bed reactor providing for hydrolysis and acidogenesis of said supernatant, wherein the pH of the supernatant in said upflow fluidized bed reactor has a pH of 5.5 to 6.5, wherein the temperature of said supernatant in said upflow fluidized bed reactor is maintained between 24° C. to 35° C., wherein said supernatant exits said upflow fluidized bed reactor at said top as filtered supernatant, wherein carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) formed in said upflow fluidized bed reactor are collected;   a packed bed reactor where methanogenic bacteria create methane gas (CH 4 ), said packed bed reactor having an inlet end and an outlet end;   a heating means, said heating means configured for heating said filtered supernatant to at least 30° C.; and   a pH adjusting means, said pH adjusting means configured for adjusting the pH of the filtered supernatant to maintain a pH of 7.8 to 8.5 in said packed bed reactor,   wherein said filtered supernatant is transferred into said packed bed reactor at or adjacent said inlet end, wherein said packed bed reactor includes a biological filter media, wherein said carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) collected from said hydrolysis tank and said upflow fluidized bed reactor are injected into said filtered supernatant within said packed bed reactor, said filtered supernatant, said injected carbon dioxide (CO 2 ) and said injected hydrogen gas (H 2 ) for digestion by said methanogenic bacteria, said packed bed reactor having a discharge port through which filtered effluent is discharged from said packed bed reactor, wherein said methane gas produced in said packed bed reactor is drawn off and stored;   wherein said collected carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) are injected into said filtered supernatant within said packed bed reactor at a location spaced from said inlet end of said reactor.   
     
     
         13 . The system of  claim 12 , wherein said packed bed reactor has an upper portion containing low angle anaerobic digester media and a lower portion containing high angle anaerobic digester media, wherein said filtered supernatant flowing through said lower portion then through said upper portion. 
     
     
         14 . The system of  claim 13 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 30° to 38° C. 
     
     
         15 . The system of  claim 13 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 49° to 57° C. 
     
     
         16 . The system of  claim 12 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 30° to 38° C. 
     
     
         17 . The system of  claim 12 , wherein said heating means is configured for heating said filtered supernatant to a temperature of 49° to 57° C. 
     
     
         18 . The system of  claim 12 , wherein carbon dioxide and hydrogen gas formed in said hydrolysis tank are collected via a raw gas collection system. 
     
     
         19 . The system of  claim 18 , wherein said raw gas collection system fluidly connects said hydrolysis tank and said upflow fluidized bed reactor to said packed bed reactor. 
     
     
         20 . A system for the anaerobic digestion of a raw feedstock containing raw organic solids, said system comprising:
 a hydrolysis tank where partial hydrolysis of the feedstock takes place, wherein the pH of the feedstock in said hydrolysis tank has a pH of 5.5 to 6.5, wherein the temperature of said feedstock in said hydrolysis tank is maintained between 24° C. to 35° C., wherein after a predetermined period of time, supernatant is drawn off said hydrolysis tank, wherein carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) formed in said hydrolysis tank are collected;   an upflow fluidized bed reactor having a top and a bottom, said bottom for receiving the drawn off supernatant from said hydrolysis tank, said upflow fluidized bed reactor providing for hydrolysis and acidogenesis of said supernatant, wherein the pH of the supernatant in said upflow fluidized bed reactor has a pH of 5.5 to 6.5, wherein the temperature of said supernatant in said upflow fluidized bed reactor is maintained between 24° C. to 35° C., wherein said supernatant exits said upflow fluidized bed reactor at said top as filtered supernatant, wherein carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) formed in said upflow fluidized bed reactor are collected;   a packed bed reactor where methanogenic bacteria create methane gas (CH 4 ), said packed bed reactor having an inlet end and an outlet;   a heating means, said heating means configured for heating said filtered supernatant to at least 30° C.; and   a pH adjusting means, said pH adjusting means configured for adjusting the pH of the filtered supernatant to maintain a pH of 7.8 to 8.5 in said packed bed reactor,   wherein said filtered supernatant is transferred into said packed bed reactor at or adjacent said inlet end, wherein said packed bed reactor includes a biological filter media, wherein said carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) collected from said hydrolysis tank and said upflow fluidized bed reactor are injected into said filtered supernatant within said packed bed reactor, said filtered supernatant, said injected carbon dioxide (CO 2 ) and said injected hydrogen gas (H 2 ) for digestion by said methanogenic bacteria, said packed bed reactor having a discharge port through which filtered effluent is discharged from said packed bed reactor, wherein said methane gas produced in said packed bed reactor is drawn off and stored,   wherein said collected carbon dioxide (CO 2 ) and hydrogen gas (H 2 ) are injected into said filtered supernatant within said packed bed reactor at a location spaced from said inlet end of said reactor, wherein said packed bed reactor has an upper portion containing low angle anaerobic digester media and a lower portion containing high angle anaerobic digester media, wherein said filtered supernatant flowing through said lower portion then through said upper portion, wherein carbon dioxide and hydrogen gas formed in said hydrolysis tank are collected via a raw gas collection system, and wherein said raw gas collection system fluidly connects said hydrolysis tank and said upflow fluidized bed reactor to said packed bed reactor.