Biogasification of solid waste with an anaerobic-phased solids-digester system

Abstract

The present invention provides methods for the generation of methane by a two phase anaerobic phase system (APS) digestion of organic substrates. Also provided is a device for practicing the methods of the invention. The APS-digester system is a space-efficient, high-rate solids digestion system. The APS-digester system consists of one or more hydrolysis reactors and one biogasification reactor.

What is claimed is:  
     
         1 . A method for methane production by two-phase anaerobic digestion of solid organic material, said method comprising: 
 (a) incubating for a first period of incubation, a first mixture comprising said solid organic material and an aqueous liquid, under anaerobic conditions, in a first hydrolysis digester having an upper portion and a lower portion and containing a hydrolysis means therein;    (b) after said first period of incubation, transferring a portion of said aqueous liquid of said first mixture residing in said lower portion of said hydrolysis reactor to a methane phase digester to form a second mixture, said methane phase digester having an upper portion, a lower portion and a methanogenesis;    (c) incubating said second mixture for a second incubation period during which methane is generated;    (d) transferring a portion of said second mixture residing in said upper portion of said methane phase digester to said first hydrolysis phase digester for a third incubation period.    
     
     
         2 . The method according to  claim 1 , further comprising intermittently agitating said second mixture.  
     
     
         3 . The method according to  claim 1 , wherein said solid organic material is a member selected from the group consisting of sewage sludge, forestry waste, food waste, agricultural waste, municipal waste and combinations thereof.  
     
     
         4 . The method according to  claim 1 , wherein said solid organic material comprises agricultural waste.  
     
     
         5 . The method according to  claim 4 , wherein said agricultural waste comprise rice straw.  
     
     
         6 . The method according to  claim 1 , further comprising collecting said methane generated in steps (c) through (e).  
     
     
         7 . The method according to  claim 1 , wherein methane is generated in step (a).  
     
     
         8 . The method according to  claim 7 , further comprising collecting said methane generated in step (a).  
     
     
         9 . The method according to  claim 1 , wherein said first mixture has a pH of from about 4.5 to about 6.5.  
     
     
         10 . The method according to  claim 1 , wherein said second mixture has a pH of from about 6.5 to about 7.5.  
     
     
         11 . The method according to  claim 1 , wherein said hydrolysis means comprises a bacterial culture.  
     
     
         12 . The method according to  claim 11 , wherein said bacterial culture is a member selected from the group consisting of Aerobacter, Aeromonas, Alcaligenes, Bacillus, Bacteroides, Clostridium, Eschericia, Klebsiella, Leptospira, Micrococcus, Neisseria, Paracolobacterium, Proteus, Pseudomonas, Rhodopseudomonas, Sarcina, Serratia, Streptococcus and Streptomyces,  Methanobacterium omelianskii, Mb. formicium, Mb. sohngenii, Methanosarcina barkerii, Ms. methanica  and  Mc. mazei  and mixtures thereof.  
     
     
         13 . The method according to  claim 1 , wherein said methanogenesis means comprises a bacterial culture.  
     
     
         14 . The method according to  claim 11 , wherein said bacterial culture is a member selected from the group consisting of Aerobacter, Aeromonas, Alcaligenes, Bacillus, Bacteroides, Clostridium, Eschericia, Klebsiella, Leptospira, Micrococcus, Neisseria, Paracolobacterium, Proteus, Pseudomonas, Rhodopseudomonas, Sarcina, Serratia, Streptococcus and Streptomyces,  Methanobacterium omelianskii, Mb. formicium, Mb. sohngenii, Methanosarcina barkerii, Ms. methanica  and  Mc. mazei  and mixtures thereof.  
     
     
         15 . The method according to  claim 2 , wherein said agitating is carried out for between 30 seconds and 10 minutes every hour.  
     
     
         16 . The method according to  claim 1 , further comprising pretreating said solid organic material prior to said first period of incubation by a method which is a member selected from the group consisting of chemical pretreatment, mechanical pretreatment, heat pretreatment and combinations thereof.  
     
     
         17 . The method according to  claim 16 , wherein said pretreating is mechanical pretreatment which is a member selected from the group consisting of cutting, grinding and combinations thereof.  
     
     
         18 . The method according to  claim 16 , wherein said pretreating is chemical pretreatment which is a member selected from the group consisting of bicarbonate treatment, radiation treatment, alkaline peroxide treatment, ammonia treatment and combinations thereof.  
     
     
         19 . The method according to  claim 16 , wherein said pretreating is heat pretreatment at a temperature from about 50° C. to about 120° C.  
     
     
         20 . The method according to  claim 19 , wherein said temperature is from about 60° C. to about 90° C.  
     
     
         21 . The method according to  claim 16 , wherein said solid organic material is rice straw and said pretreating comprises: 
 (a) grinding said rice straw;    (b) heating said rice straw; and    (c) treating said rice straw with ammonia.    
     
     
         22 . The method according to  claim 19 , wherein said grinding produces rice straw sized from about 5 millimeters to about 50 millimeters.  
     
     
         23 . The method according to  claim 22 , wherein said heating is at a temperature of from about 50° C. to about 120° C.  
     
     
         24 . The method according to  claim 23 , wherein said heating is at a temperature of from about 60° C. to about 90° C.  
     
     
         25 . The method according to  claim 22 , wherein said treating with ammonia utilizes an amount of ammonia equal to about 0.5% to about 10% of the total weight of the rice straw.  
     
     
         26 . The method according to  claim 25 , wherein said amount of ammonia is equal to about 1% to about 5% of the total weight of the rice straw.  
     
     
         27 . The method according to  claim 1 , wherein a member selected from the group consisting of said first incubation period, said fourth incubation period and combinations thereof occur in a hydrolysis reactor which is not said first hydrolysis reactor.  
     
     
         28 . An anaerobic phased solids digester system for methane production, said system comprising: 
 a first hydrolysis reactor containing therein a perforated support means separating the reactor into an upper portion and a lower portion, the upper portion having a hydrolysis reactor liquid inlet and the lower portion having a hydrolysis reactor liquid outlet;    a biogasification reactor having a biogasification reactor gas outlet, an agitating means, an upper portion and a lower portion, the upper portion having a biogasification reactor liquid outlet and the lower portion having a biogasification liquid inlet;    a first conduit connecting the hydrolysis reactor outlet to the biogasification inlet; and    a second conduit connecting the biogasification reactor outlet with the hydrolysis reactor inlet.    
     
     
         29 . The digester system according to  claim 28 , further comprising between 1 and 15 additional hydrolysis reactors.  
     
     
         30 . The digester system according to  claim 29 , wherein said hydrolysis reactors and said methanogenesis reactor are linked in a manner selected from the group consisting of parallel linking, series linking and combinations thereof.  
     
     
         31 . The digester system according to  claim 29 , wherein said hydrolysis reactors are linked in parallel with said methanogenesis reactor.  
     
     
         32 . The digester system according to  claim 29 , wherein said hydrolysis reactors are linked in series with said methanogenesis reactor.  
     
     
         33 . The digester system according to  claim 29 , wherein said perforated support means is a member selected from the group consisting of grids, filters, grates, sieves, slats, strainers and combinations thereof.  
     
     
         34 . The digester system according to  claim 27  further comprising a pump operably connected to said first hydrolysis reactor.