FERMENTATION OF WASTE GASES
The invention relates to the microbial fermentation of gaseous substrates to produce one or more products. The invention relates to the microbial fermentation of a gaseous substrate derived from the conversion of a biogas stream. The invention relates to the conversion of a biogas stream comprising methane to a gaseous substrate comprising CO or CO plus H2, and the production of one or more products from the microbial fermentation of said gaseous substrate.
1 . A method for producing at least one product by microbial fermentation, the method comprising:
a) passing a biogas stream comprising methane to a steam reforming zone, operated at reforming conditions whereby at least a portion of the methane in the biogas stream is converted to a substrate comprising CO and H 2 ; and
b) passing the substrate to a bioreactor comprising a culture of at least one carboxydotrophic microorganisms, and anaerobically fermenting the substrate to at least one product selected from the group consisting of alcohols, acids and mixtures thereof.
2 . The method of claim 1 where the biogas stream further comprises methane at least one component selected from the group consisting of CO 2 , N 2 , H 2 , H 2 S and O 2 .
3 . The method of claim 2 where the methane concentration in the biogas stream is enriched by removing at least a portion of at least one component prior to passing the biogas to the steam reforming zone.
4 . The method of claim 3 where the at least one component is removed in a pressure swing adsorption (PSA) zone.
5 . The method of claim 1 further comprising admixing a gas stream comprising CO with the substrate to provide a blended substrate having a CO:H 2 molar ratio from about 20:1 to about 1:2.
6 . The method of claim 1 where the alcohol is selected from the group consisting of ethanol, 2,3-butanediol and mixtures thereof.
7 . The method of claim 1 where the acid is selected from the group consisting of acetate, lactic acid and mixtures thereof.
8 . The method of claim 1 where the micro-organism is selected from the group consisting of Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium, Peptostreptococcus and mixtures thereof.
9 . The method of claim 8 where the micro-organism is selected from the group consisting of Clostridium autoethanogenum, Clostridium ljungdahli, Clostridium ragsdalei, Clostridium carboxydivorans and mixtures thereof.
10 . The method of claim 9 where the micro-organism is Clostridium autoethanogenum.
11 . The method of claim 9 where the micro-organism is Clostridium autoethanogenum.
12 . A method for producing at least one product by microbial fermentation, the method comprising:
a) passing a biogas stream comprising CH 4 and CO 2 to a pressure swing zone (PSA) operated at conditions to remove at least a portion of the CO 2 and provide a methane enriched biogas stream;
b) passing the methane enriched biogas stream to a steam reforming zone, operated at steam reforming conditions whereby at least a portion of the methane in the biogas stream is converted to a substrate comprising CO and H 2 ;
c) admixing a gas stream comprising CO with the substrate to provide a blended substrate having a CO:H 2 molar ratio from about 20:1 to about 1:2; and
d) passing the substrate to a bioreactor comprising a culture of at least one carboxydotrophic microorganisms, and anaerobically fermenting the substrate to at least one product selected from the group consisting of alcohols, acids and mixtures thereof.
13 . The method of claim 12 where the alcohol is selected from the group consisting of ethanol, 2,3-butanediol and mixtures thereof.
14 . The method of claim 12 where the acid is selected from the group consisting of acetate, lactic acid and mixtures thereof.
15 . The method of claim 12 where the micro-organism is selected from the group consisting of Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium, Peptostreptococcus and mixtures thereof.
16 . The method of claim 15 where the micro-organism is selected from the group consisting of Clostridium autoethanogenum, Clostridium ljungdahli, Clostridium ragsdalei, Clostridium carboxydivorans and mixtures thereof.
17 . The method of claim 16 where the micro-organism is Clostridium autoethanogenum.
18 . The method of claim 17 where the micro-organism is the Clostridium autoethanogenum strain deposited at the German Resource Centre for Biological Material (DSMZ) under the deposit number DSM 23693.
19 . A method for producing at least one product by microbial fermentation, the method comprising:
a) passing a biogas stream comprising CH 4 and CO 2 to a pressure swing zone (PSA) operated at conditions to remove at least a portion of the CO 2 and provide a methane enriched biogas stream;
b) passing the methane enriched biogas stream to a steam reforming zone, operated at steam reforming conditions whereby at least a portion of the methane in the biogas stream is converted to a substrate comprising CO and H 2 ;
c) admixing a gas stream comprising CO with the substrate to provide a blended substrate having a CO:H 2 molar ratio from about 20:1 to about 1:2; and
d) passing the substrate to a bioreactor comprising a culture of Clostridium autoethanogenum and anaerobically fermenting the substrate to a product selected from the group consisting of ethanol, 2,3-butanediol, acetate, lactic acid and mixtures thereof.
20 . The method of claim 19 where the micro-organism is the Clostridium autoethanogenum strain deposited at the German Resource Centre for Biological Material (DSMZ) under the deposit number DSM 23693.