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 and/or H2, and the production of one or more products from the microbial fermentation of said gaseous substrate.
1 - 45 . (canceled)
46 . A method for producing one or more products by microbial fermentation, the method comprising:
a) passing a biogas stream comprising methane to a conversion zone, operated at conversion conditions whereby at least a portion of the biogas stream is converted to a substrate comprising CO; and
b) passing the substrate to a bioreactor comprising a culture of one or more micro-organisms, and anaerobically fermenting the substrate to one or more products selected from the group consisting of alcohols, acids and mixtures thereof.
47 . The method of claim 46 wherein the biogas stream comprises methane and at least one component selected from the group consisting of CO 2 , N 2 , H 2 , H 2 S and O 2 .
48 . The method of claim 47 wherein the methane component in the biogas stream is enriched by removing at least a portion of the component prior to converting the gas stream to a substrate comprising CO.
49 . The method of claim 48 where the enrichment is carried out by using pressure swing adsorption (PSA).
50 . The method of claim 46 wherein CO is added to the substrate to provide a blended substrate, wherein the blended substrate comprises CO and H 2 in a molar ratio of CO:H 2 from about 20:1 to about 1:2
51 . The method of claim 46 wherein the substrate comprises from 5% to about 100% CO by volume.
52 . The method of claim 46 wherein the alcohol is selected from the group consisting of ethanol, 2,3-butanediol and mixtures thereof.
53 . The method of claim 46 wherein the acid is selected from the group consisting of acetate, lactic acid and mixtures thereof.
54 . The method of claim 46 wherein the process of converting the biogas to a substrate stream is a catalytic oxidation process.
55 . The method of claim 54 wherein the catalytic oxidation process is a steam reforming process.
56 . The method of claim 46 wherein the micro-organism is selected from the group consisting of Clostridium, Moorella, Pyrococcus, Eubacterium, Desulfobacterium, Carboxydothermus, Acetogenium, Acetobacterium, Acetoanaerobium, Butyribaceterium, Peptostreptococcus and mixtures thereof.
57 . The method of claim 56 wherein the micro-organism is selected from the group consisting of Clostridium autoethanogenum, Clostridium ljungdahli, Clostridium ragsdalei, Clostridium carboxydivorans and mixtures thereof.
58 . The method of claim 55 wherein the biogas stream is blended with CO 2 prior to passing the stream to the reforming process.
59 . The method of claim 58 wherein the blended biogas stream comprises CH 4 and CO 2 at a ratio of CH 4 :CO 2 from about 1:1 to about 3:1
60 . The method of claim 59 wherein the blended biogas stream comprises CH 4 and CO 2 at a ratio of CH 4 :CO 2 of at least 1.5.
61 . The method of claim 57 where the micro-organism is Clostridium autoethanogenum.
62 . The method of claim 57 where the micro-organism is Clostridium autoethanogenum having the identifying characteristics of the strain deposited at the German Resource Centre for Biological Material (DSMZ) under the deposit number DSMZ 23693.