Bio-assisted process for conversion of mixed volatile fatty acids to selective drop-in fuels

A bio-assisted process for production of drop-in fuels from CO2 and a volatile fatty acid rich source, said process comprising:

• (a) providing a first electrochemical system comprising at least one working electrode, at least one counter electrode, and a medium inoculated with selectively enriched electro-active bacteria selected from the group consisting of Geobacter anodireducens, Clostridium ljungdahlii, Acetobacterium woodii, Sporomusa acidovorans, Propionibacterium acidifaciens, Acetobacterium carbinolicum, Pseudomonas stutzeri MTCC 25027, Pseudomonas fragi MTCC 25025, Pseudomonas aeruginosa MTCC 5389, Psuedomonas alcaligenes, Schewanella putrefaciens, Clostridium aciditolerans, Enterobacter aerogenes MTCC 25016, Shewanella sp. MTCC 25020, and combinations thereof;
• (b) providing feedstock to the first electrochemical system of step (a), wherein the feedstock comprises CO2 with the volatile fatty acid rich source;
• (c) intensifying carboxylic acids in the feedstock of step (b) to obtain an effluent comprising intensified carboxylic acids;
• (d) providing a second electrochemical system comprising at least one working electrode, at least one counter electrode, and a medium inoculated with selectively enriched electro-active bacteria selected from the group consisting of Sporomusa ovate, Clostridium acetobutylicum, Clostridium butyricum, Clostridium acidurici, Pseudomonas aeruginosa MTCC 5388, Pseudomonas putida MTCC 5387, Clostridium carboxidivorans, Clostridium beijerinckii, Schewanella oneidensis, Geobacter sdfurreducens, Clostridium cellutolyticum, Clostridium cellulosi, Clostridium cellulovorans, Alicaligens sp. MTCC 25022, Serratia sp. MTCC 25017, Lysinibacillus sp. MTCC 5666, and combinations thereof;
• and
• (e) reducing the intensified carboxylic acids of step (c) in the second electrochemical system to obtain the drop-in fuels;
• wherein the working electrode of the first electrochemical system is composed of a material selected from the group consisting of graphite plate, carbon brush, carbon paper, graphite felt, activated carbon cloth, and combinations thereof;
• wherein the counter electrode of the first electrochemical system is modified with a material selected from the group consisting of carbon nanotube (CNT), graphene, charcoal, activated carbon, stainless steel (SS) mesh, nickel oxide, zinc oxide, and iron oxide;
• wherein the volatile fatty acid rich source comprises at least 0.5% formic acid, provided that if the formic acid is not already present in the feedstock the feedstock is supplemented with at least 0.5% formic acid;
• wherein the working electrode of the second electrochemical system is composed of a material selected from the group consisting of graphite plate, graphite rod, carbon brush, carbon paper, carbon plate, graphite felt, activated carbon cloth, and combinations thereof;
• and
• wherein the counter electrode of the second electrochemical system is modified with a material selected from the group consisting of CNT, Co9S8, graphene, FTO/NiO, Ni/Fe layered double hydroxide, Si/TiO2 nanowires, charcoal, activated carbon, nickel oxide, zinc oxide, and iron oxide;
• and
• wherein the drop-in fuels are selected form the group consisting of methanol, ethanol, butanol, acetic acid, propanoic acid, butanoic acid, valeric acid, and caproic acid.