Coupling bio geochemical processes to regenerative energy for an industrial carbon cycle

The high turnover of carbon dioxide during bacterial oxidation of sulfides witnessed in cultures of Acidithiobacillus ferrooxidans, Leptospirillum ferroxidans, and even more efficient by Sulfolobus and other thermophile bacteria e.g. Acidianus brierleyi , and the parallel rapid build up of bacterial biomass suggests a coupling of these processes to solar energy in order to develop carbon dioxide cycling technologies for sustainable future applications. Synergistic effects can be expected with biometallurgical research and technology, which also aims at a further increase of energy turnover reflected in higher leaching rates. The prospective technology has been investigated by growing bacteria on iron sulfide synthesized from iron sulfate using solar energy. A catalytical process was developed which allows sulfate to sulfide reduction at a carbon electrode at 120 C. Photovoltaic energy is used to drive the electrochemical reaction and thermal heat for maintaining the operation temperature. H2S is immediately converted in Fe2 containing solution to iron sulfide, which is supplied to bacterial cultures for biological CO2 fixation. It is estimated that solar powered biohydrometallurgical processes for CO2 fixation may reach efficiencies exceeding biological photosynthesis by one order of magnitude. In addition, they can be operated in infertile environments with very limited water. The bacterial biomass has a high quality and could be used for energy, materials and even for food production. The perspectives and challenges for coupling biohydrometallurgical processes to regenerative energy utilization are discussed