SBIR-STTR Award

Fossil fuel combustion provides most of the world’s energy needs, as well as most of the CO2 that is accumulating in the upper atmosphere with implications for serious global warming. With increasing energy demands, methods to sequester this by-product CO2 must be developed. This project will develop a novel biological method to react CO2 with H2S to simultaneously (1) convert CO2 into cellular biomass for animal feed protein, and (2) replace the expensive and energy intensive methods currently used to produce elemental sulfur from sour gases. In Phase I, laboratory fermentation experiments will be performed to define the bioreactor design, optimize the culture conditions, and scale-up parameters. Marketability of the biomass and sulfur produced will be evaluated, and process economics will be projected for a commercial demonstration.

Commercial Applications and Other Benefits as described by the awardee:
In the U.S. alone, the technology could reduce CO2 emissions by 6.5 million tons per year while saving up to $1.5 billion to remove H2S. Concurrent benefits include the possibility of building 125 new plants, creating up to 10,000 new jobs, and adding $300 million to the economy

Worldwide carbon dioxide emissions from the combustion of fossil fuels have increased at a rate of about 3 percent per year during the last 40 years to over 24 billion tons today. One candidate technology for dealing with the carbon dioxide problem involves the anaerobic bacterium Chlorobium thiosulfatophilum, which uses hydrogen sulfide and carbon dioxide to produce elemental sulfur and cell biomass. This project will develop a commercial process for the biological sequestration of carbon dioxide along with the simultaneous conversion of hydrogen sulfide to elemental sulfur. Phase I demonstrated technical and economic feasibility by utilizing the bacterium in continuous reactor studies. Economic projections showed that low quality natural gas (LQNG) can be desulfurized for about $0.23/MSCF, while subsequently converting stoichiometric quantities of carbon dioxide. Phase II will develop the engineering and scale-up parameters for commercialization of the technology. Tasks include culture isolation and optimization studies, further continuous reactor studies, light delivery studies, high-pressure studies, process scale-up, and economic projections.

Commercial Applications and Other Benefits as described by the awardee:
In addition to the sequestration of carbon dioxide in cell biomass, the technology should have immediate application in desulfurizing LQNG or other gas streams. This biological approach should be a viable economical alternative to existing hydrogen sulfide removal technology, because it would not be sensitive to the presence of hydrocarbons acting as catalyst poisons.