Carbon capture in fermentation

#This invention relates to systems and methods for improving overall carbon capture and/or improving overall efficiency in processes including microbial fermentation. In particular, the invention relates to improving carbon capture and/or improving efficiency in processes including microbial fermentation of a substrate comprising CO derived from an industrial source.

#Ethanol is rapidly becoming a major hydrogen-rich liquid transport fuel around the world. Worldwide consumption of ethanol in 2005 was an estimated 12.2 billion gallons. The global market for the fuel ethanol industry has also been predicted to grow sharply in future, due to an increased interest in ethanol in Europe, Japan, the USA, and several developing nations.

#For example, in the USA, ethanol is used to produce E10, a 10% mixture of ethanol in gasoline. In E10 blends the ethanol component acts as an oxygenating agent, improving the efficiency of combustion and reducing the production of air pollutants. In Brazil, ethanol satisfies approximately 30% of the transport fuel demand, as both an oxygenating agent blended in gasoline, and as a pure fuel in its own right. Also, in Europe, environmental concerns surrounding the consequences of Green House Gas (GHG) emissions have been the stimulus for the European Union (EU) to set member nations a mandated target for the consumption of sustainable transport fuels such as biomass derived ethanol.

#The invention will now be described in detail with reference to the accompanying Figures in which:

#FIG. 1: is a schematic representation of a system including a CO2 remover downstream of a bioreactor according to certain embodiments of the invention.

#FIG. 2: is a schematic representation of a system including a CO2 remover upstream of a bioreactor according to certain embodiments of the invention.

#In accordance with certain methods of the invention, waste or off gases from an industrial process may be used to supplement and/or support fermentation reactions with minimal additional processing or treatment steps on the gases prior to passing them to the bioreactor in which the fermentation process is performed. This is particularly surprising, because it is commonly believed that the waste or off gases contain contaminants that would be detrimental to the growth and/or survival of the micro-organisms used in the fermentation. The invention has particular applicability to waste or off gases produced during steel making processes, particularly those containing CO, which are used to produce alcohols (e.g. ethanol, butanol, isopropanol) and/or acids (e.g. butyric acid, acetic acid and/or acetate) and/or hydrogen. While there are a variety of different micro-organisms capable of performing such processes, the invention has particular applicability to fermentation processes involving the use of Clostridium autoethanogenum.

#This aspect of the invention has significant value in that it reduces the number of or eliminates the pre-processing steps performed on waste gases prior to their use in a fermentation reaction. Thus, the invention provides for wider suitability and/or applicability of such fermentation processes, particularly in established industrial plants where a limited, predetermined amount of space may be available for adding equipment to perform fermentations. Also, because no or limited scrubbing and/or pre-treatment processes are performed on the waste gases, embodiments of the invention may also ameliorate or reduce waste from industrial processes due to there being no need to process the waste or contaminants resulting from the scrubbing and/or pre-treatment processes.

#Waste gases from industrial processes other than steel manufacturing may be used in a similar fashion in the methods of the invention. The invention is readily applicable to fermentation reactions that utilise gaseous substrates other than carbon monoxide as a source of carbon and energy, produce alcohols other than ethanol, produce hydrogen, and/or which utilise micro-organisms other than Clostridium autoethanogenum.