Xu, Y., et al. Adding value to carbon dioxide from ethanol fermentations. Bioresour. Technol. (2010), doi:10.1016/
The major way to reduce carbon emission to the atmosphere is by carbon capture and storage. The article titled Adding value to carbon dioxide from ethanol fermentations is a fresh article still in press and describes the many potential uses of CO2 released from ethanol fermentation. There has been an estimated increase of 2.1% per year in the energy-related carbon dioxide release to the atmosphere. Ethanol is the fastest growing alternative fuel which is normally mixed with gasoline to be used as a fuel. Ethanol is usually produced by the fermentation of grains such as corn and does not necessarily cause a carbon release to the atmosphere since it is utilizing the crops that had captured carbon dioxide from the atmosphere in the previous year. This means that if there is a way to utilize the carbon dioxide released during ethanol fermentation, although it is less in amount, we can have a net reduction in carbon dioxide emitted to the atmosphere.
Although, ethanol fermentation still releases less carbon to the atmosphere compared to the fossil fuel energy, with growing ethanol fermentation factories, the amount of carbon released to the atmosphere will also increase. The carbon dioxide merchant markets use the carbon dioxide released from the ethanol fermentation industries. The once primary source of CO2 to the CO2 merchant market, anhydrous ammonia plant is no longer favorable since the CO2 produced from such plants are impure and less in volume. Therefore, ethanol production has taken over and is now the primary source of CO2 to such markets in the US. CO2 produced from ethanol fermentation is 99% pure and is in larger volume; between 1990 and 2008 itself, the market share for CO2 use from ethanol fermentation has increased from 20% to 33%. Besides this, another challenge lies in the cost of transporting CO2 produced from ethanol fermentation to different factories in US.
The most costly step of carbon capture, storage and sequestration step is the carbon capture which is much cheaper if the CO2 source is ethanol fermentation. This is again because the CO2 emitted is pure and in high concentration, and therefore the only step required for purification is dehydration (to remove the moisture that would otherwise react with CO2) and compression (in order to bring the CO2 pressure similar to the pipeline pressure). The use of CO2 is many- as dry ice, in beverages and food industry for carbonated sodas, sparkling wine and beers, for cryogenic freezing used for food processing, chemical industries which uses CO2 to produce chemicals such as urea and hydroxybenzoic acids, fuels and polymers. The CO2 produced can also be fed to microalgae that uses it to produce ethanol; the advantage of this is that microalgae has “rapid growth rates and high CO2 fixation capabilities compared to the conventional plants” as stated by the authors. Another benefit of this is that exhaust CO2 is used by these algae to produce new ethanol which can be used for fuel again. “Enhanced oil recovery (EOR) refers to the use of a process or technology other than primary and secondary recovery methods to enhance and improve the recovery of undeveloped oil from a reservoir (National Energy Technology Laboratory, 2005).” CO2-EOR is the most promising one so far since CO2 acts as a solvent thereby lowering the viscosity of oil and increasing the net flow of oil in the production well.
The authors of this paper depicts the many valuable ways in which CO2 emitted from ethanol fermentation could be used as well as the drawbacks of some of these methods. This paper gives some hope to the ethanol fermentation industries in that it discusses the ways in which carbon emissions to the environment can be reduced by utilizing the emitted CO2 for food, beverages and chemical industries to name a few.