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The storage of CO2 in the subsurface is a novel and promising tool. To securely use carbon capture and storage (CCS), the long-term fate of the CO2 must be properly understood. The microbial community is an extremely large component of the subsurface environment; however, the impact of CO2 storage on these microorganisms and their impact on CO2 are poorly understood. These organisms may or may not play a positive role in carbon storage. Voordouw’s team will analyze samples from a subsurface location prior and during CCS to determine the initial community composition and the changes due to CCS. This will help to describe microorganisms that thrive under CCS conditions. Under CCS conditions in the field, researchers have found that methanogenic archaea (producing methane) are an abundant microbial group and that homoacetogenic bacteria (producing acetic acid) are also frequent. These groups will be examined, at different time points, to determine the natural and engineered processes involved in microbial mediated fixation and/or the conversion of CO2.
It is not known whether microorganisms can positively or negatively influence the CCS process. One goal is to determine the microbial communities present at subsurface locations planned for CCS use or at locations that are currently used for CCS. The other goal is to study the interactions between microbes and CO2.
To properly use CCS in conjunction to microorganisms, the long-term fate of stored CO2 was tracked. For instance, microorganisms can convert CO2 to methane and water (when H2 diffuses into the geological layers). To predict if these processes are occurring, samples were collected and microbial communities were elucidated via DNA extraction and sequencing. By comparing control sites to CCS sites, the activity and presence of specific CCS microorganisms is being determined. Microbial-mediated fixation and conversion of CO2 under various types of reservoir conditions was also examined.
The information provided by this research may improve the long-term success of CCS and could potentially provide new processing options.
This research will help understand the potential of CCS, and the role of microorganisms in this process. Understanding the role of micro-organisms may help improve secure storage of CO2 in Canada and the world. Canada is, after all, heavily involved in oil and gas development since it is a part of our economy. Therefore, it is our responsibility to make the use of fossil fuels more secure.
Industry can apply these results to CCS and possibly towards enhanced oil recovery (EOR) technology. Chemical, geological and biological factors are all important to understand the long term implications of CCS. This research helps provide new knowledge on the ability of microorganisms to permanently store CO2, and the potential impacts of EOR.
Voordouw’s partners are Cenovus and Baker Hughes, and both have provided samples. Alberta Sulphur Research Limited (ASRL) has helped the team perform pressurized experiments.
Investigations were first directed on the activity of homoacetogenic and methanogenic microbes; the first converts H2 and CO2 into biomoass and acetic acid, the latter converts it into biomass and methane. Surprisingly, homoacetogenic bacteria are highly active and are the first to reduce CO2 and H2. However, field data implied methanogenic archaea are the most abundant microbial groups, and homoacetogenic bacteria are less frequent. The microbial community composition in field samples differs from activity patterns found in the laboratory.
MHGC Samples Analysis
H2 concentration present in the subsurface is very important. H2 and CO2 are both used in energy metabolism. The effect of H2 partial pressure on homoacetogenic and methanogenic activity has been determined. Homoacetogenic activity occurs first, followed by methanogenic activity. Homoacetogenic bacteria induced a significant pH reduction, since the dominant product formed was acetic acid. pH modification is important to CCS, because it may modify subsurface chemistry by changing the solubility and/or precipitation of ionic species and minerals. Bacterial activity is also impacted by pH. pH 7, homoacetogenic activity caused the pH to drop to pH 5.5, inhibiting its own activity and promoting methanogenic activity.
Studies have begun on the effects of CO2 injection on community composition, at various pressures: for example, pressured gaseous CO2 was compared with pressurized supercritical liquid CO2. It has been found that supercritical liquid CO2 is highly toxic to bacteria; nonetheless, this is the form of CO2 which is usually injected at CCS sites. As a result, there may be more activity around the edges of the storage sites than in the center, and this is being examined further.