Introduction to Microbial CO2 Sequestration
Due to the increased emissions of CO2, mainly from the burning of fossil fuels in power stations throughout the world, the carbon dioxide in our atmosphere is at its highest levels since record keeping began.
Numerous proposals have been suggested to mitigate the CO2 emissions. These include a phasing out of coal fired power stations, which are the main culprit of CO2 emissions, or mixing a biomass with the coal.
However, even though prevention is often better than the cure, carbon capture and sequestration (CCS) would appear to be the more popular means of abating CO2 emissions to the atmosphere.
CCS consists of capturing the CO2 at the source, and after pressurization and super cooling, injecting it into storage.
This is an article on carbon storage, where we will examine the storage in an underground saline aquifer, where it will be subjected to microbial processing. We begin with a list of the more popular locations which have been suggested for the storage of CO2, then going on to explain microbial sequestration technology.
Suggested Locations for CO2 Sequestration
The following list of suggested locations includes the more popular ones cited for the sequestration of CO2:
- Under the deep oceans
- In disused coal mines
- In redundant offshore oil and gas reservoirs
- In underground saline aquifers
Microbial Carbon Dioxide Sequestration Explained
One of the suggested methods for sequestration of carbon dioxide is to compress the gas and pump it into an underground saline aquifer. There are numerous of these aquifers about, some of them deep underground and capable of holding huge amounts of compressed CO2.
Up until now the effect of the injected CO2 on the microbes present in the saline solution was unknown, however scientist have been developing models and conducting experiments on an aquifer in Frio Ridge, Texas.
- Method employed
The Pressurized Carbon Dioxide was pumped into the aquifer, 5741 feet underground where the CO2 plume mixed with the brine solution as it travelled downwards. Samples were collected from various locations, then filtered and any living or dead creatures extracted and a DNA analysis carried out to determine the extent of their diversity. These results will assist in determining the capacity of the underground aquifer microbe ecosystem to store CO2.
These microbes, which despite the harsh brine water continue to settle and continue to breed, will again be collected and an attempt to cultivate them will be made.
If successful, the cultivated microbes will be subjected to a high pressure in the lab; and a strain of microbe resistant to the high pressure CO2 developed and studied to see how they would behave under an actual CO2 sequestration conditions.
Finally, some microbes excrete a fine biofilm, somewhat like the film which appears on our teeth if we don’t clean them.
This microbial biofilm will gradually build up within the aquifer and could eventually assist in the sealing of the aquifer against leaching or leaking of the stored CO2.
Reference Web: Saline Aquifers - Sequestration of CO2 Underground
Sequestration of Carbon Dioxide in Naturally Precipitated Dolomite Using Microbes
There is another microbial CO2 Sequestration experiment taking place. This uses the natural ability of some microbes present in saline lakes, to remove carbon dioxide from the air, and processing it into dolomite rock.
This process is taking place in lakes such as the Coorong hyper-saline lakes in Australia, and it is hoped that samples of the lake water and microbes can be taken, examined under laboratory conditions and reproduced in a model.
This will lead to a fuller understanding of the natural process of dolomite formation by microbes, through CO2 absorption in saline lakes. Once the laboratory experiments are complete, the scientists hope to develop a working model using identical saline water and microbes in a bioreactor tank, or preferably constructing a small saline lake on non-agricultural land, close to an industrial processing plant where the emitted CO2 can be removed from the atmosphere by the natural process. Regular air and water samples would be taken to examine the CO2 reduction and the formation of dolomite.
If this is successful, scaled up versions could be constructed sited near desalination plant saline outlets, where the microbes could be introduced and perhaps the byproduct of dolomite, could be sold to the building industry.
Reference Web: Dolomite Storage - Microbial Dolomite storage of CO2 in lakes and arid coastlines.