As the most commonly produced greenhouse gas, carbon dioxide (CO2) is one of the main drivers of climate change and the greenhouse effect. In 2019, the U.S. Energy Information Administration estimated that the United States emitted approximately 5,130 million metric tons of CO2 into the atmosphere. Global emissions were estimated to be a staggering 33,621.5 million metric tons that same year.
Geological carbon sequestration could be part of the answer to dealing with CO2 emissions and the ongoing threat of climate change.
Geological Carbon Sequestration vs. Biological Carbon Sequestration
Biological carbon sequestration is what most people think of when they hear of CO2 sequestration. This is where vegetation, aquatic environments, trees, and soils naturally store carbon. Essentially, things like trees and plants take in carbon dioxide from the atmosphere and utilize it to build tissues thus storing the carbon.
Geological carbon sequestration is a man-made process of capturing and storing CO2 in underground formations. This method is already used in what is called tertiary recovery, an enhanced oil recovery process. In this process, the CO2 is pressurized until it enters a liquid state. It is then injected into porous rock formations. In the energy industry, this allows for the reduction of oil viscosity and allows the oil to flow easier from the well. This technique is typically used in the latter years of an oil well’s life.
With modern engineering technologies, we can successfully capture and inject carbon dioxide into underground formations to keep it out of the atmosphere.
How Much CO2 Can the United Stated Store Through Geological Sequestration?
The first probabilistic nationwide assessment released in 2013 estimates a CO2 storage potential of 2,400 to 3,700 metric gigatons in the United States. To put this into perspective, one metric gigaton is equivalent to one billion metric tons.
Where Would Geological Carbon Sequestration Take Place?
While assessments still need to be made, those that have been completed indicate that the area with the most potential for CO2 storage is the Coastal Plains region. This includes the coastal basins that spread from Texas to Georgia. It is estimated that 2,000 metric gigatons can be stored in this region. Other areas with storage potential include the Rocky Mountains, Alaska, and the Great Northern Plains, but assessments have yet to be completed.
Potential Concerns of Geological CO2 Sequestration
The biggest concern of geological CO2 sequestration is leakage through transmission faults or associated fractures into groundwater, the vadose zone and atmosphere, and even buildings. Leakage of CO2 into groundwater sources could result in:
- Decreased pH
- Possible release of metal contaminants
- Increase mineral dissolution
However, an increase in the CO2 concentration in the groundwater could result in the reduction of certain metals and act as a mitigation to the migration of contaminants.
The vadose zone is the part of the earth between the top of the ground and the surface of the water table. The release of CO2 into this zone could result in changes in the composition of gases within the soil which could then flux to the atmosphere. This could also result in the release of CO2 into buildings which can reduce the oxygen levels in the indoor air.
Even with these concerns, geological carbon sequestration is a practical and environmentally sustainable approach to dealing with carbon emissions as we transition from fossil fuels to lower emission forms of energy. As we substantially decrease our carbon emissions, we can utilize lower usage of fossil fuels longer with less of an impact on the environment and help slow climate change.
Noah Chemicals Services’ team of engineers and chemists can help with proper process system design for CO2 Sequestration.