Carbon Capture: What to Do With All This Carbon?

Decarbonization has become a worldwide goal. In the power generation industry, one of the key decarbonization methods is to reduce greenhouse gas (GHG) emissions from fossil fuel-fired power plants through carbon capture and sequestration (CCS). CCS can essentially be broken into two steps: first, capturing carbon dioxide (CO₂) in the power plant’s exhaust streams and second, storing it where it will not be emitted to the atmosphere. Carbon capture technology has been studied and improved upon for many years, but since we have yet to see carbon capture on a large scale, scientists are continuing to identify the most productive and efficient ways to sequester CO₂. 

Geologic CO₂ Storage 

Many experts agree that the most effective method of long-term storage is to inject the CO₂ into geologic formations. These formations include oil and gas reservoirs or other similar, naturally-occurring storage areas. The U.S. Department of Energy (DOE) estimates that the U.S. has enough geologic storage capacity to contain 600 years’ worth of current-level emissions from sources that could be equipped with carbon capture technology. 

One of the most common—and controversial—methods for geologic storage of captured CO₂ is enhanced oil recovery (EOR). EOR is a technique used to extract higher amounts of oil from an underground oil reservoir by pumping a gas into the reservoir, displacing oil while maintaining geologic pressure.  

Benefits 

There are two key benefits to using CO2 in EOR. First, it is miscible in oil (meaning it forms a homogenous mixture), decreasing the oil’s viscosity and making it easier to extract. Second, CO₂ is not as expensive as other oil-miscible gases and liquids. The CO₂ in the extracted oil is then recovered and reinjected. This creates a closed-loop process until oil extraction is complete, with a 95% or greater sequestration rate for the injected CO₂. 

Challenges 

Skeptics of using CO₂ for EOR wonder, if we are capturing carbon from the combustion of fossil fuels, and using it to extract even more fossil fuels, can it be considered a valid decarbonization technique?  

And although using CO₂ for EOR has its benefits, it also has some risk. The stored CO₂ has the potential to leak from the storage areas, primarily through the wells used as injection points. While geologic formations themselves are able to structurally trap the CO2, fault planes near injection zones could offer a potential escape route for the gas. Additionally, the process of injecting CO₂ could potentially induce seismic activity. These concerns are studied heavily when selecting an appropriate site for geologic storage.  

Outcomes 

Currently, EOR is used to extract only about 4% of oil in the U.S. (Read the “Carbon Dioxide Enhanced Oil Recovery” article.) However, CO₂ used in EOR operations is predominantly captured from naturally-occurring geologic CO₂ sources. So with an increase captured anthropogenic (i.e., man-made) CO₂, there would be both an adequate supply of CO₂ for EOR and ample demand in the oil extraction market.  

EOR has demonstrated that CO₂ sequestration in this application can be done effectively and safely over a long-term period. Additionally, allowing fossil fuel-fired power plants to sell the CO₂ they capture by investing in carbon capture installations provides a financial incentive while reducing GHG emissions.  

As such, using captured, anthropogenic CO₂ in EOR applications is indeed a valid decarbonization technique. It displaces naturally-occurring CO₂ with anthropogenic CO₂. The result is a net decrease in CO₂ emissions emitted into the atmosphere.  

Carbon Mineralization 

Another method for sequestering CO₂ in geologic formations is called carbon mineralization … essentially, creating rock. When CO₂ is dissolved in water and injected into basalt formations, it reacts with the magnesium and calcium in the basalt to form calcite and dolomite. These solid minerals are formed within two years of the injection and are considered stable for thousands of years. This is a permanent CO₂ storage solution, and the only raw materials needed for this to work are CO₂, water and the right kind of rocks.  

Where are the right kinds of rocks located? Quite literally, all over Earth. Basaltic and other reactive types of rock formations exist in every continent and ocean. Carbfix, one of the companies on the cutting edge of this technology, has estimated that there is a capacity to store at least 7.5 trillion tons of CO₂ in the U.S. The U.S. Energy Information Administration estimates that in 2019, the U.S. emitted about 5 billion tons of CO₂. So with the U.S. storage capacity alone, we could store that level of CO₂ emissions for 1,500 years. Simply put, the storage potential across the world is more than enough to sequester all of the global anthropogenic CO₂ emissions. 

One potential downside to carbon mineralization is the amount of water necessary for the process. Typically, for each pound of CO₂, 25 pounds of water are required. However, it is currently assumed that most of the water needed for this process can be sourced from the water already available in the basalt formations. Other research has been conducted, concluding that seawater is another viable water source for this process. 

Utilizing Carbon 

Another acronym commonly used in place of CCS is CCUS, where the U stands for utilization and considers how CO₂ is put to use. CO₂ has historically been used in many different applications: carbonizing beverages, stripping caffeine from coffee, as an ingredient in fire extinguishers, as a refrigerant and as a precursor in chemical production (especially urea).  

According to the International Energy Agency, about 230 million metric tons of CO₂ are used globally each year. Over the past few years, due to supply chain issues, manufacturers of products that use CO₂ have experienced a CO₂ shortage. (Read "How to Maximize Existing Carbon Dioxide Supplies.")

And aside from these traditional uses for CO₂, there are several companies researching new innovative ways to use CO₂: algae biofuels and building materials are two promising examples. Current CO₂ utilization is less than 1% of overall emissions. So even with a significant growth in the manufacturing utilization of CO₂, this would represent a miniscule portion of potentially captured CO₂. Fortunately, every drop counts, and the potential to sell captured CO₂ could open up some new markets for using CO₂.  

Incentives for CCS 

The recently enacted Inflation Reduction Act includes a key update to the tax credit incentives (known as the 45Q tax credits) for CCS. This incentive will improve the financial incentives for installing carbon capture systems on large stationary sources. Power generation and industrial facilities with carbon capture capabilities will see the tax credit increase from $50 per ton of CO₂ captured to $85 per ton.  

Additionally, the timeframe for tax credit eligibility has been extended to the end of 2032. Facility emissions applicability thresholds have also been greatly reduced, making many more facilities eligible for the tax credits. This is expected to drive growth in the carbon capture market, with emitters able to take advantage of the tax credits to improve their bottom line. All of this captured CO₂ will be a catalyst to invest more resources in the possibilities shared in this article that answer the essential question: how are we going to store all this CO₂?

LEARN MORE: Interested in methods for decarbonizing the electric generating fleet? Watch our free on-demand webinar.

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