A Scientific American Update

Since the start of the Industrial Revolution, steadily growing carbon dioxide (CO₂) emissions have contributed to significant warming of Earth’s atmosphere.  In recent years, higher CO₂ levels have also led to rising sea levels, ocean acidification, and extreme weather events. In 2013, the International Energy Agency estimated that 61% of the world’s CO₂ emissions came from power generation and the industrial sector. The best option to return atmospheric CO₂ to safe levels is to reduce energy demands and substantially increase the use of renewable energy production in these sectors. However, until more industries move away from fossil fuel usage, one solution is to capture CO₂ emitted from power plants and then find storage options for the captured gases.

As a first step towards reducing and capturing CO₂, the Environmental Protection Agency (EPA) has begun issuing permits allowing power plants to build newer facilities that incorporate Carbon Capture and Storage (CCS) techniques in each level of production. In 2014, the EPA issued the first-ever class VI underground injection permit to FutureGen Alliance Inc, a joint project of the Department of Energy and an alliance of coal industry partners, designed to demonstrate a “clean coal” solution. In a statement to Bloomberg News, Ken Humphreys, the chief executive of FutureGen Alliance, said: “The issuance of the permit is a major milestone that will allow FutureGen 2.0 to stay on track to develop the first ever commercial-scale, near-zero emissions coal-fueled power plant with integrated carbon capture and storage.” The coal-fired plant would capture carbon emissions and inject the captured CO₂ into one of four planned wells. Annually, FutureGen expected to capture and inject 1.1 million metric tons (MMT) of CO₂ that would otherwise be released into the atmosphere. That is to say, enough CO₂ to fill 200,000 hot air balloons. Carbon capture and storage, also known as carbon capture and sequestration, is the result of research and development over the last two decades geared towards reducing carbon dioxide emissions.

In 2005, Robert Socolow, Professor of Mechanical and Aerospace Engineering at Princeton University, published an article in Scientific American about global warming and the role CCS could play in reducing emissions. At that time, Socolow was also co-principal investigator of the university’s Carbon Mitigation Initiative, supported by British Petroleum (BP) and Ford, which concentrates on global carbon management, the hydrogen economy, and fossil-carbon sequestration. His article focused on power plants which, being stationary gas emitters that account for 50% of U.S. emissions, can be retrofitted to capture CO₂. In that article, Socolow outlined the challenges facing the adoption of CCS techniques. In 2005, he felt that the cost of CCS upgrades, energy consumption of existing techniques, and risk of failure restricted the adoption of CCS. Limited CCS technology has been in commercial use since the 1930’s, but the process still costs considerably more than traditional coal-combustion plants and requires much more energy.

Capture: Can we reduce the economic and energy costs?

The economic and environmental cost of capturing CO₂ remains an issue despite advances in capture technologies. One CCS technique, “oxy-combustion,” burns coal in pure oxygen, creating flue gas that is mostly water and CO₂. This flue gas mixture allows CO₂to be easily removed. Another technique uses chemical “scrubbers” to absorb CO₂ in flue gas that can later be reclaimed and reused. Oxy-combustion and the use of chemical scrubbers are post-combustion processes. A third method is integrated gasification combined cycle (IGCC), in which fuels are altered into natural gas to siphon some CO₂ out before combustion. Chemical scrubbers are used in post-combustion to remove additional CO₂ produced from combustion of natural gas. David Biello, in his 2009 Scientific American article “How Fast Can Carbon Capture and Storage Fix Climate Change?” cited a 2007 estimate from the US Department of Energy that electricity production using the above techniques would cost $114 per megawatt-hour (MWh) compared to $63 per MWh without carbon capture. Doubling the cost of production is a huge barrier for many companies deciding whether to build a traditional coal plant or one using CCS technology. Those environmental advocates who support increased carbon capture have encouraged policy makers to write legislation that reduces the financial burden of CCS technology.

Other environmental groups, such as Sierra Club, point out that, besides the issue of cost, CCS techniques require significantly more energy than traditional plants, making CCS an energy-intensive process that itself threatens to accelerate fossil energy use and increase overall CO₂ production. A 2017 review of solar energy integration, written by Yinan Liu, Shuai Deng, Ruikai Zhao, Junnan He, Li Zhao from Tianjin University, estimates that carbon capture can require up to 15-30% more energy than traditional power plants. Power plants will still need to produce the same amount of energy, so the reduction in efficiency translates to higher demand for non-renewable energy like coal and oil. Increasing energy demand drives up the price of fuel resources, straining the environment further by increasing mining and transportation operations. Increasing fossil fuel needs in exchange for reduced CO₂ gas emitted after production is a step away from our goal to become less dependent on non-renewable fuel sources, and coal mining seriously degrades the surrounding environment local to mining sites.

Yinan Lui and her team reviewed multiple studies and demonstration projects that integrated renewable energy sources into existing capture techniques to reduce this burden. Using solar power, a renewable source, to augment energy needs during carbon capture has shown varying results.  The majority of the renewable energy CCS procedures studied required only 4-25% more energy during CO₂ processing depending on the parameters of the project. Opponents of CCS technology note that many of these techniques have not been tested in large-scale industrial use to prove reliability. Uncertainty contributes to high cost estimates for capture technology and increases risk for companies choosing how to reduce emissions. Using renewable fuel sources as a part of CCS is a promising option, but further process development is needed for full-scale deployment. Regardless which form is chosen, once a company commits to capturing CO₂ the focus shifts to storage options.

Storage: Can we manage the risks?

Capture techniques are only worth exploring as long as there are viable methods to ensure that the CO₂ can be stored and will not escape into the atmosphere. Most current research into underground storage of CO₂ focuses mainly on depleted oil fields and underground brine formations. The brine formations, also known as deep saline-filled formations, are naturally occurring cavities below the Earth’s surface filled with aqueous solutions high in salt and dissolved solids. Brine formations have an advantage of greater capacity for storage, but depleted oil fields are generally better understood due to previous work done by oil industry. According to a 2016 federal brief in the case of the State of North Dakota v. Environmental Protection Agency (EPA), oil companies began injecting CO₂ into mature oil wells to enhance the recovery of oil in the 1970’s. In 1984, over 40 CO₂ injection facilities existed and, by 2012, 142 mature oil fields practiced this technique.

Depleted oil fields are ideal for CO₂ storage because the geological formations are usually linked to pipelines and other industry infrastructure and have held hydrocarbons over time. The existing industry infrastructure around these geological formations yields extensive geological data about the sites as well as advanced monitoring possibilities. Unfortunately, as Steven Anderson, an economist working for the U.S. Geological Survey, states in his review “Cost Implications of Uncertainty in CO₂ Storage Resource Estimates,” these formations are estimated to constitute only 2-5% of the capacity of onshore US storage formations. The remaining 95%-98% of storage locations are deep saline-filled formations.

Unlike depleted oil fields, where extensive geological data already exists, locating, mapping, and monitoring underground brine formations presents a major challenge. Each formation considered for storage must be checked for natural fractures, faults, or other imperfections that could release injected CO₂ to the surface. CCS would be pointless if the storage process cannot ensure that CO₂ remains underground. Anderson compares many studies in his review highlighting the variability in storage estimates and points out that some studies do not differentiate between open saline formations and closed saline formations.

Closed formations naturally have well-understood boundaries but relatively limited capacity.  Open formations can, theoretically, store more CO₂, but such extensive systems are difficult to map.  Reliable mapping is important to facilitate the monitoring of pressure in the system both during and after injection. Anderson writes that monitoring pressures can greatly reduce the risks of gas finding natural escape routes, but monitoring remains a challenge in an open system. CO₂ travels along the cap rock at the top of the formation, causing areas of increased pressure and spreading out until finally reaching a barrier. A cloud of CO₂ gas 10 km in area can extend over 100km or more below ground, meaning any open system must be mapped and monitored over a much greater area than needed for storage. Closed systems pose a higher risk of fracture due to pressure build-up during injection, but the tradeoff is that monitoring and mapping is more reliable than for open systems. To avoid setbacks, any company seeking to integrate storage into an existing carbon-capture system must consider the incomplete data used in some estimates. Research alone is not sufficient; industry and commercial facilities must be prototyped and tested to encourage confidence in CCS technology.

Testing Techniques in the Real World

Several projects have begun integrating some form of capture and storage into their production techniques to demonstrate the possibilities when CCS solutions are included in industrial production. These demonstration projects have achieved some promising results. The EPA court brief from 2016 highlights successful CCS projects such as two large-scale projects opened in Sleipner and Snohvit Norway. Sleipner has stored 16.2 million megatons (MMT) of CO₂ since it opened in 1996 and Snohvit has stored 3 MMT since 2008. To put that in perspective, Biello’s 2009 article says the yearly CO₂ emissions contribution from human activity is about 30 billion metric tons (BMT). Although this disparity between the amount of CO₂ that can be captured and the amount that can be stored seems daunting, as we await optimal CO₂ emission solutions, energy production continues to pollute the atmosphere. Emissions increases today mean further emission restrictions down the line if we want to keep atmospheric CO₂ at safe levels. In Biello’s article, he quotes the manager of technology and engineering for CCS at BP’s alternative energy arm: “for every five years of inaction, it requires an extra gigaton of reductions.” In the end, although capture and storage still pose risks, proceeding too carefully could be just as dangerous as doing nothing to reduce emissions.

The projects practicing CCS also provide examples of the limitations to overcome. In 2011, the Snohvit facility detected a pressure build-up in one injection well. The company was able to alter the injection well and continue operation. Another saline storage in In Salah, Algeria operated from 2004 to 2011 until pressure build-up caused the program to be discontinued. In the 2016 court brief, the EPA argues that these projects did not experience any leaks and that monitoring systems proved effective. Additionally, the EPA points out that the In Salah project has sequestered 3.8 MMT of CO₂ which, in itself, is a success for the environment. These storage projects give a realistic view of what can be expected of different storage options. 

In 2015, the EPA established new source performance standards (NSPS) to guide emissions reduction in the United States. The standard does not specify any particular technology and applies different standards to each type of emission-producing plant. The 2016, a federal court brief for the State of North Dakota v. the EPA discusses several plants that have already met or exceeded the NSPS.

A Canadian project, the Boundary Dam (opened in 2014), retrofitted an existing plant to be the first in the world to use CCS technology and has captured and stored 0.8 MMT in just one year. In the United States, the Petra Nova project near Houston, Texas, which has been in planning and permitting stages for several years, began operation in 2017 and is designed to capture 1.4 MMT each year. Another United States project mentioned in the court brief is the Archer Daniels Midland Plant in Illinois that captured 1 MMT of CO₂ during the initial phase of the project between 2011 and 2014. Still, large-scale commercial operations are few and far between. For example, according to the “Carbon Capture and Sequestering at MIT” webpage, as of 2015 the injection well project by FutureGen mentioned at the beginning of this article had been cancelled. This project and many like it were cancelled due to flawed cost estimates, lack of support, and lack of funding, as well as unforeseen setbacks due to the relatively new nature of CCS technology.

A Look Toward the Future

In 2005, Socolow identified several major barriers to the deployment of CCS technology: the risk of increasing emissions, lack of public and government support, uncertainties about capture and storage practices, and the cost of the retrofitting and building new low-emission plants.

The issues are largely unchanged. Inconsistencies in research and experimentation cast considerable doubt on the effectiveness of CCS. Building new low-emission facilities or installing carbon-capture systems onto existing plants remain an expensive option for industrial companies. Stronger emission regulation could guide more companies to choose cleaner technology, but the fact remains that carbon capture will increase energy demands. The efficiency of carbon capture techniques has improved, but much of the existing technology still needs to be proven commercially viable. At the same time, some companies are working with the regulation and economic barriers to demonstrate how CCS can be integrated with the existing energy industry. Each project, successful or not, improves our understanding of CCS implementation, but the slow adoption is not keeping pace with increasing emissions worldwide. If we cannot commit to CCS technology and keep pace with emissions, it may be time to abandon CCS techniques as a solution to reducing greenhouse gases in the atmosphere. The restrictive approach to regulating clean technology may have taken its toll–meaning we may very well need to abandon the idea that there is still time for a technological solution to come along and allow us to continue using fossil fuels as we have been over the past few decades.

 

 

Further Reading

1. Anderson, Steven T. “Cost Implications of Uncertainty in CO₂Storage Research Estimates: A Review.” Natural Resources Research, vol. 26, no. 2, 2 Apr. 2017, pp. 137–159
2. Biello, David. “How Fast Can Carbon Capture and Storage Fix Climate Change?” Scientific American, 10 Apr. 2009, www.scientificamerican.com/article/how-fast-can-carbon-capture-and-storage-fix-climate-change/
3. EIA – Independent Statistics and Analysis. U.S. Energy Information Administration, 10 May 2017, www.eia.gov/tools/faqs/faq.php?id=77&t=11.
4. Herzog, Howard. “As of September 30, 2016, the Carbon Capture and Sequestration Technologies Program at MIT Has Closed. The Website Is Being Kept Online as a Reference but Will Not Be Updated.” Carbon Capture and Sequestration Technologies @ MIT, Massachusetts Institute of Technology, 30 Sept. 2016, sequestration.mit.edu/tools/projects/illinois_industrial_ccs.html
5. Liu, Yinan. Deng, Shuai. Zhao, Ruikai and He, Junnan; Zhao, Li. “Energy-Saving Pathway Exploration of CCS Integrated with Solar Energy: A Review of Innovative Concepts.” Renewable and Sustainable Energy Reviews, vol. 77, 28 Apr. 2017, pp. 652–669.
6. United States Court of Appeals for the District of Columbia Circuit. State of North Dakota, Et Al., v. U.S. Environmental Protection Agency, Et Al. 21 Dec. 2016, p. 36, edf.org/sites/default/files/content/2016.12.14_epa_brief.pdf