By Tim O’Connor, Attorney / Climate Policy Analyst
A recent issue of the UK Guardian has brought to the forefront the findings of paper published in the Journal of Petroleum Science and Engineering. This paper, purporting to call into question the ability of carbon capture and sequestration (CCS) technology to serve as a solution for greenhouse gas emissions (GHG) is making waves in the scientific and climate change policy communities. Titled “Sequestering carbon dioxide in a closed underground volume,” the article suggests CCS is not a viable solution to the current problem of these emissions from fossil fuel power plants, an assertion flying in the face of accepted wisdom on the subject to date.
Published by perhaps the only Texas-based husband and wife team specializing in petroleum and chemical engineering, Christine Ehlig-Economides and Michael Economides, the journal article has resulted in a significant amount of consternation in the scientific community and an unfortunate level of attention by news outlets looking for a reason (scientifically supportable or otherwise) to undermine CCS as a bridge technology for greenhouse gas mitigation.
In essence, the paper argues that CCS will require a much larger subsurface geographic area than previously thought to be effective. According to the article, a single 500-MW power plant could require a land area about the size of a small U.S. state. Due to this projected massive land need, the authors argue that CCS will be cost-prohibitive, essentially a boondoggle of the highest proportions in almost every foreseeable application. Such an opinion is certainly not a sound bite the U.S. Department of Energy (which recently announced a $3 billion investment in CCS research, development and deployment) or power plants such as the proposed Tenaska Trailblazer site (projected to sequester 85% of its emissions using CCS) are likely to take seriously.
This article has been met with an outpouring of support for CCS from a supermajority of experts making up the broader scientific community on this subject. Indeed, a read of the responses to the journal, coupled with a review of the litany of CCS literature, show that the authors' opinions on CCS potential are extreme outliers in the growing scientific consensus surrounding carbon sequestration.
In response to journal article and Guardian story, no fewer than four formal responses by leading CCS experts in the scientific community have been added to the public discussion, with more likely to be published.
In addition, the World Resources Institute (WRI) and American Petroleum Institute (API) issued statements in response to the article, pointing out the authors’ misapplication of known petrochemical and reservoir management principles combined with improper assumptions. Of note is that no responses from the scientific community have supported the authors’ extreme projections on subsurface area needs, or their conclusions regarding limitations on pore space "injectivity" that are known to be posed by pressure considerations or other factors.
In general, scientific community responses to the article include five fundamental critiques of the authors’ methodology:
- A mischaracterization of reservoir outcropping leakage potential
- A misunderstanding of pore space dynamics and availability
- Fundamental errors in authors’ numerical model related to vertical and lateral migration potential (questioning the absolute impermeable boundaries assumption)
- Failure to take evidence from current CCS projects into account
- Inaccurate perception of reservoir pressure management at CCS sites
A sixth critique by the API questions the authors' estimates (or underestimates) of the amount of enhanced oil recovery available for CO2 sequestration, a critical part of their assertion that the U.S. doesn’t have enough capacity to mitigate emissions on the level necessary to meet long-term reduction targets.
Such critiques, however, while tending to disprove the authors' overall characterization of how much CO2 can be injected into an individual site, and how it will migrate, must make room for the valuable messages that can be drawn from their work.
First and foremost, the authors and response papers agree that, as an important first step to any project, it is necessary to confirm the aquifer size and characterize subsurface geologic conditions through an aquifer appraisal process before starting sequestration. This process of site selection will be the only way to know the subsurface characteristics of the injection site, model the probable plume migration pathways and make projections about storage potential.
Second, and perhaps as important, is that the authors and responders agree that reservoir pressure is linked to overall injectivity, and that detailed formation-scale capacity assessments should take pore volume and pressure into account.
Finally, since injected CO2 plumes can migrate laterally or vertically underground depending on geologic and injection conditions, it is critical that sequestration projects be equipped with sufficient subsurface monitoring to track CO2 migration once injection begins.
According to the Intergovernmental Panel on Climate Change, when properly sited, operated and monitored, geologic sequestration projects can be expected to retain 99% of injected CO2 in the subsurface for 1000 years or more.
This finding underscores the importance of CCS as a low-carbon technology and shows the importance of educating the public about the merits of the technology. With the fresh gut check provided by the Economides and the overwhelming response from both the scientific community, API and WRI, the desire to make CCS work as a mitigation option is receiving the attention is deserves.
The completion of a few successful commercial scale projects at home and abroad should quell concerns such as those raised in the article and allow CCS technology to grow as a major solution for reducing emissions and provide another reason to invest in innovative technologies that can help us transition to a clean energy economy.
 Guardian, April 27, 2010, “US research paper questions viability of carbon capture and storage”
 Ehlig-Economides and Economides, Journal of Petroleum Science and Engineering 70 (2010) 123–130
 Haszeldine et al., Response to the article April 27, 2010 article in the Guardian
 Canada Free Press, Feb., 25, 2010, “Geologic Carbon Storage Can Never Work, says new US study”
 The Clean Economy Group, April 19, 2010, “Tenaska agrees to capture, sequester 85% of CO2 emissions in settlement with Environmental Defense Fund”