Carbon capture and storage (CCS) is being touted as a promising method of reducing carbon dioxide emissions into the atmosphere.
The oil industry for decades has injected CO2 underground in enhanced oil recovery projects, so some science and technology exists for CCS, although many questions remain regarding both sequestration and climate change. Researchers have yet to demonstrate that CCS can be accomplished on a grand-enough scale to stabilize CO2 concentration levels.
CCS envisions capturing CO2 from power plants, petrochemical plants, and other industrial users and sequestering it underground into depleted oil and gas fields, saline aquifers, and unmineable coal seams.
The commercialization of CCS faces various obstacles, said climate researchers participating in an Offshore Technology Conference panel session on CO2 sequestration in early May. Sally M. Benson, executive director of Stanford University’s global climate and energy project, summed up the problem:
“In principle, sequestration is straightforward,” Benson said. “In practice, there is a great deal of science and engineering that underpin safe and effective sequestration.... The question of scale cannot be ignored.” She and other researchers suggest that thousands of projects will be needed to reduce CO2 emissions.
“Each of the projects will [need to] be 5-10 times larger than any of the existing projects,” Benson adds. Major existing sequestration projects are the Sleipner project off Norway, the Weyburn project in Saskatchewan, and the In Salah project in Algeria.
Potential consequences
Benson said potential consequences stemming from large-scale sequestration must be assessed, and methods developed to avoid negative consequences.
Daniel Schrag, Harvard University professor of earth and planetary sciences, advocates financial incentives to accelerate CCS research. He believes “there would be a lot of commercial bidders” if the US government were to let contracts for large-scale CCS projects.
“It’s time to get going, not just with small test projects, but with full-scale industrial experiments,” Schrag said. “I think what is missing—in the US at least—is the political will to do it.” However he notes widespread change in public perception within the past 3 years regarding CO2 levels.
The Intergovernmental Panel on Climate Change reports the current atmosphere CO2 concentration is about 380 ppm and rising at a rate of 2 ppm/year. Researchers are calculating the volume of CO2 emissions that must be reduced and in what time span in order to stabilize CO2 concentrations.
Their efforts raise underlying questions for which there are no definitive answers as yet. Schrag calls the situation, “an experiment on a planetary scale that hasn’t been done for millions of years. There will be surprises.” He also emphasizes the need for CCS on a big scale.
“We have to think of ways to [capture and store] hundreds of megatonnes and gigatonnes each year,” Schrag said. Deep-sea sediments in 3,000 m of water could provide permanent offshore storage by gravitational trapping, he said, but that has yet to be field tested.
Heleen Groenenberg, scientific researcher with Energy Research Center policy studies of the Netherlands, said technical uncertainties must be resolved.
“How we deal with these uncertainties is a difficult task,” she said. The key question is: “When will which technologies appear?” CCS operations are capital intensive and will involve a long-running financial commitment, she noted.
Legal liabilities
Stanford’s Benson sees legal liability issues as another obstacle for CCS projects. For instance, questions arise as to who will be responsible for long-term monitoring and who might pay to remediate a CCS site if it starts to leak in 100 years. She said more research is needed to advance geophysical imaging to assess sequestration reservoirs and seals. Scientists are working on geophysical monitoring technology to assure that sequestered CO2 stays sequestered.
Meanwhile, various public and privately funded projects are under way or in the planning stages for demonstration projects on a scale commensurate with sequestering the 5-10 million tonnes/year of CO2 that a typical coal-fired power plant emits. “Without definitive results from these and even larger scale tests, policy makers, investors, and society will not have the confidence to proceed with widespread deployment of CCS,” Benson said.
Oil and gas companies having stakes in deepwater projects are accustomed to the need to resolve a myriad of questions and interrelated complexities to prove technology will work safely on a commercial scale and within budget.
This type of experience is likely to be useful for multidisciplinary researchers as they work to reduce atmospheric CO2 and understand global climate change.
