Is CCS Ready for Deployment? Is it safe?
As would be expected, our organisations have approached CCS with caution. The prospect of injecting millions of tons of compressed carbon dioxide in the subsurface has to be taken seriously. After long and careful study of the available science, we have concluded that CCS can be carried out safely and effectively, provided it is adequately regulated. Our conclusions are based on and are backed by an overwhelming consensus of the scientific literature and prominent research institutions.
Research on CCS has been taking place for many years now, with major international conferences occurring since the early 1990s. Since then, scientific knowledge on the subject has greatly expanded, to the extent that the IPCC issued a special report on CCS in 2005. This report represents the most significant landmark in terms of relevant publications, and underwent the well known, rigorous Intergovernmental Panel on Climate Change (IPCC) peer review standards. There is a very high degree of consensus on the science of CCS.
CO2 capture is a reality today. CO2 is stripped from the slipstreams of power plants or industrial facilities to supply the food industry. It is also routinely removed in natural gas processing facilities and at synthetic fuel production facilities to reduce the CO2 content of the gas to commercial specifications and at synthetic fuel production facilities. Several large-scale capture projects at power plants are also operating today. With additional experience applying CO2 capture to power plants over the coming few years, considerable progress is expected in terms of efficiency and cost in CO2 capture.
Pipelines operate as a mature market technology and are the most common method for transporting CO2. The first long-distance CO2 pipeline came into operation in the early 1970s. In the US today, over 3900 miles17 of pipelines in the US annually transport approximately 65 million tons of CO2.18
Some 72 million tons of CO2 annually in the US19 are injected in mature oil for the purposes of (EOR), a practice that has been around for several decades. The CO2 aids in retrieving oil that is otherwise stranded in reservoirs, which would be near the end of their economic life without such advanced techniques. Although the objective in this process initially was to maximise oil yields and not to sequester CO2, the two processes are fundamentally similar and share much of the same operational engineering.
Moreover, several commercial and research projects worldwide capture and/or inject CO2 in geological formations. Of these, three stand out because of their scale and their widely publicised results: Sleipner in Norway, Weyburn in North Dakota/Canada and In Salah in Algeria. These projects have been operating since 1996, 2000 and 2004 respectively, and have been studied intensely.
These projects give us a great deal of confidence that CO2 can remain permanently stored in geological reservoirs. There are multiple trapping mechanisms for CO2 in these reservoirs, operating at various time scales. Residual trapping limits CO2 mobility in a formation through capillary forces, much like a sponge traps air that has to be squeezed repeatedly in order to let water in. Solubility trapping, whereby CO2 dissolves in the formation fluids, ensures that the CO2 is no longer buoyant and therefore tends to sink rather than rising towards the surface. Stratigraphic trapping occurs when overlying, impermeable rock formations prevent any upward movement of CO2 from the underlying reservoir rock, effectively acting as lids (Figure 3). Appropriately selected CO2 injection sites will possess several layers of such caprocks, and thus multiple reinforcements to the other trapping mechanisms. Finally, mineralisation trapping takes place when the CO2 over time forms carbonate minerals and essentially becomes part of the solid rock into which it was injected. In fact, fluids in nature such as oil and gas, CO2 and brines, have had residence times in the order of millions to hundreds of millions of years. Nature sequestered CO2 in different forms well before we embarked on it as a human endeavour!
In assessing the global risks associated with CCS, the IPCC Special Report concluded the following:
“Observations from engineered and natural analogues as well as models suggest that the fraction retained in appropriately selected and managed geological reservoirs is very likely to exceed 99% over 100 years and is likely to exceed 99% over 1000 years. For well-selected, designed and managed geological storage sites, the vast majority of the CO2 will gradually be immobilised by various trapping mechanisms and, in that case, could be retained for up to millions of years. Because of these mechanisms, storage could become more secure over longer timeframes.”
In support of that statement, an 20 concluded that:Institute of Technology (MIT) study
“Although substantial work remains to characterise and quantify these mechanisms, they are understood well enough today to trust estimates of the percentage of CO2 stored over some period of time – the result of decades of studies in analogous hydrocarbon systems, natural gas storage operations, and CO2-EOR. Specifically, it is very likely that the fraction of stored CO2 will be greater than 99% over 100 years, and likely that the fraction of stored CO2 will exceed 99% for 1000 years. Moreover, some mechanisms appear to be self-reinforcing. Additional work will reduce the uncertainties associated with long-term efficacy and numerical estimates of storage volume capacity, but no knowledge gaps today appear to cast doubt on the fundamental likelihood of the feasibility of CCS.”
The remaining 1% is a number used by IPCC authors to take into account any uncertainties such as very small amounts of CO2 that might be vented during the operation of sites due to human factors over those very long periods, and does not reflect reduced confidence in the underlying geology or the ability of formations to retain the overwhelming majority of the injected CO2. There is every possibility that even this small fraction will not reach the atmosphere with proper site operation and regulation, bringing the total retained fraction to 100%. The 1% figure in no way implies leakages that could harm human health or the environment.
A sound regulatory framework for the safe injection and proper monitoring and accounting of captured, transported and sequestered carbon dioxide is paramount. This framework should cover enhanced hydrocarbon recovery projects as well as deep saline injection. Rigorous regulation is necessary to ensure that projects are sited and operated responsibly by capable entities, that shortcuts are not taken that could endanger public health or the environment, and to establish public trust in the application of the technology.
Globally, there has been tremendous progress toward developing and implementing environmental health and safety regulations for CCS. Regional and country and state/province-specific regulations are in force in the European Union, the US,21 Canada, and Australia.22 Many other countries are currently drafting their CCS regulations. In addition to environmental regulations, the UNFCCC has adopted modalities and procedures for CCS actions under the Clean Development Mechanism, and the International Organization for Standardization has formed a technical committee to develop international CCS standards.
These existing rules reflect a unified understanding of protecting human health and the environment during CCS, including the following provisions:
- siting requirements that address geologic characteristics to ensure the integrity of the storage site;
- requiring that site-specific be conducted and contingency plans be developed prior to injection;
- rigorous processes for establishing a monitoring area, based on simulation models and actual data collected during operation; and
- ensuring that the area for monitoring goes beyond the injected CO2 itself to encompass any areas of elevated pressure within the subsurface reservoir.
First generation CCS technology is ready to be used in large-scale projects today. All three components of CCS – the capture, transportation and injection of CO2 – have been demonstrated at large scale in commercial projects. Significant technical and cost improvements are, naturally, expected after wider uptake, and combining those components does involve additional operational, regulatory and financial burden. Nonetheless, the technological pieces are in place to allow the first wave of CCS plants to be built and operated safely and effectively. Below we examine the barriers that stand in the way of CCS deployment, the critically needed policy steps and assessment of their prospects for adoption in the near term.
17 Dooley JJ, RT Dahowski, and CL Davidson. 2009. “Comparing Existing Pipeline Networks with the Potential Scale of Future US CO2 Pipeline Networks.” In Energy Procedia: 9th International Conference on Control Technologies (GHGT9), vol. 1, no. 1, pp. 1595-1602. Elsevier, London, United Kingdom. doi:10.1016/j.egypro.2009.01.209.
18 Melzer, L. S. (2012). Carbon Dioxide Enhanced Oil Recovery (CO2 EOR): Factors Involved in Adding Carbon Capture, Utilization and Storage (CCUS) to Enhanced Oil Recovery.
19 Advanced Resources International, (2011). Improving Domestic Energy Security and Lowering CO2 Emissions with ”Next Generation” CO2-Enhanced Oil Recovery (CO2-EOR).