Current Administration and congressional climate proposals depend heavily on geological sequestration to reduce CO2 emissions from coal-fired power plants and other major sources and tend to presume that sources in every state will have access to nearby underground storage capacity.  While some federal agencies and studies consider widespread localized sequestration to be viable, a nationwide rollout faces significant obstacles.  In areas where local sequestration is impractical, emissions sources will be forced to transport captured CO2, by pipeline, ship or other mode, to a viable sequestration site.  To date, however, federal climate proposals have given limited attention to developing the CO2 transport infrastructure. 

This series reviews three obstacles to a 50-state sequestration strategy and discusses the need for a national infrastructure to support medium to long-range transport of CO2.

Part 1: The Porosity Problem (below)
Part 2: Not Under My Back Yard
Part 3: 50-States, 50 Hurdles

Recognizing these obstacles and honestly confronting them is a critical step to making geological sequestration work.  And, without a successful geologic sequestration program, the United States’ ability to achieve emissions reduction targets is astronomically more difficult.

Part 1: The Porosity Problem

While there are many different factors that determine the suitability of a geological formation to store liquefied carbon, one important threshold consideration is porosity.  An effective sequestration site must contain deep layers of porous rock, capable of absorbing and retaining injected CO2 within its void spaces, much like a sponge that absorbs and holds water.  This porous rock must be covered by an upper layer of dense and highly impermeable cap rock that will prevent upward migration of CO2 toward drinking water aquifers or the surface.  

Citing private and public studies conducted to date, the Environmental Protection Agency (EPA) and the Department of Energy (DOE) have estimated that 95% of all coal-fired plants are within 50 miles of an “ideal” candidate sequestration site.  Other government analyses, however, suggest that not all regions and states are geologically equal when it comes to underground storage capacity.  Indeed, federal researchers have had mixed success in identifying viable sequestration sites with the proper geological characteristics based on theory and scientific testing alone. 

EPA and DOE are working to demonstrate the feasibility of geological sequestration at a wide range of host geological sites nationally, but to date, most successful CCS projects have been sited at current or former oil and gas fields.  For decades, the oil and gas industry has injected liquid CO2 underground to promote enhanced oil recovery.  If CCS storage potential is tied to oil and gas production potential, however, there are likely to be significant disparities in storage potential from one region to another.  DOE’s own website acknowledges that “there is a mismatch between largest [CO2 emission sources] and the largest oil and gas traps.”  A 50-state sequestration strategy will force the CCS industry to diversify its portfolio of storage sites.  Federal studies indicate that unmineable coal seams and deep saline formations offer promising storage potential, but the practicality of such formations remains untested in many parts of the country, despite considerable efforts at regional characterization.

For example, there are large numbers of CO2 emitting sources in the Appalachian Basin, making it an important test area for the viability of DOE’s localized sequestration strategy.  In a recent report on progress at a small-scale sequestration field test in the Appalachian Basin of Ohio, researchers found that “porosity, void space and permeability of the target formations were lower than expected.”  DOE’s difficulty in pinpointing a viable sequestration site location for a small regional pilot project illustrates the uncertainties that remain when it comes to siting at the local level.  

DOE is addressing this nationwide site characterization challenge aggressively, investing department resources and grant funding into projects to improve understanding of sequestration capacity in different geological settings.  Earlier this month, DOE announced its intent to offer an additional $50 million in grants to support site characterization work. 

Missing from both Congress and DOE is a serious Plan B in the event that localized geologic sequestration is not feasible in major portions of the country.  Federal policymakers will need a plan to transport captured CO2 from “pore-locked” emissions sources to areas where high-volume sequestration is practicable. 

The prevailing hope of widespread access to local sequestration capacity could become reality within the timeframes policymakers will need to support U.S. climate mitigation plans.  The U.S. experience with project siting on the basis of geology alone suggests strongly that this hope is a dim one.  Geologic sequestration is critical to U.S. climate policy and Congress and the Administration need to address the available alternatives should the local sequestration strategy prove untenable. 

For further information about this topic, please contact Akin Gump.