Carbon capture and storage (CCS) technologies capture gaseous CO2 from point source emissions – power plants and industrial facilities – and either inject them underground for long-term storage within deep rock formations, or repurpose them for other productive uses, called carbon capture, utilization, and storage (CCUS). To capture CO2 emissions at an existing pulverized coal power plant, for example, the plant’s flue stacks could be retrofitted with technologies that scrub CO2 using different chemical processes, such as sorption, membrane filtration, or cryogenic separation.
The appeal of CCS/CCUS is that all the necessary infrastructure components are already in use today in natural gas and petroleum industries’ exploration, production, transportation, and refining sectors. Many of those companies operate in Pennsylvania’s Marcellus Shale, providing in-state businesses an opportunity to establish themselves as technological leaders in the field.
In 2008, Governor Rendell signed Act 129 into law. Though best known for establishing the state’s energy efficiency and conservation program, Act 129 also ordered the Department of Conservation and Natural Resources (DCNR) to explore the potential for in-state CCS. In partnership with the Clinton Climate Initiative, DCNR produced three reports assessing the opportunities for, and risk and viability of, large-scale CCS in Pennsylvania:
- Geological Carbon Sequestration Opportunities in Pennsylvania
- Assessment of Risk, Legal Issues, and Insurance for Geological Carbon Sequestration in Pennsylvania
- Viability of a Large-Scale Carbon Capture & Sequestration Network in Pennsylvania
In his summary of this work, former DCNR Secretary John Quigley highlighted three major findings:
- An at-scale, in-state CCS network would be cost competitive.
- The CCS network could be safely developed, with “well-understood” and “quantifiable” risks.
- Pennsylvania’s geology has a large potential capacity to store CO2. The deployment of an at-scale CCS network would rely on acquiring adequate pore space through land ownership.
After capture, CO2 is injected underground, either as a gas or in liquid form, into an appropriate geologic reservoir, or “sink.” CO2 may be injected underground at the point of capture or after transport via pipeline elsewhere. Suitable sinks include deep salt-water-bearing rocks, emptied or abandoned oil-and-gas fields, unmineable coal beds, carbonaceous shales, and thick salt deposits. Additional geologic factors affect the adequacy of a sink for long-term CO2 storage, including its depth, thickness, overlying “cap” rock, pore space, and structural features, like fault lines.
The DCNR studies found that Pennsylvania’s geology has the capacity to store roughly 300 years’ worth of CO2 emissions (at current emissions rates), totaling roughly 88.5 billion metric tons of CO2. (For comparison, Pennsylvania emitted 245 million metric tons of CO2 in 2014, making it the third highest emitting state that year.) The bulk of CO2 storage in Pennsylvania could be made in deep saline formations and carbonaceous shales, where it would be trapped for thousands to millions of years.
Prior to long-term underground storage, CO2 can be used in several industrial and manufacturing processes (adding the utilization term to CCUS). For example, enhanced oil recovery, a well-proven technology, involves the pumping of liquid CO2 into partially depleted oil fields to help increase pressure and extract viscous oil deposits. Analogous enhanced-recovery applications also exist for gas and shale gas extraction.
Other CCUS applications under development include use in coal bed methane production and enhanced geothermal systems. For an extensive list of existing and emerging CO2 storage and reuse technologies, see the Global CCS Institute.
To further investigate the potential for CCS/CCUS as part of a deep decarbonization strategy in Pennsylvania, PEC will be convening a stakeholder group to review the work previously completed and assess potential opportunities and risks. Stay tuned for more details on this work.
Rachel Valletta, PhD, served as an Energy Fellow with PEC during the summer of 2017, through a partnership with the Kleinman Center for Energy Policy at the University of Pennsylvania.