Geologic storage and the fight against climate change

CSUB’s Dr. Liaosha Song researches carbon and hydrogen storage

By California State University, Bakersfield

November 9^th, 2023

A problem as big and complex as climate change doesn’t have one easy solution to fix it. Mitigating its effects on the world requires a full toolbox of practical, scientific methods. At California State University, Bakersfield, Dr. Liaosha Song is researching two of them.

An associate professor in CSUB’s Department of Geological Sciences, Dr. Song’s work in geologic storage presents two promising tools to fight climate change: carbon (CO2) sequestration to remove the greenhouse gas from the earth’s atmosphere and hydrogen (H2) storage to save and reuse hydrogen to help power renewable energies.

“Number one, the purpose is to mitigate one of the things that is impacting everybody’s livelihood — that is the severe climate change over the past decades,” Dr. Song said, mentioning extreme heat waves, floods, wildfires and storms. “And particularly for Bakersfield and Kern County, geologic storage also makes a lot of sense in terms of generating new jobs and fueling new power to the local industry.”

Geologic storage for both carbon and hydrogen involves injecting the gas into subsurface rocks, though the duration of storage is different for each. For carbon, the purpose is long-term storage for tens of thousands of years, putting the gas underground and lower the CO2 concentration in the atmosphere. Hydrogen, however, is temporarily stored and can be retrieved to support intermittent clean energies, like wind and solar, that do not continuously generate energy depending on time of day and weather.

While as a student Dr. Song was initially drawn to geology’s broader, “big picture” processes of how the earth works, his professional work on geologic storage focuses on much smaller processes on the nano- and micrometer scales. He and the students in his lab evaluate the subsurface rocks in California, focusing on the “caprocks” that block the injected carbon dioxide and hydrogen from leaking. Understanding the porosity and chemical makeup of the caprocks plays an important role in determining if it is suitable for storage.

“When we are researching this, it’s different from a traditional geology study where you go to the field and put a hammer on a rock,” said Dr. Song, explaining that his team studies rock samples called cores taken from well sites drilled by oil and gas companies or from CSUB’s California Well Sample Repository. “We take these subsurface rock samples, and we analyze them in the labs.”

Dr. Song studies the internal structure of a caprock sample on the scanning electron microscope.

Dr. Song holds a sandstone core sample in the California Well Sample Repository, which is one of the most promising rock formations for CO2 or H2 underground storage in California.

In the lab, Dr. Song and his student researchers study three main areas related to geologic storage. First is the chemical composition of rocks, which they must understand because in the subsurface condition, carbon dioxide and hydrogen react to certain types of minerals and these reactions may create leakage pathways and thus jeopardize the integrity of the caprock.

The second set of research is the pore system in the caprocks, where Dr. Song’s team analyzes the rock samples with scanning electron microscopy. Carbon or hydrogen leaking from the rocks would trigger new problems, so assessing the caprock’s ability to retain them is essential.

“The pores inside the caprocks must be small enough to generate a high enough capillary force, which is basically a resisting force that’s keeping gas and liquid underneath and ensures the CO2 and hydrogen have very little chance of penetrating the cap,” Dr. Song explained.

This specific area of his research was recently sponsored by a National Science Foundation Major Research Instrumentation grant of $520,050, which allowed Dr. Song to purchase a field emission scanning electron microscope. This equipment offers an ultra-high-resolution and allows the research team see the finest features of the rock, Dr. Song said.

The final area of his lab’s research uses a nano-tomography scanner, which Dr. Song said has a fundamental function similar to a medical CT scanner but with much higher resolution.

“This can give us a 3D distribution of the interior of the rock to help us further understand the mineralogy, the pore space and how they are connected,” Dr. Song said. “This 3D fashion essentially decides how well the CO2 or hydrogen reacts in transporting or migrating through the rock.”

On this aspect of his research, Dr. Song and his team is collaborating with Lawrence Berkeley National Laboratory, which houses a synchrotron CT that is the best of its kind in the world, he said. This summer, five of his undergraduate students interned at Berkeley Lab to work on geologic storage research as part of that partnership.

Jennifer Rubalcaba, a senior geology student at CSUB, and her fellow interns are analyzing micro and nano CT images to evaluate the pore structure of reservoir rocks and caprocks to find potential storage sites in the Central Valley. Living in Bakersfield, where oil and agriculture are major industries, has given Rubalcaba a greater perspective on this research.

“Growing up in a city so heavily influenced by the oil industry has surrounded me in the ongoing debate over fossil fuels and air pollutants,” Rubalcaba said. “Likewise, growing up around agriculture has made me more keenly aware of the impacts of air pollution on the land, and how it affects food production and public health. For these reasons, contributing to research that could result in the safe and effective geologic sequestration of carbon and storage of hydrogen is important.”

Working on carbon and hydrogen storage research with Dr. Song and at Berkeley Lab has been “an eye-opening” experience for Rubalcaba, one she said has exposed her to many more fields within the earth sciences than she previously knew existed. Her internship has confirmed that she wants to pursue a career in energy geosciences, she said.

“Being able to get this kind of firsthand experience doing research under my mentors has been an enriching experience,” she said. “Using breakthrough technology such as the NanoCT scans, learning and utilizing new software and having the opportunity to analyze datasets which have never been seen before has been exciting.”

Jennifer Rubalcaba, a senior geology student at CSUB, stands in front of Lawrence Berkeley National Laboratory's Advanced Light Source building.

The research Dr. Song, his collaborators at Berkeley Lab and CSUB students are doing is truly cutting edge. While carbon sequestration has gained steam as a promising tool against climate change in recent years, hydrogen storage is rather new and Dr. Song himself has only been studying it since early 2022.

Though the methods of carbon dioxide and hydrogen storage share similarities, hydrogen’s smaller molecule size means an appropriately impenetrable caprock for carbon might not work for hydrogen.

“Hydrogen molecules are much smaller than carbon dioxide, and we need to do a lot of extra research to ensure the security and the integrity of the seal that’s blocking hydrogen from leakage,” Dr. Song explained. “So, this is my new research interest, to ensure that our caprock in the subsurface that has successfully blocked CO2 is also capable — or not — of blocking hydrogen from leaking.”

Dr. Song’s research could impact worldwide efforts to reduce the effects of climate change, but here in Kern County it could also impact local industry. Per a report by Lawrence Livermore National Laboratory, Kern County is one of the two most promising candidates for geologic storage of CO2. The area’s oil industry lends itself well to geologic storage.

“We have so many oil and gas wells, we have the experts, and we have some preexisting data base for the subsurface,” Dr. Song said. “All of these contribute to a good understanding of the subsurface, which also contributes to this large pool that’s sitting underneath us, and if we use it properly it can be repurposed as a safe box for CO2, and this could trigger a lot of new development in terms of economy.”

Geologic storage and the fight against climate change

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Footnotes

Story by Kelly Ardis, communications specialist, School of Natural Sciences, Mathematics and Engineering (NSME); Photos by Albert Baker, videographer/photographer

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FootNotes

Story by Kelly Ardis, communications specialist, School of Natural Sciences, Mathematics and Engineering (NSME); Photos by Albert Baker, videographer/photographer