UNIVERSITY PARK, Pa. — The latest episode of the "Growing Impact" podcast explores the process of injecting carbon dioxide underground and mineralizing it to permanently sequester the gas, a path toward reducing carbon emissions and mitigating climate change. A Penn State research team is developing a model to understand the ramifications of injecting carbon dioxide underground and how to optimize the underground storage space being used.
“Anytime you're extracting a resource from the subsurface or injecting something like carbon dioxide, or if you're relying on a rock formation to store some sort of energy or waste product, you need to ensure that the fluid itself is not going to react with the surrounding rock in a way that compromises the integrity of that formation,” said Anne Menefee, assistant professor of energy and mineral engineering in the College Earth and Mineral Sciences.
In the case of injecting carbon dioxide with the intention of mineralizing it, engineers must consider how quickly the fluid will mineralize, also known as precipitation. This helps ensure the storage space underground is optimally used. Additionally, precipitation is a secure method of disposal for a compound like CO2 because once precipitated, it is immobile.
“If the reaction happens really fast, you’re going to clog up the area around the well, and now suddenly you can't inject anymore because you've plugged it up,” said Yashar Mehmani, assistant professor of energy and mineral engineering. “You want the process to be slow enough so that the compound travels out. But you also want it not to sit there for very long because the longer it sits, the risk of it breaching and leaking increases. So, you want it to mineralize quickly, but not too quickly.”
The research team said developing better predictive tools and capabilities to understand what will happen before CO2 is injected underground has a lot of important implications for regulators, companies and facilities that are trying to do this at an industrial scale.
“If you inject CO2 into one of these rock types, that sparks a series of geochemical reactions through which the CO2 is converted to a solid carbonate mineral,” said Menefee. “Understanding how minerals are dissolving and precipitating in these environments is crucial to being able to predict and even control fluid transport through the subsurface for applications like carbon storage, geothermal energy or understanding groundwater flow.”
Two frequent questions that people ask about storing CO2 underground are: how much can be stored and how quickly can it happen.
“Whenever you want to scale this process up to make a dent in climate change, you not only have to understand the fundamental physics, but you must also be able to control them. And I'm not sure we're there yet,” said Mehmani. “That is why projects like this collaboration between Anne and I are helping to improve that reliability so that ultimately it can work at the gigaton scale.”
“Growing Impact” is a podcast by the Institute of Energy and the Environment (IEE). It features Penn State researchers who have been awarded IEE seed grants and discusses their foundational work as they further their projects. The podcast is available on multiple platforms, including YouTube, Apple, Amazon and Spotify.