As the world slowly evolves to find more environmentally friendly energy solutions, researchers understand the importance of discovering ways to enhance the current norm: fossil fuels. A team of University of Pittsburgh’s Swanson School of Engineering researchers have developed a computational modeling method that aims to more quickly usher in new carbon capture and storage (CCS) technology and materials for coal-fired power plants.

The team, led by Christopher Wilmer, assistant professor of chemical and petroleum engineering, worked with Jan Steckel, research scientist at the U.S. Department of Energy’s National Energy Technology Laboratory, and Pittsburgh-based AECOM on hypothetical mixed matrix membranes. According to their recently published study, these membranes would provide a more economical solution than current methods.

“Our computational modeling of both hypothetical and real MOFs [metal-organic frameworks] resulted in a new database of more than a million mixed matrix membranes with corresponding CO2 capture performance and associated costs,” Wilmer said. “Further techno-economic analyses yielded 1,153 mixed matrix membranes with a carbon capture cost of less than $50 per ton removed. Thus, the potential exists for creating an economically affordable and efficient means of CO2 capture at coal power plants throughout the world and effectively tackling a significant source of fossil fuel-generated carbon dioxide in the atmosphere.”

A metal-organic framework (HKUST-1) embedded in a polymer matrix can be used as a membrane to more efficiently separate gas. (Image courtesy of Kutay Sezginel.)

The team’s findings are built on its existing research in metal-organic frameworks (MOFs). These highly-porous crystalline materials are created via the self-assembly of inorganic metal with organic linkers. MOFs have the ability to store a higher volume of gases than traditional tanks. They are also versatile and can be created using various materials, as well as offer options for custom designs that have specific properties.

“Polymer membranes have been used for decades to filter and purify materials but are limited in their use for carbon capture and storage,” Wilmer said. “Mixed matrix membranes, which are polymeric membranes with small, inorganic particles dispersed in the material, show extreme promise because of their separation and permeability properties. However, the number of potential polymers and inorganic particles is significant, so finding the best combination for carbon capture can be daunting.”

The collaborative team began by looking into existing databases of hypothetical and real MOFs. This resulted in discovering more than 1 million potential mixed matrix membranes. Their next step was to compare potential gas permeation of each material with established data and evaluate them using a three-stage capture process. The team especially took note of flow rate, capture fraction, pressure and temperature conditions as part of membrane properties. This enabled them to identify specific mixed matrix membranes that could reduce carbon capture cost.

What are the implications of the cost savings? The group believes they could be tremendous. According to the U.S. Energy Information Administration, coal-generated power plants in the United States contributed about 1,207 million metric tons of CO2 in 2017. With estimates that range from $69 to $103 per ton for current CCS methods, dropping that to less than $50 amounts to significant savings.

While this has the potential to enhance the byproducts of societal dependency on fossil fuels, the importance of establishing renewable energy sources also remains on the forefront of researchers’ minds. Check out Oil Company Says Renewable Energy is Cost-Competitive with Fossil Fuels and Keeping the Lights On in a Clean Energy Grid is Doable: Study for more on other energy sources.