When the Illinois Sustainable Technology Center (ISTC) launched a front-end engineering and design study for a carbon capture system at the Prairie State Generating Company’s (PSGC) Energy Campus in Marissa, Illinois, identifying a sustainable source of water was a priority from the start.  

Once completed, PSGC’s carbon capture system will be the largest post-combustion capture plant in the world. Initially, the system will require approximately 14 million gallons of water per day (MGD), which almost doubles the current PSGC water demand.   

The challenge: find adequate and reliable water sources to keep the carbon capture system running without compromising fragile aquatic ecosystems, local economies, and nearby communities’ water supply. Fortunately, ISTC knew the right expertise was close at hand in another unit within its parent Prairie Research Institute. The Water Survey’s Watershed Science team, led by Illinois State Hydrologist Laura Keefer, specializes in solving these types of problems.  

Jason Zhang, water supply hydrologist, and Elias Getahun, watershed hydrologist, focus on surface water supply, water availability, and hydrologic modelling, and Guangping Qie and Andres Felipe Prada Sepulveda, postdoctoral researchers, produced climate and hydrologic model results. 

“We are one of the first large-scale projects to explicitly address carbon capture and water supply issues together,” said Zhang. “With our proximity to the Mississippi River and Lake Michigan, people assume we have lots of water, which is true, but we do have to think about water supply risks due to spatial and temporal distribution of water resources.” 

To answer those questions, ISWS conducted a water availability analysis using streamflow frequency analysis and yield analysis. Currently, PSGC sources its water from one of the largest rivers in Illinois—the Kaskaskia River system, which includes Lake Shelbyville and Carlyle Lake. 

There are some unknown factors in the water-energy equation, such as the future impact of climate change, but we know one thing for certain—the Kaskaskia doesn't always have enough water to meet the demands of the carbon capture system if an appropriate water supply strategy is not planned and implemented.   

“When we have serious droughts like in the 1930s and 1950s, there won’t be enough water to meet demands, so if nothing is done, we cannot run the carbon capture system in extreme dry conditions,” said Zhang. 

ISWS combined a hydrologic model with climate model outputs to look ahead to 2100. Hydrological modeling and climate assessments predict future hydrologic conditions will have greater variability, with drier conditions in the summer and early fall leading to lower flows in the Kaskaskia system, even though average annual precipitation is expected to be greater. These dry, low-flow conditions are likely to coincide with the increased energy demand typically seen during the summer. 

ISWS recommended using a storage pond to collect excess water during the wet seasons and to provide a backup water supply when streamflow in the Kaskaskia River is too low to supply water to the carbon capture system. Based on the ISWS analysis, the storage pond should be able to store water to meet the needs of the carbon capture system for 26 days.