As AI data centers spring up across the country, their energy demand and resulting greenhouse gas emissions are raising concerns. With servers and energy-intensive cooling systems constantly running, these buildings can use anywhere from a few megawatts of power for a small data center to for a hyperscale data center. To put that in perspective, the average large natural gas power plant built in the U.S. generates .
When the power for these data centers comes from fossil fuels, they can become major sources of climate-warming emissions in the atmosphere – unless the power plants capture their greenhouse gases first and then lock them away.
Google recently entered into a unique corporate power purchase agreement to support the in Illinois designed to do exactly that through carbon capture and storage.
So how does carbon capture and storage, or CCS, work for a project like this?
I am an engineer who wrote . Here’s the short version of what you need to know.
How CCS works
When fossil fuels are burned to generate electricity, they , a powerful greenhouse gas that remains in the atmosphere for centuries. As these gases accumulate in the atmosphere, they , holding heat close to the Earth’s surface. Too high of a concentration heats up the Earth too much, , including worsening heat waves, rising sea levels and intensifying storms.
Carbon capture and storage involves capturing carbon dioxide from power plants, industrial processes or even directly from the air and then transporting it, often through pipelines, to sites where it can be safely injected underground for permanent storage.
The carbon dioxide might be transported as a – which is right at the phase change from liquid to gas and has the properties of both – or dissolved in a liquid. Once injected deep underground, the carbon dioxide can become permanently trapped in the geologic structure, dissolve in brine or become mineralized, turning it to rock.
The goal of carbon storage is to ensure that carbon dioxide can be kept out of the atmosphere for a long time.
Types of underground carbon storage
There are several options for .
have plentiful storage space and the added benefit that most are already mapped and their limits understood. They already held hydrocarbons in place for millions of years.
Carbon dioxide can also be injected into working oil or gas reservoirs to push out more of those fossil fuels while leaving most of the carbon dioxide behind. This method, known as , is the used by carbon capture and storage projects in the U.S. today, and from environmental groups.
Volcanic and are considered good candidates for safe and long-term geological storage because they contain calcium and magnesium ions that interact with carbon dioxide, . Iceland using its bedrock of volcanic basalt for carbon storage. Basalt also covers most of the oceanic crust, and scientists have been exploring the potential for .
In the U.S., a fourth option likely for industrial carbon dioxide storage – deep saline aquifers, which is what Google plans to use. These widely distributed aquifers are porous and permeable sediment formations consisting of sandstone, limestone or dolostone. They’re filled with highly mineralized groundwater that cannot be used directly for drinking water but is very suitable for storing CO2.
Deep saline aquifers also have large storage capacities, ranging from about 1,000 to 20,000 gigatons. In comparison, the nation’s were about 4.9 gigatons.
As of fall 2025, across the U.S. used carbon capture and storage, including industries producing natural gas, fertilizer and biofuels, according to the Global CCS Institute’s 2025 report. Five of those use deep saline aquifers, and the rest involve enhanced oil or gas recovery. Eight more industrial carbon capture facilities were under construction.
Google’s plan is unique because it involves a power purchase agreement that makes building the power plant with carbon capture and storage possible.
Google’s deep saline aquifer storage plan
Google’s , to be built with , is designed to capture about 90% of the plant’s carbon dioxide emissions and pipe them underground for permanent storage in a deep saline aquifer in the nearby .
The Mount Simon sandstone formation is a huge saline aquifer that lies underneath most of Illinois, southwestern Indiana, southern Ohio and western Kentucky. It has a layer of that makes it an ideal candidate for carbon dioxide injection. To keep the carbon dioxide in a supercritical state, that layer needs to be .
A thick layer of Eau Claire shale sits above the Mount Simon formation, that helps prevent stored carbon dioxide from escaping. Except for some small regions near the Mississippi River, Eau Claire shale is considerably thick – more than 300 feet (90 meters) – throughout most of the Illinois basin.
The of the Mount Simon formation ranges from 27 gigatons to 109 gigatons of carbon dioxide.
The Google project plans to use an existing injection well site that was part of the first large-scale carbon storage demonstration in the Mount Simon formation. Food producer Archer Daniels Midland there from nearby corn processing plants in 2012.
Carbon capture and storage has had challenges as the technology developed over the years, including a in 2020 that forced evacuations in Satartia, Mississippi, and caused several people to lose consciousness. After a recent in Illinois, the Environmental Protection Agency in 2025 required the company to improve its monitoring. Stored carbon dioxide had migrated into an unapproved area, but no threat to water supplies was reported.
Why does CCS matter?
Data centers are expanding quickly, and utilities will have to build more power capacity to keep up. The artificial intelligence company OpenAI is urging the U.S. to of new capacity every year – doubling its current rate.
Many energy experts, including the International Energy Agency, believe to slow climate change and keep global temperatures from reaching dangerous levels as energy demand rises.
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