Carnegie Mellon University
April 24, 2015

Carbon-Conscious: Mitigating the Effects of CO2

Carbon-Conscious: Mitigating the Effects of CO2 It’s no secret that carbon dioxide (CO2) emissions are a problem—because they increase the amount of CO2 in our atmosphere, they are one of the largest anthropogenic contributions to climate change. By reducing CO2 emissions, we can start to mitigate the greenhouse effect that is causing temperatures to rise. But figuring out how to do that isn’t as easy.

“CO2 is being emitted by many, many processes and activities today,” explains PhD candidate Argha Namhata. “By developing alternative energy sources, we can try to reduce it. But we can’t stop CO2 emissions all of the sudden. So it’s very important to think about how to deal with the CO2 that is already present in our environment.”

One way of dealing with carbon emissions is to store excess CO2 underground in geological reservoirs. Doing so could significantly reduce the amount of greenhouse gases being emitted to our atmosphere. However, because this method is yet to be executed on a large industrial scale, engineers are still unsure of the risks involved.

To aid the industry and the scientific community in making more informed decisions about where and how to store the CO2, Namhata is developing an engineering tool to assess the risks involved. Specifically, his research is centered on predicting the fate of the injected CO2 in the subsurface environment, ensuring that it can remain in the storage reservoir without impacting the overlying groundwater resources.

“This will be an important piece in the research because industry doesn’t really have the engineering tools they need to assess the risk to the atmosphere and the groundwater,” he says. “So I’m trying to fill that gap.”

Like Namhata, PhD candidate Kenneth Sears realizes the importance of developing smarter, more efficient ways of dealing with CO2 emissions. “Eventually, we will get off fossil fuels, but it’s not going to happen right away,” he says. “Until then, we’re going to have to keep using these older systems. But if we’re going to be using them, we should be doing in the most environmentally-protective way we can.”

Carbon Capture and Sequestration (CCS), which separates CO2 from the mixture of gasses that are emitted by transportation vehicles and factories and stores the CO2 in the subsurface, can go a long way in mitigating the effects of CO2 in our atmosphere. However, Sears explains that operating these systems comes with a cost—especially for thermoelectric power plants, the most common type of electric power production in the country and one of the biggest polluters and consumers of water on the planet.

When these plants burn fuel, the heat emitted boils water, producing the steam that powers the plant. The plants then use water to condense the steam back into water, which is then used to make more steam. This process, known as the Rankine cycle, is by far the largest use of water in a plant. And as Sears explains, because CCS systems demand more power, plants will need to produce more steam, and will therefore require more water for cooling.

According to Sears, the one way to help mitigate this strain on water supply is to develop carbon capture technologies that also will allow plants to reclaim some of the water that escapes as steam along with the flue gas. Capturing water along with CO2 will allow plants to use their water more efficiently, thereby reducing the strain they pose on local water supply.

“Many power plants already strain regional water supplies, and increases with carbon capture could dangerously lower these water sources,” he explains. “My research encourages carbon capture technologies to consider water capture separation and reuse.”

Ultimately, Sears wants to ensure that we are well-equipped to deal with the challenges associated with climate change. “We’re going to have an altered climate with a lot of uncertainties, like unpredictable precipitation and temperature. So we want to have the most efficient power plant-cooling systems possible,” he says. “I’m hoping this project will be a part of the solution.”

Namhata and Sears will present their research at the 14th annual Carbon Capture Utilization and Storage (CCUS) Conference to be held in Pittsburgh. This international conference brings decision makers and technical experts together to discuss ways to mitigate the effects of carbon dioxide in the environment by finding ways to accelerate the commercialization of CCS systems.

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