BY Megan McRainey
Georgia Tech researchers have developed a strategy to capture, store and eventually recycle carbon from vehicles to prevent the pollutant from finding its way from a car tailpipe into the atmosphere. They envision a zero-emission car and a transportation system completely free of fossil fuels.
Technologies to capture carbon dioxide emissions from large-scale sources such as power plants have recently gained some impressive scientific ground, but nearly two-thirds of global carbon emissions are created by much smaller polluters — automobiles, transportation vehicles and distributed industrial power-generation applications.
The Georgia Tech team's goal is to create a sustainable transportation system that uses a liquid fuel and traps the carbon emission in the vehicle for later processing at a fueling station. The carbon would then be shuttled back to a processing plant where it could be transformed into liquid fuel. Currently, Tech researchers are developing a fuel-processing device to separate the carbon and store it in the vehicle in liquid form.
"Presently, we have an unsustainable carbon-based economy with several severe limitations, including a limited supply of fossil fuels, high cost and carbon dioxide pollution," said Andrei Fedorov, associate professor in the Woodruff School of Mechanical Engineering at Georgia Tech and a lead researcher on the project. "We wanted to create a practical and sustainable energy strategy for automobiles that could solve each of those limitations, eventually using renewable energy sources and in an environmentally conscious way."
Tech's short-term strategy involves an onboard fuel processor designed to separate the hydrogen from the carbon. Hydrogen would be used to power the vehicle, while the carbon would be stored onboard the vehicle in a liquid form until it could be disposed at a refueling station. It then could be sequestered in a permanent location, such as geological formations, under the oceans or in solid carbonate form.
In the long-term strategy, the carbon dioxide will be recycled to form a closed-loop system involving synthesis of high-energy density liquid fuel suitable for the transportation sector.
"We had to look for a system that never dilutes fuel with air because once the CO2 is diluted, it is not practical to capture it on vehicles or other small systems," said David Damm, a doctoral candidate in the School of Mechanical Engineering, Fedorov's collaborator on the project and the lead author on a paper published in Energy Conversion and Management.
Electric vehicles could be part of a long-term solution to carbon emissions, but the Tech team raised concerns about the limits of battery technology, including capacity and charging time.
The possible hydrogen solution to carbon emissions does present a roadblock — infrastructure. While liquid-based hydrogen carriers could be conveniently transported and stored using existing fuel infrastructure, the distribution of gaseous hydrogen would require the creation of a new and costly infrastructure of pipelines, tanks and filling stations.
The Georgia Tech team has already created a fuel processor, called the CO2/H2 active membrane piston reactor, capable of efficiently producing hydrogen and separating and liquefying CO2.
The Georgia Tech paper also details the subsequent long-term strategy to create a truly sustainable system, including moving past carbon sequestration and into a method to recycle the captured carbon back into fuel. The liquid carbon dioxide deposited at the fueling station would be piped to a facility to be converted into a synthetic liquid fuel.
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