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ScienceShot: A Smokestack's Hidden Treasure

The CO2-ridden plumes rising from industrial smokestacks and power plants may be warming the planet, but they could also be a new source of electrical power. Researchers have developed a two-stage process to harvest some of the chemical energy in carbon dioxide emissions, using a device called a capacitive electrochemical cell. Built roughly like a battery, the cell has two electrodes—one surrounded by a membrane that allows hydrogen ions to flow in and out, and the other that does the same with bicarbonate ions, produced when carbon dioxide is bubbled through water. In the first stage of the process, researchers pump water flushed with carbon dioxide through the cell, which causes the hydrogen and carbonate ions to flow into their respective electrodes—a separation of ions that charges the cell and can drive an electrical current. (In a full-scale system, carbon dioxide will be pulled from smokestacks, whose emissions typically include between 5% and 20% of the greenhouse gas.) Once the electrodes have absorbed as many ions as they can, the researchers then begin to pump air-bubbled water through the cell—a process that drives the ions out of the electrodes and back into the cell. By constantly alternating between these two stages, the cell can produce electrical power, the team reports online today in Environmental Science & Technology Letters. By tapping into existing carbon dioxide emissions from coal- and gas-fired power plants, industrial smokestacks, and residential heating worldwide, the new process could generate about 1570 terawatt-hours of power each year—about 400 times that produced by Hoover Dam, all without adding to global carbon dioxide emissions