How engineers are finding ways to turn carbon dioxide waste into electricity, Kaushik Vada

Updated: Jan 30, 2021

In the past few decades, people have been struggling with the fact that CO2 is the leading reason for global warming and odd climate changes. Scientists around the world are working around the clock to find a way to end this problem. But, if a solution is approved in an industrial setting and adopted on a large scale, the process could give the world breathing space and create a transition towards a green economy.


Harvesting Energy from Waste

Finding a way to harvest energy from waste products is not a simple thing to achieve however, scientists have in fact found a way to harvest energy by using chemistry. Chemistry states that every chemical reaction takes place in some exchange of energy. In a solution, the entropy of energy involves electrons and ions that go to negative or positive ions. In a mix of two different solutions, the final mixture has an energy content lower than the total of the original two solutions and since energy cannot be created nor destroyed, there must be some energy available for utilization. To investigate this further, Bert Hamelers, a chemical engineer at The Center for Water Excellence in the Netherlands, and his colleagues from Wageningen University conducted an experiment in 2014 where they pumped carbon dioxide through water or other liquids and produced a flow of electron which created a build-up of electricity. According to the United Nations Environment Programme (UNEP), power-generating stations release about 12 billion tonnes of carbon dioxide every year as they burn natural resources. On the other hand, homes, heating, and treatment plants release another 11 billion tonnes of carbon dioxide. “This would be enough to create 1,750 terawatt-hours of extra electricity annually: about 400 times the output of the Hoover Dam in the US, and all without adding an extra gasp of carbon dioxide into the atmosphere,” states Hamelers in his 2013 Environmental Science and Technology Letters review. So the exhaust from one cycle of electricity production could be used immediately to deliver another flow of power to the grid. That is not the only solution that scientists have come up with.


Creating a New Fuel Source

Scientists have long dreamed of mimicking photosynthesis, by using the energy in sunlight to knit together hydrocarbon fuels from carbon dioxide (CO2) and water. Now, a cheap new chemical catalyst has carried out part of that process with record efficiency, using electricity from a solar cell to split CO2 into energy-rich carbon monoxide (CO) and oxygen. The new work is “a very nice result,” says John Turner, a renewable fuels expert at the National Renewable Energy Laboratory in Golden, Colorado.


The process begins when CO2 is broken down into oxygen and carbon monoxide (CO), the latter of which can be combined with hydrogen to make a variety of hydrocarbon fuels, like rocket fuel. Over the last 2 decades, researchers have discovered a number of catalysts that enable that first step and split CO2 when the gas is bubbled up through the water in the presence of an electric current. One of the best-studied catalyst conducted in Switzerland is a cheap, plentiful mix of copper and oxygen called copper oxide. The trouble is that the catalyst splits more water than it does CO2, making molecular hydrogen (H2), a less energy-rich compound, says Michael Graetzel, a chemist at the Swiss Federal Institute of Technology in Lausanne, whose group has long studied these CO2-splitting catalysts.


In 2016, researchers were looking into the details of how copper oxide catalysts work. They put a layer of them on a tin oxide-based electrode, which fed electrons to a beaker containing water and dissolved CO2. Instead of splitting mostly water—like the copper oxide catalyst—the new catalyst generated almost pure CO. “It was a discovery made by serendipity,” Graetzel happily says. Overall, their discovery has 90% of the CO2 into purely CO, Hydrogen, and Oxygen. Graetzel decided to use these byproducts as a fuel source to power the world. As a result, their work has led to the creation of lightweight and highly concentrated rocket fuel, and hydrogen-fuel cell-powered cars. But their work could one day lead to methods for making essentially unlimited amounts of power for the world’s future.


Citations:

Graetzel, Michael. “Cheap Catalysts Turn Sunlight and Carbon Dioxide into Fuel.” Science, 8 Feb. 2018, www.sciencemag.org/news/2017/06/cheap-catalysts-turn-sunlight-and-carbon-dioxide-fuel.


Radford, Tim. “Waste CO2 Could Be Source of Power.” Our World, 2013, ourworld.unu.edu/en/waste-co2-could-be-source-of-power.

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