Turning carbon emissions into methane fuel

Turning carbon emissions into methane fuel

New method offers potential for abundant energy savings, study finds

Chemists have developed a novel way to capture and convert carbon dioxide into methane, suggesting that future gas emissions could be converted into an alternative fuel using electricity from renewable sources.

Carbon dioxide (CO₂) is a greenhouse gas that accounts for a large part of Earth's warming climate, and is produced by power plants, factories and various forms of transportation. Typical carbon capture systems aimed at reducing its presence in the atmosphere work to lower carbon dioxide emissions by isolating CO₂ from other gases and converting it to useful products. However, this process is difficult to implement on an industrial scale due to the massive amount of energy required for these systems to operate.

Now, using a special nickel-based catalyst, researchers have figured out a way to save much of this precious energy by turning captured carbon dioxide directly into methane, said Tomaz Neves-Garcia, lead author of the study and a current postdoctoral researcher in chemistry and biochemistry at The Ohio State University.

By employing nickel atoms laid out on an electrified surface, the team was able to directly convert carbamate, the captured form of carbon dioxide, to methane. They found that nickel atoms, a cheap and widely available catalyst, were extremely good at making this conversion.

"We are going from a molecule that has low energy and producing from it a fuel that has high energy," said Neves-Garcia. "What makes this so interesting is that others capture, recover and then convert carbon dioxide in steps, while we save energy by doing these steps simultaneously."

Most importantly, streamlining the carbon capture process helps reframe what scientists know about the carbon cycle, and is a vital step to setting up more complex strategies for faster and more efficient climate mitigation technologies.

"We need to focus on spending the lowest energy possible for carbon capture and conversion," said Neves-Garcia. "So instead of performing all the capture and conversion steps independently, we can combine it in a single step, bypassing wasteful energy processes."

The paper was recently published in the Journal of the American Chemical Society.

Although many carbon capture methods are still in their early stages, with researchers from an array of fields working to improve them, the field is a promising one, said Neves-Garcia.

Converting CO₂ into a fuel using renewable electricity has the potential to close the carbon cycle. For example, when methane is burned to generate energy, it emits carbon dioxide, which, if captured and converted back to methane, could lead to a continuous cycle of energy production without adding to Earth's global warming burden.

The study also represents the first time that researchers discovered they could use electrochemistry to achieve carbamate conversion to methane. Although many attempts have been made to convert captured CO₂ into useful products, until now most researchers have only shown the ability to produce carbon monoxide.

"Methane can be a really interesting product, but the most important thing is that this opens a path to develop more processes to convert captured CO₂ into other products," he said.

Moving forward, the team expects to keep exploring other chemical clean energy alternatives to help inspire the creation of a variety of sustainable carbon capture routes.

"Everything always goes back to energy, and there's a lot of excitement and effort invested in the future of this field to save more of it," said Neves-Garcia.

Other co-authors include Quansong Zhu and L. Robert Baker from Ohio State, Liane M. Rossi from the University of Sao Paulo, Mahmudul Hasan and Robert E. Warburton from Case Western Reserve University, Jing Li and Hailiang Wang from Yale University, as well as Zhan Jiang and Yongye Liang from the Southern University of Science and Technology.

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