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The clean future of fossil fuels

All the energy, none of the pollution

Ever heard of chemical looping? Because it could be the future of emissions-free energy from fossil fuels.

Engineers at The Ohio State University are developing technologies that could economically convert fossil fuels and biomass into useful products, such as electricity and methanol, without spewing carbon dioxide (CO2) into the atmosphere.

In their research papers published in Energy & Environmental Science, the researchers and engineers report that their process can transform shale gas into methanol and gasoline — all while consuming carbon dioxide instead of producing it.

With this new process and scenario, CO2 doesn’t have to be buried — it can be converted into useful, value-added products.

The process, known as chemical looping, uses metal oxide particles in high-pressure reactors to “burn” fossil fuels and biomass without the presence of oxygen in the air. The metal oxide provides the oxygen from air for the reaction with the fossil fuels and biomass. Chemical looping can be used to “burn” fossil fuels and biomass to produce electricity or for chemical production, such as methanol, while emitting less than 1 percent of the CO2 present in these fuels.

Chemical looping, according to the engineers, can act as a stopgap technology that provides clean energy while renewable sources, such as solar and wind, become more available and affordable.

“Renewables are the future,” said Liang-Shih Fan, Distinguished University Professor in Chemical and Biomolecular Engineering, who leads the effort. “We need a bridge that allows us to create clean energy until we get there.”

Five years ago, Fan and his research team demonstrated a technology called coal-direct chemical looping (CDCL) combustion, in which they were able to release energy from coal while capturing more than 99 percent of the resulting carbon dioxide.

CDCL uses iron oxide particles, which supply the oxygen for chemical combustion of coal in a moving bed reactor to produce electricity. After combustion, the particles take back the oxygen from air, and the cycle begins again.

The challenge then, as well as now, was how to keep the particles from wearing out, said Andrew Tong, research assistant professor of chemical and biomolecular engineering at Ohio State.

Five years ago, the iron oxide particles for CDCL lasted through 100 cycles, which was tested in an eight-day continuous operation of a CDCL sub-pilot plant.

Now, they’ve developed a new formulation that lasts for more than 3,000 cycles, or more than eight months of continuous use in a commercial plant.

Another advancement involves the engineers’ development of chemical looping for production of syngas, which in turn provides the building blocks for many other useful products, such as methanol, ammonia, plastics or even carbon fibers.

That means that this process not only consumes CO2, but also potentially renders it as a useful raw material for producing everyday products.

Renewables are the future. We need a bridge that allows us to create clean energy until we get there.

Liang-Shih Fan, Chemical and Biomolecular Engineering professor

Usually when CO2 gets scrubbed from power plants, it’s buried in the ground so it doesn’t get released into the atmosphere. With this new process and scenario, it doesn’t have to be buried — it can be converted into useful, value-added products.

Taken together, Fan said, these advancements bring Ohio State’s chemical looping technology many steps closer to commercialization.

He calls the most recent advances “significant and exciting,” and they’ve been a long time coming. True innovations in science are uncommon, and when they do happen, they’re not sudden.

They’re usually the result of decades of concerted effort — or, in Fan’s case, the result of 40 years.

“This is my life’s work,” Fan said.