Mimicking plants to upgrade contaminant emissions

By Elisa Nuñez Acosta

Imagine you are lying on the beach to get a nice sun tan while your body takes advantage of the sunlight to get you all the fuel you need to live. This is a special superpower that human beings do not have, but plants do.

Plants catch sunlight through their leaves and use this energy to convert the CO₂ that they get from air into fuel to live. The only extra ingredient they need is water, and the plants will do the magic. It sounds like a very efficient system to obtain fuel, isn’t it?

Researchers have been mimicking such a process to convert CO₂ into a kind of natural gas widely used to produce electricity and heat. A group of scientists, led by Dr. D. J. Heldebrant from the Pacific Northwest National Laboratory in the U.S., converted CO₂ into synthetic natural gas. This finding was published in Chemistry Sustainability Energy Materials in August 2021.

This technology could not only help us obtain new sources of fuel, but it also could reduce contaminant CO₂ emissions and their effects on the environment by reducing global warming.

Let me walk you through it. The team of scientists has been making pre-existing technology more sustainable. Like plants, they trigger CO₂ transformation in a laboratory by using visible light, such as the sunlight. This method also uses an electrical current to keep the procedure going. The mechanism additionally uses a catalyst to speed up the reaction. For all the above, the full name of such technology is photoelectrocatalysis and it can transform CO₂ into fuel.

Scientist have learned from plants how to transform the energy from sunlight into fuel. Green plants have their characteristic color because they have a pigment called chlorophyll. This pigment works like an antenna able to absorb intensely the sunlight. The light absorbed allows plants to trigger an avalanche of reactions that integrate water and CO₂ from air to create fuel.

Carbon dioxide is very stable which means that it is very difficult to break it down. Scientists have succeeded in doing this by using visible light, such as the sunlight for the CO₂ transformation. Researchers have also used compounds that work similarly to chlorophyll catalyzing an avalanche of reactions that transform CO₂ into fuel. This kind of method has been evolving since the late 70’s.

You might think how Heldebrant’s team could do different than earlier similar investigations. They not only took advantage of visible light, but they also used only moderate temperatures and pressures during the whole process. Before its transformation, the researchers captured CO₂ using energy coming from renewable energies, while the subsequent conversion of CO₂ saved energy. These conditions created a masterful system that offsets energy. As a result, this technology is more sustainable than previous ones that are high-energy consumers. And this is not all; the novel method is potentially cheaper than other processes in terms of the capital investment and the selling price of the output.

Could this new finding help us massively generate fuel in a sustainable way? Although this technology is promising, it still has some caveats. For instance, it uses ruthenium metal to speed up the CO₂ transformation. This metal is very expensive and rare in the Earth’s crust. And here, there is an area of opportunity to make such a procedure more feasible, for instance using more affordable and abundant metals. The recent finding is firmly setting the basis to implement such procedures on a large-scale in a future, although.

If researchers are able to develop a system with the superpower of creating fuel from our CO₂ waste, its large-scale implementation will not depend only on them. Investments from governments and the private sector are key, as well. And it deserves our attention as we are taxpayers, voters and ultimately generators of CO₂ emissions.