What if we could convert carbon dioxide into fuel at scale?

1 Nov 2023

Image: © Zamrznuti tonovi/Stock.adobe.com

Scientists at MIT and Harvard have found a new and efficient way to convert carbon dioxide into formate, a fuel that can then be scaled to produce electricity.

Last month was the hottest September on record, and 2023 is on track to become the hottest year on record. Beyond just the data, this warming has also led to several natural calamities such as heatwaves and famines in some parts of the world and unprecedented flooding in others.

Perhaps the most potent contributing factor in this largely human-induced climate crisis is greenhouse gas emissions, which, scientists say, have reached an all-time high.

The question of what to do about the increasing amounts of greenhouse gases pumped into the atmosphere strikes at the heart of research on the climate crisis. What do we do with all the excess carbon dioxide? We seem to have an answer.

Formate – a silver bullet?

Scientists at Massachusetts Institute of Technology (MIT) and Harvard University have developed a novel process that can convert carbon dioxide into formate, a material that can be used to power a fuel cell – much like hydrogen or methanol – to generate electricity.

Potassium or sodium formate, which can be either in liquid or solid form, is already produced at an industrial scale for a variety of purposes, most commonly as a de-icer for roads and pavements during the winter months.

Formate is non-toxic, non-flammable and easy to store and move around. It also stays stable in ordinary steel tanks to be used months, or even years, after its production. So could this be the silver bullet we’ve been looking for?

Developed by Zhen Zhang, Zhichu Ren, Alexander Quinn and Prof Ju Li of MIT and Dawei Xi of Harvard, the process was detailed this week in the journal Cell Reports Physical Science.

They demonstrated the process in which carbon dioxide gas is captured and converted into a solid formate powder. This is then used in a fuel cell to produce electricity in a laboratory scale. The hope is this method can be scaled to eventually provide power to homes or even industries.

90pc efficiency

Conventional approaches to converting carbon dioxide into fuel incorporate a two-step process involving conversion of the gas into calcium carbonate and then heating the resultant solid to drive off the carbon dioxide and convert it to a fuel feedstock such as carbon monoxide.

The second step, according to the team, has very low efficiency, converting less than 20pc of the gaseous carbon dioxide into the fuel. The team claims that the new process involving formate achieves a more than 90pc conversion rate and eliminates the need for heating.

“Traditionally, it is difficult to achieve long-term, stable, continuous conversion of the feedstocks,” said Zhang, who is a doctoral student at MIT. “The key to our system is to achieve a pH balance for steady-state conversion.”

Now, the team hopes that their study, supported by the US Department of Energy, can have applications in anything from home-sized units to large-scale industrial or grid storage systems.

Initial applications will likely involve an electrolyser unit about the size of a refrigerator to capture and convert the carbon dioxide into formate that can be stored in an underground or rooftop tank.

“This is for community or household demonstrations,” Zhang went on. “But we believe that also in the future it may be good for factories or the grid.”

10 things you need to know direct to your inbox every weekday. Sign up for the Daily Brief, Silicon Republic’s digest of essential sci-tech news.

Vish Gain is a journalist with Silicon Republic