Every plant, animal, and person owes their life to one sequence of chemical reactions: photosynthesis. The process, which converts water and carbon dioxide into food using sunlight, first evolved in cyanobacteria more than 2 billion years ago.
That’s right. Plants weren’t the ﬁrst organisms to develop photosynthesis, though they are better known for it. Cyanobacteria are the ones that originally ﬁlled the atmosphere with photosynthesis’s gaseous by-product, oxygen (O2), which set the stage for more diverse life on Earth.
As beneﬁciaries of photosynthesis, humans depend on plants in a sort of carbon seesaw. Plants take in CO2 and release O2. They store that carbon as sugar. Hanging vines, grass, and trees all grow by pulling carbon atoms out of the air. We do the reverse, taking in O2 and releasing CO2. Finally, everything we eat completes the handoff: Human eats plant (or the animal who already did), human exhales, plant stores carbon, and the cycle continues.
This seesaw is part of the much broader carbon cycle that has affected the radiation balance of our planet. Cutting down huge swaths of forests and the burning of carbon-based fossil fuels causes the levels of CO2, a major greenhouse gas, to rise. And plants on Earth along with other natural parts of the carbon cycle can’t restore the balance on their own.
But what if we could copy what plants do to grab some of that excess CO2 to make fuels sustainably, instead of relying so heavily on fossilized carbon?
“Artiﬁcial photosynthesis is a really attractive approach,” says Jillian Dempsey, a chemist at the University of North Carolina, Chapel Hill. “You’re able to store the energy of the sun in the bonds of [molecules].”
At a large enough scale, such sun-powered processes could give us enough energy-storing molecules to make fuels out of thin air and water like plants and cyanobacteria do.