‘Artificial Photosynthesis' - The More Efficient System?

Innovative Science & Technology: Research & Latest Trends / Vol. 29

A University of Chicago breakthrough might enable the creation of methane fuel from elements, such as carbon dioxide, water and light. The scientists have proven to show an innovative new system for artificial photosynthesis that is more productive than previous artificial systems by an order of magnitude.

Humans have always relied on fossil fuels for concentrated energy. The lifetime of our planet and the millions of years of a convenient, energy-dense photosynthesis has been packed into the two factors convenience and energy-density with finite supply. However, current fossil fuel consumption has tremendous negative impact on Earth’s climate (see post from Jan. 6, 2019 on "Climate Change: Systemic Challenges to the Planet and Remaining Tactics to Meet Them"). Even nature doesn’t seem to provide a solution for the overall amount of energy use - not even with photosynthesis. Without natural photosynthesis, there wouldn’t be life in Earth, as it produces the oxygen we breathe and makes the food we eat, but it doesn’t seem to be efficient enough to supply our essential chemicals in sufficient quantity.

One possible option is ‘artificial photosynthesis’ which is re-working the complex plant system to fuels. However, the chemical equipment in even one single leaf can be very complex, and even harder to turn it to such a purpose (see University of Chicago working paper from Nov. 2022). The University of Chicago breakthrough works at the molecular level and could produce ethanol, methane, or other fuels. In contrast, regular photosynthesis produces carbohydrates from carbon dioxide and water. Their method gives scientists a new direction to explore, and may eventually be useful for production of other chemicals.

In nature, photosynthesis is performed by several very complex assemblies of proteins and pigments, that take in water and carbon dioxide, then break the molecules apart, and finally rearrange the atoms to make carbohydrates—a long string of hydrogen-oxygen-carbon compounds. The trouble is that photosynthesis is only creating carbohydrates (see post from Nov. 5, 2017 on "Can Photosynthesis Solve the Planet’s Energy Dilemma?").

Scientists looking to find alternates to fossil fuels have to re-engineer the photosynthesis process to create more energy-dense fuels, such as ethanol or methane. Vehicles for example do need more concentrated energy. Scientists, however, need to rework the reactions to instead produce a different arrangement with just hydrogen surrounding a juicy carbon core, also known as methane.

This re-engineering process is very complex and tricky. The University of Chicago lab team has tried adding amino acids that to date weren’t included by artificial photosynthesis systems. They started with a class of compounds made up of metal ions held together by an organic linking molecule. Then they designed a single layer, in order to provide the maximum surface area for chemical reactions, and submerged everything in a solution that included a cobalt compound to ferry electrons around. Finally, they added amino acids and experimented to find out the best-working solution. They were able to make improvements to both sides of the chemical reactions, the process that breaks apart water and the one that adds electrons and protons to carbon dioxide. In both cases, the amino acids helped the reaction go more efficiently.

This breakthrough can also be applied widely to numerous chemical reactions. Although a lot of fuel for it needs to be produced in order to have an impact at all, much smaller quantities of some molecules are needed, such as starting materials to make pharmaceutical drugs and nylons, and more. Many of the fundamental processes are the same and can be plugged into many systems.

Even with such a significantly improved performance, ‘Artificial Photosynthesis’ has still a long way ahead before it can produce enough fuel as base to be relevant for widespread use. It still needs to scale up by a multiple in order to make a sufficient amount of methane for consumption. And a significant question remains: Is more methane what the planet’s environment really needs? (see post from Nov. 9, 2022 on "CO2 Grouting and Carbon Dioxide Repository")