Aircrafts transport people, ship goods, and perform military operations, but the petroleum-based fuels that power them are in short supply. In research published on June 30 in the journal Joule, researchers at the Lawrence Berkeley Lab have found a way to generate an alternative jet fuel by harvesting an unusual carbon molecule produced by the metabolic process of bacteria commonly found in soil.
"In chemistry, everything that requires energy to make will release energy when it's broken. When petroleum jet fuel is ignited, it releases a tremendous amount of energy, and the scientists at the Keasling Lab at the Lawrence Berkeley Laboratory thought there must be a way to replicate this without waiting millions of years for new fossil fuels to form,” said lead author Pablo Cruz-Morales, a microbiologist at DTU Biosustain, part of the Technical University of Denmark.
The idea was born years ago, when Jay Keasling, a chemical engineer at University of California, Berkeley, approached Cruz-Morales, who was a postdoc in his lab at the time, to see if he could synthesize a tricky molecule that has the potential to produce a lot of energy. "Keasling told me: it's going to be an explosive idea," according to Cruz-Morales. The molecule that Keasling wanted to recreate was called Jawsamycin, created by the common bacteria streptomyces, an organism that Cruz-Morales had worked with in the past.
"The recipe already exists in nature," says Cruz-Morales. The jagged molecule is produced by native metabolism of the bacteria as they munch away on glucose. "As they eat sugar or amino acids, they break them down and convert them into building blocks for carbon-to-carbon bonds," he said.
"You make fat in your body in the same way, with the same chemistry, but this bacterial process has some very interesting twists. These twists, which give the molecules their explosive properties, are the incorporation of cyclopropane rings -rings of three carbon atoms arranged in a triangular shape," he added. After careful analysis, the team determined that the enzymes that were responsible for the construction of these high-energy cyclopropane molecules were polyketide synthases.
"Polyketide synthases are the ultimate biological tool to make organic chemistry," says Cruz-Morales.
Cruz-Morales explains that the fuel produced by the bacteria would work a lot like biodiesel. It would need to be treated so that it could ignite at a lower temperature than the temperature needed to burn a fatty acid, but when ignited, it would be powerful enough to send a rocket into space.
"If we can make this fuel with biology there's no excuses to make it with oil. It opens the possibility of making it sustainable," says Cruz-Morales.
In the future, Cruz-Morales hopes that he and the team of Department of Energy researchers who worked on the project will be able to scale up this process so that their alternative fuel could actually be used in aircrafts.
"You can see this as a preparation for the moment because we are going to run out of fossil fuels, and there's going to be a point, not far from now, when we will need alternative solutions," Cruz-Morales explained.