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Humanity’s relationship with fossil fuels allowed us to build complex and efficient societies flush with incredible technology. By burning oil and other naturally occurring chemicals gathered from within the Earth, we can travel to distant locales by road or air. We can even use those chemicals to send people to the Moon, and machines to other planets. But all of these incredible advances come with a cost.
That same relationship with fossil fuels has dumped incredible amounts of previously sequestered carbon into the atmosphere, warming the planet and eroding ecosystems. The consequences of anthropogenic climate change are staggering and ongoing. And the need to develop alternative fuel sources is huge.
A recent study by Zhen Q. Wang from the Department of Biological Sciences at the University of Buffalo, and colleagues, describes a process by which modified microbes convert sugar into hydrocarbons to create fuels. Their findings were published in the journal Nature Chemistry.
Researchers developed a modified strain of E. coli bacteria capable of acting as a factory for the production of complex molecules including some which can be used as a fuel source to replace existing petrochemicals. The bacteria were modified in order to become harmless to humans, a necessary step if the plan is to produce enough of them to scale the process to compete with existing industries.
The bacteria are fed glucose, a form of sugar. Some of that sugar is consumed to feed the bacteria and keep it alive, and in turn the E. coli produce enzymes which convert the glucose into 3-hydroxy fatty acids. At this stage, the produce isn’t yet suitable for fuel usage. Bacteria are good at creating a great many things, but ready-use petrochemicals aren’t one of them. The molecular chains they pump out carry too much oxygen and other atoms which need to be removed before they can be used for fuel.
Part of the modification process included changing the bacteria so that they created molecules which carried less baggage and could be more easily reduced. Scientists then take these molecules and expose them to a catalyst known as niobium pentoxide (Nb2O5) to remove unwanted parts, leaving them with a collection of olefins.
Olefins are simple hydrocarbons which are unsaturated, meaning they don’t contain any extraneous parts. They are simply hydrogen and carbon with at least one double or triple bond. The number of the bonds has an impact on the nature of the hydrocarbon and the sorts of materials they are used for. Some of these mirror the molecules present in common fuels like gasoline.
Using biologically produced hydrocarbons as a fuel source might seem like trading one combustive fuel for another, and that’s partly true. But fuels derived from glucose are more environmentally friendly than the alternative. The glucose used to feed microbes is derived from plant biomass. Those plants necessarily pull carbon out of the air as they grow, so the carbon released when the fuel is burned is the very same carbon which was removed from the atmosphere during its production.
This gives biofuel processes the potential to be renewable and carbon neutral. Still, there’s no such thing as a free lunch and there are challenges to bringing this process, and processes like it, into the world. Today, processing hydrocarbons with microbes is inefficient. It takes approximately 100 molecules of glucose to produce 8 olefin molecules, and there’s the question of how much energy was put into the system in order to complete the transformation, and where that energy comes from.
Scientists are looking for ways to optimize production by E. coli such that the output is greater, and the energy costs are lowered. With any luck, and with continued research, a whole fleet of modified bacteria could one day make commuting to work, going on vacation, and traveling to the stars just a little bit sweeter.