Consuming alcohol causes the enzymes present in our liver to disintegrate the ingested molecules into carbon dioxide, along with a number of other byproducts. With the help of a similar set of enzymes, a team of Austrian scientists are trying to conduct the reverse reaction, in which CO2 is directly converted to alcohol. What makes this research significant is the fact that the alcohol produced can serve as valuable biofuel, thereby reducing our dependency on fossil fuels.
Converting carbon dioxide into methanol or butanol actually lowers the level of greenhouse gases in the atmosphere, which in turn has a positive effect on the current climate change. Although burning alcohol biofuel generates CO2, when used appropriately in large-scale, it might prove to be the ideal alternative to traditional fuels. Furthermore, the alcohol produced, via this process, can be utilized as raw materials in other industries. Speaking about the project at the recent Materials Research Society’s meeting in Boston, Stefanie Schlager of Austria-based Johannes Kepler University said:
We are trying to reduce the CO2 electrochemically… It is, in my opinion, a very convenient approach.
For the reactions, the team used the dehydrogenase group of enzymes and, added them to a composite mixture of alginic acid and silicates. The alginic acid- a type of carbohydrate present in algae-together with the silicates, help gel the enzymes into beads. Next, the enzymes were transferred into a flask containing a buffer solution, to which nicotinamide adenine dinucleotide hydrogenase(NADH) was added. NADH is a naturally occurring enzyme, present in living cells, that supplies hydrogen and electrons needed for the reaction to proceed. The entire process took place in three, different steps, each of which was controlled by different sets of enzymes. At the final stage, CO2 was added to the mixture, which got converted first into acids, then aldehydes and lastly, to alcohol.
However, one major problem with this approach is the fact that NADH is very expensive. In order to reverse its oxidation that occurs during the reaction, an exorbitant amount of energy is required, making the whole setup unsustainable and wasteful. Consequently, the researchers designed an intricate electrochemical reaction, that wouldn’t rely on the use of NADH. For this, an electrode was constructed with the help of felt, made out of carbon fiber. The felt served as a sponge, causing the entire electrode to be coated with beads of the enzymes. Applying electricity resulted in the production of more complex alcohol molecules, like ethanol and butanol. One advantage with such molecules is that they possess greater amounts of energy, thus acting as an important source of biofuel. Using electricity actually makes the process repeatable. Furthermore, utilizing solar power-generated electricity offers a far more eco-friendly alternative to traditional fossil fuels.
Via: IEEE Spectrum