Scientists are saying that they have bionically replicated the fuel-making process of a leaf.
Chemist Daniel Nocera of Harvard University and his team joined forces with synthetic biologist Pamela Silver of Harvard Medical School and her team to craft a kind of living battery, which they call a bionic leaf for its melding of biology and technology. The device uses solar electricity from a photovoltaic panel to power the chemistry that splits water into oxygen and hydrogen, then adds pre-starved microbes to feed on the hydrogen and convert CO2 in the air into alcohol fuels. The team’s first artificial photosynthesis device appeared in 2015—pumping out 216 milligrams of alcohol fuel per liter of water—but the nickel-molybdenum-zinc catalyst that made its water-splitting chemistry possible had the unfortunate side effect of poisoning the microbes.
[My emphasis]
The possibilities of real-world applications of such a technology are wide open.
With this new catalyst in the bionic leaf, the team boosted version 2.0's efficiency at producing alcohol fuels like isopropanol and isobutanol to roughly 10 percent. In other words, for every kilowatt-hour of electricity used the microbes could scrub 130 grams of CO2 out of 230,000 liters of air to make 60 grams of isopropanol fuel. That is better than the efficiency of natural photosynthesis at converting water, sunlight and air into stored energy.
And there is no reason to think that the R. eutropha could not be made to generate other products—perhaps complex hydrocarbon molecules like those found in fossil fuels or even the whole range of chemicals currently synthesized from polluting resources, such as fertilizers. "You have bugs that eat hydrogen as their only food source, and the hydrogen came from solar energy water splitting. So you have renewable bugs and the synthetic biology to make them do anything," Nocera says. "You can start thinking about a renewable chemicals industry." The hybrid team reports in theScience paper that they have already induced R. eutropha to make a molecule that can ultimately be transformed into plastics.
This product is still far, far away from being economically viable as the power produced is still minuscule compared to fossil fuels. But the path this opens up is very intriguing.
That hope is that this technology can be hooked up to photovoltaic cells, so that the energy of the sun is used to drive the water-splitting reaction. The bacteria could then be engineered to convert the hydrogen's energy into a multitude of carbon-based products, including biofuels and plastics, "essentially making products out of thin air," as co-author Brendan Colón describes it in a podcast.
Thus one of the major drawbacks of solar power – its inability to store energy to tide it through the hours of darkness – could be remedied. This research even has the potential to herald a breakthrough in worldwide efforts to reduce carbon dioxide in the atmosphere and turn that carbon into something useful.