Cyborg Bacteria Could Turn CO2 Into Fuel

Cyborg Bacteria Could Turn CO2 Into Fuel

With a simple modification, bacteria can be made to absorb carbon dioxide and make acetic acid, which can then be turned into fuel.

Getty Ian Cuming
 
By Avery Thompson

If we want to fix our climate problem, it's not enough to simply stop burning fossil fuels. At this point, we have to actively take CO2 out of the air. There are a few technologies designed to remove CO2 from the air, but many of them are inefficient or expensive. But new research from Harvard might provide a low-cost, effective way to convert CO2 into something useful: The researchers discovered that adding compounds like cadmium or mercury to bacteria will trigger them to grow tiny semiconductors, converting CO2 into acetic acid.

Many heavy metals like cadmium, mercury, and lead are toxic to both large and small creatures alike, and some bacteria have evolved a defense. When exposed to these heavy metals, the bacteria use them to build semiconductor crystals on their surfaces, effectively neutralizing them. The Harvard researchers realized these crystals could be used as a sort of artificial photosynthesis.

When exposed to water, light, and carbon dioxide, the crystals on these bacteria make acetic acid—vinegar, basically. This reaction is around 80 percent efficient, more than six times as efficient as regular photosynthesis. More importantly, all it takes is bacteria and some cadmium for the reaction to start taking place.

"You grow them in their liquid broth and you just add small aliquots of cadmium solution and you wait a couple of days and out pops these photosynthetic organisms," says researcher Kelsey Sakimoto. "It's all very simple, mix-in-a-pot-chemistry."

While this by itself would be good news if we had a vinegar shortage, this process can also be combined with existing methods to convert the acetic acid into fuels or plastics. That means we can recycle some of our existing fuels without having to worry about adding more CO2 into the atmosphere.

"We have collaborators who have a number of strands of E. coli that are genetically engineered to take acetic acid as their food source and they can upgrade it into butanol and a polymer called polyhydroxybutyrate," says Sakimoto.

The researchers are next looking to see if they can improve the efficiency or use different metals, but this technology already has a lot of advantages that would make it ideal for mass production. The bacteria self-replicate, so all that's required is a giant tank of water and cadmium to be placed in the sun. Perhaps giant tanks of bacteria and heavy metals might be able to save our planet.

And if they don't, hopefully something else will.