On Mars or Earth, biohybrid can turn carbon dioxide into new products

Bacteria on nanowires convert sunlight, carbon dioxide and water to organic building blocks

University of California – Berkeley

A device to capture carbon dioxide from the air and convert it to useful organic products. On left is the chamber containing the nanowire/bacteria hybrid that reduces carbon dioxide to form acetate. On the right is the chamber where oxygen is produced. Credit UC Berkeley photo by Peidong Yang
A device to capture carbon dioxide from the air and convert it to useful organic products. On left is the chamber containing the nanowire/bacteria hybrid that reduces carbon dioxide to form acetate. On the right is the chamber where oxygen is produced. Credit UC Berkeley photo by Peidong Yang

If humans ever hope to colonize Mars, the settlers will need to manufacture on-planet a huge range of organic compounds, from fuels to drugs, that are too expensive to ship from Earth.

University of California, Berkeley, and Lawrence Berkeley National Laboratory (Berkeley Lab) chemists have a plan for that.

For the past eight years, the researchers have been working on a hybrid system combining bacteria and nanowires that can capture the energy of sunlight to convert carbon dioxide and water into building blocks for organic molecules. Nanowires are thin silicon wires about one-hundredth the width of a human hair, used as electronic components, and also as sensors and solar cells.

“On Mars, about 96% of the atmosphere is CO2. Basically, all you need is these silicon semiconductor nanowires to take in the solar energy and pass it on to these bugs to do the chemistry for you,” said project leader Peidong Yang, professor of chemistry and the S. K. and Angela Chan Distinguished Chair in Energy at UC Berkeley. “For a deep space mission, you care about the payload weight, and biological systems have the advantage that they self-reproduce: You don’t need to send a lot. That’s why our biohybrid version is highly attractive.”

The only other requirement, besides sunlight, is water, which on Mars is relatively abundant in the polar ice caps and likely lies frozen underground over most of the planet, said Yang, who is a senior faculty scientist at Berkeley Lab and director of the Kavli Energy Nanoscience Institute.

The biohybrid can also pull carbon dioxide from the air on Earth to make organic compounds and simultaneously address climate change, which is caused by an excess of human-produced CO2 in the atmosphere.

In a new paper to be published March 31 in the journal Joule, the researchers report a milestone in packing these bacteria (Sporomusa ovata) into a “forest of nanowires” to achieve a record efficiency: 3.6% of the incoming solar energy is converted and stored in carbon bonds, in the form of a two-carbon molecule called acetate: essentially acetic acid, or vinegar.

Acetate molecules can serve as building blocks for a range of organic molecules, from fuels and plastics to drugs. Many other organic products could be made from acetate inside genetically engineered organisms, such as bacteria or yeast.

The system works like photosynthesis, which plants naturally employ to convert carbon dioxide and water to carbon compounds, mostly sugar and carbohydrates. Plants, however, have a fairly low efficiency, typically converting less than one-half percent of solar energy to carbon compounds. Yang’s system is comparable to the plant that best converts CO2 to sugar: sugar cane, which is 4-5% efficient.

Yang is also working on systems to efficiently produce sugars and carbohydrates from sunlight and CO2, potentially providing food for Mars colonists.

Watch the pH

When Yang and his colleagues first demonstrated their nanowire-bacteria hybrid reactor five years ago, the solar conversion efficiency was only about 0.4% — comparable to plants, but still low compared to typical efficiencies of 20% or more for silicon solar panels that convert light to electricity. Yang was one of the first to turn nanowires into solar panels, some 15 years ago.

The researchers initially tried to increase the efficiency by packing more bacteria onto the nanowires, which transfer electrons directly to the bacteria for the chemical reaction. But the bacteria separated from the nanowires, breaking the circuit.

The researchers eventually discovered that the bugs, as they produced acetate, decreased the acidity of the surrounding water — that is, increased a measurement called pH — and made them detach from the nanowires. He and his students eventually found a way to keep the water slightly more acidic to counteract the effect of rising pH as a result of continuous acetate production. This allowed them to pack many more bacteria into the nanowire forest, upping the efficiency nearly by a factor of 10. They were able to operate the reactor, a forest of parallel nanowires, for a week without the bacteria peeling off.

In this particular experiment, the nanowires were used only as conductive wires, not as solar absorbers. An external solar panel provided the energy.

In a real-world system, however, the nanowires would absorb light, generate electrons and transport them to the bacteria glommed onto the nanowires. The bacteria take in the electrons and, similar to the way plants make sugars, convert two carbon dioxide molecules and water into acetate and oxygen.

“These silicon nanowires are essentially like an antenna: They capture the solar photon just like a solar panel,” Yang said. “Within these silicon nanowires, they will generate electrons and feed them to these bacteria. Then the bacteria absorb CO2, do the chemistry and spit out acetate.”

The oxygen is a side benefit and, on Mars, could replenish colonists’ artificial atmosphere, which would mimic Earth’s 21% oxygen environment.

Yang has tweaked the system in other ways — for example, to embed quantum dots in the bacteria’s own membrane that act as solar panels, absorbing sunlight and obviating the need for silicon nanowires. These cyborg bacteria also make acetic acid.

His lab continues to search for ways to up the efficiency of the biohybrid, and is also exploring techniques for genetically engineering the bacteria to make them more versatile and capable of producing a variety of organic compounds.


The research is supported by a grant from NASA to the Center for the Utilization of Biological Engineering in Space (CUBES), a multi-university effort to develop techniques for biomanufacturing in space.

UC Berkeley co-authors of the paper are current or former graduate students Yude Su, Stefano Cestellos-Blanco and Ji Min Kim, who contributed equally to the work; and graduate students Yue-xiao Shen, Qiao Kong, Dylan Lu, Chong Liu, Hao Zhang and Yuhong Cao.

From EurekAlert!

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March 31, 2020 10:40 pm

And explain to me again why these bacteria haven’t taken over planet Earth…..much less expect them to do OK in the sterile, cold, 95% vacuum of Mars ?

Reply to  DMacKenzie
March 31, 2020 11:20 pm

Bacteria that do this won’t take over the Earth – acetic acid is a waste product. Natural evolution favors organisms that produce a minimum of waste products, not a maximum.

Walter Sobchak
Reply to  Writing Observer
April 1, 2020 12:01 pm

Unless you are making vinegar.

March 31, 2020 11:19 pm

“The biohybrid can also pull carbon dioxide from the air on Earth to make organic compounds and simultaneously address climate change, which is caused by an excess of human-produced CO2 in the atmosphere.”

As soon as you see a statement like that, you know they are total shysters. !

Rod Evans
Reply to  fred250
March 31, 2020 11:55 pm


Reply to  fred250
April 1, 2020 8:29 am

Um, yeah…like that’s exactly how bacteria work.
Not a really ground breaking discovery. Humans harnessed that power a few millennia ago. Any moonshiner can tell you that.

David Blenkinsop
March 31, 2020 11:46 pm

If you really want to be a Farmer in the Sky, don’t you have to plant some potatoes too?

Reply to  David Blenkinsop
April 1, 2020 3:16 am

Are you confusing science fiction stories? “Farmer in the Sky” was a long time before “The Martian” and a different author.

Joel O’Bryan
March 31, 2020 11:59 pm

Mars water is certainly not fresh water. While the Mars ice may be “fresh” at the crystalline level, it is likely heavily layered with perchlorate. Perchlorate ClO4- is the end result what happened to Mars’ NaCl laden liquid oceans in its first billion years. The water went to the atmosphere. Solar UV dissociated it. The hydrogen escaped to space. The oxygen mixed with the remaining chloride ion and Fe to make iron oxides. Eventually Mars got cold and dry as the oceans evaporated and turned to perchlorate salt wastelands. The perchlorate is in the soil, on top of any ice. Now deal with that perchlorate laden water Mr. bacteria nanowires.

April 1, 2020 12:02 am

“On Mars 96% of the atmosphere is CO2.”
It’s no wonder all life is extinct on that planet – proof of the disaster caused by MGW. The place is way to overheated to support the Martian ecology. At least that put an end to all that insane technological development and restored the Martians to a state of peaceful harmony with nature. RIP.

Dodgy Geezer
April 1, 2020 12:43 am

I have a better idea.

Bioengineer huge termites to live in that atmosphere, send them up to build huge termite mounds, then go and live in them….

Patrick MJD
April 1, 2020 1:27 am

Plants do this, right?

Reply to  Patrick MJD
April 1, 2020 3:10 am

Not quite. Plants make carbohydrates, which is the basis of all life on Earth, not useless acetate.

John M
Reply to  tty
April 1, 2020 6:52 am

Especially “two carbon molecules that are essentially vinegar.”

Suspect they are making some sort of inorganic aceate (NaOAc, CaOAc2, etc. If they are making organic esters, those would not be “two carbon molecules”.

Acetic acid can be used as a chemical feedstock. Inorganic acetates? Not so much.

Patrick MJD
Reply to  tty
April 2, 2020 12:07 am

Well the title was “…biohybrid can turn carbon dioxide into new products…” I read that as plants do that. So nothing new under the sun in other words.

Patrick MJD
April 1, 2020 1:31 am

I think they think energy is free, and completely ignore the laws of thermodynamics (Again).

High Treason
April 1, 2020 2:39 am

April Fools

April 1, 2020 3:07 am

“Plants, however, have a fairly low efficiency, typically converting less than one-half percent of solar energy to carbon compounds. ”

Wrong, photosynthesis usually has an efficiency of 3-6%, after the energy needed for the plants to live is subtracted. Those low 0.5% figures come from biofuel projects where most of the organic material is thrown away.

Reply to  tty
April 1, 2020 7:47 am

Yes. Decades ago when it was still a superb magazine, Scientific American published an article about the energy efficiency of a pine forest, and concluded that the forest converted 4% of the incident Solar radiation into recoverable energy.

David Dibbell
April 1, 2020 4:34 am

So … in this concept, carbon dioxide from the Martian atmosphere is a feedstock, not a pollutant. Maybe we can try thinking of it that way here on Earth!

John Bell
April 1, 2020 5:04 am

Hard to imagine ever setting foot on Mars, not worth the money needed, let alone setting up factories and farms there, it is nothing like the moon – too much science fiction.

April 1, 2020 7:12 am

CO2 is the new “perpetual-motion” machine. All kinds of miracles and uses from CO2, as long as whatever scheme is being touted uses up CO2 (which is the actual desired end). As others have said, there’s an ancient biological process that plants use that already does that.

Rich Davis
April 1, 2020 8:10 am

This one was obviously EurekAlert! crap just from looking at the headline.

Experts have a plan to do something impractical and useless at an exorbitant cost and it will save us from climate change.

April 1, 2020 8:16 am

So, after we already know that solar is fairly inefficient on the planet we live on, they want to set up commercial solar on Mars? Having said that, if you have no electricity, a solar panel can be a real godsend if you have any viable sunlight. I am currently camped out in the remote northern mountains with sat internet/TV with a big part of my energy supply solar, and is certainly cheaper than diesel generation. Thank goodness it is April 1 and not Oct 31. But you wouldn’t know it from the local weather.. -20 C this Am and the 5 feet of snow hasn’t even started to melt yet.

The whole process would be a lot more efficient when they have Gen 7 nuclear and a lot of 24/7 electricity available. Same for the good Earth. I have no truck with manufacturing long chain molecules out of CO2 for a multitude of products and will most certainly be the only option available for any extended stay on Mars, if and when that ever happens. I think this is a good use of R&D because it has practical applications for the long term future, both here and potentially on Mars. Learning practical technologies should be the point of R&D, so we can scale it up commercially if the circumstances arise if and when that it is needed. Knowledge is good.

And this will probably be the backbone of the future economy for the next 1000 years here on our planet, whenever the price of fossil fuels is more expensive than this scaled up general process. But based upon the price of WTI this week, I think that date might be quite a few decades out, if not a century if we really want to keep utilizing fossil fuels. I don’t think we will ever give up carbon based fuels and of course, carbon products…it just has too high an energy density per Kg for the price. In our long term future, or on Mars, CO2 will just be how we source the long chain carbon molecules for feedstock for a multitude of products we currently make out of fossil fuels. Carbon and CO2 is the back bone of life…period. Doesn’t matter if it comes out of the ground or the atmosphere. The only thing that really matters is price point. But let’s make sure we double the CO2 in our atmosphere first so as we can keep the good Earth green for the long term future. And hopefully it does add 2 degree C for the long term future, since I think we are going to need it.

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