Environment

Artificial photosynthesis breakthrough turns CO2 emissions into plastics and biofuel

Artificial photosynthesis brea...
Researchers have developed an artificial photosynthesis technology that could be a win/win for the environment (Photo: Shutterstock)
Researchers have developed an artificial photosynthesis technology that could be a win/win for the environment (Photo: Shutterstock)
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The process turns water, sunlight and CO2 into useful chemicals (Image: LBNL)
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The process turns water, sunlight and CO2 into useful chemicals (Image: LBNL)
Cross-sectional SEM image of the nanowire/bacteria hybrid array used in the new artificial photosynthesis system (Image: LBNL)
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Cross-sectional SEM image of the nanowire/bacteria hybrid array used in the new artificial photosynthesis system (Image: LBNL)
Researchers have developed an artificial photosynthesis technology that could be a win/win for the environment (Photo: Shutterstock)
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Researchers have developed an artificial photosynthesis technology that could be a win/win for the environment (Photo: Shutterstock)
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Scientists at the Lawrence Berkeley National Laboratory and the University of California, Berkeley have created a hybrid system of bacteria and semiconducting nanowires that mimics photosynthesis. According to the researchers, their versatile, high-yield system can take water, sunlight and carbon dioxide and turn them into the building blocks of biodegradable plastics, pharmaceutical drugs and even biofuel.

Although renewable energy is making up a growing portion of the world’s energy production, scientists have suggested that the current trends of CO2 buildup in our atmosphere are still likely to lead to serious consequences, and do so sooner than we had anticipated.

One way to keep harmful emissions under control could be to trap the CO2 coming out of smokestacks using materials like polymers or sponges. Some scientists are even going one step further, working on technology that can convert carbon dioxide into useful byproducts like calcium carbonate or biofuels such as methanol and isobutanol. However, these systems are still either very low-yield or in an early experimental phase.

Taking inspiration from Mother Nature, scientists have now devised a system that uses sunlight and water to convert carbon dioxide into a wide range of useful chemicals. Artificial photosynthesis is not a new concept  –  it’s been used to split water into hydrogen and oxygen and synthesize formic acid  –  but this new approach could be a game changer because of its versatility and the high yields it produces.

"Our system has the potential to fundamentally change the chemical and oil industry in that we can produce chemicals and fuels in a totally renewable way, rather than extracting them from deep below the ground," says Peidong Yang, who led the study along with Christopher and Michelle Chang.

Cross-sectional SEM image of the nanowire/bacteria hybrid array used in the new artificial photosynthesis system (Image: LBNL)
Cross-sectional SEM image of the nanowire/bacteria hybrid array used in the new artificial photosynthesis system (Image: LBNL)

Their invention uses two different types of bacteria interspersed within arrays of silicon and titanium nanowires. The silicon nanowires act like a miniature solar cell, capturing incoming light and releasing electrons. These electrons are then absorbed by Sporomusa ovata, an anaerobic bacterium that combines them with water and turns carbon dioxide into acetate, a versatile chemical precursor. Meanwhile, the titanium portion of the structure takes the positive charge left in place of the electron and uses it to extract oxygen from water. The oxygen is used by genetically engineered E. Coli bacteria to synthesize the desired chemicals.

The nanowire array also acts as a layer of protection for the bacteria, burying them in something akin to tall grass so that these usually-oxygen sensitive organisms can survive in adverse environmental conditions like flue gases.

As a proof of principle, the scientists showed that their system can reduce CO2 to chemicals including fuels, polymers and pharmaceutical precursors. The yields were up to 26 percent for butanol, 25 percent for amorphadiene, a precursor to the antimalarial drug artemisinin, and 52 percent for PHB, a renewable and biodegradable plastic, although these figures could rise even further with future optimizations.

The process turns water, sunlight and CO2 into useful chemicals (Image: LBNL)
The process turns water, sunlight and CO2 into useful chemicals (Image: LBNL)

Solar energy conversion efficiency was at 0.38 percent after 200 hours under simulated sunlight, which the researchers say is about the same as an actual leaf. But the team is already working to improve on this.

"We are currently working on our second generation system which has a solar-to-chemical conversion efficiency of three-percent," says Yang. "Once we can reach a conversion efficiency of 10 percent in a cost effective manner, the technology should be commercially viable."

The team's research appears on the latest issue of the journal Nano Letters.

Source: LBNL

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8 comments
David Clarke
I would imagine that putting these nano wire arrays in flue gases, could very quickly become clogged with fine particulate matter, and the bacteria may well be killed by the high-temperatures. Carbon dioxide is a natural requirement for photosynthesis, so the more of it there is, the better it works. Planting more trees has got to be a good idea. Carbon dioxide is not a pollutant. It constitutes only 0 .04% of the atmosphere.
Robert in Vancouver
If enviro groups were honestly concerned about the environment they would focus on creating ways to use CO2 such as described in the article. But they are just a business and their easiest and biggest source of revenue is carbon trading/taxes and scaring people into donating money. Lots of gullible people donate money to enviro businesses because they've been brainwashed into believing that's how to 'save the planet'.
Neil Farbstein
that efficiency is too low.
S Michael
Hey.... it's a start.. Good work.
Douglas Bennett Rogers
It makes more sense from a thermodynamic standpoint to use the solar energy directly and save the carbon for engineering. Until recently, the carbon has been more valuable as fuel and no value has been assigned to the CO2.
Jane Morrow
It does sound fantastic doesn't it? But do you know where silicon comes from? I live in the south west of Western Australia and it is made very close to my home town. They take quartzite and roast it in a reducing environment to drive off the oxygen. It is an amazing process. The only problem is that the best fuel to use, and the reason why the plant is located here, is Jarrah logs from the spectacular old growth forest of this remarkable biodiversity hotspot. We have a small population here and our voice is drowned out by the industries that are intent on selling silicon based technologies to the world. People just don't know the truth. I would be immensely grateful if you would take the trouble to Google some images of the Jarrah forest and maybe even SIMCOA log piles.
Peter Lang
you can make solar hydrogen with graphene cells too http://graphenesolarcells.blogspot.com
Magrim
The top two comments need a reality check. First off it doesn't matter what percentage it is, it matters how much it affects the accumulation of heat by our atmosphere. The next important factor is the thousands to hundreds of thousands of years it will remain. This number has gone up 25% in the last 50 years! Numbers that are astonishing. Over 50% of the ocean's coral died in the last 35Enter years from the warming of our oceans, which is responsible for 35% of life in the ocean. Star fish another key component in the ocean food chain is seeing a mass extinction period. Dinosaurs died off because the oceans acidified due to CO2 and we are on a much faster path than they were. (Gizmag had an article but I can't access the search feature here on this PC). BTW, charging people carbon tax and "donations" is not a motive. If these scientists were looking to get a well paying job lying they would just work for an oil company that would probably pay them quadruple from what they're making now. It's not like the carbon tax goes right into all the climatologists in the world's pocket (ludicrous!). You grasphing at finding a conspiracy motive for 99% of all climatologists is laughable (the 1% work for fossil fuel companies). The reality is you just want dirty cheap energy and you don't want to change your lifestyle or pay anymore in exchange for passing major problems to the generations that will come after us.