Berkeley's Artificial Leaf Can 'Photosynthesize' Global Warming, for Good

The debate over global warming's role in causing the current Californian drought notwithstanding, a team of researchers from Berkeley have a solution to the world's mounting carbon emissions: the artificial leaf.

A semiconductor-bacteria hybrid, the artificial leaf mimics photosynthesis to produce precursors for biodegradable products, from carbon dioxide (CO₂) emissions. Like natural leaves, it uses sunlight to power bacteria that reduce CO_2, and later synthesize it into chemicals including liquid fuels and pharmaceutical drugs.

"We believe our system is a revolutionary leap forward in the field of artificial photosynthesis. 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," said Peidong Yang, a chemist at Berkeley Lab's Materials Sciences Division.

The silicon and titanium oxide nano-wires up on exposure to sunlight provide the electrons that trigger bacteria to reduce CO₂ to something like acetate. Researchers used Sporomusa ovata for the reduction reaction. Later, genetically modified E.coli synthesized chemicals from the reduction.

Researches achieved an efficiency of 0.38 percent in converting 200 hours of solar energy to chemicals, which they say is just as efficient as a leaf. The team obtained a 26 percent yield for Butanol, 25 percent for amorphadiene and an encouraging 52 percent for the environment friendly plastic. Further refinements through targeted genetic engineering of bacteria are expected to improve yield.

Improvements could also see a single-step reduction and synthesis process, which currently is separated in semiconductor-bacteria hybrid design. The design outdoes ongoing efforts, which in themselves leave a carbon footprint, to tackle emissions as it reduces CO_2­ before its release and uses renewable solar energy.

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

The study was published in the journal Nano Letters.