The amount of carbon dioxide in the atmosphere is already at its highest level over the course of three million years with the burning of fossil fuels known to have significantly contributed to this phenomenon that has been attributed to current concerns on global warming.

Fossil fuels, however, particularly coal, appears to continue being an important source of energy. Technologies that sequester carbon before it gets into the atmosphere are being considered, but all of these require storing the carbon captured, which in itself comes with environmental challenges.

An artificial photosynthesis developed by a group of researchers, however, solves this carbon storage problem by finding a means to beneficially use the captured carbon dioxide. The breakthrough was achieved by creating a hybrid system of semiconductor nanowires and bacteria that imitate nature's photosynthetic process through which plants make use of solar energy to synthesize water and carbon dioxide into carbohydrates.

The artificial photosynthetic system, however, differs in that it synthesizes carbon dioxide and water into acetate, which is currently the most prevalent building block for biosynthesis. The new system captures carbon dioxide before they are released into the atmosphere and with the energy from sunlight, convert it into valuable chemical products that include pharmaceutical drugs, biodegradable plastics and liquid fuels.

For the study, the researchers used the bacterium Sporomusa ovata, which accepts electrons directly from the surrounding and utilize this to reduce carbon dioxide.

"We were able to uniformly populate our nanowire array with S. ovata using buffered brackish water with trace vitamins as the only organic component," said Biosynthesis expert Michelle Chang.

When the bacterium reduces the carbon dioxide to acetate, the artificially engineered E.coli are used to target chemical products.

Catalysts for carbon-neutral energy conversions expert Chris Chang said that in the natural photosynthesis, leaves collect energy from the sun and carbon dioxide is reduced and combined with water for use in the synthesis of molecular products which form biomass. With the artificial photosynthetic system, the nanowires collect the energy from sunlight and deliver electrons to bacteria where the carbon dioxide is reduced and combined with water to synthesize chemical products.

Experts see the new system as one that offers a win/win situation for the environment. Chang said that the system an emerging alliance between biology and material sciences.

Peidong Yang, from Berkeley Lab's Materials Sciences Division described their system as a leap in the field of artificial photosynthesis, which can potentially change the oil and chemical industry in a way that makes it possible to produce chemicals and fuels through renewable means instead of extracting them from below the ground.

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