How reverse photosynthesis uses sunlight to make fuel

Using a natural process described as “reverse photosynthesis,” scientists say they can use the energy of sunlight to break down biomass into chemicals, fuels, and other products that would otherwise take a long time to produce.

“It has always been right beneath our noses, and yet no one has ever taken note.”

“This is a game changer, one that could transform the industrial production of fuels and chemicals, thus serving to reduce pollution significantly,” says University of Copenhagen Professor Claus Felby, who heads the research.

“It has always been right beneath our noses, and yet no one has ever taken note: photosynthesis by way of the sun doesn’t just allow things to grow, the same principles can be applied to break plant matter down, allowing the release of chemical substances.

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“In other words, direct sunlight drives chemical processes. The immense energy in solar light can be used so that processes can take place without additional energy inputs,” says Felby.

Postdoc David Cannella says the discovery means that by using the sun, “we can produce biofuels and biochemicals for things like plastics—faster, at lower temperatures, and with enhanced energy efficiency. Some of the reactions, which currently take 24 hours, can be achieved in just 10 minutes by using the sun.”

How reverse photosynthesis works

Monooxygenases, a natural enzymes also used in industrial biofuel production, multiply their effectiveness when exposed to sunlight.

“We use the term ‘reverse photosynthesis’ because the enzymes use atmospheric oxygen and the sun’s rays to break down and transform carbon bonds, in plants among other things, instead of building plants and producing oxygen as is typically understood with photosynthesis,” says postdoc Klaus Benedikt Møllers.

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Researchers do not yet know how widespread reverse photosynthesis–using light, chlorophyll, and monooxygenases–is in nature, but there are many indications that fungi and bacteria use reverse photosynthesis to access sugars and nutrients in plants.

Reverse photosynthesis has the potential to break down chemical bonds between carbon and hydrogen, a quality that may be developed to convert biogas-plant sourced methane into methanol, a liquid fuel, under ambient conditions.

As a raw material, methanol is very attractive because it can be used by the petrochemicals industry and processed into fuels, materials, and chemicals.

The Danish Council for Independent Research supported the work, which appears in Nature Communications.