'Artificial leaf' may yield power source

Turbo-charging photosynthesis - by which plants and bacteria turn sunlight into food and energy - in an "artificial leaf" could yield a vast commercial power source, scientists said.

Photosynthesis is "unfortunately not very efficient," Anne Jones, an assistant professor and biochemist at Arizona State University, told the American Association for the Advancement of Science meeting in Vancouver this weekend.

"In fact, all of our current fossil fuels are products of this process," she said. But photosynthesis efficiency "could be boosted to increase food yields or sustainable biofuel production."

The world's energy consumption is expected to surge by 100 percent in the next 40 years.

That is expected even as oil and gas reserves are being used up, according to researchers,who are weighing a range of approaches to harness the power of photosynthesis to power engines.

Scientists said that given the low efficiency of photosynthesis, the top theoretical yield for squeezing energy out of the process with major crops such as wheat or sugar beets would be about 5 percent.

But if efficiency could be forced up by even a few percentage points, they could be sitting on major biofuel production potential.

Jones said that when the enzyme that catalyzes steps in CO2 fixation, called Rubisco, becomes saturated, the process of producing carbohydrate slows down and that most absorbed light energy is lost as heat.

"When it's sunny, a plant's molecular machinery produces more electrons than the Rubisco carbohydrate-producing engine can handle, and a lot of those electrons are wasted," she said.

The situation, she said, was akin to a power plant unconnected to distribution grid, in which excess energy goes to waste.

"In this sense photosynthesis is like a badly connected electrical grid," Jones said.

Scientists want to harness the excess solar energy by transferring energy absorbed in a photosynthetic light harvesting cell via biological nanowires to a separate cell that will produce fuel.

Questions:

1. How much is the world's energy consumption expected to surge by in the next 40 years?

2. What potential does photosynthesis have if efficiency could be forced up?

3. What's the enzyme that catalyzes steps in CO2 fixation called?

Answers:

1. 100 percent

2. Major biofuel production potential

3. Rubisco