Chemistry’s greatest challenge (Image: Andrio Abero)

LOOK at a plant soaking up the sun, and it is hard not to feel a tinge of jealousy. There they sit, day after day, extracting vast amounts of fuel from sunlight, all the while expelling nothing more objectionable than the oxygen we need to breathe. Our fuel-making exploits are ruinously costly and disruptive by comparison: we rip coal, oil and gas from the ground and burn it to produce far more planet-baking carbon dioxide than anyone can use.

What we wouldn’t give to mimic the tactics of plants, the true green warriors. “More energy hits the Earth from the sun in 1 hour than mankind uses in an entire year,” says Nate Lewis, a chemist at the California Institute of Technology in Pasadena. We know how to turn that energy into electricity – that is what photovoltaic cells are all about. But the sun does not always shine when and where we want it to. Through photosynthesis, plants have the enviable ability to convert sunlight into fuels that they can store now and burn later. If we could do the same, saving solar energy for a rainy day, transporting it to gloomier climes or pumping it straight into a fuel tank, a large part of our energy problems would be solved.

Now megabucks are flowing from, among others, the US government and big energy corporations to try to make that happen. The challenge of artificial photosynthesis is set – but it is proving to be one of the greatest challenges of all.

No one said photosynthesis was easy. It took plants millions of years to …