The race is on to create a biofuel that sucks carbon out of the sky and locks it away where it can't warm the planet

(Image: Mathis Rekowski - agencyrush.com/Artists/Mathis_Rekowski/)

THE green sludge burbles away quietly in its tangle of tubes in the Spanish desert. Soaking up sunshine and carbon dioxide from a nearby factory, it grows quickly. Every day, workers skim off some sludge and take it away to be transformed into oil. People do in a single day what it took geology 400 million years to accomplish.

Indeed, this is no ordinary oil. It belongs to a magical class of “carbon negative” fuels, ones that take carbon out of the atmosphere and lock it away for good. The basic idea is fairly simple. You grow plants, in this case algae, which naturally draw CO 2 from the atmosphere. After you extract the oil, you’re left with a residue that holds a substantial portion of the carbon. This residue is the key to carbon negativity. If you can store the carbon where it won’t decompose and return to the air, more CO 2 is taken out of the atmosphere than the fuel emits.

Such carbon negative fuels are no accounting sleight of hand – they could be the most realistic short-term solution we have to curb climate change. And although it is still early days, companies like General Electric, BP and Google are putting their money behind the idea.