DRIP, BABY, DRIP

To produce pure hydrogen, just inject the right microbes into depleted oil wells. The technique could help fuel a zero-carbon future.

- CHRIS BARANIUK

THERE WAS NO prospect of pumping more oil out of the old well. It was just a depleted cavern deep beneath the sun-baked Texas soil. But in July, some folks from a Houston-based biotech firm called Cemvita Factory came along and squirted a liquid into it. When they returned five days later, it was no longer an oil well-it had transformed into a hydrogen production plant.

The liquid they spritzed down the bore hole was a carefully mixed cocktail of bacteria and nutrients. Once inside the well, the microbes began breaking down residual oil hydrocarbons-dregs that would be unprofitable to extract in order to produce hydrogen and carbon dioxide. This field test, though small in scale, was a "huge success," says Cemvita's chief business officer, Charles Nelson, who would not comment on the specific bacteria and nutrients the company uses.

Hydrogen releases zero carbon emissions when burned and has long been touted as a future fuel. It's also the most abundant element in the universe, but here on Earth most of it is bound up in water and other molecules, which means unlocking large quantities is not a simple operation. There are so many techniques currently vying for supremacy that people have taken to color-coding them: When renewable energy is used to split water molecules into oxygen and hydrogen, that's called green hydrogen. Blue hydrogen, meanwhile, involves extracting the element from natural gas.

Cemvita describes its product as gold hydrogen-"to pay homage to the past era of oil as the black gold and it now being used as a feedstock to make subsurface hydrogen," says cofounder and CEO Moji Karimi.