The average automobile gas tank holds more than 1000 tons of ancient plant matter. Jeffrey Dukes, a terrestrial ecologist at the University of Massachusetts, Boston, has figured it out.
"My wife and I were driving through southern Utah in the lab's big Suburban, and I was thinking about how much gas we were burning," he says. So he decided to trace that fuel to its source: dying phytoplankton.
Dukes put together various bits of information that geologists had published. Only about 2% of the plankton make their way to the ocean floor, where they are buried under thousands of meters of rock. Heat from Earth's core pressure-cooks the remains, about half of which becomes oil. A small fraction of this squeezes toward the surface, accumulating in wells where humans can get at about one-quarter of it.
A lot is lost along the way. Multiplying the losses, Dukes calculates that only 0.01% of ancient plant matter that was in the right place at the right time contribute to the oil we can extract. If two-thirds of the oil is gasoline, 90 metric tons of dying phytoplankton went into making each gallon (roughly 4 liters) of gasoline. That's the equivalent of 16 hectares of wheat. And all the green the planet grows in 400 years wouldn't quite produce the fossil fuels we burn in one, Dukes concludes in a study published in the November issue of Climatic Change.
There is a lot of uncertainty in these estimates, notes Leslie Magoon, a petroleum geologist at the U.S. Geological Survey in Menlo Park, California. Even so, Magoon is intrigued. It's a new approach, he says, and "new things come from new ways of thinking."
Information about where oil comes from