Green Gets Real at Geneva Auto Show

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Hydrogen hasn't been forgotten either. Daimler CEO Dieter Zetsche says he has already test-driven prototype Mercedes cars powered by fuel cells. "They are ready for the market," he told reporters. The problem is that Mercedes needs to mass-produce the cars for them to be affordable, yet there is unlikely to be a large market until drivers have a place they can tank up with hydrogen. "The one element still missing, which we can't solve on our own, is the availability of infrastructure," Zetsche said. He estimated it will take until the middle of the next decade to create a market.

Getting the Most from Gasoline

While exotic technologies get most of the press, the best way to save fuel and reduce emissions in the short term is to make conventional cars lighter and more efficient. BMW unveiled a hybrid version of its X6 SUV, and said it will launch its first hybrid models in 2009. But BMW Chief Financial Officer Michael Ganal maintains that, while it makes sense to develop hybrid technology, diesels are still the cleanest and most fuel-efficient form of power today.

A diesel BMW Mini, he says, produces no more CO2 than a Toyota hybrid Prius and costs $5,000 less. And even the most efficient cars still don't use anywhere near the full energy potential of petroleum-based fuels, meaning there is still lots of room for energy improvements. "Petroleum will continue to be the most important form of mobile energy for decades," Ganal says. "Hybrid isn't yet better than diesel. Maybe it will be in combination with a diesel motor, but we're talking about decades, not years."

Even Toyota, which plans to be offering 18 hybrid models by the end of 2009, is doing research into other alternatives. "To what extent petroleum will still be available must be considered," Toyota President Katsuaki Watanabe said at a press conference. "There is no single technology on which we can place all our bets."

Ewing is BusinessWeek's European regional editor .