Oct. 23, 2007 A series of Reuters reports from the Tokyo Autoshow this week show car makers confronting the harsh reality of a carbon-constrained world and still coming up short.

Manufacturers are struggling to develop new alternative engine technologies despite the knowledge that failure may result in extremely hard times for the sector, according to one report.

"In the long-term, it's very clear that on-road transportation has to decouple from petroleum for both dependency and greenhouse gas emissions reasons, and the pathway for that is electric drive," Michael Milikin, editor of Green Car Congress, told Reuters.

Various technologies each have their drawbacks, from hybrids (which still use fossil fuel) to hydrogen (energy intensive) to batteries and fuel cells (large and expensive) to biofuels (divert arable land from food production).

Mazda is banking on hydrogen, pointing out that hydrogen fuel can still be used with internal combustion engines.

"We have to prepare for sustainable zoom-zoom," says Mazda executive Nobuhiro Hayam. "We have to make a link with the hydrogen society of the future."

Technical obstacles to Mazda's approach include limited supplies of platinum, which is used as a catalyst, and lower ignition temperatures for hydrogen fuel, which may result in abnormal combustion. (Click here for the latest research on a possible alternative to platinum.) Hayam says the combustion problem can be avoided by using rotary engines.

Another Japanese car maker, Nissan, is focusing on batteries. The company believes that the main changes in engines and emission control over the next 15-20 years will come from further developments on existing engine and transmission systems, according to senior vice president Minoru Shinohara.

"In the long term, there is no doubt that batteries will play a big role," Shinohara says.

For now, fuel-saving hybrid technology is the most viable and marketable solution, as evidenced by the success of the Toyota Prius. New emissions rules in California, Japan, and the European Union have helped spur sales, although the European market for hybrids looks weak compared to North America and Japan, according to forecasts by auto supplier Robert Bosch GmbH. The findings haven't stopped Honda, which is planning a major rollout of new hybrid vehicles for 2009.

The bottom line? Car makers are racing against the clock and each other to develop the greener car of the future.

For more, read this article from the New York Times.