Buck Rogers is alive and well, and he’s producing cars in Europe. It wasn’t all that long ago that cars were powered by gas and diesel engines, and that’s about it, since both electric and steam had peaked by 1910. But now batteries have come back with a vengeance, and we’re investigating a number of other promising technologies, including synthetic natural gas and running hybrid cars on compressed nitrogen. And they’re going into production like that!

The Audi A3 Sportback G-Tron is a fascinating idea. It’s a little station wagon/crossover hatch with two tanks for “synthetic methane,” a form of carbon-neutral “e-gas” actually created by Audi. The automaker combines hydrogen from a plant in Germany’s Lower Saxony with waste carbon dioxide it gets from a nearby biogas plant. The process is carbon neutral, because the CO2 it captures would otherwise be released into the atmosphere. E-gas is basically compressed natural gas, or CNG, so there’s plenty of infrastructure to move it around and pump it into cars.

The G-Tron is a limited edition, debuting at the end of 2013. The plant can make enough e-gas to power 1,500 cars for 9,300 miles a year, so that’s probably how many they will make. But one imagines these cars could easily run on regular CNG, and that’s much more widely available.

e-gas car from Citreon

No, the new technology from Peugeot/Citroën (PSA) isn’t the “air car” we’ve all heard about, though that tech is French, too. We probably won’t see air cars anytime soon, but the PSA models (above) are hybrids, and headed for production around 2015 or 2016.

The heart of the system is a reversible hydraulic pump, which compresses not air but nitrogen gas in a hydraulic fluid-filled cylinder. When the driver hits the brakes or slows down, the nitrogen pushes the fluid through a gearbox, and that’s what acts as supplemental power to the small gasoline engine. The lightweight nitrogen system (220 pounds) doesn’t store much energy, but it helps enough to deliver a car with 81 mpg around town, PSA says. The price, says the New York Times, is estimated at $26,000. India and China are potential target markets. Here's a video close-up of how it works:

I wrote about a big Ford truck that used hydraulic power some years ago, and the company is still at it, working with Center for Compact and Efficient Fluid Power and Folsom Technologies. It claims it can get to 40 mpg in a huge F-150 with the hydraulic hybrid system. Chrysler is pursuing similar tech in an iconic Town & Country minivan.

Buck Rogers had rockets, but that show was set in the 25th century. Down here on Earth, even the jet pack isn’t really ready for prime time, yet. But e-gas and hydraulic hybrids? Those we can do.

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