Natural gas contains only one carbon and four hydrogen atoms per molecule, making it the cleanest of fossil fuels.

FORBES: Magazine Article

And sure enough, Mathur found that among the nearly 800 participants she tested, those with higher levels of methane (three or more parts per million over 90 minutes) and hydrogen gases (20 or more parts per million) in their breath also tended to be heavier, with a BMI about 2.4 points greater than those with normal levels of the gases and about 6% more body fat on average.

CNN: Can you smell obesity?

Warren Zapol, of the Massachusetts General Hospital and a professor of anaesthesia at Harvard Medical School, along with his colleagues, monitored the vital signs of mice exposed to low-dosages (80 parts per million) of hydrogen sulphide for several hours.

ECONOMIST: Researchers find hydrogen sulphide can lower metabolism

The BMW Hydrogen 7, for example, uses 254 kWh per 100 km, but the average fossil car in Europe uses 80 kWh per 100 km.

CNN: Commentary: Let's get real about alternative energy

They shed bubbles of material at speeds of thousands of miles per second, which collide with surrounding dense clouds of hydrogen.

CNN: Stellar nursery in nearby galaxy teems with activity

There would always be hydrogen, though: The U.S. market is on the order of 19 million tons per year.

FORBES: Magazine Article

To compress the hydrogen to a manageable volume, Ford must make a fuel system good for 5, 000 pounds per square inch of pressure, using exotic techniques and materials.

FORBES: The Guilt-Free Consumer