Source:
http://www.clean-air.org/H2%20Today%2019-12.pdf
Got hydrogen? The United States produces 9 million tons of hydrogen a year, mostly by reformatting natural gas. That’s enough to fuel 34 million cars. Unlike oxygen which is commonly used by hospitals and welders, hydrogen is not quite so readily available in small quantities. Your neighbors will certainly object to a 40’ hydrogen tube truck parked in your driveway. A simpler source of hydrogen for your Briggs & Stratton lawnmower experiments is to buy or rent a cylinder from a local welding supplier.
My last refill, which was actually a tank exchange, cost $49.47. A ‘K’ cylinder is 9 inches in diameter and 56 inches high. It holds 196 cubic feet of hydrogen at about 2600 psi. That’s roughly one pound of hydrogen gas. Now if a cubic foot of hydrogen is equal to 0.00246 equivalent gallons of gasoline, then a full cylinder holds 0.48 gallons worth of gas. In other words, my $49 would take my Toyota Corolla only about 15 miles.