These are not fuel cell cars. The hydrogen is, instead, burnt as normal within adapted versions of the internal combustion engine that powers the petrol RX-8.
The hydrogen, which has less energy by volume than petrol or diesel, is carried in large, highly pressurised tanks that rob the RX-8 and Premacy of much of their boot space.
Hydrogen releases no CO2 when it combusts, the main byproduct being water, although a tiny amount of nitrous oxides (NOx) are also released.
A fuel cell using hydrogen produces no NOx, and more energy, but Mazda has used traditional engines, since the manufacturing cost is far lower.
Click here to see a diagram of the Premacy's internal set-up.