Germany unveils Zero Emissions Train that only emits steam

Pure hydrogen is not naturally occurring. It takes energy to split off a free hydrogen atom. Hydrogen combustion or fuel cell approaches are innovations of energy storage and point of use (converting to electricity at the final stage to power a motor) and *not* emissions. Where things matter is earlier in the energy supply chain. What power source was used to free hydrogen? And the answer usually falls under the main categories of geothermal, solar, wind, nuclear, hydroelectric, and fossil fuel.