Distinguish between green hydrogen and blue hydrogen.

• A. Green hydrogen is produced from natural gas with CCS; blue hydrogen is produced by electrolysis using renewables.
• B. Green hydrogen is produced by electrolysis using renewable electricity; blue hydrogen is produced from natural gas with CCS to capture CO2.
• C. Green hydrogen uses coal; blue hydrogen uses biomass.
• D. Green hydrogen is stored underground; blue hydrogen is stored in tanks.

Answer: (B)

The main idea being tested is how hydrogen is categorized by its production method and carbon management. Green hydrogen is produced by electrolysis powered by renewable electricity, splitting water into hydrogen and oxygen with little or no direct CO2 emissions because the energy comes from clean sources. Blue hydrogen is produced from natural gas using processes like steam methane reforming, but with carbon capture and storage to trap the CO2, reducing the carbon footprint compared with conventional fossil-based hydrogen.

So green hydrogen avoids fossil fuels in the production path and relies on renewables for energy, while blue hydrogen uses a fossil fuel feedstock but mitigates emissions through CCS. The other options mix up these definitions: producing green hydrogen from natural gas with CCS is actually describing blue hydrogen; producing blue hydrogen via electrolysis with renewables is green hydrogen; and storing hydrogen underground versus in tanks is about storage, not the production pathway that defines the color labels.