Gray Hydrogen
Hydrogen produced from natural gas via steam methane reforming (SMR) without capturing the resulting CO2 emissions. This is how 95% of hydrogen is produced today, emitting about 10 kg of CO2 per kg of H2.
Why It Matters
Nearly all hydrogen used in industry today is gray hydrogen. Transitioning to green or blue hydrogen is necessary for hydrogen to be a climate solution rather than a contributor.
Related Topics
Related Terms
Green Hydrogen
Hydrogen produced by splitting water (electrolysis) using renewable electricity. The process produces zero direct greenhouse gas emissions. Currently costs $4-$8/kg vs. $1-$2/kg for conventional (gray) hydrogen.
Blue Hydrogen
Hydrogen produced from natural gas with carbon capture and storage (CCS) applied to capture 85-95% of the CO2 emissions. Costs between gray and green hydrogen.