Energy & Climate

Types of hydrogen

Understand hydrogen production types and color labels.

Hydrogen terminology

Hydrogen colors are shorthand for production context

Hydrogen is colorless; green/blue/grey labels are not physical properties but conventions about feedstock, energy source, and carbon management.

This reference pairs color labels with pathway and carbon-handling assumptions so the table can be read beyond shorthand terminology.

Identical labels can hide different carbon intensities, depending on renewable power matching, capture rates, and methane leakage.

Use it as a quick glossary when interpreting hydrogen-related energy and climate data.

Read color labels carefully

Green, blue, grey, turquoise, pink, yellow, white, and orange are vocabulary shortcuts, not quality levels.

Route drives meaning

Electrolysis, reforming, gasification, pyrolysis, nuclear heat, and other routes have different upstream emissions characteristics.

Carbon intensity first

Track emissions with boundary, carbon capture, and leakage assumptions before concluding clean share.

Glossary note

Color taxonomies are not globally uniform; definitions vary by region and reporting framework.

Color labels are not a cleanliness ranking; compare pathway and carbon-handling assumptions first.

Types 15

Categories 7

Definition variants 5

Sources 12

TABLE

Data preview

15 rows


Green hydrogen	Electrolysis	Early commercial	Water electrolysis. Some references also include renewable bio-based low-emission pathways.	Near-zero direct CO2 during operation, but lifecycle emissions from equipment, electricity matching, and water supply still matter.	The core question is whether the electricity is truly additional renewable power.
Blue hydrogen	Fossil-based	Pilot	Natural gas reforming (SMR/ATR), and in some taxonomies coal gasification, combined with CCS or CCUS.	Lower than grey when capture rates are high, but upstream methane leakage and uncaptured CO2 remain.	Actual capture rate, methane leakage, and kgCO2e/kgH2 matter more than the color label.
Grey hydrogen	Fossil-based	Commercial	Mostly steam methane reforming (SMR) or autothermal reforming (ATR).	CO2 from production is emitted to the atmosphere.	No emissions at the point of use does not mean low emissions at production.
Brown and black hydrogen	Fossil-based	Commercial	Lignite or hard-coal gasification	Very high CO2 and air-pollutant emissions.	Some references split brown and black; others group them under fossil grey hydrogen.
Turquoise hydrogen	Fossil-based	Pilot	Methane pyrolysis	Produces solid carbon instead of CO2; emissions depend on energy input, methane leakage, and carbon handling.	Climate benefit drops if solid carbon is oxidized later or used in short-lived products.
Pink, purple, and red hydrogen	Nuclear-based	Research	Nuclear-powered electrolysis, nuclear electricity plus heat for high-temperature electrolysis, or nuclear heat-driven water splitting.	Low direct emissions, but nuclear lifecycle, waste, and safety considerations remain separate questions.	Definitions overlap across sources, so grouping them as nuclear-based hydrogen is often clearer.
Yellow hydrogen (solar)	Electrolysis	Pilot	Water electrolysis using solar power	Low direct emissions, with lifecycle solar equipment, storage, and grid balancing to consider.	Some references instead define yellow hydrogen as grid-powered electrolysis.
Yellow hydrogen (grid)	Electrolysis	Early commercial	Water electrolysis using grid electricity	Can be low or high depending on the grid emissions factor.	Actual emissions depend on grid carbon intensity and hourly power mix.
White or gold hydrogen	Geologic hydrogen	Early exploration	Exploration, drilling, extraction, or capture of naturally occurring hydrogen.	Manufacturing energy can be small, but exploration, drilling, leakage, and purification require lifecycle assessment.	Academic and institutional sources often prefer natural or geologic hydrogen over white/gold labels.
Orange hydrogen (geologic)	Geologic hydrogen	Research	Injecting water into iron-rich formations to stimulate mineral reactions.	Potentially low-emission, but drilling, pumping, purification, and leakage must be assessed.	Orange hydrogen can also mean waste-derived hydrogen in other references.
Orange hydrogen (waste)	Bio and waste	Pilot	Waste or biomass pyrolysis, gasification, or reforming.	Biomass carbon can be biogenic, but plastic waste can still emit fossil carbon.	CCS and the fossil-carbon share of feedstock must be checked together.
Biohydrogen	Bio and waste	Pilot	Biomass gasification, biogas reforming, fermentation, and microbial or photobiological routes.	Can be low or even negative with sustainable feedstock and CCS, but land-use change matters.	References classify it differently: green, orange, or a separate biohydrogen category.
By-product hydrogen	By-product	Commercial	Recovery from primary-product processes such as brine electrolysis.	Emissions depend on electricity emissions factors and allocation method.	No stable color label; allocation rules matter.
Low-carbon or clean hydrogen	Policy and certification	Policy standard	Eligible pathways can include renewables, nuclear, fossil plus CCS, and bio plus CCS.	DOE targets 4.0 kgCO2e/kgH2, while the EU uses a framework based on at least 70% GHG savings versus a fossil comparator.	Check system boundary, kgCO2e/kgH2, and certification conditions before trusting the label.
Renewable hydrogen	Policy and certification	Policy standard	Usually renewable-powered electrolysis, with requirements such as additionality, temporal correlation, and geographic correlation under EU RFNBO rules.	EU rules include GHG accounting requirements such as at least 70% savings.	Often overlaps with green hydrogen, but legal renewable hydrogen can be stricter.