⚡ Energy

Types of Hydrogen

Green, blue, grey, and other hydrogen colour classifications

Reading the data

Read hydrogen colour names by production route and carbon handling

Hydrogen itself is colourless. Names such as green hydrogen, blue hydrogen, and grey hydrogen are better understood as conventions that describe feedstock, energy, production process, and carbon handling, not the quality of the hydrogen.

How to read it

Colour names are familiar, but real judgement should focus on production pathway and carbon-handling conditions. For example, blue hydrogen can be assessed very differently depending on carbon capture rate and methane leakage, while green hydrogen can mean different things depending on the electricity used.

What this page shows

Hydrogen type, colour name, production pathway, feedstock, and energy input
CO2 profile, maturity, definition differences, and points to check in real evaluations
Colour map, key checkpoints, and a comparison table by type

Data basis

The classification summarizes widely used categories from public references including IEA, U.S. DOE, European Commission, ISO, and World Energy Council.

Colour names are not fully unified international standards, so lifecycle emissions, accounting boundary, and real energy conditions should be considered together.

Types covered 15

Pathway groups 7

Definition variants 5

Reference sources 12

1 Pathway first

Read each colour as a production route: electrolysis, reforming, gasification, pyrolysis, nuclear, geologic, bio/waste, or by-product recovery.

2 Carbon intensity matters

A colour can hide large differences. Blue hydrogen depends on capture rate and methane leakage; green hydrogen depends on renewable electricity matching.

3 Most hydrogen is still fossil

IEA estimates low-emission hydrogen is still below 1% of global hydrogen production, so maturity should be shown with every colour.

Hydrogen colour map

A compact route map before the full comparison table.

Green hydrogen Electrolysis · Early commercial

Blue hydrogen Fossil-based · Pilot

Grey hydrogen Fossil-based · Commercial

Brown and black hydrogen Fossil-based · Commercial

Turquoise hydrogen Fossil-based · Pilot

Pink, purple, and red hydrogen Nuclear-based · Research

varies

Yellow hydrogen (solar) Electrolysis · Pilot

varies

Yellow hydrogen (grid) Electrolysis · Early commercial

varies

White or gold hydrogen Geologic hydrogen · Early exploration

Orange hydrogen (geologic) Geologic hydrogen · Research

varies

Orange hydrogen (waste) Bio and waste · Pilot

varies

Biohydrogen Bio and waste · Pilot

By-product hydrogen By-product · Commercial

Low-carbon or clean hydrogen Policy and certification · Policy standard

Renewable hydrogen Policy and certification · Policy standard

⚡ Hydrogen types comparison

15 types

Type	Meaning	Production route	CO₂ profile	Maturity	Watch point
Green hydrogen Green hydrogen Electrolysis	Hydrogen made by electrolyzing water with renewable electricity	Water electrolysis. Some references also include renewable bio-based low-emission pathways. Feedstock: Water and renewable electricity Energy: Wind, solar, hydro, geothermal, and other renewables	Near-zero direct CO₂ during operation, but lifecycle emissions from equipment, electricity matching, and water supply still matter.	Early commercial Clear decarbonization pathway for renewable power storage, industrial feedstock, fertilizer, and refining. Cost, electrolyzer supply chains, renewable additionality, time and location matching, and water use remain constraints.	The core question is whether the electricity is truly additional renewable power.
Blue hydrogen Blue hydrogen Fossil-based	Fossil-based hydrogen paired with CO2 capture and storage	Natural gas reforming (SMR/ATR), and in some taxonomies coal gasification, combined with CCS or CCUS. Feedstock: Natural gas, methane, and sometimes coal Energy: Fossil process heat plus CCS/CCUS infrastructure	Lower than grey when capture rates are high, but upstream methane leakage and uncaptured CO₂ remain.	Pilot Can reuse gas and reforming infrastructure and may scale faster in the near term. Needs CCS cost control, storage sites, transport networks, and proof of durable storage.	Actual capture rate, methane leakage, and kgCO₂e/kgH2 matter more than the color label.
Grey hydrogen Grey hydrogen Fossil-based	Today’s mainstream natural-gas hydrogen without CO2 capture	Mostly steam methane reforming (SMR) or autothermal reforming (ATR). Feedstock: Natural gas and methane Energy: Fossil process heat	CO₂ from production is emitted to the atmosphere.	Commercial Mature and low-cost, with stable supply for refining, ammonia, and methanol. High emissions conflict with long-term decarbonization goals.	No emissions at the point of use does not mean low emissions at production.
Brown and black hydrogen Brown and black hydrogen Fossil-based	Coal-gasification hydrogen; brown often means lignite, black often means hard coal.	Lignite or hard-coal gasification Feedstock: Coal Energy: Coal gasification process	Very high CO₂ and air-pollutant emissions.	Commercial Technically mature and easier to source in coal-rich regions. Very carbon-intensive and environmentally weak.	Some references split brown and black; others group them under fossil grey hydrogen.
Turquoise hydrogen Turquoise hydrogen Fossil-based	Hydrogen from methane pyrolysis, producing solid carbon	Methane pyrolysis Feedstock: Natural gas or methane Energy: Process heat or electricity	Produces solid carbon instead of CO₂; emissions depend on energy input, methane leakage, and carbon handling.	Pilot May avoid CO2 storage by handling solid carbon and could create a valuable co-product. Large-scale proof is limited and solid-carbon markets may be small.	Climate benefit drops if solid carbon is oxidized later or used in short-lived products.
Pink, purple, and red hydrogen Pink, purple, and red hydrogen Nuclear-based	Hydrogen made with nuclear electricity or heat	Nuclear-powered electrolysis, nuclear electricity plus heat for high-temperature electrolysis, or nuclear heat-driven water splitting. Feedstock: Water Energy: Nuclear electricity and high-temperature heat	Low direct emissions, but nuclear lifecycle, waste, and safety considerations remain separate questions.	Research Firm power can raise electrolyzer utilization, and high-temperature heat can improve efficiency. Nuclear cost, build time, public acceptance, and high-temperature process complexity.	Definition varies Definitions overlap across sources, so grouping them as nuclear-based hydrogen is often clearer.
Yellow hydrogen (solar) Yellow hydrogen: solar-powered Electrolysis	Hydrogen from water electrolysis powered by solar electricity	Water electrolysis using solar power Feedstock: Water and solar electricity Energy: Solar power	Low direct emissions, with lifecycle solar equipment, storage, and grid balancing to consider.	Pilot Good cost potential in strong solar-resource regions. Intermittency, electrolyzer utilization, land, and transmission constraints.	Definition varies Some references instead define yellow hydrogen as grid-powered electrolysis.
Yellow hydrogen (grid) Yellow hydrogen: grid-powered Electrolysis	Hydrogen from water electrolysis powered by the mixed grid	Water electrolysis using grid electricity Feedstock: Water and grid electricity Energy: Regional electricity mix	Can be low or high depending on the grid emissions factor.	Early commercial Flexible siting and operation for electrolyzers. Hard to call green when the grid is coal- or gas-heavy.	Definition varies Actual emissions depend on grid carbon intensity and hourly power mix.
White or gold hydrogen White or gold hydrogen Geologic hydrogen	Natural or geologic hydrogen found or generated underground	Exploration, drilling, extraction, or capture of naturally occurring hydrogen. Feedstock: Subsurface rocks, groundwater reactions, and natural hydrogen reservoirs Energy: Exploration, drilling, purification, and compression energy	Manufacturing energy can be small, but exploration, drilling, leakage, and purification require lifecycle assessment.	Early exploration Potentially low cost and low emissions if the resource is accessible. Resource size, recharge rate, capture feasibility, and geologic risk are uncertain.	Academic and institutional sources often prefer natural or geologic hydrogen over white/gold labels.
Orange hydrogen (geologic) Orange hydrogen: stimulated geologic Geologic hydrogen	Hydrogen made by stimulating subsurface rock reactions	Injecting water into iron-rich formations to stimulate mineral reactions. Feedstock: Subsurface rock and water Energy: Injection, circulation, drilling, and purification equipment	Potentially low-emission, but drilling, pumping, purification, and leakage must be assessed.	Research Long-term potential to generate and extract hydrogen underground. Technology, geology, and environmental effects remain under-tested.	Definition varies Orange hydrogen can also mean waste-derived hydrogen in other references.
Orange hydrogen (waste) Orange hydrogen: waste-derived Bio and waste	Hydrogen from plastic waste, municipal waste, or biomass	Waste or biomass pyrolysis, gasification, or reforming. Feedstock: Plastic waste, municipal waste, biomass, and organic waste Energy: Process heat, electricity, and waste-treatment equipment	Biomass carbon can be biogenic, but plastic waste can still emit fossil carbon.	Pilot Can combine waste treatment with hydrogen production. Feedstock variability, contaminants, and real carbon-reduction claims are contested.	Definition varies CCS and the fossil-carbon share of feedstock must be checked together.
Biohydrogen Biohydrogen Bio and waste	Hydrogen from biomass, biogas, or biological pathways	Biomass gasification, biogas reforming, fermentation, and microbial or photobiological routes. Feedstock: Agricultural and forestry residues, food and sewage organics, biogas, microbes Energy: Biomass process heat, electricity, and biological processes	Can be low or even negative with sustainable feedstock and CCS, but land-use change matters.	Pilot Can use waste resources and combine with existing gasification or reforming technology. Sustainable feedstock supply, land and food competition, and process complexity.	References classify it differently: green, orange, or a separate biohydrogen category.
By-product hydrogen By-product hydrogen By-product	Hydrogen recovered from chemical processes such as chlor-alkali production	Recovery from primary-product processes such as brine electrolysis. Feedstock: Brine, electricity, and chlorine or caustic soda production Energy: Tied to the primary production process	Emissions depend on electricity emissions factors and allocation method.	Commercial Using hydrogen that is already produced adds limited production burden. Volume is limited and tied to demand for the main product.	No stable color label; allocation rules matter.
Low-carbon or clean hydrogen Low-carbon or clean hydrogen Policy and certification	Not a color, but a group of pathways that meet an emissions threshold	Eligible pathways can include renewables, nuclear, fossil plus CCS, and bio plus CCS. Feedstock: Varies by policy standard Energy: Renewables, nuclear, fossil plus CCS, and others	DOE targets 4.0 kgCO₂e/kgH2, while the EU uses a framework based on at least 70% GHG savings versus a fossil comparator.	Policy standard Enables performance-based comparison instead of color-label debate. System boundaries and thresholds differ by jurisdiction and certification scheme.	Check system boundary, kgCO₂e/kgH2, and certification conditions before trusting the label.
Renewable hydrogen Renewable hydrogen Policy and certification	A legal or policy category tied to renewable energy and feedstock rules	Usually renewable-powered electrolysis, with requirements such as additionality, temporal correlation, and geographic correlation under EU RFNBO rules. Feedstock: Water, renewable electricity, and renewable feedstocks Energy: Renewable energy	EU rules include GHG accounting requirements such as at least 70% savings.	Policy standard Legal definitions and certification can improve market trust and tradability. Rules are complex and can constrain project design and electricity procurement.	Often overlaps with green hydrogen, but legal renewable hydrogen can be stricter.

How to read any hydrogen claim

Use these checkpoints before accepting a colour label as clean.

System boundaryDoes the number cover only the plant, or the full well-to-gate lifecycle?

Energy sourceIs the electricity renewable, nuclear, grid-mixed, or fossil process heat?

Carbon handlingFor blue and turquoise routes, what is captured, stored, leaked, or left as CO₂?

MaturityA route can be promising but still research-stage, exploratory, or dependent on certification rules.

Hydrogen colour names are not fully standardized international labels. This page uses common industry terms and pairs them with production route, carbon profile, and maturity.

Sources and licenses

Data sources and terms of use

This page is based on public data from the original providers below. Each dataset follows the original provider's license or terms of use.

Source	Dataset/API	Terms	Onul Works processing
IEA	Hydrogen and energy reference materials	Terms	Reorganizes color labels by production pathway, carbon characteristics, and maturity.
U.S. DOE	Hydrogen Program resources	Terms	Reorganizes color labels by production pathway, carbon characteristics, and maturity.
European Commission	Hydrogen policy and reference materials	Terms	Reorganizes color labels by production pathway, carbon characteristics, and maturity.
ISO	Hydrogen standards references	Terms	Reorganizes color labels by production pathway, carbon characteristics, and maturity.
World Energy Council	Hydrogen reference materials	Terms	Reorganizes color labels by production pathway, carbon characteristics, and maturity.

Normalization, translation, merging, caching, or unit conversion by Onul Works does not imply warranty or endorsement by the original providers.