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エネルギー/気候

水素の種類

グリーン水素、ブルー水素など、水素の生産方式と色分けを一目で確認できます。

水素用語

水素の色は物理的性質ではなく、生産文脈を表します

水素は無色です。グリーン・ブルー・グレーは、原料、エネルギー供給源、炭素管理条件を要約した業界共通語として読むべきです。

このページでは、色名だけでクリーン度を判断しないために、生産経路とCO2管理条件をあわせて整理します。

同じ色名でも、再エネ電力の比率、回収率、漏えい管理水準によって実質的な炭素強度は異なることがあります。

このページは、エネルギー・気候データ解釈時の水素関連用語を素早く確認できる参考表です。

色名の解釈

グリーン、ブルー、グレー、ターコイズなどは水素分子の色ではなく、生産経路を簡潔に表す記号です。

生産ルートの重要性

電気分解、改質、ガス化、熱分解、原子力熱、天然ガス由来経路などは、必要エネルギーが異なるため、同じ「水素」でも意味が変わります。

炭素強度の確認

排出を評価する際は、算定境界、サプライチェーン排出、回収・貯留・漏えい対策の有無をあわせて確認します。

用語辞書

定義は地域や報告枠組みにより異なるため、色の種類は国家規格のように固定されたラベルではないことを前提にしてください。

色ラベルはクリーン度の序列ではありません。生産経路と炭素管理条件をあわせて確認してください。

種類 15
カテゴリ 7
定義バリエーション 5
出典 12

テーブル

データプレビュー

15 行
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.