In 2024, the world consumed nearly 100 million tons of hydrogen, according to theInternational Energy Agency‘s Global Hydrogen Review 2025. Less than 1 percent of that amount was low-emission. The rest came from fossil fuels without CO₂ capture.
“Green hydrogen,” “blue,” and “gray” have become commonly used words in the European energy debate. They evoke a color taxonomy that seems to order things: green for clean, gray for dirty, blue for something in between. The molecule produced, however, is always the same: H₂. Colors do not describe the final product. They describe the upstream process and the emissions it generates.
“Gray” hydrogen is produced from natural gas through a process called steam methane reforming. It emits between 9 and 12 kilograms of CO₂ for every kilogram of hydrogen produced. Today it accounts for the vast majority of the hydrogen consumed in the world, used mainly in refineries and to produce ammonia and fertilizer. “Blue” hydrogen is the same thing with CO₂ capture and storage added downstream in the process. Emissions are reduced, but not to zero, and depend on the effectiveness of capture and methane losses along the supply chain. “Green” hydrogen is produced by electrolysis, separating water into oxygen and hydrogen with renewable electricity. If the electricity is truly renewable and additional, direct emissions are close to zero.
Confusion arises when public language treats these three things as equivalent versions of the same technology, differentiated only by a gradation of color. The analogy is that of the egg. An egg produced on an intensive farm and an egg produced by free-range hens are physically indistinguishable once broken in the frying pan. The environmental footprint of the two supply chains is not. Hydrogen produced by electrolysis with renewables, natural gas with CCS, and natural gas without capture are three different industrial chains, with different infrastructure, different costs, different orders of magnitude emissions. They are not gradations of the same product. They are three different products that share an identical final molecule.
The full scale tells what is happening today. Also according to the IEA, global production of low-emission hydrogen (green and blue together) in 2024 was less than 1 million tons. Projections to 2030 based on projects already with a final investment decision come in at 4.2 million tons, about 4 percent of expected global demand. Announced projects would reach 49 million tons, but only 3.4 million are in the FID phase, the rest are in planning and remain vulnerable to cancellation. No new blue hydrogen projects have been started in 2024.
In Italy, the trajectory is even lower. The 2024 National Integrated Energy and Climate Plan projects 0.25 million tons of renewable hydrogen consumption and 3 gigawatts of installed electrolyzer capacity in 2030. The 2020 guidelines called for 5 gigawatts and 0.7 million tons: the new strategy reduces both production and capacity. For comparison, Germany aims for 10 gigawatts by 2030, France 6.5 gigawatts, and Spain 12 gigawatts. According to an AGICI analysis presented in Milan in November 2025, to reach even the 180,000 tons per year target in the Italian Strategy would require operating incentives of 4 billion euros over the next five years, in addition to full transposition of the RED III directive, which is currently blocked.
The color taxonomy has an additional specific problem. The term “blue hydrogen” compacts projects with widely varying performance into one category. Some plants capture 90 percent of the CO₂ from the main process; others capture 50 percent. Emissions along the methane supply chain, from drilling to transportation, are not always accounted for. A “blue” hydrogen with low capture efficiency and high upstream losses can have similar emissions per kilogram as a “gray” hydrogen. The color is the same, the climate load is very different.
European legislation is seeking to replace color taxonomy with emissions-based definitions. Delegated Regulation 2023/1184 on Renewable Fuels of Non-Biological Origin (RFNBO) sets precise standards on the conditions under which hydrogen produced from renewable electricity can be counted as such: additionality of renewables, temporal and geographic correlation, and traceability. These are stringent requirements that make the perimeter of “green hydrogen” much narrower than the word suggests. The International Organization for Standardization is developing a methodology for quantifying emissions, expected by 2026.
However, color language remains in use, in institutional and corporate communication, because it is simple. The cost of simplicity is that a complex industrial supply chain appears unified, and two kilograms of hydrogen with upstream emissions of different orders of magnitude can end up in the same advertising phrase.
This column explores climate words whose technical meaning diverges from common perception. Hydrogen colors add a new mechanism: not the single ambiguous term, but a taxonomic system that flattens out differences of orders of magnitude. The final molecule is identical. The supply chain emissions are not.
The next time you read “blue hydrogen” or “green hydrogen” in an investment announcement or strategy document, the question to ask yourself is one: how many kilograms of CO₂ per kilogram of hydrogen, measured where and how?
