What a irony to discuss the color of hydrogen, a colorless, odorless and tasteless gas !
We’ll take a look at the different forms of hydrogen production according to its conventional color while highlighting the carbon intensity of the process.
Hydrogen on a Spectrum
The international color codes for hydrogen refer to the source or process used to make the hydrogen. Those codes are: green, blue, gray, brown or black, turquoise, red, pink, purple, and white.
White hydrogen refers to hydrogen found in nature in its most natural state.
Green hydrogen is primarily produced by splitting water (i.e., electrolysis of water) using electricity generated from renewable energy sources. The reason it is called green is that there are no CO2 emissions associated with the production of hydrogen or its use. When used in a fuel cell, the only by-product of its use is the pure water that was used to produce it. Although “green” hydrogen often refers to hydrogen produced using electricity generated from renewable energy sources, it can also refer to hydrogen produced by various methods using other renewable sources such as biogas, biomethane, biowaste and other renewable sources. These methods are less common than water electrolysis but also produce very low or zero emissions.
Blue hydrogen refers to hydrogen derived from natural gas, which is a fossil fuel. However, most (but not all) of the CO2 emitted in the process would be captured and stored underground (carbon sequestration) or bound to a solid product (like bricks) and used. This is called carbon capture, storage and utilization (CCSU).
Because CO2 emissions are limited, the process of producing blue hydrogen is considered low carbon.
Gray hydrogen is produced from fossil fuels and typically uses the steam methane reforming (SMR) method. During this process, CO2 is produced and ultimately released into the atmosphere. It accounts for about 95% of the hydrogen produced in the world today.
Black / Brown Hydrogen
Produced from coal, the colors black and brown refer to the type of bituminous coal (black) and lignite (brown). Coal gasification is a method used to produce hydrogen. However, it is a very polluting process, which produces CO2 and carbon monoxide as by-products and is released into the atmosphere.
Extracted using the thermal splitting of methane via methane pyrolysis, this process (although in an experimental stage) removes carbon in a solid form instead of CO2 gas.
Red hydrogen is produced by the catalytic splitting of water at high temperature using nuclear thermal energy as the power source.
Pink hydrogen is produced by electrolysis of water using electricity from a nuclear power plant.
Purple hydrogen is produced using nuclear energy and heat by combined chemical-thermal electrolysis of water.
Water Electrolysis and Renewable Energy in Quebec
While many other colors have been added to the palette as shown, the emphasis on color is not very important. What really matters is the carbon intensity of the production process, that is, the kilograms of carbon produced for each kilogram of hydrogen.
In the case of hydrogen produced by electrolysis of water, the emphasis must also be placed on the source of the electrical current used in the process. If, in addition, the power used comes from a renewable energy source (hydroelectricity, wind or solar energy), all the elements of the production cycle have a low carbon footprint. This production technique therefore generates very few greenhouse gas emissions. The hydrogen produced is called green hydrogen.
Quebec has the necessary assets to be a major producer of green hydrogen since the province can count on significant hydroelectricity and wind power resources to produce it. This production could be used primarily to help Quebec meet its greenhouse gas reduction targets and eventually be used for export.
A Promising Future for Green Hydrogen
Green hydrogen represents about 2% of the world production because its production costs are currently higher than those of gray hydrogen produced with hydrocarbons. However, it should benefit from the decrease in the cost of renewable energies and electrolysers over the next few years.
Hydrolux is positioned on the entire hydrogen value chain since production, transport and distribution are an integral part of the service offer for its customers.
By combining our artificial intelligence with a decentralized production model, we will offer a clean fuel at a reasonable price. This will offer a low-carbon solution to existing uses in the heavy, long-distance or intensive mobility sector.
- The Colors of Hydrogen. Hydrogen Europe.
- Hydrogen colours codes. H2 bulletin
- Grey, blue, green – why are there so many colours of hydrogen? World Economic Forum
- Green Hydrogen. Hydrogen production. Gouvernement du Québec.
- Why green hydrogen — but not grey — could help solve climate change. Dr. Walter Mérida. The University of British Columbia.