The Three Colors of Hydrogen

The Three Colors of Hydrogen

Hydrogen, along with  renewables and natural gas, has an important role to play in the global transition to a cleaner energy landscape. Hydrogen is in the top tier of global discussions about CO2 emissions as many realize that simply decarbonizing through renewable electricity will be insufficient to get us to the goal of net zero by 2050. As its visibility continues to rise, it is clear that hydrogen can complement renewables and help decarbonize industrial processes  that renewables cannot reach. There is now a global effort across many industries and sectors to make hydrogen commercially viable for a range of applications. Many companies are doing their part to deliver the technologies and solutions that will realize this potential, and help establish a viable market with robust demand for hydrogen over the next few decades.

Hydrogen is the fuel of choice for industries looking to decarbonize, but not all hydrogen is created the same. Although the gas only emits water when burned, its contribution to carbon neutrality depends on how it is produced.

Mitsubishi Heavy Industries Group (MHI Group) has prepared a video describing the three main colors of hydrogen. This video link looks at the three different types of hydrogen – gray, blue and green – and briefly examines their environmental impact.

What is green hydrogen?

In the kaleidoscope range of hydrogen colors, green hydrogen is the one produced with no harmful greenhouse gas emissions. Green hydrogen is made by using clean electricity from surplus renewable energy sources, such as solar or wind power, and used to electrolyze water. Electrolyzers use an electrochemical reaction to split water into its components of hydrogen and oxygen, and emitting zero-carbon dioxide in the process.

Green hydrogen currently makes up a small percentage of the overall hydrogen, because its production is expensive. Just as the cost of energy from solar and wind power has shown great reductions in price, green hydrogen will come down in price as the production technology is commercialized.

What is blue hydrogen?

Blue hydrogen is mainly produced from natural gas and steam, using a process called steam reforming. The product output is hydrogen and carbon monoxide (CO). The CO, if not used, is then converted to CO2 and hydrogen by a water-gas shift reaction. That means carbon capture and storage (CCS) is essential to trap and store this carbon or convert it to other products. Blue hydrogen is sometimes described as “low-carbon hydrogen”.

  • Steam-methane reforming reaction

CH4 + H2O  →  CO + 3H2

  • Water-gas shift reaction

CO + H2O  → CO2 + H2

What is gray hydrogen?

Currently, this is the most common form of hydrogen production. Grey hydrogen is created from natural gas, or methane, using steam methane reformation but without capturing the greenhouse gases made in the process.

Other Hydrogen Colors

  • Black and brown hydrogen

Using black coal or lignite (brown coal) in the hydrogen-making process, these black and brown hydrogen are the absolute opposite of green hydrogen in the hydrogen spectrum and the most environmentally damaging. Also, some say that any hydrogen made from fossil fuels through the process of “gasification” is sometimes called black or brown hydrogen interchangeably.

  • Pink hydrogen

Pink hydrogen is generated through electrolysis powered by nuclear energy. Nuclear-produced hydrogen can also be referred to as purple hydrogen or red hydrogen.

In addition, the very high temperatures from nuclear reactors can be used in other hydrogen productions by producing steam for more efficient electrolysis or fossil gas-based steam methane reforming.

  • Turquoise hydrogen

This is a new entry in the hydrogen color charts and production has yet to be proven at scale. Turquoise hydrogen is made using a process called methane pyrolysis to produce hydrogen and solid carbon.

  • Yellow hydrogen

Yellow hydrogen is a relatively new phrase for hydrogen made through electrolysis using solar power.

  • White hydrogen

White hydrogen is a naturally-occurring geological hydrogen found in underground deposits and created through fracking. There are no strategies to exploit this hydrogen at present.

Greendrogen is actively helping customers to find solutions in producing green hydrogen, and accelerate the world’s transition to renewable energy.