Hydrogen is emerging as a critical component of the global energy transition. As countries around the world move to decarbonize their economies and shift away from fossil fuels, hydrogen is poised to play a major role as a clean fuel and energy carrier. Not all hydrogen is equal, however. How hydrogen is produced makes a big difference in its overall environmental impact. This brings us to the concept of “Green Hydrogen.”

What is Green Hydrogen?

Hydrogen is considered “green” when it is produced through 100% renewable energy sources. The most common method is using electrolysis powered by renewable electricity to split water molecules into hydrogen and oxygen. The hydrogen can then be used directly or converted into fuels like ammonia. Other renewable sources like biogas from waste or solar thermal energy can also be used to extract hydrogen.

The key distinction is that Green Hydrogen relies solely on renewable energy, not fossil fuels. This gives it a significant environmental advantage over conventional “Grey” Hydrogen made from natural gas through steam methane reforming. Grey Hydrogen has a large carbon footprint since it uses fossil fuels and emits CO₂ during production.

Why Green Hydrogen?

The excitement around Green Hydrogen stems from its potential to provide clean energy across multiple sectors of the economy. Here are some of its main advantages:

• Zero-carbon fuel at the point of use: When used in a fuel cell or burnt, hydrogen emits only water vapour and no CO₂. This makes it a carbon-free energy carrier.
• Alternative for hard-to-decarbonize sectors: Sectors like heavy industry and heavy transport that are difficult to electrify can leverage hydrogen for low-carbon fuel.
• Energy storage and grid balancing: Green Hydrogen can store intermittent renewable electricity and distribute it as needed. This provides crucial grid-balancing services.
• Export potential: Countries with abundant renewable energy resources can produce Green Hydrogen for export. This provides a new type of clean energy export.
• Sustainable alternative to fossil fuels: Green Hydrogen allows almost complete de-fossilization of the energy system. From feedstocks to fuels, it can replace fossil fuels.

Categories of Hydrogen

There are several ways to categorize hydrogen based on its production method:

• Green Hydrogen: Produced by electrolysis of water, using electricity from renewable sources like solar, wind, etc. Zero CO₂ emissions are produced.
• Blue Hydrogen: Produced from natural gas paired with carbon capture and sequestration to store emissions and is considered low-carbon but not zero-carbon.
• Grey Hydrogen: Produced from natural gas without any carbon capture. This constitutes the bulk of hydrogen made today.
• Brown Hydrogen: Produced from coal gasification. This method results in the highest carbon emissions.
• Pink Hydrogen: Produced from nuclear energy. Low-carbon but dependent on nuclear power as a primary energy source.

Green Hydrogen has the potential to enable deep decarbonization across multiple economic sectors. Its growth will depend on continued cost declines in electrolyzers and renewables and supportive government policies. In the global clean energy transition, this versatile carbon-free energy carrier is poised to play an integral role and build more sustainable energy systems.