Different Types of Hydrogen:
Hydrogen gas is completely invisible and colourless. However, the energy industry assigns different “colours” to hydrogen based entirely on the production method and the resulting carbon footprint (emissions). Understanding this spectrum is highly important for UPSC examinations.
1. Grey Hydrogen (Highly Polluting)
- Current Status: This is the most commonly produced type of hydrogen in the world today.
- Source: It is produced from Natural Gas (methane).
- Process: Uses a process called Steam Methane Reforming (SMR), where steam reacts with methane to produce hydrogen and carbon dioxide ().
- Emissions: The generated () is released directly into the atmosphere, making this a highly polluting process
2. Black and Brown Hydrogen (Most Polluting)
- Source: Produced from Coal.
- Process: Black hydrogen uses hard bituminous coal, while Brown hydrogen uses softer lignite coal.
- Emissions: The coal is gasified, releasing massive amounts of carbon dioxide and toxic carbon monoxide into the air without any capture. This is the most environmentally damaging method.
3. Blue Hydrogen (Low Carbon / Transitional)
- Source: Produced from Natural Gas using the same Steam Methane Reforming (SMR) process as Grey Hydrogen.
- The Difference: The crucial difference is that the carbon dioxide produced is not released into the air. Instead, it is captured and buried deep underground using Carbon Capture and Storage (CCS) technology.
- Emissions: It is considered a “low-carbon” fuel. However, it is not perfectly clean, as 10% to 20% of the carbon emissions can still escape capture
4. Green Hydrogen (Zero Carbon / Cleanest)
- Source: Produced purely from Water (2H₂O).
- Process: Uses an electric current to split water into hydrogen and oxygen (a process called Electrolysis).
- The Difference: The electricity used for this electrolysis comes strictly from renewable energy sources (like wind or solar power).
- Emissions: Because no fossil fuels are used at any stage, it produces zero greenhouse gases. It is the ultimate goal for global decarbonization, though it currently accounts for a very small percentage of global production due to high costs.
5. Pink Hydrogen
- Source & Process: Produced through the electrolysis of water, identical to Green Hydrogen.
- The Difference: The electricity used to split the water comes entirely from a Nuclear Power Plant. Because nuclear energy does not emit carbon dioxide, Pink Hydrogen is also classified as a clean, low-carbon source.
6. Yellow Hydrogen
- Source & Process: This is a highly specific sub-category of Green Hydrogen. It refers to hydrogen produced through electrolysis where the electricity comes exclusively from Solar Power.
