Types of Hydrogen, India’s Potential, Advantages & Challenges

Hydrogen is often referred to by colour codes that reflect how it is produced and its carbon footprint. Each colour type has distinct production methods and environmental impacts. 

Green Hydrogen: 

1. Production Method: Green hydrogen is produced through the electrolysis of water using electricity generated from renewable energy sources such as solar, wind, and hydropower. This process splits water into hydrogen and oxygen without emitting any carbon dioxide, making it a clean and sustainable fuel alternative.

2. Environmental Impact: Green hydrogen contributes significantly to India’s climate goals by providing a zero-emission fuel option that reduces greenhouse gas emissions in hard-to-decarbonize sectors. Its adoption aligns with the country’s commitments under the Paris Agreement and supports the transition to a low-carbon economy.

3. Usage: It is increasingly used in fuel cell technologies for transport, power generation, and as a green input in industries like steel and fertilizers, where direct electrification is difficult. Green hydrogen’s role is crucial for achieving India’s broader energy security and sustainable development objectives, as highlighted in recent government and NITI Aayog reports.

Blue Hydrogen:

1. Production Method: Blue hydrogen is produced from natural gas using a process called Steam Methane Reforming (SMR) or Auto Thermal Reforming (ATR), where methane reacts with steam to produce hydrogen and carbon dioxide. The CO₂ generated is captured through Carbon Capture and Storage (CCS) technology, which stores it underground to reduce emissions.

2. Environmental Impact: While not completely carbon-free, blue hydrogen offers a lower-emission alternative to conventional fossil fuels by significantly reducing CO₂ release through CCS. However, challenges like methane leakage during natural gas extraction and energy-intensive production remain concerns.

3. Usage: Blue hydrogen acts as a transitional clean fuel in industries and power generation where direct electrification is difficult. It is compatible with existing natural gas infrastructure, making it an important stepping stone towards the adoption of fully renewable green hydrogen.

Grey Hydrogen: 

1. Production Method: Grey hydrogen is produced primarily through Steam Methane Reforming (SMR), where natural gas (mostly methane) reacts with steam to generate hydrogen and carbon dioxide. This method is currently the cheapest and most common hydrogen production process but does not capture the CO₂ emissions.

2. Environmental Impact: Unlike green or blue hydrogen, production of grey hydrogen releases significant amounts of CO₂ into the atmosphere, contributing to greenhouse gas emissions and climate change. It is considered carbon-intensive and less sustainable than other hydrogen types.

3. Usage: Grey hydrogen is mainly used in industries like fertilizer manufacturing (ammonia production), oil refining, and methanol production. It forms the bulk of India’s current hydrogen use but faces pressure for transition towards cleaner alternatives under national hydrogen missions.

Other Important types of Hydrogen

1. Black/Brown Hydrogen: It is derived from coal gasification. Black hydrogen (from hard coal) and brown hydrogen (from lignite) produce H₂ while releasing CO₂ and carbon monoxide. These are the most polluting types, as emissions are uncontrolled.

2. Turquoise Hydrogen: It is produced by methane pyrolysis, which thermally splits methane into H₂ and solid carbon. If powered by renewable energy, it has low emissions. The solid carbon is easier to handle than CO₂. Turquoise hydrogen is still experimental.

3. Pink/Purple (Red) Hydrogen: It is made by electrolysis using nuclear energy. Sometimes called purple hydrogen or red hydrogen, it uses nuclear heat or electricity to split water. It is zero-emission if the nuclear source is clean. Pink and purple generally refer to similar nuclear-based processes.

4. Yellow Hydrogen: It is produced by electrolysis using solar power. It is essentially green hydrogen from solar electricity.

5. White Hydrogen: A naturally-occurring hydrogen found in underground deposits. It is extracted by drilling, similar to oil or gas. White (geological) hydrogen comes from natural geologic processes like water-rock reactions.

6. Gold Hydrogen: An emerging type where microbes ferment waste or water underground to produce H₂. This process (biological conversion) can be low-cost and carbon-neutral, and may extend the life of oil fields.