Blue vs Green Hydrogen – Be careful when considering hydrogen

09-09-2021 |   |  By Robin Mitchell

Hydrogen is quickly becoming a candidate for future power storage and generation thanks to its lack of CO2 emission upon use. Why is hydrogen potentially better than batteries, what is blue and green hydrogen, and why should we exercise caution in hydrogen generation?

Why is hydrogen a potentially better source of energy storage than batteries?

Lithium-ion battery technology is by far the most ideal candidate for energy storage when it comes to batteries. It has a high energy density allowing it to store large amounts of energy in a small space. It can provide large instantaneous currents and is practical for mobile applications, including vehicles.

While lithium-ion is the most ideal method for storing electrical energy, it is not necessarily the most ideal form of energy storage. For example, pumped hydro storage operates similarly to a dam whereby water is pumped to a higher location and this store’s gravitational potential energy. When the energy is needed, the water is allowed to fall to a lower reservoir which drives a turbine that generates electrical energy. Such a hydro plant has some advantages over battery technologies, including the non-flammability of the stored energy, being more environmentally friendly to manufacture, and being naturally compatible with power grids (i.e. AC output).

Hydrogen is another energy storage method that has some advantages over lithium-ion batteries. While hydrogen itself is flammable, stored hydrogen is less likely to catch fire during failure than lithium-ion batteries as hydrogen systems are not self-igniting. Hydrogen also has a more significant energy density than lithium-ion batteries meaning that any storage solution would be smaller or store more energy. Hydrogen is also potentially less damaging to the environment as it does not require large-scale mining, unlike lithium, which destroys local wildlife and water sources.

Blue vs Green Hydrogen

There is much talk around hydrogen as a future energy storage technology, and the terms Blue and Green hydrogen are frequently used. Creating hydrogen can be done in numerous different ways; one method is to dissolve aluminium in hydrogen peroxide, but such chemical reactions would not supply the amount of hydrogen needed by an entire energy market.

Electrolysis of water is another method for producing hydrogen from water, and this method can be as efficient as 80%. Hydrogen can also be produced by reacting naturally occurring methane with steam, and this is an ideal method for refineries that have easy access to methane.

The terms blue and green hydrogen refer to the production method used, but there are some disagreements on the exact definition. Generally speaking, Blue Hydrogen is made using the steam and methane process, whereas Green Hydrogen uses the electrolysis process. However, some only consider hydrogen to be green if the electrolysis is produced using renewable energy, and Blue hydrogen can only be regarded as blue if the resulting CO2 is captured.

Why should we be cautious about hydrogen?

There is no doubt that hydrogen will be a suitable energy storage method, but exactly how that hydrogen is produced matters. While electrolysis is efficient and runs on electricity, the resulting hydrogen may be environmentally harmful if fossil fuels were used to power the electrolysis.

In the case of Blue hydrogen, creating hydrogen from methane is rendered mute if the resulting CO2 is released into the atmosphere. Of all process methods that exist, Green Hydrogen made from renewable energies is the only solution for tackling climate change and reducing CO2 in the atmosphere.

However, there is another factor to using hydrogen, and it doesn’t need to be green or renewable to be beneficial. There is an age-old argument against electric cars that if the electricity used by the vehicle is generated by fossil fuels, then it’s pointless. While this argument does hold in climate change, it does not hold up in the case of environmental damage and improvement.

It is far easier to target and control CO2 emissions by shifting all energy production to power stations. For example, if all vehicles are replaced with hydrogen/electric systems, producing that electricity and/or hydrogen is solely done at power stations. Therefore, it is easier to reduce CO2 levels by installing filters and scrubbers into chimney stacks.

The second advantage is that congested areas in cities and towns will not produce any pollutants. Power stations out in the countryside can emit far more pollutants without affecting the environment as a whole compared to city environments that can trap air. The result of this would be a reduction of asthma and other respiratory conditions in built-up areas.

Overall, the use of hydrogen should be carefully considered if the goal is to reduce overall CO2 emissions, as some hydrogen production methods can be just as bad for the environment as fossil fuels.


By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.

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