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The current corona pandemic has created a situation where in order to save lives, there is a huge huge requirement for clinical oxygen (which is taken from the environment) all over the world. Now, there is a great hype about (and industrial migration towards) the hydrogen fuel cell tech which can replace the current polluting fossil fuel infrastructure. Which is great and I'm personally an enthusiast of this emerging field.
Traditional hydrocarbons had their chemical reaction as:
hydrocarbon + oxygen => carbon (di/mono)oxide + other harmful residual gases
Which is certainly polluting and is causing climate change and global warming. Whereas hydrogen fuel cell overall (both fuel cell anode and cathode) reaction is:
hydrogen + oxygen => water (vapor) + electricity
Here we become relaxed as we know that water isn't toxic to the environment and some FCEV (fuel cell electric vehicle) manufacturers claim that the water from the exhaust of their vehicles is fit for drinking.
But the common factor in both of the reactions is that the environmental oxygen is entrapped in either some oxide form or water, which will need a definite amount of external energy to again be in the form of oxygen molecule.
The question is, who is going to spend that energy? Hydrogen production, storage and delivery is already a very energy and capital consumptive process and even the businesses that generate hydrogen through mass scale water electrolysis will use/sell the oxygen by product to add to their overall profits.
Tree Plantation/Reforestation cannot compensate for these oxygen losses alone.
It seems that we are not actually solving the whole of the problem and the part which is being ignored, can itself be the next crisis.