Electrolysis reduces water consumption.
This statement might sound a bit surprising, but we’ll carefully explain how we’ve reached this conclusion.
To put things into context and establish the basis of our argument, let’s start by citing directly from Spain’s renewable hydrogen roadmap.
“Currently, hydrogen consumption in Spain is around 500,000 tons per year, mostly gray hydrogen, used primarily as a raw material in refineries (around 70%) and chemical manufacturers (25%), with the remaining residual consumption in sectors such as metallurgy. In many cases, production is carried out directly at the consumption site through natural gas steam reforming facilities.”
In summary, Spain consumes half a million tons per year of gray hydrogen, mainly through natural gas steam reforming (in English: Steam Methane Reformer – SMR), which is key here.
Natural gas reforming requires water, as demonstrated by this chemical reaction:
CH4 + 2H2O -> CO2 + 4H2
Stoichiometrically, it requires half the water of electrolysis, meaning 4.5 kg of water per kg of hydrogen (electrolysis requires 9). As we said, these are stoichiometric values, but in reality, more water is needed. We’ll look at this in detail below.
Electrolysis requires between 11 and 15 kg per kg of hydrogen. Reforming requires between 6 and 13 kg, plus the reject water (source link here). According to other sources, like HYGEAR, a natural gas reformer manufacturer, consumption can reach nearly 24 kg of water per kg of hydrogen produced. In cases like this, we can categorically state that electrolysis reduces water consumption.
In summary, whether we use the first source or the second, the water consumed by SMR is equivalent to that consumed by electrolysis, so, going back to those 500,000 tons of hydrogen produced annually in Spain through SMR, we can expect that progressively replacing this fossil hydrogen with renewable gas won’t require additional water consumption, and in some cases, we can expect that each kg of gray hydrogen removed from the market will allow for the production of around two kg of green hydrogen.
The water issue is of utmost importance for Spain. That’s why we’ve created several posts about this topic. Interested in this subject? Click on the following link and keep reading about water and hydrogen here.
If you’ve made it this far, hold on because there’s still more to learn. We want you to know that at Lean Hydrogen, we can help you with your hydrogen project. We are a consulting and engineering firm specializing in hydrogen production projects through electrolysis, injection into natural gas (blending), and mobility (hydrogen refueling stations).
Visit our blog “Lean Hydrogen” for more interesting content about this gas: https://leanhydrogen.whdev.es/blog/.
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