In most cases, green hydrogen is spoken of in conjunction with electrolysis of water. In fact, definitions of GH2 even by some fairly authoritative sources run as follows: “green hydrogen is hydrogen produced by splitting of water by electrolysis powered by green electricity.”
But is green hydrogen only about zero carbon or low carbon electrolysis?
Perhaps a more practical definition of green hydrogen is “hyrdogen from non-fossil sources with a very low or zero carbon footprint”.
If the above definition is acceptable, then we should also consider producing green hydrogen from biomass.
Why?
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Consider this:
Hydrogen can be produced from biomass in different ways, one prominent method being the use of gasification – convert biomass into synthetic gas (syngas, a mixture of CO and H2) and then extract H2 from it.
Another could be to convert biomass into biogas, and extract hydrogen from the methane in biogas.
All the above methods are technically feasible, though there are significant questions around yields and economics.
Economic uncertainties apart, what about the energy required for the processes? Won’t they have a significant carbon footprint? What about the carbon that is let out from the biomass when H2 is separated (process carbon emissions)?
Well, where electricity can be used, we can use green power pretty much the way we use it for electrolysis. Where heating is needed, we can use the mid-stream gases (biogas or syngas) as heating fuels.
For these pathways, where ever there are CO2 emissions, if the intermediate gases are used these emissions represent carbon that was originally present in the atmosphere, so it likely can be considered very low carbon or net zero emissions.
Any process CO2 emissions from the carbon present in the biomass lead are also net zero for the same reason.
In cases where solid wastes or animal waste are used as feedstock, it could even be considered better than zero carbon, as they are ensuring that in the worst case scenario, CO2 is emitted back to into the atmosphere instead of methane, which is what would have happened had these wastes gone to the landfill and decomposed over time.
The EU considers bio-hydrogen as green, though their nomenclature is more nuanced and intricate – they are European! The Indian government too has classified bio-based hydrogen as green hydrogen. I’m sure there are more who look favorably upon bio-hydrogen.
All said, however, you will find few pilot or commercial projects around the world exploring green hydrogen from biomass – essentially, an order of magnitude lesser attention compared to that for electrolysis-based hydrogen.
Perhaps this scenario should change? Could more interest drive deeper evaluation and feasibility analyses for bio-based green hydrogen?
What are your thoughts?
(See all my decarbonization posts from 𝐍𝐞𝐭 𝐙𝐞𝐫𝐨 𝐛𝐲 𝐍𝐚𝐫𝐬𝐢 – https://shorturl.at/jx137 )
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