Green Hydrogen Production

Introduction

Hydrogen is the most abundant resource in the universe. It’s estimated that 90% of all atoms are hydrogen! They are also the oldest atoms, together with helium, since they formed not long after the Big Bang. Due to its lightness, however, it easily floats away from Earth escaping its gravitational pull. That’s why we don’t have much of it floating around on Earth, and that’s why we must produce it. You might remember from chemistry classes that you can produce hydrogen via electrolysis. That’s sadly a small percentage of total hydrogen.

Types of Hydrogen Production

There are multiple types of hydrogen production processes:

• Green (excess renewable energy)
• Pink (nuclear energy)
• Yellow (mixed origin)
• Blue (natural gas or coal)
• Turquiose (natural gas)
• Grey (natural gas)
• Brown (brown coal)
• Black (black coal)
• Biomass

In this article, we will focus only on green & biomass hydrogen production.

Green Hydrogen Production

Green hydrogen could be a much better alternative to electric cars in an effort to decarbonize our economies. For example, hydrogen-powered vehicles… only emit water. That’s right, no exhaust fumes, just pure water (H2O).

Electrolysis: Splitting Water for Clean Energy

Electrolysis is a fundamental process in the production of green hydrogen, involving the splitting of water into hydrogen and oxygen using electricity. This method is crucial for generating hydrogen without emitting carbon dioxide, especially when powered by renewable energy sources like solar, wind, or hydroelectric power either during the peak or off-peak with the energy coming from energy storage systems (such as molten salt batteries or any other energy stores).

Electrolysis isn’t the only process in which we produce hydrogen.

Other Green Methods for Hydrogen Production

In addition to electrolysis, several innovative methods are being explored to produce green hydrogen. These methods aim to leverage natural processes and advanced technologies to create sustainable hydrogen production processes.

Biological Hydrogen Production

It’s quite fascinating that there are microorganisms that can produce hydrogen from organic matter. This process, known as biohydrogen production, can occur through various ways, including fermentation and photosynthesis. Biohydrogen is a promising area of research due to its potential to convert waste materials into valuable energy sources.

Thermochemical Water Splitting

Thermochemical water splitting involves using heat and chemical reactions to extract hydrogen from water. This method typically requires high temperatures, often provided by concentrated solar power or nuclear reactors. Thermochemical cycles, such as the sulfur-iodine cycle, can efficiently split water molecules to produce hydrogen and oxygen. The integration of renewable heat sources is essential to ensure that this process remains environmentally friendly.

Direct Solar Water Splitting

Direct solar water splitting is an emerging technology that harnesses solar energy to produce hydrogen directly from water. This process involves using photoelectrochemical (PEC) cells or solar thermochemical reactors. PEC cells use semiconductor materials to absorb sunlight and drive the water-splitting reaction, while solar thermochemical reactors concentrate sunlight to achieve the high temperatures needed for the reaction. Direct solar water splitting holds great promise for large-scale, decentralized hydrogen production, particularly in regions with abundant sunlight such as Arizona or California.

Hydrogen Production from Biomass

If you think that biowaste such as coffee grounds (but not only) are useless, then think again. Hydrogen production from biomass is an upcoming technology that offers a sustainable and carbon-neutral pathway to generate this versatile energy carrier. By converting agricultural residues, forestry waste, and organic municipal waste into hydrogen, we can reduce waste generation, boost resource efficiency, and promote a circular economy.

The process of producing hydrogen from biomass involves several key steps:

1. Gasification or pyrolysis: These thermochemical processes use high temperatures to convert biomass into hydrogen-rich syngas. Gasification involves heating biomass with a controlled amount of oxygen and/or steam, while pyrolysis occurs in the absence of oxygen.
2. Fermentation: Certain microorganisms can ferment biomass to produce hydrogen through dark fermentation or photofermentation. Dark fermentation uses anaerobic bacteria to consume carbohydrates and release hydrogen as a byproduct, while photofermentation relies on photosynthetic bacteria under illumination.
3. Water-gas shift reaction: The syngas produced from gasification or pyrolysis is further processed to increase the hydrogen content. The water-gas shift reaction converts carbon monoxide and steam into hydrogen and carbon dioxide.
4. Purification: The final step involves separating and purifying the hydrogen using adsorbers or membranes to remove any remaining impurities.

Biomass-derived hydrogen offers several advantages that the other processes do not offer. Firstly, utilizing organic waste streams as feedstock reduces waste generation and enhances resource efficiency. Local production from abundant biomass resources promotes energy security and resilience by reducing dependence on imported fossil fuels, which is potentially economically significant for smaller communities. Lastly, biomass-to-hydrogen technologies can be integrated into existing energy systems, offering a versatile solution.

While the cost of hydrogen production from biomass depends on various factors, such as feedstock availability, conversion technology, and scale of operation, the advantages of this process make it a promising solution on a road towards a sustainable and carbon-neutral future.

Conclusion

Even though hydrogen is the most widespread element in the universe, we need to produce it here on Earth. Its importance for the energy transition is incredibly high. We can power our vehicles with it, use it as a way to store energy, decarbonize steel and cement production, heating & power generation, and so much more. But, in order to make it as environmentally friendly as possible, we need to ensure that we don’t emit more greenhouse gases than we eliminate.