The Hydrogen Production Rainbow
Hydrogen can be produced via several methods, and each method is typically associated with a different “color” label. The color serves as an easy way to understand the method and its environmental impact. Here are the most commonly discussed:
- Grey Hydrogen: This is the most common form of hydrogen production. It’s produced from natural gas via steam methane reforming. This process emits a lot of carbon dioxide, hence it’s called “grey”.
- Blue Hydrogen: This is similar to grey hydrogen because it’s also produced from natural gas. The difference is that the carbon dioxide emitted during the production process is captured and stored, reducing the overall carbon footprint. The carbon capture and storage (CCS) method isn’t 100% efficient, however, and some CO2 still escapes into the atmosphere.
- Green Hydrogen: This form of hydrogen is produced via electrolysis of water, powered by renewable energy sources such as wind or solar power. This method doesn’t produce any CO2 emissions, making it the most environmentally friendly method of hydrogen production.
- Turquoise Hydrogen: This type of hydrogen is produced by splitting methane into hydrogen and solid carbon. This method could potentially be more environmentally friendly than grey or blue hydrogen as it doesn’t produce CO2, but the technology is still being developed and isn’t widely used.
- Pink Hydrogen: This is hydrogen produced by electrolysis but with the electricity sourced from nuclear power.
- Brown and Black Hydrogen: These types of hydrogen are produced from coal, either through gasification or pyrolysis. They’re not commonly used due to their high environmental impact.
- Yellow Hydrogen: This type of hydrogen is produced via electrolysis powered by solar power specifically.
It’s important to note that these colors aren’t universally agreed upon and some sources might use different color labels or definitions. The above list should give you a general idea of the different methods and their environmental impact.
The terms “clean” and “dirty” when it comes to energy production are often used to refer to the environmental impact, particularly the emission of greenhouse gases like carbon dioxide (CO2). Here’s a summary of the hydrogen production methods in terms of these concepts:
Clean Methods:
- Green Hydrogen:
- Turquoise Hydrogen
- Pink Hydrogen
Dirty Methods:
- Grey Hydrogen
- Blue Hydrogen
- Brown and Black Hydrogen
Special Cases:
- Yellow Hydrogen: This is hydrogen produced via electrolysis powered by solar power specifically. It is essentially a subset of green hydrogen and is also considered clean.
- Gold Hydrogen: “Gold hydrogen” or “geologic hydrogen” refers to two related but distinct concepts:
- Hydrogen produced naturally underground: For more than a century, geologists have been studying natural hydrogen sources underground. Some processes, such as radiolysis, can cause molecules to break apart and release hydrogen. This typically happens with crystalline rocks, such as granite, rather than sedimentary rocks. This type of hydrogen was named “gold hydrogen” by geologist Jon Gluyas​.
- Hydrogen produced by biotechnology in old oil wells: A biotech firm in Texas, Cemvita Factory, has also used the term “gold hydrogen” to describe their product. They use a carefully selected combination of bacteria and nutrients in spent oil wells. The bacteria break down the residual oil hydrocarbons in the wells, which are otherwise unprofitable to extract, to generate hydrogen and CO2. The firm’s goal is to use bacteria to enable steady, long-term hydrogen production, potentially lasting for decades. The existing infrastructure above and around the well for gas removal could be reused to collect the hydrogen. However, it’s important to prevent the CO2 byproduct from leaking into the atmosphere and contributing to climate change. Cemvita Factory argues that they can keep the CO2 locked underground, use other microbes to somehow fix it, or find commercial uses for the greenhouse gas. The exact solutions used in each location and their success rates are not yet known. This biotechnological process is distinct from natural geological hydrogen production, but the term “gold hydrogen” is used to pay homage to the past era of oil as “black gold” and the use of old oil wells as a feedstock for hydrogen production​.
Remember, the terms “clean” and “dirty” are somewhat simplified and subjective. There are other factors to consider, such as the environmental impact of manufacturing solar panels or wind turbines, or the land use changes required for large-scale renewable energy. The overall environmental impact of each method can vary depending on a lot of factors.
Production of Hydrogen From Methanol
One method of hydrogen production that has not been assigned a color yet, is the production of hydrogen from alcohols like methanol. It makes sense, since alcohols methanol are saturated with hydrogen bonds, just like a methane molecule, except one of the -H bons is replaced with an -OH bond. This also causes alcohols to be liquids as opposed to gasses like their hydrocarbon analogues (e.g. methane, ethane, propane, and butane are all gasses at room temperature, while methanol, ethanol, propanol (rubbing alcohol), and butanol are all liquids at room temperature.
It’s beneficial to work with a liquid as opposed to gas for several reasons. A big one is that pumping efficiency (i.e. how much energy it takes to move a kg of the fluid) of a gas is much lower than the pumping efficiency of a liquid. Gasses tend to be more explosive than liquids, and if you want to liquefy a gas to store it in a smaller volume, it will take a lot of energy to cool it down into a liquid.
Use the Right Colors in Clean Hydrogen Job Searches
When you’re looking for a clean hydrogen job, be sure to use green, turquoise, pink, yellow, and gold as search terms for clean hydrogen jobs.
Happy hunting.