Hydrogen in gas form is odorless, tasteless, and colorless which brings up the question, why do news sites like Bloomberg or FCEV makers like Toyota talk about green or grey hydrogen? After all, if hydrogen is colorless than how can it be pink or blue? Is the hydrogen somehow flowing through a rainbow in the sky and randomly getting assigned a color by rainbow fairies?
Thankfully the answer is no, there are no rainbow fairies working overtime to assign each new hydrogen molecule a color. Instead, the answer regarding why hydrogen has “colors” is due to the fact that hydrogen is found almost everywhere. However, since producing hydrogen requires extracting it from something that already has hydrogen like water, trash, and natural gas, the color scheme was created to help differentiate the origin of hydrogen.
Here are just a few of the colors of hydrogen you may have heard about.
Black hydrogen refers to extracting hydrogen from coal, which is perhaps the worst way to obtain it. Using coal releases an extreme amount of carbon monoxide (CO) and carbon dioxide (CO2).
Blue hydrogen uses steam methane reforming (SMR) with carbon capture to extract hydrogen from natural gas.
Pink uses the electricity produced by nuclear reactors to capture hydrogen from water by way of electrolysis.
Of course, green hydrogen is the most popular since it is seen as the “cleanest” of all methods by which to obtain hydrogen. An example of green hydrogen would be using solar power to run electrolyzers that breakdown water into hydrogen and oxygen.
However, the hydrogen color scheme does not address the issue of the amount of greenhouse gases (GHG) that go into producing hydrogen. While most people agree that black hydrogen is beyond redemption, what about blue hydrogen? For example, if the electricity needed to create blue hydrogen comes from a small independent solar farm, then that would be better than getting electricity from an electric grid that has its electricity generated by burning coal. Deriving hydrogen from natural gas using a solar farm and carbon capture would result in the production of a very modest amount of GHG emissions. But just because some GHGs are produced, does that mean that such a hydrogen extraction method is not a responsible way to obtain hydrogen?
This is why the global economy is moving towards referring to how hydrogen is produced not by a color wheel but by carbon intensity (CI). Measuring how much carbon it takes to produce hydrogen directly correlates to how climate-friendly that hydrogen is, and decarbonizing the global economy is one of the primary reasons for switching to hydrogen.
Unfortunately, at present, creating a CI score for how efficiently hydrogen can be derived from various sources has not been standardized globally. Generally speaking, though, a score of zero or below zero means very little GHGs result from a particular hydrogen extraction method, and at 100 and higher the greater the production of GHGs in a hydrogen extraction process.
Perhaps the best way to think about how low CI scores are generated by an organization like the California Air Resources Board (CARB) is by thinking about ways that involve the least amount of carbon at the beginning and the end of the hydrogen separation process.
For example, BayoTech can extract hydrogen from the dung produced by a cattle dairy and Raven SR can obtain hydrogen from green clippings, household trash, and other forms of waste. The feedstock for both BayoTech and Raven SR has little to no value to society, and the machinery needed to extract the hydrogen in minimal. In fact, Raven SR’s process can get all of the electricity it needs each day from a small array of solar panels. Both companies have the ability to ensure that any carbon produced during hydrogen extraction is also entirely mitigated. Therefore, a CI score for both organizations would be at or below zero, because the amount of carbon it takes to build the facilities, the feedstock going into each, and the hydrogen extraction process all involve minimal amounts of carbon. Plus, both organizations are recycling matter that would otherwise go on to create GHGs, which further lowers the scores of both.
It is important to note that CI scores are not a perfect measure of how climate friendly a hydrogen derivation method is. For example, building a nuclear electric production facility involves a lot of materials, and while the carbon from creating the materials and building the plant can be offset over time the nuclear waste generated by the power plant cannot be offset. The same is true for wind turbines. While the materials and building a wind farm may be less than that of a nuclear plant, the blades of the turbines eventually need to be replaced. That waste presently is not being recycled, which makes wind farms more carbon intensive than they appear to be.
Given that essentially all of the methods by which hydrogen can be obtained are still maturing it is reasonable to expect that CI scores will continue to change over the next five to ten years, and likely the methods by which CI ratings are derived from will continue to evolve as well. However, what remains clear is that there are a multitude of available hydrogen separation processes, and many of them result in few to no GHGs being produced as a byproduct. If the world’s economy responsibly blends those methods, then it will be able to produce all the hydrogen humanity needs while keeping carbon emissions to a bare minimum. With that hydrogen supply, responsible global governmental policies supporting hydrogen and sundowning fossil fuels, and the acceleration of fuel cells being integrated into more products, GHGs will go down and Earth’s climate can begin to recover from two centuries of neglect.