Hydrogen, a colorless, odorless, and tasteless gas, is the most abundant element in the universe, and it is highly combustible. We can generate power with hydrogen through specific chemical reactions; however, harvesting pure hydrogen is very difficult as this element is typically paired with oxygen in the form of water. To extract hydrogen, we need other energy sources, which is where the hydrogen color wheel comes in.
The methods we use to extract hydrogen are divided into different categories. Scientists delineate these categories using colors, but what are the different colors of hydrogen, and what do they mean?
Green Hydrogen: Water
You may be familiar with the term green hydrogen, as it is frequently used during discussions surrounding renewable energy. Green hydrogen refers to the process of harvesting hydrogen through the electrolysis of water. This involves passing a strong electrical current through the water with an electrolyzer, which splits the water into hydrogen and oxygen, allowing scientists to harvest the separate elements with zero carbon emissions.
However, to truly be green hydrogen, the electrolysis process must be powered by renewable energy sources, such as solar or wind. To make the harvesting process fully renewable, engineers are exploring what exactly biodegradable lubricants are and converting their equipment to use these lubricants and more easily recyclable parts.
Blue, Grey, and Turquoise Hydrogen: Natural Gas
Blue, grey, and turquoise hydrogen refer to hydrogen extraction processes that use natural gas. Blue hydrogen uses steam reformation to separate hydrogen molecules from natural gas, which produces carbon emissions, but it also uses carbon capture technology to prevent harm to the atmosphere. Grey hydrogen uses the same steam reformation process without the use of carbon capture technology, releasing emissions into the atmosphere.
Turquoise hydrogen refers to the process of extracting hydrogen via pyrolysis, which is a method that heats natural gas to such high temperatures that it breaks down into hydrogen. This process technically isn’t emissions-free as it breaks down carbon in its solid form.
Brown and Black Hydrogen: Coal
There are two main types of coal: brown (ignite) and black (bituminous). Brown and black hydrogen involve a hydrogen harvesting process that utilizes gasification, using heat to turn the carbon within the coal into gas. This process also releases hydrogen within the coal. However, because coal is mostly made of carbon, this process produces a high amount of carbon emissions, all of which releases into the atmosphere.
Pink, Purple, and Red Hydrogen: Nuclear
Pink, red, and purple hydrogen all use nuclear energy as their main power source for the extraction process. Pink hydrogen uses the electrolysis process but is powered by commercial nuclear power plants. Red hydrogen uses the heat from a nuclear power plant to conduct thermolysis. Thermolysis is the high-temperature catalytic splitting of water, breaking it down into hydrogen and oxygen. Purple hydrogen also uses the heat from nuclear power plants to conduct a combination of electrolysis and thermolysis. While nuclear energy itself doesn’t release carbon emissions, the massive amounts of uranium mining and refining needed to run nuclear power plants do.
Now that you know the different colors of hydrogen and what they mean, where do you think the future of hydrogen harvesting is headed? With the ever-increasing push for sustainable practices, it’s hard to say for sure.
Categories: Science Talk Stuff
