Hydrogen is an essential element for our effort to reduce carbon emissions. In order to meet the climate change targets for 2030 and 2050, renewable energies are crucial. While wind and solar energy have gained prominence, especially with the decrease in photovoltaic panel prices, we mustn’t disregard the importance of hydrogen.
Although hydrogen is the most abundant chemical element in the universe and on Earth, it’s often found combined with other elements, such as oxygen in water (H2O) or with carbon in hydrocarbons (CH4, C2H6, etc.).
To use hydrogen as an energy source, it needs to be separated from the elements it’s combined with. However, not all extraction methods are environmentally friendly, which is why there are different types of hydrogen categorized by color.
The Colors of Hydrogen and Their Meaning
If you’re particularly interested in renewable energy, you might be familiar with the term “green hydrogen.” However, did you know there’s also blue hydrogen? Have you ever heard about brown hydrogen?
Experts categorize hydrogen into different colors, depending on how it’s produced and the associated environmental impact.
The colors of hydrogen, from the most sustainable to the most polluting, are as follows:
- Green hydrogen. Also known as renewable hydrogen, it’s the cleanest form and is produced using renewable energies such as solar, wind, or hydroelectric energy. This production process doesn’t result in any CO2 emissions and typically involves the use of water in an electrolysis process. Additionally, methods such as biochemical conversion of biomass or biogas reforming can be employed, as long as they meet sustainability requirements.
- Pink hydrogen. It’s produced using the same electrolysis process as green hydrogen, but instead of using energy from renewables, it relies on electricity from a nuclear power plant.
- Blue hydrogen. It’s produced from natural gas or other hydrocarbons such as methane or liquefied petroleum gases. A treatment is later applied to capture and store the carbon resulting from the process, resulting in an estimated 95% reduction of CO2 emissions generated in the extraction process.
- Turquoise hydrogen. Like blue hydrogen, it’s also extracted from natural gas, but through a methane pyrolysis process. This process decomposes methane into hydrogen and solid carbon instead of CO2, resulting in reduced emissions.
- Yellow hydrogen. It’s extracted by electrolysis, but unlike pink (from nuclear energy) and green hydrogen (from renewable energy), the electricity comes from the primary electricity grid, which can be powered by fossil fuels.
- Gray hydrogen. It’s similar to blue hydrogen but lacks CO2 capture techniques. It’s estimated that more than 95% of the hydrogen consumed in the U.S. is of this type and isn’t environmentally friendly, considering it’s of fossil origin.
- Black/brown hydrogen. It’s the most polluting because hydrogen is extracted by coal gasification.
Image: Acciona Energía
There’s another form of hydrogen called golden hydrogen, which is found in nature without being combined with other elements. Although there are plans to extract it, the most practical way to bring about energy change and reduce CO2 in the atmosphere is by transitioning the industry to use green hydrogen instead of gray hydrogen.
Experts expect this change to play a key role in transforming energy use across various industries as well as in land, sea, and air transportation. The main challenge lies in the cost, with green hydrogen being almost eight times more expensive than gray hydrogen.
This article was written by Alejandro Alcolea and originally published in Spanish on Xataka.
Image | Spain’s Ministry for the Ecological Transition and the Demographic Challenge | LONGi
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