To meet the global and national energy demand while achieving energy efficiency and decarbonization targets, the industry looks at every potential source to reduce GHGs. Hydrogen has been identified as a key element to successfully managing this energy transition.
So, what is hydrogen? Hydrogen itself is a colorless gas, but there are nine color codes to identify hydrogen, referring to the source or the process used to make it:
Blue hydrogen is produced mainly from natural gas, using a process called steam methane reforming or SMR. In this process, the CO2 is captured and stored underground through carbon sequestration. The utilization of the captured carbon is called carbon capture, storage, and utilization (CCSU). Since no CO2 is released in the production of blue hydrogen, the process is carbon neutral.
Gray hydrogen, also produced through SMR, is the most common type of hydrogen. Due to its carbon footprint, companies have been looking to other types of hydrogen as a solution to decarbonization.
Black or brown hydrogen is produced from coal. The black and brown colors refer to bituminous (black) and lignite (brown) coal. The gasification of coal is a method used to produce hydrogen. However, CO2 and carbon monoxide are produced as by-products and released into the atmosphere.
Turquoise hydrogen is extracted using methane’s thermal splitting via methane pyrolysis. Though at the experimental stage, the process removes the carbon in a solid form instead of CO2 gas.
Purple hydrogen is made using nuclear power and heat through a combined chemo thermal electrolysis splitting of water.
Pink hydrogen is generated through electrolysis powered by nuclear energy.
Red hydrogen is produced through the high-temperature catalytic splitting of water using nuclear power thermal as an energy source.
White hydrogen refers to naturally occurring hydrogen.
Green hydrogen – also called “clean hydrogen” – is produced by using clean energy from surplus renewable energy sources, such as solar or wind power, to split water into two hydrogen atoms and one oxygen atom through electrolysis. The next NWGA blog will discuss green hydrogen in detail.
Hydrogen can also be generated from biomass and, depending on the type of biomass and CCS technologies can have lower net carbon emissions than black/brown or grey hydrogen.