The Hydrogen Colour Spectrum — Where We Are & Where We’re Going
Many notable pathways to a net-zero carbon economy involve green hydrogen. This has created quite the buzz around hydrogen and its potential to fill gaps as a fuel source for direct combustion, as an industrial feedstock, or as a high-density fuel for transportation.
But what is green hydrogen? And for that matter, what are all the other colours of hydrogen?
Black hydrogen. Gray hydrogen. Blue hydrogen. Green hydrogen…
All hydrogen is colourless and odourless — the hydrogen rainbow simply defines how the hydrogen was produced. While the structure and properties of the hydrogen molecule do not change between the colours, the production method does play a significant role in how carbon-intensive the hydrogen lifecycle is.
Black & Brown Hydrogen — The Dirtiest
Black and brown hydrogen are both produced from the fossil fuel coal-black hydrogen is from bituminous coal and brown from lignite. These are the dirtiest methods of hydrogen production because it is created through the gasification of coal, which releases CO2 and other greenhouse gasses into the atmosphere.
Gray Hydrogen — The Most Common
Gray hydrogen is produced from natural gas, and it is the most common type of hydrogen produced and used worldwide. The primary process used in gray hydrogen production is steam-methane reforming, a reaction involving natural gas, steam, and heat that works to isolate hydrogen. In addition to hydrogen gas, the process also creates CO and CO2 which are released into the atmosphere.
Although using natural gas is not as carbon-intensive as gasification of coal, it is still a fossil fuel. As such, its use in hydrogen production is non-renewable and emits GHG emissions that contribute to climate change.
Blue Hydrogen — Low-Carbon Intensity
Blue hydrogen is also produced from natural gas, but the process involves carbon capture and storage (CCS) technology that prevents the majority of carbon emissions created by the steam reforming process from being released into the atmosphere.
Due to the involvement of CCS technology, blue hydrogen has a reduced carbon intensity and may even be referred to as carbon neutral (although that may be a bit misleading as the CCS technology will not capture 100% of the GHG emissions).
Blue hydrogen production is less carbon-intensive than black, brown or gray hydrogen, but its dependence on fossil fuels does not make it as environmentally sound as green hydrogen.
Green Hydrogen — The Cleanest
Green hydrogen is often referred to as ‘clean hydrogen’ because it is produced using electricity from clean energy sources — such as solar or wind power — to split water into hydrogen and oxygen atoms through a process called electrolysis.
Because solar and wind power do not emit greenhouse gases when delivering electricity, this green hydrogen method offers a clean alternative to hydrogen production. Although it is not yet economically competitive at a commercial scale, green hydrogen could be a major contributor to decarbonizing hard-to-abate sectors such as steel manufacturing and the chemicals industry, which rely on fossil fuel feedstocks in the production process.
In addition to replacing portions of gray hydrogen, green hydrogen also poses potential as a clean hydrogen source for the transportation, building, and power sectors. Green hydrogen can serve as a key precursor ingredient in producing synthetic jet fuel and derivatives. Adopting this clean fuel would allow the shipping and aviation industries, which have been historically difficult to decarbonise given the infeasibility of direct electrification, to transfer to low-carbon intensive fuels and effectively reduce their GHG emissions.
There are several barriers to the widespread adoption of green hydrogen, such as constructing refuelling infrastructure, lowering costs, and developing storage strategies. The buzz around green hydrogen is growing, and as it becomes a more popular option, analysts assert that it will become more economic than gray hydrogen.
Future Outlook For Hydrogen
Talk on hydrogen is trending, yet it’s important to note that hydrogen production is a mature market that has served the international industry for decades. Hydrogen is used as an industrial feedstock in prominent processes such as oil refining and ammonia production. Hydrogen production has increased over the past decade, a trend that is anticipated to continue for the foreseeable future.
Advancements and scaling of green hydrogen technology could play a significant role in replacing gray (black & brown) hydrogen, and it could also provide clean fuel for transportation or stored energy to complement intermittent renewable energy sources. Considering how economic solar and wind power have become, it is now critical that we develop innovative techniques and strategies to drive down capital costs of electrolytic equipment and to effectively interconnect hydrogen solutions into our energy framework. Doing so will open up incredible potential for hydrogen to complement the larger global transition to a clean energy economy.
Australia is actively embracing opportunities around hydrogen. Green hydrogen energy hubs are part of the NSW Renewable Energy Zone (REZ) buildout plan, and The Australian Renewable Energy Agency (ARENA) has secured $105 million to fund three commercial green hydrogen facilities slated for Victoria and Western Australia.
With national and international commitments to reduce carbon emissions and reach net-zero status by 2050, green hydrogen can play a critical role in decarbonising industry and establishing a reliable clean energy grid. So as the world transitions to a clean energy economy, green hydrogen may not only be a way for Australia to decarbonise… it could also be the nation’s next big export opportunity.