Rainbow colors of Hydrogen
Credit — pixabay.com

Pot of Gold? Yes, but only at one end of the Hydrogen Rainbow

Sandeep Chandra
8 min readMay 16, 2021


Not many would imagine Hydrogen as a colorful commodity. But it is — metaphorically speaking! The colors of Hydrogen are many — green, purple, yellow, turquoise, blue, grey and brown — and they make up a rainbow of sorts. This rainbow is unique and it promises a pot of gold at the end of the rainbow … but at only one end! So, let’s go hunting for this pot of gold.

Once we locate this pot of gold, we will see why there is buzz about Hydrogen in today’s world.

Hydrogen in its natural form is colorless, no doubt about that. However, the list of colors mentioned above is part of industry-wide accepted nomenclature (originated by NACFE — North American Council for Freight Efficiency and now widely used across the Hydrogen industry) [1].

The Hydrogen industry gurus assigned colors to Hydrogen to describe the source or method of production of Hydrogen. The end product in each production method is the same Hydrogen, H2, but the manner in which this Hydrogen is produced has important implications and varying degree of impact on our environment [2]. Hence, to differentiate these production methods, the produced Hydrogen is assigned a different color. Let us get to the bottom of this Hydrogen color conundrum.

Hydrogen color spectrum sourced from NCEF.org
Credit — NACFE, www.nacfe.org

Going Through the Hydrogen Rainbow

Let us step through the main colors — ones with a material impact on the environment

Brown H2

Hydrogen produced from the traditional method of coal gasification is termed Brown Hydrogen. Using coal (and brown coal is optimal for this purpose), water and air, at very high temperatures (>700℃) coal is subject to controlled combustion resulting in production of synthetic mix of gases — syngas — which contains CO2, CO, CH4, ethylene and molecular H2. Separating Hydrogen from here is easy but this process is environmentally dreadful because of vast quantities of CO2 produced alongside this. See Table below.

Similarly, currently trending waste-to-energy incinerators and biomass feedstock incinerators fall within this category as these also produce syngas containing CO2 and CO.

Not only that, produced Hydrogen has to be transported to customer site and in the process even more greenhouse gases (GHGs) are produced. Therefore, this method is not a good one. Next.

Grey H2

Currently the most widely used method, because it is the cheapest now, for obtaining Hydrogen is a process called Steam Methane Reforming (SMR). This uses a pressurized mixture of Natural Gas (which contains mainly Methane) and superheated Steam to run over catalysts which produces H2 and CO. In the second round, this CO interacts with water and coverts to CO2 but produces even more H2.

Although the cheapest method, it suffers from the same problems relating to production of GHGs as does Brown Hydrogen.

Blue H2

Enter Blue Hydrogen. This has mainly come about due to the need to remove CO2 from syngas produced with Grey and Brown methods. Its aim is to achieve net-zero emissions. There are three principal aspects to this — capture of CO2 at the source, transportation of captured CO2 to storage site and storage of CO2 for long term or permanently. So it is termed CCS — Carbon Capture and Storage.

Another use of CCS besides Hydrogen re-coloring is in CO2 capture in the most emissions intensive industries like steel, cement and chemicals. Once the CO2 is captured it is transported in pipelines to storage sites. There exist several thousand kilometers of pipelines already in the US, Europe and many other countries plus there are established transportation hubs where trucks and ships are deployed to carry away CO2 storage sites. The destined storage sites are often abandoned, out-of-service, spent or depleted oil and gas fields and even deep sea beds. Storage is either as CO2 in gas form or alternatively in solid form as metallic carbonates or as liquid CO2 (which is denser than sea water and will stay locked at the bottom [2])

Proponents of CCS argue that production facilities that employ CCS techniques to eliminate CO2 have an advantage today that they get a fixed cost view of CO2 generation now rather than face costs from potential tariffs for CO2 generation in the future [3].

Geological surveys have confirmed the potential for CO2 storage is immense. It is predicted that in US, Europe, Africa and Australia there is so much room in rock formations to store CO2 that even the most pessimistic estimates can still provide 10 x times the space required to capture all the CO2 predicted by 2030

There is also a variant on the CCS — CCUS — where once CO2 is captured, part of it is utilized in manufacture of plastics, concrete and chemicals with remainder heading to geological storage [4].

While CCS / CCUS presents a very rosy picture they are fraught with problems. Current technology is unable to capture more than 80–90% of CO2 produced at the point source. The balance CO2 thus left in the atmosphere would still be many times more than emissions produced in the making of solar wind and nuclear [5] [6].

Also, the number of CCS projects that exist around the world have not had a stellar record. Apart from being marred by ineffective capture of CO2, these projects have had large cost and schedule overruns and operational issues like CO2 leakages, which have meant the uptake of CCS option is slow. Critics go as far as suggesting that CCS is only an attempt to prolong the life of polluting fossil fuels in our energy systems [7]

Green H2

At the end of the Hydrogen rainbow is the most desirable color — green. It is the ultimate goal of hydrogen resource as it uses renewable energy to produce Hydrogen. The electricity produced by the renewable energy plant is used to split water molecules (H2O), using electrolysis, and Hydrogen is then captured. The other by-product — molecular Oxygen, O2, is utilized for medical and other purposes.

Overview of H2 Production Methods

Table — Hydrogen Production Methods by Colors — by Author (Sandeep Chandra)

What’s the buzz with Hydrogen?

Hydrogen is a cool fuel. It is light, storable, energy-dense, upon burning produces no direct emissions of pollutants or greenhouse gases, it is abundant and is so versatile as a fuel that it has applications in industry, transportation and power generation [8]. Therefore, in the global quest to achieve a net-zero emission society, Hydrogen clearly has a significant role to play.

Since, Hydrogen is not found naturally on Earth and therefore needs to be extracted from substances that contain it, like methane, biomass, etc. According to IEA (International Energy Agency) estimates, each year 70 million tonnes of Hydrogen is produced and in the process 830 million tonnes of CO2 is generated per year [ibid]. Since, fuel costs are the single largest component (45%-75% of the overall Hydrogen production cost), the economics dictates use of the cheapest possible fuel for its production. The cheapest fuel used is Natural Gas and Coal, both prime culprits in generating CO2 and other GHGs, both therefore dirty fuels (grey and brown).

The real buzz with Hydrogen now is that alternate methods of hydrogen production that do not generate GHGs, such as water electrolysis, have become economically viable. As costs for renewable energy — Solar PV and Wind — come down, clean Hydrogen produced from these renewable energy methods (green) is now an attractive proposition.

For this reason, Hydrogen is currently enjoying unprecedented political and business interest, around the world — particularly in Europe, US, Japan and lately China, Australia and India — with respective Governments releasing and updating Hydrogen Strategy papers, policies and missions with a goal of net-zero emissions in respective economies [11] [12].


So this brings us to the end of the rainbow …

Hydrogen as a fuel, in its green avatar, offers tantalizing promises of a cleaner industry with net-zero emissions, producing only water as a by-product.

Once considered a perennial “fuel of the future” [13], the clean green Hydrogen future has already begun. It is here and now. Strong momentum and support from governments and businesses, billion-dollar federal programs, large-scale green Hydrogen plants being setup are sure signs that the Hydrogen economy is revving up. When it comes to scale, Hydrogen easily outshines other alternatives. For instance, the big Hydrogen facility in Texas can hold 1,000 x times as much electricity as the world’s largest lithium-ion battery complex in South Australia [14]

At the end it is about getting a carbon-free and cost-effective solution. The costs of green Hydrogen continue to drop the day is not far when green Hydrogen will be cheaper than grey Hydrogen (which is currently the cheapest). In that event switch to green Hydrogen powered economy will be swift. In my following article we examine the trends in costs of Hydrogen production, developments in green Hydrogen and new application areas.

Hydrogen can help to achieve a clean, secure and affordable energy future for all on this planet. Now that is a veritable pot of gold, who wouldn’t want it?


1. www.nacfe.org

2. https://cdm.unfccc.int/about/ccs/docs/CCS_geo.pdf

3. What colour is your hydrogen? A Power Technology jargon-buster (power-technology.com) (https://www.power-technology.com/features/hydrogen-power-blue-green-grey-brown-extraction-production-colour-renewable-energy-storage/)

4. Hydrogen production — Wikipedia

5. The technological and economic prospects for CO 2 utilization and removal | Nature (https://www.nature.com/articles/s41586-019-1681-6)

6. Hydrogen economy — Wikipedia

7. What is Carbon Capture and Storage? | Climate Council (https://www.climatecouncil.org.au/resources/what-is-carbon-capture-and-storage/)

8. The Future of Hydrogen — Analysis — IEA (https://www.iea.org/reports/the-future-of-hydrogen)

9. Green hydrogen costs ‘can hit $2/kg benchmark’ by 2030: BNEF | S&P Global Platts (spglobal.com)

10. Hydrogen Production Cost — an overview | ScienceDirect Topics (https://www.sciencedirect.com/topics/engineering/hydrogen-production-cost)

11. Australia’s National Hydrogen Strategy, COAG Energy Council, 2019

12. Indian National Hydrogen Mission -https://www.insightsonindia.com/2021/02/19/national-hydrogen-mission/

13. What are the safest and cleanest sources of energy? — Our World in Data (https://ourworldindata.org/safest-sources-of-energy)

14. How hydrogen can offer a clean energy future | World Economic Forum (weforum.org) (https://www.weforum.org/agenda/2019/06/how-hydrogen-can-offer-a-clean-energy-future/)

15. Hydrogen produced from nuclear will be considered ‘low-carbon’, EU official says — EURACTIV.com (https://www.euractiv.com/section/energy-environment/news/hydrogen-produced-from-nuclear-will-be-considered-low-carbon-eu-official-says/)

16. Brown, blue, or green… What colour is your hydrogen? | Nel Hydrogen (https://nelhydrogen.com/blog/brown-blue-or-green-what-colour-is-your-hydrogen/#:~:text=Brown%20hydrogen%2C%20the%20most%20abundant%20in%20use%20today%2C,bluntly%2C%20production%20of%20brown%20hydrogen%20is%20very%20dirty.)

17. Solar, wind and nuclear have ‘amazingly low’ carbon footprints, study finds (carbonbrief.org)



Sandeep Chandra

International Hydrogen Consultant with investment stakes in Green & Blue Hydrogen production, HRS, FCEVs , FCs and Hydrogen application areas