With the backdrop of surging gas prices in the UK and continental Europe causing seven England-based power companies to collapse, a re-examination of potential fuels to drive the energy transition may seem imminent. One such energy source which has been gaining media attention following discussions about it at President Biden’s Leaders Summit on Climate this spring is also the most-common element in the universe: hydrogen.
By no means is hydrogen always a low-emissions fuel; it is key to consider how it is produced. The most commonly produced form of hydrogen, for instance, is grey hydrogen, so called since ten tonnes of carbon dioxide are generated for every tonne of hydrogen generated. Such a polluting production process should be expected given that it involves conventional fuels such as natural gas undergoing a process called methane steam reforming. In essence, water heated to 700-1000 degrees celsius (steam) reacts with methane to produce hydrogen and carbon monoxide.  The carbon monoxide subsequently reacts with more steam in a ‘water-gas-shift reaction’ to generate more hydrogen and carbon dioxide. A total of 95% of the hydrogen produced in the US is generated in this way, a fact to consider when being tempted to necessarily associate the fuel with reducing carbon emissions.
On the next rung down of the pollution-intensity scale comes blue hydrogen. This form of the fuel is generated through the identical steam-methane-reforming process as mentioned above yet the carbon dioxide generated is captured and stored. This process of carbon capture and storage (CCS), involves three phases.  First, the carbon dioxide is separated from any other gases which are produced in industrial processes, and it is then compressed for transportation through ships, pipelines or road transport to a storage site. Finally, the greenhouse gas is injected into rock formations located deep underground, where it is permanently stored. These rock formations could be depleted reservoirs of oil and gas or saline aquifers, which are permeable rocks that are highly saturated with water.
Such a form of the colourless gas has gained notable attention in the press recently due to a paper published in the Energy Science & Engineering journal.  This somewhat shocking study revealed that the production of blue hydrogen may generate as much as 20% more greenhouse gases than coal and 60% more than petrol. Said result may seem surprising given the CO2 released is stored yet the chemical reactions also generate methane, a particularly potent greenhouse gas, and require a significant amount of energy to first separate and store the carbon dioxide. Some of this stored gas can even escape into the atmosphere.
The last colour of hydrogen which is arguably significant for society and the broader energy transition is so-called green hydrogen. The production of this variant involves no hydrocarbons, and instead uses electricity generated from renewable energy sources to electrolyse water and split it into oxygen and hydrogen. No carbon dioxide is emitted in the process, yet it is notably costly, with its price ranging from $2.50 to $6/kg as opposed to being between $1.30 and $2.90/kg for blue hydrogen and a mere $0.70-$2.20 for grey. [4, 5]
Although demand for this last, clean form of hydrogen is projected to burgeon as it is set to form key strategic pillar in countries’ and corporations’ transition to net zero emissions, the current scale at which the gas is produced is minute. Indeed, it currently represents approximately 1% of global hydrogen supply, despite the fact that the market for it is due to proliferate by 900% by 2050.  Hence, the issue that firms which produce green hydrogen currently face is how to upscale green-hydrogen production capacity at a price which is commercially viable.
The degree to which this is possible may also hinge on how aggressive senior decision makers are in the corporate and government-policy circles. Therefore, while the potential for green hydrogen to meet the energy demands of the future is promising, various logistical and policy-related factors may determine when and at what scale the colourless gas can do so.
 https://www.rechargenews.com/energy-transition/green-hydrogen-will-be-cost-competitive-with-grey-h2-b y-2030-without-a-carbon-price/2-1-1001867
 https://home.kpmg/xx/en/home/insights/2020/11/the-hydrogen-trajectory.html#:~:text=Inherently%2C%20 blue%20hydrogen%20cannot%20be,converting%20natural%20gas%20to%20hydrogen.&text=In%20the %20short%2Dterm%2C%20green,%2D6%20USD%2Fkg%20H2
 https://energymonitor.ai/tech/hydrogen/how-green-hydrogen-will-grow-up-into-a-global-market; https://www.ft.com/content/7eac54ee-f1d1-4ebc-9573-b52f87d00240