Green hydrogen is the most focused subject in the world today, as it is believed that the optimal utilisation of green hydrogen as feedstock and energy source could be the most desirable strategy for achieving the target of zero emission in the next few decades.
In recent months, there have been several announcements and statements from governments, technologists, investors and large companies all over the world about their commitment to promote hydrogen industry. Obviously, these entities are of the view that the ultimate solution for the impending global climate crisis is the massive production of hydrogen that would substitute the use of fossil fuels, since hydrogen is an eco-friendly gas that can be used as fuel as well as feedstock to some extent. At the same time, there are also sceptics who think that hydrogen production technology in an eco-friendly manner at economic cost is yet to be adequately and optimally developed and advocacy of hydrogen industry as immediate cure to overcome the climate crisis is somewhat premature and is similar to the act of putting the cart before the horse.
Hydrogen can certainly be used as fuel, though some technology issues remain with regard to storage and transportation of hydrogen gas at acceptable cost level, which can be overcome soon. However, use of hydrogen as feedstock for the production of derivative products does not have much scope, while substituting use of fossil fuels by hydrogen. For example, several petrochemicals such as ethylene, propylene, toluene, etc. which are all strong building blocks and which are presently produced from petrochemical feedstock such as natural gas, crude oil or coal, cannot be produced from hydrogen.
Alternate ways of producing hydrogen
Hydrogen produced by a process that leaves some carbon footprint is not eco-friendly green hydrogen. Most of the hydrogen today is produced by steam reforming of methane (natural gas) which produces some carbon dioxide. When the nomenclature brown hydrogen is used, it refers to hydrogen produced from coal. Hydrogen produced from natural gas or crude oil is called grey hydrogen, If grey or brown hydrogen is produced and the carbon dioxide generated is captured and stored safely away, such hydrogen is called blue hydrogen.
Green hydrogen is hydrogen produced by a process that does not emit any greenhouse gases such as carbon dioxide or methane. The best example of green hydrogen is the hydrogen produced by splitting water using electricity from solar plants or wind turbine or hydro power projects.
Most of the hydrogen produced in the world today and several new projects announced for hydrogen production in recent time are based on fossil fuel such as natural gas. In the case of such brown, grey or blue hydrogen, there is inherent climate warming component in the feedstock used for the hydrogen generation, though hydrogen, by itself, is an eco-friendly product.
Challenges in green hydrogen production
Green hydrogen should be produced by the electrolysis of water using renewable energy. The major challenge is cost of production of green hydrogen. To bring down cost, the cost of the electrolyser, which splits water has to be reduced. Possibly, scale of green hydrogen plant capacity can bring down the cost to some extent. Another challenge is the efficiency of the electrolysers – basically, how much electricity it consumes to produce a kg of hydrogen.
As far as the existing technology is concerned, the water electrolytic process for generation of green hydrogen is power intensive and production cost is higher for the green hydrogen than the cost of production of hydrogen presently made by alternate routes. Today, the power requirement for production of green hydrogen is as high as 55 kWhr per kg of hydrogen.
Non availability of renewable power
Claiming it to be the production of green hydrogen, several existing and new projects use power generated from fossil fuel for operating the electrolytic process for green hydrogen. This is a counter-productive way.
The power generated from fossil fuel is being used, since the installed capacity for power generation from renewable source such as hydro, wind, solar are not adequate and are unlikely to be adequate in future when large capacity for green hydrogen production would be planned for build-up. Further, the capacity utilisation of solar and wind power and hydro power plant are much lower than the thermal power plant. Moreover, generation of solar power, wind power and hydro power are seasonal and undependable due to possible climate changes and depending on monsoon conditions from time to time. Under the circumstances, large scale production of green hydrogen -based on electrolysis of water using renewable power source is unrealistic and wishful thinking.
Case study – How much green hydrogen India needs?
The current consumption of hydrogen in India is about 5.6 million tons, but almost all of it comes from the ‘steam methane reforming’ process, based on fossil fuel, which emits the dreaded greenhouse gas carbon dioxide. Another 1.9 million tons of hydrogen is embedded in the methanol and fertilisers that the country imports. So, today, if India were to replace all the hydrogen in use with green hydrogen, the demand for green hydrogen would be around 7.5 million ton per annum.
To produce this much, electrolyser capacity of 130-140 GW is required. Roughly, the production of 1 ton per annum of green hydrogen requires 18 GW of electrolyser capacity, equivalent to 26 GW of solar power. Considering that the average capacity utilisation of renewable power industry (hydro, solar and wind) is only around 20 percent or even less, it is unrealistic to think that all the hydrogen that India would need could be switched over to green hydrogen.
Alternate process development for green hydrogen
It is necessary to improve and optimise the electrolyser manufacturing for producing green hydrogen. There is not much to choose from in the immediate future except the age-old alkaline technology. While electrolysis of water is the prevailing process for production of green hydrogen, alternate routes are under development.
Alternate technologies are under development such as proton exchange membrane (PEM), anode exchange membrane (AEM), high temperature reactors (HTR), production from biomass, production using sunshine, etc. All such possible technologies are under development and their commercial suitability is yet to be firmly established.
As such, the above technologies and a few more can best be termed as technology under development, whose date of commercial exploitation, if found feasible, cannot be reasonably predicted at the present time. The technology development efforts to produce eco-friendly green hydrogen at economical cost is at fluid stage at present.
Green hydrogen – Hope or hype?
Several world governments seem to be assuming that development of cost-effective green hydrogen production technology would happen sooner or later, perhaps, sooner than later. Obviously, plans of the several governments are based on hope. However, by not adequately explaining the present limitations of green hydrogen technology and challenges involved in developing the commercially exploitable green hydrogen production technology in public domain and the world media not discussing the issues involved in depth, there is a hype today on appropriate green hydrogen technology emerging very soon.
Under the circumstances, it is strange that the Government of India through its national hydrogen mission have announced specific policy interventions to push for the widespread adoption of green hydrogen in India. The Indian government wants to make it mandatory for industries (first fertilisers and oil refining) to use green hydrogen for certain specified percentage of its overall energy requirements. Such a requirement is called Green Purchase Obligation (GPO). This strategy of the Government of India amounts to planning in vacuum, as no one can be sure at present time as to when the green hydrogen would be adequately available in the market.