It's important to understand that there is a difference between what is
technically and practically possible and what is
economically feasible.
It's very difficult to find objective information about hydrogen because almost all available information comes sources which have vested interests, and rather too many so called 'climate activists' (anarchists), exhibit an almost religious fervour that whatever it takes must be done instantly and we must 'suffer for our sins' (despite the fact that they conduct their lives in a similar manner to everyone else).
As with so many emotive topics, rational' objective debate is next to impossible.
For a long time to come, the UK will continue to depend on oil, gas and to a small extent coal. By the new government restricting extraction in the UK (with the very best of intentions), much of it will continue to be imported, increasing the UK's fuel insecurity and energy costs. That's not a political statement, just a fact of life.
Hydrogen is the most abundant chemical structure in the universe but unlike fossil fuels such as coal, methane gas and oil, it does not exist as a primary fuel source - it has to be extracted from primary fuel feedstocks. Whichever process is used, it is costly, takes a lot of energy to extract hydrogen, and most process involve the release of carbon, which needs to be captured and stored. Only the electrolysis of water into hydrogen and oxygen uses a renewable feedstock, but again, the process takes a lot of electricity which - to be 'green' - needs to be from renewable sources (wind and solar). Solar electricity is of course only available during daylight hours, so any hydrogen generated during daylight hours will need to be stored. The cost of the electricity needs to be factored into the price of hydrogen, and the 'opportunity cost' is that if used to generate hydrogen, that electricity cannot be used as a primary source of energy for heat, light, or power. Thus hydrogen will never be cheaper than electricity.
If it's ever produced on a grand scale, who knows what it might do to the rain cycle? In nature, water in the oceans and earth's surface evaporates, forms clouds, and falls as rain or snow, often in the wrong places, sometimes causing floods or droughts. If ever hydrogen from electrolysis of water is adopted on a huge scale (big 'if') vast quantities of 'man made' water vapour will be released into the atmosphere, then what? Just a passing thought.
When you hear of buses, cars, central heating boilers running on hydrogen, the focus is always on the undoubted environmental benefit at the point of use. A bus or car in the centre of a city only emits water vapour. However, the hydrogen won't be 'green' as only 4% of the world's current production of hydrogen is 'green'. There are four main sources for the commercial production of hydrogen:
natural gas,
oil,
coal, and electrolysis; which account for 48%, 30%, 18% and 4% of the world's hydrogen production respectively. Fossil fuels are the dominant source of
industrial hydrogen. Hydrogen is usually produced by the
steam reforming of natural gas. One ton of hydrogen produced will also produce 9 to 12 tons of CO2, a greenhouse gas that may be
captured.
So when you see a hydrogen bus, car or central heating boiler, the harmful emissions occur at the reforming plant - not the car's tailpipe, and the hydrogen comes from non-renewable sources. It makes little economic sense and even less environmental sense, to use electricity to convert methane (CH4) into carbon dioxide and hydrogen, with all the costs that entails, to power hydrogen central heating boilers, when the methane (natural gas), could - as it is now - be burnt directly in gas central heating boilers.
This is often referred to as 'grey' hydrogen, when emissions are released to the atmosphere, and 'blue' when emissions are captured through
carbon capture and storage (CCS) Blue hydrogen has been estimated to have a
carbon footprint 20% greater than burning gas or coal for heat and 60% greater when compared to burning diesel for heat.
Words such as' green' hydrogen, 'blue' hydrogen are bandied about without most of us knowing what they actually mean, so it might be worth a mention:
Black, brown and grey hydrogen:
Grey hydrogen is the most common form and is generated from natural gas, or methane, through a process called “steam reforming”.
This process generates just a smaller amount of emissions than black or brown hydrogen, which uses black (bituminous) or brown (lignite) coal in the hydrogen-making process. Black or brown hydrogen is the most environmentally damaging as both the CO2 and carbon monoxide generated during the process are not recaptured.
Blue hydrogen
Hydrogen is labelled blue whenever the carbon generated from steam reforming is captured and stored underground through industrial carbon capture and storage (CSS). Blue hydrogen is, therefore, sometimes referred to as carbon neutral as the emissions are not dispersed in the atmosphere.
However, some argue that “low carbon” would be a more accurate description, as
10-20% of the generated carbon cannot be captured.
Green hydrogen
Green hydrogen – also referred to as “clean hydrogen” – is produced by using clean energy from renewable energy sources, such as solar or wind power, to split water into two hydrogen atoms and one oxygen atom through a process called electrolysis. Renewables cannot always generate energy at all hours of the day and green hydrogen production could help use the excess generated during peak cycles. It currently makes up about
0.1% of overall hydrogen production, but this is expected to rise as the cost of renewable energy continues to fall. Many sectors also now see
green hydrogen as the best way of harmonizing the intermittency of renewables – storing excess energy at times of low demand to be fed back into the grid when demand rises – while decarbonizing the chemical, industrial and transportation sectors. Hydrogen produced from
nuclear energy via electrolysis is sometimes viewed as a subset of green hydrogen, but can also be referred to as 'pink' hydrogen.
Other colours of hydrogen:
Turquoise hydrogen refers to a way of creating the element through a process called methane pyrolysis, which generates solid carbon.
As such, there is no need for CCS and the carbon can be used in other applications, like
tyre manufacturing or as soil improver.
Its production is still in the experimental phase. Pink hydrogen, like green hydrogen, is created through electrolysis of water is powered by nuclear energy rather than renewables. The extreme temperatures from nuclear reactors could also be used in other forms of hydrogen production by producing steam for more efficient electrolysis, for example.
Meanwhile yellow hydrogen is the term used for hydrogen made through electrolysis of water using solar power, although some use it to mean hydrogen generated through electrolysis of water using mixed sources depending on what is available.
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.
Biomass:
Biomass, is a renewable organic resource, includes agriculture crop residues (such as corn stover or wheat straw), forest residues, special crops grown specifically for energy use (such as switchgrass or willow trees), organic municipal solid waste, and animal wastes. This renewable resource can be used to produce hydrogen, 'along with other by-products, by gasification'. Note that 'other by-products' is the 'sanitised' term for carbon dioxide and carbon monoxide.
https://www.weforum.org/agenda/2021/07/clean-energy-green-hydrogen/
In terms of distribution and storing of hydrogen (for example, to filling stations and re-fuelling cars), To turn hydrogen into a liquid to transport and store it, the pressures used are usually either 350 bar or 700 bar (5,000 – 10,000 PSI). The challenges that involves in creating the infrastructure (as compared to having say 2,000 litres of petrol or diesel sloshing about in a petrol/diesel tanker at normal atmospheric pressure) is self evident, and another debate!
The problem with looking into crystal balls to predict the future, is that we see more balls than crystals.
Hope that's of interest.
(I claim no special expertise, and have no axes to grind on this topic).
David.
