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VIEWS AND OPINION

What exactly is green hydrogen?

For a colourless gas, hydrogen gets described in very colourful terms.

by Jason Deign, Greentechmedia

ompanies and industry groups often join together to promote their products. Far more
unusual was the step taken last month by ten major European energy companies and
Ctwo of the continent’s top renewable industry bodies, which joined up to launch a
campaign touting a product that none of them actually sell. That product is renewable or
“green” hydrogen. And while it’s not a central concern today for those companies or industry
groups, all see green hydrogen playing a vital role in achieving deep decarbonisation of the
energy system.
Interest in green hydrogen is skyrocketing among major oil and gas firms. Europe is planning
to make hydrogen a big part of its trillion-dollar Green Deal package, with an EU-wide green
hydrogen strategy expected to be published in July. Jason Deign
“We cannot electrify everything,” said WindEurope CEO Giles Dickson. “Some industrial
processes and heavy transport will have to run on gas. And renewable hydrogen is the best gas. It
is completely clean. It will be affordable with renewables being so cheap now.” for other energy carriers, from ammonia to
According to the nomenclature used by market research firm Wood Mackenzie, most of the synthetic hydrocarbons, or to directly power
gas that is already widely used as an industrial chemical is either brown, if it’s made through the fuel cells in cars and ships, for example.
gasification of coal or lignite; or grey, if it is made through steam methane reformation, which To start with, you can use it simply to
typically uses natural gas as the feedstock. Neither of these processes is exactly carbon-friendly. replace the industrial hydrogen that gets
A purportedly cleaner option is known as blue hydrogen, where the gas is produced by steam made every year from natural gas and which
methane reformation, but the emissions are curtailed using carbon capture and storage. This amounts to around 10-million t in the US
process could roughly halve the amount of carbon produced, but it’s still far from emissions-free. alone. The main problem with satisfying all
Green hydrogen, in contrast, could almost eliminate emissions by using renewable these potential markets is in getting green
energy — increasingly abundant and often generated at less-than-ideal times — to power the hydrogen to where it is needed. Storing and
electrolysis of water. transporting the highly flammable gas is
A more recent addition to the hydrogen-production palette is turquoise. This is produced not easy; it takes up a lot of space and has a
by breaking methane down into hydrogen and solid carbon using a process called pyrolysis. habit of making steel pipes and welds brittle
Turquoise hydrogen might seem relatively low in terms of emissions because the carbon can and prone to failure.
either be buried or used for industrial processes such as steelmaking or battery manufacturing, Because of this, the bulk transport
so it doesn’t escape into the atmosphere. of hydrogen will require dedicated
However, recent research shows turquoise hydrogen is actually likely to be no more pipelines (which would be costly to build),
carbon-free than the blue variety, owing to emissions from the natural-gas supplies and pressurising the gas, or cooling it to a
process heat required. liquid. Those last two processes are energy-
intensive and would further dent green
How do you make green hydrogen? hydrogen’s already underwhelming round-
With electrolysis, all you need to produce large amounts of hydrogen is water, a big electrolyser, trip efficiency.
and plentiful supplies of electricity. If the electricity comes from renewable sources such as wind,
solar or hydro, then the hydrogen is effectively green; the only carbon emissions are from those Why is green hydrogen suddenly such
embodied in the generation infrastructure. a big deal?
The challenge right now is that big electrolysers are in short supply, and plentiful supplies of One of the paths to near-total
renewable electricity still come at a significant price. Compared to more established production decarbonisation is electrifying the whole
processes, electrolysis is very expensive, so the market for electrolysers has been small. And while energy system and using clean renewable
renewable energy production is now sizable enough to cause duck curves in California and grid power. But electrifying the entire energy
problems in Germany, overproduction is a relatively recent development. Most energy markets system would be difficult, or at least much
still have a need for plenty of renewables just to serve the grid. more expensive than combining renewable
generation with low-carbon fuels. Green
How do you store and use this stuff? hydrogen is one of several potential low-
Theoretically, there are lots of useful things you can do with green hydrogen. You can add it to carbon fuels that could take the place of
natural gas and burn it in thermal power or district heating plants. You can use it as a precursor today’s fossil hydrocarbons.

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