Green hydrogen has long been touted as a kind of silver bullet for phasing out fossil fuels and cleaning up our hard-to-decarbonize industrial, shipping, and manufacturing sectors. It can burn like a traditional carbon-based fuel, and up to temperatures hot enough to make steel, but laves behind nothing but water vapor. So it’s obviously the holy grail of clean energy, right? But of course, nothing is ever that simple. In reality, creating hydrogen – a process which involves splitting water molecules – is extremely energy intensive, and presents some significant associated trade-offs which have impeded its growth. Hydrogen is already being used in industrial processes around the world, but almost none of it is “green.” Hydrogen is only as clean as the energy source that’s used to make it, and green hydrogen only refers to hydrogen made using renewable energies. Gray hydrogen is the name for hydrogen made with fossil fuels. Some people also include a third category – blue hydrogen – which is made from natural gas, making it a lower-emissions option compared to oil or coal. Currently, creating green hydrogen costs more than twice as much as gray hydrogen, at about $5 per kilogram.
Transitioning our economy away from carbon-based fuels to green hydrogen would therefore require massive amounts of green energy and that other green stuff: cash. On top of economic issues, the International Energy Agency has said that diverting too much green energy away from other applications to be used in green hydrogen production would be counterproductive. In short: instead of solving the climate crisis, we’d just be moving resources and emissions around in a zero-sum game.
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Another issue is that green hydrogen production requires massive quantities of pure water, which is an increasingly scarce resource. This means that scaling up green hydrogen production could seriously exacerbate already pressing global freshwater shortages. “Generating 1 kilogram of hydrogen using electrolysis takes some 10 kilograms of water,” Science recently reported. “Running trucks and key industries on green hydrogen could require roughly 25 billion cubic meters of fresh water a year, equivalent to the water consumption of a country with 62 million people.”
In response to this dilemma, some researchers have been looking at ways to make green hydrogen out of saltwater instead. This innovation would mean that we could theoretically use the ocean as an inexhaustible source of water to produce clean-burning hydrogen. And some of them are saying that they’ve cracked the code. Three different research groups – at RMIT University in Melbourne, the University of Adelaide, and the Nanjing University of Technology – have reported major advancements in their separate quests to apply electrolyzers to seawater.
The issue is that working with saltwater – as opposed to freshwater – creates the unfortunate byproduct of chlorine gas, which is highly corrosive and causes electrolyzers to fail in just hours, when they can normally last for years. All three research groups have made major progress in finding ways to work around this effect, by coating their electrodes in various compounds and membranes. All three teams have had success, but the Nanjing University of Technology produced the most impressive breakthrough, as their electrolyzer has now reportedly been running for 3,200 hours without showing signs of degradation.
While these breakthroughs are extremely exciting, the water problem is just one of the many issues facing green hydrogen. Energy and cost are still enormous barriers to scaling up and scaling out the use of green hydrogen in widespread industrial applications. However, the work being done by these research groups are nonetheless a beacon of hope. If the water problem can be solved, it’s not inconceivable that, in due course, the other problems could be similarly mitigated. If the potential of green hydrogen is unlocked, it’s almost impossible to overstate the impact it would have on the climate, the economy, and the world.
By Haley Zaremba for Oilprice.com
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