Green hydrogen is a form of renewable energy that, if taken up widely, could reduce global greenhouse gas emissions. It is produced by splitting water molecules into hydrogen and oxygen using renewable power. This clean, zero-emissions fuel is mainly used by industries like steel manufacturing and chemical refining. Heavy transport sectors such as maritime shipping, aviation and long-haul trucking could also use it.
But green hydrogen comes at an environmental cost too: huge amounts of water are needed to produce it. In Africa, the regions that have the best solar and wind resources to produce this clean energy are also those with the least water on the planet.
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The colder, northern hemisphere countries that lack the sunlight to produce solar energy are most in need of green hydrogen. Morocco, Algeria and Egypt are rapidly positioning themselves as primary suppliers for European clean energy markets.
The European Union aims to import 10 million tonnes of renewable hydrogen every year by 2030. The green hydrogen plants in north Africa aren’t built yet, but dozens of mega-projects have signed memorandums of understanding to set up or are in early-stage development or pilot plant stage.
Egypt has signed US$40 billion worth of agreements with international developers to build green hydrogen and ammonia hubs in the Suez Canal Economic Zone. Morocco proposes to set aside one million hectares of land for developers of green hydrogen projects. Algeria plans to pipe green hydrogen directly to Europe via the planned SoutH2 Corridor.
A few pilot facilities are already operating. But most large-scale commercial production and export infrastructure is scheduled to come online between 2027 and 2035.
As a researcher in materials and environmental science, I recently published a paper examining how large-scale green hydrogen production affects local water supplies and ecosystems in dry regions of Australia, Chile and north Africa where hydrogen is being produced for export. I wanted to understand what the move to green hydrogen means for water resources and the environment.
My co-author, Mustafa Gazi, and I reviewed engineering and environmental data from around the world. We used this evidence to build a computer model of a 10-hectare, 1-gigawatt hydrogen plant operating in a hot, dry climate. The model calculated its total water needs, including water used to produce hydrogen, treat supplies and cool equipment.
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We then assessed the likely environmental risks of large hydrogen production and export projects planned for Australia, Chile and north Africa.
Finally, we examined gaps in international rules for deciding whether hydrogen qualifies as “green”. These focus almost entirely on cutting carbon emissions. They overlook how much water local ecosystems can spare and whether communities will have enough for drinking and farming.
Our research found that producing green hydrogen in desert areas in Australia, Chile and north Africa needs far more water than the industry claims. We also found serious environmental risks that had been overlooked. If plants used seawater to meet their freshwater needs, removing the salt would use large amounts of energy. It would also produce very salty wastewater containing chemicals that could harm coastal and marine life. We also found that ancient groundwater reserves that do not refill on human timescales could be depleted.
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The research identifies a pattern of “green extractivism”. This is where affluent countries which import green hydrogen benefit environmentally by reducing their own greenhouse gas emissions. But the countries producing the green energy bear the ecological damage and water strain.
The way that “green” energy is measured by international certification bodies, governments and carbon-accounting frameworks needs to change. Clean energy policies must also prioritise protecting ecosystems and ensuring fair access to water – not just look at the benefits of cutting carbon emissions.
The actual costs
My research shows that the costs, and impact, of producing green energy in the three arid regions of the world exceed what’s been suggested in crucial respects.
Firstly, the industry claims that it will take only about nine litres of water to produce one kilogram of green hydrogen. This is a myth. This is just the minimum needed for the chemical reaction, not the total a working plant uses.
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Hydrogen plants need extremely pure water, and some water is discarded during purification. In hot, dry regions, cooling systems also lose large amounts through evaporation. Our model found that, once these needs are included, plants may draw between 35 and 170 litres of water for every kilogram of hydrogen produced.
This massive demand for water will cause the most problems in north Africa, where regional groundwater is already severely depleted.
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Desalinating seawater will be the way to provide the freshwater needed to produce green hydrogen. But our findings show that desalination could cause severe secondary environmental damage. Desalination plants produce large amounts of very salty wastewater, known as brine, which is released back into the sea. It also contains chemicals used to stop mineral deposits building up on equipment, remove impurities and clean filters.
When dumped into semi-enclosed coastal waters, such as lagoons, this dense, chemical-laden brine settles onto the seafloor. It suffocates marine life and damages local fisheries.
What needs to happen next
Based on our findings, we make a number of recommendations.
Firstly, international regulators define sustainability almost entirely by greenhouse gas emissions. They assume that low-carbon hydrogen is automatically sustainable. This fails to account for whether using up water dehydrates local watersheds or pollutes marine habitats.
We recommend that international rules for certifying hydrogen as “green” require projects to measure their effects on local water supplies and ecosystems. We proposed two measures: a Water Sustainability Index to assess whether water use is sustainable, and a score that assesses how salty wastewater could harm marine life.
Projects should not qualify as “green” if they use more water than the local environment can safely spare.
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Future hydrogen plants should work with nearby cities to reuse treated sewage, purifying it further to make hydrogen. This would reduce competition with communities, farms and ecosystems for freshwater and avoid the salty wastewater that desalination plants release into the sea.
Stabilising the global climate through clean energy must be guided by ecosystem-sensitive planning. This will ensure that the transition away from fossil fuels does not come at the expense of water security.
Akeem Adeyemi Oladipo does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
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