Sizing up hydrogen’s hydrological footprint

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Arid, sandy ground with multiple rows of rectangular solar panels on it. Far off in the background are houses and mountains.

Solar energy is the most affordable supply of renewable power obtainable to supply hydrogen.Credit score: Timothy Hearsum/Getty Photos

To steer economies away from fossil fuels and to chop carbon emissions, hydrogen must be produced from low-carbon power sources, similar to wind and solar energy. This inexperienced hydrogen is especially engaging to sure big-energy customers such because the transport, aviation and metal industries, which might battle to run on batteries or plug into renewable power straight by way of energy grids. And producing hydrogen is simple: electrical energy zapped into water splits the H2O molecules into hydrogen and oxygen, which bubble off as gaseous H2 and O2. The hydrogen can then be piped to the place power is required.

In a world of rising water stress, nonetheless, the method’s reliance on water is elevating alarm (see ‘Watering the facility plant’). Earlier this 12 months, the non-governmental group Meals & Water Watch in Washington DC warned that, by 2050, hydrogen manufacturing may gulp down as a lot water as is utilized by 34 million US residents annually. A spate of research over the previous few years supplies a extra constructive image, nonetheless, presenting proof that scaling up hydrogen manufacturing needn’t threaten water provides. “Water withdrawals for hydrogen manufacturing are negligible in comparison with complete water withdrawals,” says Lorenzo Rosa, an environmental engineer who makes a speciality of hyperlinks between water, power and meals on the Carnegie Establishment for Science in Palo Alto, California.

A barchart shows that water needed to power and operate hydrogen-generating electrolysers have a large hydrological footprint compared to other types of power plants.

Supply: E. Grubert. Clear. Prod. Lett. 4, 100037 (2023).

Nonetheless, Rosa says that water issues ought to form how and the place hydrogen is produced, particularly as a result of warmth and altered precipitation pushed by local weather change are tightening strain on water provides. “Hydrogen’s water consumption is small in comparison with what’s at the moment utilized in fossil-energy conversion and inconsequential in comparison with agricultural water use,” says Jack Brouwer, director of the Clear Vitality Institute on the College of California, Irvine. “However there are critical water availability and supply challenges on the native and regional ranges that can should be thought of.”

Brouwer and Rosa say that increasing hydrogen-production applied sciences and water-treatment choices may allow hydrogen producers to faucet into a variety of non-potable water assets — together with seawater — or to slash their water consumption. On the identical time, geospatial analyses that maps water and renewable-energy assets towards projected hydrogen manufacturing and demand can pinpoint the place investing in water-saving know-how — or deciding to import moderately than produce hydrogen — will probably be key to minimizing stress between the push for hydrogen and the necessity to protect water assets.

A thirsty course of

The water necessities for producing hydrogen by electrolysis start with a easy calculation: each kilogram of H2 molecules requires 9 litres of H2O. Therapy to purify that water — eliminating minerals that will gum up the works — consumes one other 15 litres of water per kilogram of H21.

That’s not the tip of the story, nonetheless. There’s much more water use to be counted if the renewable power that powers the method is included. The operation of photo voltaic panels and wind generators may not devour a lot water, however manufacturing them does. All informed, manufacturing a wind turbine provides 11 litres to inexperienced hydrogen’s water footprint. And the manufacture of right this moment’s main number of solar energy provides an enormous 124 litres, largely from the fabrication of silicon photovoltaic wafers.

Nonetheless, the water necessities of hydrogen manufacturing appear to be manageable. As a part of an evaluation co-led by Rosa, one situation for a net-zero international economic system in 2050 that consumes 400 megatonnes of inexperienced hydrogen per 12 months would use a meagre 0.13% of the world’s obtainable water provide if the power got here fully from wind energy, and about 0.56% if all of it got here from solar energy 2.

International locations that already face water shortage, Rosa and his colleagues argue, may select to import hydrogen to fulfill home wants moderately than ramping up manufacturing. In actual fact, most of the international locations that their research recognized as land-limited are already working to foster a hydrogen commerce, together with Japan and components of Europe. Different areas and nations — together with areas of sub-Saharan Africa, South America, Canada and Australia — have adequate land and water to turn into main hydrogen exporters, and lots of are already gearing as much as fulfil this position.

A number of elements counsel that the impacts of inexperienced hydrogen on regional water might be much more restricted than Rosa’s findings counsel. For instance, over the previous few years analysts and power planners have lowered their estimates of how a lot inexperienced hydrogen will probably be produced over the long run. In its September prediction for limiting international temperature rise to 1.5 °C, the Worldwide Vitality Company (IEA) initiatives there will probably be one-fifth much less hydrogen use in 2050 than it had predicted in its 2021 report.

One other necessary consideration when computing hydrogen’s hydrological footprint is the capability of hydrogen to be an alternative choice to fossil fuels, that are themselves water-intensive sources of power. Most research to date don’t account for the impact of such a substitution. Rosa and his colleagues, for instance, assume a fivefold discount in petroleum refining between 2020 and 2050, as the usage of gasoline and diesel is phased down. However they don’t work in a corresponding discount in water use, which may additional enhance hydrogen’s hydrological footprint. And if inexperienced hydrogen replaces pure fuel, the substantial water consumption by fuel producers that use hydraulic fracturing will probably be lowered. For instance, many jurisdictions in america and Europe are contemplating utilizing inexperienced hydrogen to gas gas-fired energy vegetation to cowl gaps in provide from photo voltaic and wind farms.

Love that soiled water

In lots of instances, hydrogen producers may have the ability to keep away from including pressure to potable water provides by tapping polluted or salty water, as a substitute of potable water. Choices embody municipal waste water, waste water from oil and fuel manufacturing and even seawater. Water therapy and desalination vegetation are costly to construct, however the funding is relatively small relative to the general price of hydrogen manufacturing.

White male wearing blue shirt and grey trousers kneeling beside a large container, within which are pipes, tubes and metal cylinders.

Jack Brouwer, director of the Clear Vitality Institute on the College of California, Irvine, demonstrates the electrolysis stack in a system used to make renewable hydrogen.Credit score: Steve Zylius/UCI

In 2022, an evaluation 3 by a group at Yale College in New Haven, Connecticut, concluded that even to deal with seawater — the hardest water supply to arrange as enter to such a facility — would require solely 0.3% of an electrolysis plant’s complete power funds. “The underside line is that “we don’t have to devour freshwater assets used for ingesting” to supply hydrogen, says Lea Winter, a chemical and environmental engineer at Yale and the research’s lead writer. The Worldwide Renewable Vitality Company agrees, concluding in 2020 that: “Even in locations with water stress, seawater desalination can be utilized with restricted penalties on price or effectivity.”

In California, electrolyser producer Plug Energy in New York plans to construct a water-treatment plant and hand it over to the native municipality, in return for a supply of water for hydrogen manufacturing. Mendota, the place the plant is to be constructed, is at the moment depleting floor water to fulfill demand for potable water. Metropolis officers say that the brand new plant will clear up sewage to extend the town’s water provide, in order that it may well scale back its use of floor water and promote water to Plug Energy.

Utilizing seawater presents virtually limitless potential, but additionally troubling environmental impacts. Some desalination vegetation launch heated brines laden with therapy chemical compounds again into the ocean; they’ll additionally suck in and destroy marine creatures. Probably the most vital ecosystem affect of those vegetation, in accordance with a 2020 assessment4, is deadly osmotic shock to marine organisms, together with fish, plankton and algae when super-salty brines trigger their cells to dehydrate. Most in danger are organisms in semi-closed seas such because the Crimson Sea, the Mediterranean and the Persian Gulf. Practically half of the world’s desalination capability is concentrated within the Persian Gulf.

Some observers, nonetheless, foresee potential environmental dividends if hydrogen producers faucet seawater and waste water. Thomas Adisorn, a political scientist at Germany’s Wuppertal Institute for Local weather, Surroundings and Vitality, sees potential for initiatives similar to that of Plug Energy to enhance the setting by supporting worldwide improvement. “Placing extra effort into utilizing recycled waste water in growing international locations which are exporting hydrogen may increase their capability to construct wastewater infrastructure,” says Adisorn, who organized a gathering in 2022 to assist officers from water-scarce Jordan who have been planning its hydrogen economic system.

New know-how and engineering integrations promise to trim the price of non-conventional water use even additional, whereas capturing different helpful advantages that pay for the additional water therapy. One energetic space of analysis and improvement, for instance, would monetize inexperienced hydrogen’s oxygen by-product. Cardio therapy tanks at wastewater vegetation depend on pumped air to maintain their waste-eating microbes. In keeping with Brouwer, some giant wastewater vegetation pump in pure oxygen as a substitute of air to spur quicker digestion. With an electrolyser they may get that oxygen without cost, says Brouwer, moderately than working expensive air-separation items.

Researchers with the municipal water authority Sydney Water and the College of Sydney, Australia, estimated in 2022 that integrating electrolysers into wastewater therapy vegetation may save the town about US$1.5 million per 12 months 5. They calculate that the town’s 13.7 gigalitres per 12 months of unused effluent may yield 0.88 megatonnes of inexperienced hydrogen per 12 months — one-tenth of the quantity Australia and New Zealand are anticipated to supply in 2030, in accordance with analysts S&P International in New York. Sydney Water says that its unpublished analysis confirms the viability of hydrogen and oxygen manufacturing utilizing its handled water, following additional purification.

One other innovation that might show a significant profit to utilizing seawater for hydrogen manufacturing is the power to function electrolysers offshore. Over the previous 12 months, groups in China and Europe have deployed platforms combining desalination tools and electrolysers. The hope is that the floating electrolysis vegetation — if they’ll function reliably amid storms and different assaults to offshore {hardware} — will minimize the price of offshore wind power. Delivery hydrogen by way of pipelines is mostly cheaper than transferring the equal quantity of power by way of electrical transmission strains, and hydrogen proponents are betting that this rule will maintain for passing power from offshore wind farms again to land.

The hydrogen producer Lhyfe’s 1-megawatt pilot platform operated offshore for five months this 12 months utilizing desalinated seawater, and a 10-megawatt platform is deliberate for Belgian waters in 2026. Lhyfe in Nantes, France, desires to mitigate the affect of desalination by eschewing chemical components in its therapy course of, and by diluting brine with further seawater, says Stéphane Le Berre, Lhyfe’s offshore mission supervisor.

Lhyfe is now exploring whether or not the oxygen from offshore electrolysis may counteract declining ranges of dissolved oxygen within the ocean — circumstances which are stunting marine ecosystems in some areas. In July, researchers projected that synthetic oxygenation from international deployment of offshore wind farms and electrolysers may scale back the quantity of severely hypoxic zones by 1.1–2.4%6. However additionally they reported some counterintuitive regional impacts. For instance, their simulation projected that oxygen injection may enlarge an present hypoxic zone within the Indian Ocean’s Bay of Bengal.

Recognized unknowns

Technological wild playing cards, in the meantime, may alter water consumption calculations round hydrogen manufacturing. In a assessment, the IEA recognized 40 firms which are exploring a possible hydrogen supply that is perhaps cleaner than electrolysis: pure pockets of the fuel, a few of which is perhaps tapped utilizing little water. However, as with injecting oxygen in to the ocean, seemingly water-saving applied sciences may have perverse results. Accessing ‘geological’ hydrogen may require fracturing of rock layers akin to hydraulic fracturing or ‘fracking’ used to recuperate oil and fuel. And a few of the hydrogen prospectors plan to stimulate hydrogen manufacturing in situ by injecting water into iron-rich rock formations.

Inexperienced-energy firm Eden GeoPower in Somerville, Massachusetts, plans to check hydrogen stimulation within the peridotite rock formations of water-scarce Oman, in collaboration with the nation’s Ministry of Vitality and Minerals. The corporate hopes to extend underground permeability utilizing its water-free electrical fracturing know-how. Chief govt Paris Smalls, says “again of the envelope calculations” counsel that web water consumption will probably be comparable with that of electrolysis per kilogram of hydrogen delivered.

Eden GeoPower’s consideration to water assets is the exception to the rule amongst hydrogen producers. Water provide just isn’t talked about within the IEA report or in a 2022 “vital” assessment of hydrogen-production know-how 7.

On condition that hydrogen manufacturing and water use are inextricably certain, it’s unlikely that water provide will proceed to be omitted. The inconvenient reality, say each Brouwer and Rosa, is that photo voltaic power is the most affordable supply of low-carbon energy obtainable to supply hydrogen, however the areas with the perfect photo voltaic assets are additionally a few of the most parched.

Brouwer is likely one of the important group members behind California’s hydrogen-development programme, which picked up $1.2-billion of the $7 billion in US federal funds awarded in October to regional ‘hydrogen hubs’ that hyperlink producers and shoppers. He says that hydrogen vegetation can faucet into standard water provides or clear up waste water, however that reaching net-zero carbon emissions in California will finally require much more photo voltaic panels within the desert.

Changing that photo voltaic power to hydrogen will drive the state to construct extra infrastructure, and to make an necessary selection. As Brouwer places it: “We’re going to ultimately have to determine whether or not we wish to run massive wires from the photo voltaic useful resource to the place the water is, or massive pipes sending water to the desert.”

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