Offshore Hydrogen Production: Global Deployment of Artificial Oxygen from Electrolysers and Wind Farms Can Counteract Ocean Subsequently Stable Hypoxic Zones

Climate change and heat are putting a strain on the water supply so it’s important that water considerations are taken into account when producing hydrogen. “Hydrogen’s water consumption is small compared to what’s currently used in fossil-energy conversion and inconsequential compared to agricultural water use,” says Jack Brouwer, director of the Clean Energy Institute at the University of California, Irvine. There are serious water availability and delivery challenges at the local and regional level that will need to be considered.

Countries that already face water scarcity, Rosa and his colleagues argue, could choose to import hydrogen to meet domestic needs rather than ramping up production. In fact, many of the countries that their study identified as land-limited are already working to foster a hydrogen trade, including Japan and parts of Europe. Other regions and nations — including areas of sub-Saharan Africa, South America, Canada and Australia — have sufficient land and water to become major hydrogen exporters, and many are already gearing up to fulfil this role.

Lhyfe is now exploring whether the oxygen from offshore electrolysis could counteract declining levels of dissolved oxygen in the ocean — conditions that are stunting marine ecosystems in some regions. In July, researchers projected that artificial oxygenation from global deployment of offshore wind farms and electrolysers could reduce the volume of severely hypoxic zones by 1.1–2.4% (ref. 6). But they also reported some counterintuitive regional impacts. For example, their simulation projected that oxygen injection might enlarge an existing hypoxic zone in the Indian Ocean’s Bay of Bengal.

For 5 months this year, a 1-megawatt pilot platform used desalinated ocean water, while a 10-megawatt platform is planned for Belgian waters. Lhyfe in Nantes, France, wants to mitigate the impact of desalination by eschewing chemical additives in its treatment process, and by diluting brine with extra seawater, says Stéphane Le Berre, Lhyfe’s offshore project manager.

Plug Power, a New York-based company that makes electrolysis technology, is planning to build a water-treatment plant in California and give it to the localmunicipality in exchange for a source of water for hydrogen production. Mendota, where the plant is to be built, is currently depleting ground water to meet demand for potable water. City officials say that the new plant will clean up sewage to increase the city’s water supply, so that it can reduce its use of ground water and sell water to Plug Power.

Some observers, however, foresee potential environmental dividends if hydrogen producers tap seawater and waste water. Thomas Adisorn, a political scientist at Germany’s Wuppertal Institute for Climate, Environment and Energy, sees potential for projects such as that of Plug Power to improve the environment by supporting international development. Adisorn says that more effort should be made to use recycled waste water in developing countries that are exporting hydrogen to raise their capacity to build wastewater infrastructure.

Using seawater presents almost limitless potential, but also troubling environmental impacts. Some desalination plants can release heated brines laden with treatment chemicals back into the sea, and they can also destroy marine creatures. The most significant ecosystem impact of these plants, according to a 2020 review4, is lethal osmotic shock to marine organisms, including fish, plankton and algae when super-salty brines cause their cells to dehydrate. Most at risk are organisms in semi-closed seas such as the Red Sea, the Mediterranean and the Persian Gulf. Nearly half of the world’s desalination capacity is concentrated in the Persian Gulf.

In many cases, hydrogen producers might be able to avoid adding strain to potable water supplies by tapping polluted or salty water, instead of potable water. The options include waste water from oil and gas production, as well as municipal waste water. Water treatment and desalination plants are expensive to build, but the investment is comparatively small relative to the overall cost of hydrogen production.

The water requirements for producing hydrogen by electrolysis begin with a simple calculation: every kilogram of H2 molecules requires 9 litres of H2O. Treatment to purify that water — eliminating minerals that would gum up the works — consumes another 15 litres of water per kilogram of H2 (ref. 1).

However, there is more to this story. There’s a lot more water use to be counted if the renewable energy that powers the process is included. The operation of solar panels and wind turbines might not consume much water, but manufacturing them does. All told, manufacturing a wind turbine adds 11 litres to green hydrogen’s water footprint. The manufacturing of a wide variety of solar power adds more than 100 litres.

What the Hell is Water? A Case Study of Floods and Resilience in Arid Regions, a Source of Life and Strife

David Foster Wallace made an old joke that is famous, in which one fish tells another how the water is. The second fish replies: “What the hell is water?”

Water can be a threat, even if it sustains life. Flooding can ravage communities. In a live webcast earlier this month, specialists shared their latest thinking about flood resilience. They painted a frightening picture of how floods affect the world’s poor people even in rich countries like the United States. Almost all of the 1.9 billion people who live in areas at risk of flooding are from low- and middle-income countries. Some researchers say that much of the infrastructure put in place to tame waterways is proving inadequate, or even counterproductive. They advocate rethinking how water is handled in the built environment, including re-establishing the abandoned practices of ancient cultures.

But only so far can you go. Rivers, wells and artificial reservoirs provide ample supplies for much of the world, but arid regions still struggle. Some researchers in these water-starved regions are turning their attention to the wet sponge that is the planet’s atmosphere. New technologies could extract clean fresh water from thin air, and sharply reduce water scarcity.

No matter how abundant the supply, of course, water intended for drinking also needs to be clean and free of contaminants. Among the most harmful chemicals are the ones that are held together by chemical bonds in nature, and impervious to most attempts to break them down. But engineers are devising various methods to crack them apart and purify PFAS-contaminated water.

Source: Water: a source of life and strife

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