Despite its promise of a major contribution to a cleaner energy system, green hydrogen must find its place in a landscape with immense competition for a finite water supply.
Hydrogen has come a long way through Australia’s energy debate, according to Dr Kate Holland, a CSIRO Principal Research Scientist and Groundwater Management Group Leader. As the Grattan Institute niftily phrased it, hydrogen has progressed from hype, to hope and now to “hard work”.
For those in the water sector, this shift presents a vexing question of whether Australia can sustainably provide enough water to support the large-scale production of green hydrogen.
Arup’s Victorian Water Team Lead Priyani Madan MIEAust CPEng said while green hydrogen was quite topical two years ago, momentum has slowed recently.
Even as progress on major projects slows, engineers are expected to provide answers around the viability of the green hydrogen sector. Water makes an important contribution to those solutions, alongside other technical challenges such as production efficiency, storage, infrastructure, safety and a skilled workforce.
How much water does green hydrogen need?
Holland’s CSIRO team looked at 28 Australian hydrogen projects, including four operating electrolysers being fed with potable water. Those plants required nine to 15 L of water per kilogram of green hydrogen produced.
“That’s a relatively small amount of water, but remember those facilities are pilots,” she said.
When the feed water is less pure – if it’s saline, coastal or brackish, as would likely be the case for large-scale hydrogen hubs – water needs rise dramatically.
“We developed an upper bound estimate … around 100 L per kilogram of hydrogen,” Holland said. “That consisted of the nine litres for the stoichiometric number and 15 L for a low-salinity source, plus about 40 L per kilo for cooling and 45 for the waste brine stream.”
Real-world estimates could be even higher. CSIRO found one seawater project requiring 240 L of water per kilogram of hydrogen produced.
“In reality, the nine litres per kilogram is unrealistic for large-scale production, which is why we landed on 15 L per kilogram as our lower-bound figure,” Holland said.
These ranges are in alignment with Arup’s Water for Hydrogen paper, prepared for the Department of Climate Change, Energy, the Environment and Water and Australian Hydrogen Council which suggested typical real-world consumption of roughly between 30-70 L per kilogram, depending on specific conversion processes and technologies, cooling configurations and water sources. Totals are dominated by the water demands of cooling.
Quenching hydrogen’s thirst
When the challenge of producing green hydrogen on a national scale is brought into broad focus, the scale becomes clear.
“Based on figures from the last State of Hydrogen report – from 2022, so it hasn’t been updated for the latest one – you’d need an additional water supply equivalent to the water demand of half of Melbourne’s population to meet the hydrogen demand,” Madan said.
That’s just for the demands of Victoria. NSW would require water supply worth half of Sydney’s requirements, or around 150 GL per year. Queensland would need 160 GL, or 1.2 times the annual water requirements of Brisbane, and Western Australia 260 GL, or 2.3 times Perth’s annual needs.*
“When you compare it to other sectors like agriculture or mining, it’s not the biggest in terms of demand,” Madan said. “But it’s definitely not the smallest.”
Water has previously been considered quite a cheap input into the green hydrogen process.
“But we’re planning for the long-term resilience of Australia’s water sources and it is a scarce and variable resource.”
A major challenge, according to Holland, is not so much about whether a region has enough water to supply the green hydrogen sector, but rather about balancing demands. With water already scarce and increasingly perceived as highly valuable, projects requiring a large and sustainable water source can have a hard time getting off the ground.
Are there other water sources?
The analysis from Arup discussed comparative benefits and risks of various types of water.
- Recycled water: Abundant in cities, exceptional circular economy benefits, requires significant upgrades and is also being considered for competing uses such as purified recycled water for drinking
- Groundwater: Potential for reasonable quality but is already “almost fully allocated” and will always face serious challenges around social licence
- Surface water: Already required for drinking water, significantly dependent on rainfall, already almost fully allocated and faces social licence challenges
- Stormwater: Plentiful in short bursts, good for circular economy, good quality but high construction/storage costs and unreliable supply
- Seawater: Reliable at scale and could provide co-benefits for cities, but high construction costs and high energy use
So, is green hydrogen viable as a fossil-fuel substitute in Australia?
From the point of view of water engineering, it is viable in the right places and with technology that is more efficient than most of what we see in operation today. The most recent National Hydrogen Strategy 2024 has shifted to specific industrial applications and heavy transport.
Madan says from her understanding, the slowing of momentum has occurred because of the various broad challenges.
“The cost, infrastructure and market development has made it difficult for green hydrogen’s development to be as widespread as once planned,” Madan said.
Holland suggested the sector could provide a valuable co-benefit.
“We were looking up in the Pilbara, and if you can produce water for hydrogen, then it could also become an additional community water supply,” she said. “That was a bright light in some of our conversations.”
*These figures are based on indicative numbers and scenarios, annual domestic and export hydrogen demand as found in the National Hydrogen Infrastructure Assessment: Final Report (Arup, 2022), with hydrogen demand split by state/territory, central demand scenario, export demand distributed evenly between port locations.
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