July 2025, Vol. 252, No. 7
Guest Perspective
Why Australia’s Hydrogen, CO2 Pipelines Can’t Be a Copy of Gas Networks
By Peter Cox, Vice President, Upstream Onshore & Midstream, Worley
(P&GJ) — Australia has made hydrogen and carbon capture and storage (CCS) central pillars of its net zero strategy. While electrification has a major role in cutting emissions, it is not always viable for sectors such as heavy industry, chemicals and long-distance transport.
Hydrogen and CCS offer practical alternatives in these harder-to-abate areas but delivering them at scale will require an enormous expansion of national infrastructure.
The Net Zero Australia Study found that reaching net zero by 2050 using today’s technology could require nearly 9,350 mi (15,000 km) of hydrogen pipelines, 12,500 mi (20,000 km) of carbon dioxide (CO2) pipelines and about (8,000 km) of water pipelines, depending on the scenario.
To put that in perspective, Australia has built roughly 26,100 mi (42,000 km) of gas pipeline over the last 60 years. That feat will now need to be repeated in just 25 years.
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Complicating matters, hydrogen and CO2 behave differently from natural gas, and existing infrastructure needs to be adapted to suit their unique properties. Existing infrastructure is also often still needed for gas or is not in the right location for the new services required.
By designing new pipelines around these differences from the outset, we can ensure they are safe, resilient and future-ready. Advanced digital tools and simulations now allow us to model performance in advance, fast-tracking delivery and supporting Australia’s net zero strategy.
Clean Slate
For some regions, repurposing parts of the existing gas network for hydrogen or CO2 makes practical and economic sense. In Europe, for example, falling natural gas demand and greater pipeline redundancy have created conditions suitable to converting entire stretches of network to hydrogen, which will help reduce costs and accelerate progress.
However, most of Australia’s current gas network is still essential for domestic, export and industrial energy supply meaning there is very limited capacity that can be taken offline or converted. Only a handful of pipelines, such as part of the Parmelia Gas Pipeline in Western Australia, are being explored for conversion, and those require upgrades to meet safety and performance requirements.
Since repurposing is only likely to play a small role, Australia has a rare opportunity to build an entirely new network from the ground up, without the compromises of adapting infrastructure designed for an earlier energy system. With a clean slate, we can design purpose-built hydrogen and CO2 pipelines that are safer, more efficient and better integrated with renewables, storage and industrial demand from the very beginning.
However, building from scratch also means tackling the distinct technical challenges these new energy carriers present. From material selection to pressure management, the engineering must be tailored to the unique behaviors of each, yet it must also be optimized for lower costs, to build the business case for their construction.
Material Challenges
When it comes to hydrogen, one of the most critical issues is how it interacts with pipeline materials. It introduces a range of material risks, including hydrogen embrittlement, a weakening of steel caused by long-term exposure to hydrogen. This makes pipelines more prone to cracking, particularly under mechanical stress and pressure fluctuations.
In hydrogen systems, especially those used for storage or those linked to variable renewable energy, pressure rises and falls as production ramps up and down. These fluctuations place repeated stress on the pipeline and, when combined with embrittlement, can increase the rate at which cracks form and grow.
Hydrogen — and the impurities that can be present within it — can also cause other forms of degradation, such as hydrogen-induced cracking, blistering and sulfide-stress cracking. Managing these risks requires fatigue to be factored into the design from the beginning. Pipeline steel must be carefully selected for hydrogen service, as not all grades provide the fracture toughness and fatigue crack growth resistance needed to withstand cyclic loading over time.
In some cases, thicker walls are needed, and the safety margins used for natural gas pipelines often need to be adjusted to reflect hydrogen’s different behavior.
Defects that may meet acceptance criteria in conventional pipelines, such as ovality, edge offset or small surface flaws, can significantly reduce fatigue life in hydrogen service. These imperfections act as stress concentrators, making cracks more likely to initiate and grow over time. Advanced modelling is needed to help manage these risks from the start.
Tools like fracture mechanics and finite element analysis allow engineers to assess how such flaws might behave under real operating conditions, well before materials are selected or installed.
Rethinking Welding
Another consideration is that, at present, there are no welding codes specifically written for hydrogen pipelines. Some existing standards may still be useful, but these standards do not address key risks, such as pressure cycling or the residual stresses left behind after welding.
In the absence of hydrogen-specific standards, Engineering Critical Assessments (ECAs) offer a practical and well-established method to assess weld integrity under these conditions. Commonly used in strain-based pipeline design, ECAs can be adapted for hydrogen service by incorporating relevant material properties, such as fracture toughness, to manage the fatigue crack growth rate. Paired with digital modelling, they provide a more realistic understanding of weld performance under variable pressure.
Pipelines for CO2
While the engineering approach for CO2 shares similarities with hydrogen, its transportation brings a different set of technical challenges. Meeting the need for up to 12,425 mi (20,000 km) of pipelines will require infrastructure that is tailored to CO2’s properties, including how it behaves under pressure and in the presence of impurities.
CO2 is ideally transported in a dense, high-pressure state to make pipelines more efficient. However, if a failure occurs — due to unauthorized excavation, for instance — the way the CO2 decompresses is different than natural gas. The pressure does not drop all at once. Instead, it remains relatively constant as the phase changes, which maintains the stress at the crack tip and can allow cracks to keep running, unless the pipeline is designed specifically to arrest them.
Fracture arrestors are one option, but they are costly. A more effective strategy is to analyze fracture behavior early and use that information to guide choices on materials, layout and wall thickness. With the right combination, pipelines can be designed to contain a failure to the vicinity in which it occurs. Digital fracture modelling allows engineers to test failure scenarios and refine design parameters before committing to construction.
Corrosion is another critical factor. CO2 can carry significantly more water than methane, and when that water condenses inside the pipeline — especially during temperature drops on depressurization — it becomes highly corrosive. Impurities such as hydrogen sulfide and oxygen increase the risk further. To reduce this, dehydration needs to be much more stringent than in natural gas systems. However, even with tighter specifications, residual moisture can still pose a threat once operating conditions change.
As with fracture control, early modelling plays a key role. In this case, the focus is on how dense-phase CO2 behaves chemically and thermally over time. Tailored corrosion models that account for flow rate, pressure, temperature and impurities allow engineers to design systems that minimize the risk of material degradation and extend pipeline life with greater confidence.
Getting It Right
The engineering bar for hydrogen and CO2 pipelines is high, and it must be. These pipelines are critical to Australia’s energy future and will need to operate safely and reliably for decades. Mistakes made during design can’t easily be corrected later. With the scale and complexity of this infrastructure, getting it right the first time is essential.
The good news is that new digital technologies and modeling tools make this possible. By leveraging these innovations, Australia can meet the ambitious pace of the energy transition and build the infrastructure needed for long-term success.
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