Hydrogen Transport via Pipelines: Infrastructure, Materials, and Repurposing Strategies

As the world shifts towards a low-carbon energy future, hydrogen is emerging as a central pillar of decarbonization strategies, particularly in hard-to-abate sectors such as heavy industry, long-haul transport, and chemical manufacturing. However, a robust hydrogen supply chain is essential to enable its widespread adoption, and pipeline transport plays a critical role in delivering hydrogen safely and economically over long distances.

This article explores the key technical, material, and economic considerations in transporting hydrogen via pipelines, highlighting the feasibility of repurposing natural gas pipelines, the challenges of hydrogen embrittlement, and case studies assessing Levelized Cost of Hydrogen (LCOH) for pipeline-based delivery.

Hydrogen Pipeline Infrastructure: The Need and the Challenge

Hydrogen can be transported via compressed gas trucks, liquefied hydrogen tankers, or pipelines. Among these, pipelines offer an efficient and cost-effective solution for large-scale, continuous, and long-distance transport.

Currently, hydrogen pipeline infrastructure exists in industrial clusters, particularly in the United States, Germany, Belgium, and France, primarily to serve petrochemical and refinery applications. For example, the U.S. Gulf Coast region hosts more than 1,600 miles (2,575 km) of hydrogen pipelines, mostly operated by industrial gas companies (IEA, 2021).

Yet, expanding this infrastructure to accommodate the hydrogen economy of the future, including green hydrogen produced via renewable-powered electrolysis, presents significant challenges. Chief among them is ensuring pipeline integrity, safety, and economic viability, particularly when using existing natural gas infrastructure.

Materials of Construction: Natural Gas vs Hydrogen Pipelines

Traditional natural gas pipelines are made from carbon steels (API 5L Grade B to X70), known for their mechanical strength, weldability, and cost-effectiveness. These materials perform well under the operating conditions typical for natural gas: pressures ranging from 30 to 100 bar and ambient temperatures.

However, hydrogen transport poses unique challenges:

• Molecular diffusivity: Hydrogen is the smallest molecule and can penetrate materials more easily than natural gas.
• High diffusivity leads to embrittlement: Hydrogen atoms can permeate steel and cause hydrogen embrittlement, reducing ductility and toughness.
• Leakage risk: Hydrogen molecules can escape through joints, valves, and even porous pipeline walls.

Therefore, dedicated hydrogen pipelines often use stainless steels (316L, 304) or polymer-lined pipelines, especially where higher pressures or aggressive environments are expected.

Repurposed Natural Gas Pipelines for Hydrogen: A Practical Approach

Given the high capital costs associated with new hydrogen pipelines, repurposing existing natural gas pipelines emerges as a highly attractive and cost-effective alternative.

Advantages:

• Utilizes existing rights-of-way and infrastructure
• Minimizes permitting and environmental hurdles
• Reduces capital expenditure by up to 60-70% (IRENA, 2022)

Challenges:

• Material compatibility and embrittlement risk
• Leak detection system upgrades
• Compressor modifications (due to hydrogen’s lower density)
• Risk of hydrogen-induced fatigue cracking

Options to Repurpose Natural Gas Pipelines

There are three primary strategies for repurposing:

1. Hydrogen Blending

Start by blending up to 5-20% hydrogen into existing natural gas pipelines, which many utilities have already initiated in Europe, Australia, and North America. This offers a low-cost, low-risk entry point.

2. Partial Conversion

Segments of a pipeline network are converted to carry higher hydrogen concentrations, with upgraded compressors and leak detection systems.

3. Full Conversion

The pipeline is entirely dedicated to 100% hydrogen. This requires material testing, weld inspection, and often retrofitting or replacing compressor stations, valves, and meters.

Inhibitors to Avoid Pipeline Embrittlement

To prevent hydrogen embrittlement and material degradation, several mitigation strategies are deployed:

• Material Selection: Use embrittlement-resistant alloys like austenitic stainless steel, or composite pipes.
• Surface Coatings: Internal epoxy or polymer coatings reduce hydrogen diffusion and corrosion.
• Cathodic Protection: Applied to buried pipelines to mitigate corrosion-induced embrittlement.
• Operational Adjustments: Lowering pressure cycling frequency and limiting peak operating pressure reduces fatigue risks.

Importantly, aging infrastructure with a history of micro-cracking or corrosion is less suitable for repurposing without rehabilitation.

Material of Construction for Hydrogen Pipelines

New-build hydrogen pipelines must consider long-term integrity and cost:

In addition, non-metallic composite pipelines are increasingly being evaluated for onshore and offshore hydrogen transport due to their corrosion resistance and ease of installation.

Case Study: Pipeline Transport and Levelized Cost of Hydrogen (LCOH)

To assess the economic viability of pipeline transport, several techno-economic models have been developed. A recent study by the International Renewable Energy Agency (IRENA, 2022) evaluated the LCOH for various transport scenarios.

Parameters:

• Distance: 300 km
• Flow rate: 1,000 tons/day
• Pipeline material: repurposed carbon steel
• Pressure: 100 bar (with booster compression every 150 km)
• CAPEX: $0.5-1 million/km
• OPEX: 2-4% of CAPEX annually

Results:

• LCOH for pipeline transport alone: ~$0.15-0.30/kg H₂
• Blending into existing pipelines: ~$0.10/kg H₂
• New-build hydrogen pipeline: ~$0.25-0.50/kg H₂

These values are significantly lower than trucking (compressed gas ~ $0.5–1.0/kg) or liquefaction (~$1.0–2.0/kg) for the same distance, underlining the economic edge of pipeline delivery, especially at scale.

Global Hydrogen Pipeline Projects

Several pilot and commercial-scale projects are underway globally:

• HyNet (UK): Repurposing existing gas pipelines in North West England to transport low-carbon hydrogen by 2025.
• H₂ercules (Germany): 1,200 km hydrogen backbone connecting industrial regions and ports by 2030.
• European Hydrogen Backbone (EHB): A vision to create a 39,700 km hydrogen pipeline network across 28 European countries by 2040, with ~60% being repurposed gas pipelines.

These initiatives are not just regional milestones but critical enablers of international hydrogen trade.

Way Forward: Planning the Hydrogen Pipeline Economy

Developing a national or regional hydrogen pipeline network requires an integrated approach involving:

• Material compatibility assessments
• Safety regulations and codes
• Incentive frameworks for repurposing
• Hydrogen-ready infrastructure mandates
• Cross-border coordination

From a policy standpoint, governments must support pre-commercial investments, especially in the early stages of pipeline hydrogen transport infrastructure, where risks outweigh immediate returns.

Conclusion

Hydrogen pipelines offer a technically feasible and economically competitive route for large-scale, long-distance hydrogen transport. While material compatibility and embrittlement remain challenges, advances in metallurgy, coatings, and pipeline monitoring offer viable mitigation pathways.

Repurposing existing natural gas pipelines provides a transitional bridge, reducing cost and accelerating hydrogen infrastructure deployment. Strategic investments, international cooperation, and clear regulatory frameworks will be critical in transforming today's gas grids into tomorrow's hydrogen highways.

References

• International Energy Agency (IEA). (2021). Global Hydrogen Review 2021. Paris: IEA. https://www.iea.org/reports/global-hydrogen-review-2021
• International Renewable Energy Agency (IRENA). (2022). Global Hydrogen Trade to Meet the 1.5°C Climate Goal: Part II – Technology Review of Hydrogen Carriers. Abu Dhabi: IRENA. https://www.irena.org/publications
• Wulff, A., Kreitmeier, F., & Theisen, A. (2021). Hydrogen pipelines: A review of material challenges and design considerations. International Journal of Hydrogen Energy, 46(43), 22459–22472. https://doi.org/10.1016/j.ijhydene.2021.03.082
• Melaina, M. W., Antonia, O., & Penev, M. (2013). Blending Hydrogen into Natural Gas Pipeline Networks: A Review of Key Issues. National Renewable Energy Laboratory (NREL/TP-5600-51995). https://www.nrel.gov/docs/fy13osti/51995.pdf
• European Hydrogen Backbone (EHB). (2023). EHB Initiative: Expanding Hydrogen Infrastructure across Europe. https://ehb.eu/