As the world transitions to net-zero emissions, urban gas networks face an uncertain future. With increasing electrification and the decline of natural gas use for residential and commercial heating, the question arises: what happens to the vast infrastructure of gas pipelines beneath our cities? This paper explores potential pathways for repurposing, decommissioning, or maintaining these networks in a sustainable energy system.

1. Introduction

Australia’s urban landscapes are built on extensive gas distribution networks, supplying homes and businesses with natural gas for heating, cooking, and industrial use. However, with state governments implementing gas substitution policies and promoting electrification, the long-term role of these networks is in flux (2024 Gas Statement of Opportunities [GSOO]).

This paper examines the fate of gas pipelines beneath Australian cities, assessing decommissioning options, repurposing for renewable gases, and the economic and environmental challenges of maintaining legacy infrastructure.

2. The Decline of Urban Gas Use

2.1 Policy and Market Shifts

Governments are accelerating gas phase-out strategies, particularly in Victoria and the ACT, where new gas connections are being restricted (2024 WA Gas Statement of Opportunities [WA GSOO]). Key factors driving this decline include:

• Building electrification mandates reducing new gas connections.
• Rising gas prices making electricity a more competitive option (2024 Electricity and Gas Networks Performance Report).
• Emissions reduction targets promoting low-carbon heating solutions.

2.2 Declining Consumer Demand

Residential and small business gas demand is expected to plummet over the next two decades, leaving cities with underutilised pipeline networks (Gas Demand Forecasting Methodology 2020).

3. The Fate of Underground Gas Infrastructure

3.1 Decommissioning and Removal

One option is the full decommissioning of gas networks, which involves:

• Capping or removing pipelines to prevent leaks.
• Transitioning gas network workers to new roles in electricity and renewables.
• Minimising long-term maintenance costs for utilities and governments.

However, decommissioning presents financial and logistical challenges, including the high costs of excavation and public safety concerns (Consultation Paper – Stage 2 of the Reliability and Supply Adequacy Framework).

3.2 Repurposing for Hydrogen and Biomethane

An alternative is repurposing gas networks for renewable gases such as:

• Hydrogen: Some pipelines can be modified to transport blended hydrogen or 100% hydrogen.
• Biomethane: A direct substitute for natural gas, biomethane can be injected into existing pipelines (Future Gas Strategy Analytical Report).

While repurposing gas infrastructure is technically feasible, it requires significant investment in upgrades, particularly in leak-prone older networks (2024 WA GSOO Visual Overview).

3.3 Hybrid Energy Systems

Some proposals suggest integrating district heating systems or thermal energy storage into existing pipeline routes, creating new urban energy solutions without full network decommissioning (2024 Gas Statement of Opportunities [GSOO]).

4. Economic and Environmental Considerations

• Stranded Asset Risk: As electrification progresses, existing gas infrastructure risks becoming obsolete, creating financial losses for utilities and governments (2024 Electricity and Gas Networks Performance Report).
• Environmental Concerns: Abandoned gas pipelines may pose risks such as methane leaks if not properly decommissioned (2024 WA Gas Statement of Opportunities [WA GSOO]).
• Workforce Transition: Gas utilities will need to retrain workers for electrification, hydrogen, and infrastructure maintenance roles (Future Gas Strategy Analytical Report).

5. Conclusion

The future of gas networks under cities depends on policy direction, economic feasibility, and technological advancements. While full decommissioning is costly, repurposing for hydrogen or biomethane offers potential pathways to maintain their relevance. Governments and industry must carefully plan the transition to ensure urban energy resilience, minimise financial losses, and support a sustainable future.

References
(Sources cited throughout the paper, including 2024 GSOO, Future Gas Strategy Analytical Report, Electricity and Gas Networks Performance Report, and relevant government policies.)