Scaling carbon capture, utilisation and storage (CCUS) requires a rapid build-out of CO₂ transport infrastructure. Repurposing existing natural gas pipelines can significantly reduce lead time and upfront CAPEX relative to new CO₂ corridors where assets meet integrity and routing requirements, but it is not universally suitable. In practice, technical feasibility and economics depend on detailed assessments of materials, pressure regimes, impurities and regulatory classifications, drawing on benchmark CO₂ transport studies in Europe and other regions. At Energy Solutions, we evaluate when repurposing provides a technically robust, cost-efficient option and when new-build CO₂ pipelines remain the lower‑risk choice for long-term CCUS networks.
Large-scale CCUS deployment requires moving tens to hundreds of millions of tonnes of CO₂ per year from capture sites to storage or utilisation locations, in line with net-zero pathways that foresee multi‑gigaton deployment of CCUS by mid-century. In some systems, point-to-point projects can rely on dedicated pipelines, but many regions are planning shared CO₂ backbones collecting flows from multiple industrial clusters and power plants.
Existing natural gas networks often have spare capacity due to efficiency improvements, demand shifts or energy transition dynamics. This raises a practical question for system operators: can some of these pipelines be converted to CO₂ service to reduce the cost and lead time of creating CO₂ corridors, while meeting safety and regulatory requirements?
CO₂ has very different physical properties from natural gas, particularly when transported in dense-phase (supercritical) conditions to maximise capacity and reduce compression costs. Design envelopes therefore differ from legacy gas service and must reflect phase behaviour, impurities and fracture control for the expected operating window.
| Parameter | Typical Natural Gas Pipeline | Dense-Phase CO₂ Pipeline |
|---|---|---|
| Operating Pressure | 30–80 bar | 80–150 bar |
| Fluid State | Compressible gas | Dense-phase (near liquid-like) |
| Key Integrity Concern | Fatigue, corrosion | Corrosion with water, running fracture |
The chart below illustrates a simplified view of operating envelopes for gaseous vs dense-phase CO₂ and typical pipeline operating windows. It is indicative rather than a substitute for project-specific thermodynamic analysis.
Cost comparisons between new-build and repurposed pipelines depend heavily on context, but some indicative benchmarks are possible and broadly align with ranges reported in major European CO₂ transport cost studies for onshore networks of comparable scale.
| Option | Capacity | Distance | CAPEX Range | Indicative Transport Cost |
|---|---|---|---|---|
| New-Build CO₂ Pipeline | 5–10 MtCO₂/year | 150–300 km | 400–900 million USD | 15–30 USD/tCO₂ |
| Repurposed Gas Pipeline (Favourable Case) | 3–8 MtCO₂/year | 150–300 km | 200–500 million USD | 10–20 USD/tCO₂ |
| Repurposed Network Segment (Complex Upgrades) | 2–6 MtCO₂/year | 150–300 km | 300–700 million USD | 15–28 USD/tCO₂ |
Values exclude compression at capture sites and injection wells. Actual costs vary widely with terrain, permitting, material upgrades and utilisation, and should be cross-checked against regional benchmarks from recent CO₂ network studies before investment decisions.
The bar chart below shows how under-utilisation can increase transport costs for both new-build and repurposed pipelines, illustrating the importance of securing stable throughput for cost-effective backbone development.
Material integrity is a central concern when converting gas pipelines to CO₂ service. Operators must address the interaction between CO₂, water and impurities, and verify that steel toughness and wall thickness are adequate for dense-phase operating envelopes and potential decompression events.
A declining onshore gas region with an existing 250 km, 36" gas transmission pipeline explores repurposing one parallel string for CO₂ transport from industrial clusters to a storage hub.
A coastal industrial cluster (steel, cement, chemicals) aggregates CO₂ volumes of 8–10 MtCO₂/year for offshore storage. The project uses a repurposed onshore gas trunk for part of the route and a new-build offshore segment.
The case shows that hybrid solutions can leverage existing infrastructure where appropriate while acknowledging that new-build offshore lines are often unavoidable for access to deep storage.
Repurposing pipelines requires navigating regulatory frameworks that were often written with hydrocarbon transport in mind. Key questions include how CO₂ is classified, which codes apply, and how monitoring and verification obligations evolve over the asset life.
Clear frameworks for permitting, monitoring and liability transfer are critical for investment decisions, particularly for cross-border projects and multi-user networks.
The chart below shows a stylised breakdown of pipeline CAPEX, compression, OPEX and monitoring contributions to total transport cost; in many real projects, pipeline CAPEX dominates even more strongly, especially for long onshore routes.
There are strong reasons to be cautious about widespread repurposing, even where individual assets appear technically suitable.
These factors imply that repurposing is best targeted to assets with strong data quality and clear long‑term roles in regional decarbonisation plans, rather than being a blanket strategy for entire gas networks.
By 2035, several regions are likely to have established multi-user CO₂ transport networks, with corridor designs increasingly co-optimised with hydrogen backbones, high-voltage cables and other critical infrastructure. This creates opportunities to use rights-of-way efficiently but also raises competition between energy carriers.
Strategic planning at the national and regional level can help minimise regret investments, for example by:
For TSOs, midstream companies and industrial clusters, a structured screening framework improves decision quality and clarifies where repurposing is justified relative to new-build options.
No. Suitability depends on materials, wall thickness, weld quality, historical loading, corrosion status and route relevance. Only a subset of pipelines will meet technical, safety and economic criteria for CO₂ service.
In favourable cases, repurposing can reduce CAPEX by 20–50%. However, required upgrades can narrow this gap, especially where extensive modifications or new compression are needed. Under-utilised repurposed lines may end up with similar or higher transport costs than well-utilised new-build lines.
Severe internal or external corrosion, inadequate fracture toughness, incompatible materials for expected CO₂ and impurity conditions, and insufficient documentation of asset condition can all disqualify pipelines from safe CO₂ service without very costly remediation.
Some corridors may be better suited to hydrogen, others to CO₂. Strategic network planning should assess long-term decarbonization pathways and avoid short-term decisions that preclude higher-value uses of critical corridors.
In many jurisdictions, regulations are evolving. Some have begun updating pipeline and safety codes to include CO₂, while others still rely on hydrocarbon-based frameworks. Early engagement with regulators is essential to clarify expectations for design, monitoring and liability.
Liability allocation is context-specific. In some models, operators retain responsibility for as long as the line is in service; in others, state entities may assume long-term stewardship after a closure period. Clear contractual and regulatory arrangements are critical for investor confidence.
Reconversion is technically possible but may be constrained by material degradation, regulatory classification and economic viability. Decisions to convert to CO₂ service should therefore be made with a long-term perspective on regional energy and infrastructure needs.
From initial screening to operational CO₂ service, repurposing projects may require 4–7 years, including engineering studies, integrity assessments, permitting, financing and construction of upgrades. This is shorter than some greenfield projects but still substantial relative to climate timelines.