PCS TG 003 Transport System Guidance_v1.0
Document Control
Document identification
Document code: PCS-TG-003
Title: Technical Guidance for CO₂ Transport Systems
Scope: Guidance for pipeline, ship, road, and rail CO₂ transport; transport boundary definition; CO₂ quality maintenance; metering points; mass balance and reconciliation; losses/venting; leak detection; calibration; uncertainty; and reporting under PCS
Application: Supports application of the PCS CCS methodology and informs VVB assessment of transport MRV integrity and loss accounting
Version history and change log
Table DC-1. Revision history
v1.0
TBD
Draft
Release for public consultation
PCS
TBD
Superseded versions
No superseded versions for v1.0.
Governance note on versioning and archiving
Only the latest approved version of this Technical Guidance shall be used for new project registrations and related submissions. Superseded versions shall be archived and retained for traceability and audit purposes, including for projects registered under earlier versions where applicable, consistent with PCS governance rules.
Purpose and scope summary
Purpose
This Technical Guidance sets technical expectations for accurate, conservative, and verifiable accounting of CO₂ transported from capture to storage, including quantification of losses and emissions within the transport boundary.
Scope summary
This guidance applies to all CO₂ transport modes used by PCS projects and provides technical depth to ensure consistent monitoring, reconciliation, and reporting for verification.
Relationship to PCS standards and methodologies
This guidance supports the CCS methodology suite and shall be read alongside applicable PCS requirements on MRV, safeguards, and governance. Where conflict exists, the PCS Framework, Program Manual, and applicable Methodology/Module prevail.
Chapter 1 — Introduction And Scope Of CO₂ Transport Guidance
1.1 Purpose of the Transport Technical Guidance
The safe and reliable transport of CO₂ is a critical link between capture facilities and geological storage sites. Transport systems ensure that CO₂ captured upstream is delivered in a condition that meets the physical, chemical, and regulatory requirements for permanent storage. Although transport does not change the mass of CO₂ in a chemical sense, it introduces operational conditions and technical risks that may lead to losses or emissions if not carefully managed.
This guidance provides the technical expectations for monitoring, measurement, engineering integrity, and reporting associated with CO₂ transport under the Planetary Carbon Standard (PCS). It supports developers, operators, and Validation and Verification Bodies (VVBs) by defining the principles needed to manage transport risks, quantify CO₂ flows accurately, and maintain system transparency. While the PCS methodology specifies how CO₂ transport is accounted for in emissions reduction projects, this document explains how transport systems must be designed and operated to meet those requirements in practice.
1.2 Scope of Application
This guidance applies to all CO₂ transport systems associated with PCS-registered projects, regardless of transport mode, pipeline diameter, pressure regime, CO₂ phase, or carrier system. It covers:
Pipeline transport of CO₂ in gaseous, dense-phase, or supercritical form
Ship-based CO₂ transport systems using refrigerated or pressurized vessels
Road tanker and rail transport for smaller-scale CO₂ movement
Temporary storage systems such as buffer tanks, terminal storage units, or loading facilities
The guidance addresses both single-user and multi-user networks. Multi-user systems, including shared pipelines or coastal terminals, may require additional coordination in monitoring and mass balance reconciliation.
The document applies equally to onshore and offshore transport systems and covers both newly constructed and repurposed infrastructure. Operators must demonstrate that transport conditions remain compatible with downstream injection, storage operations, and safety requirements.
1.3 Relationship to PCS Methodologies and Other Technical Guidance
This Transport Technical Guidance complements two other PCS documents:
Capture Technical Guidance, which defines the CO₂ quality and monitoring requirements upstream of transport; and
Geological Storage Technical Guidance, which defines requirements for CO₂ injection and long-term containment downstream.
Transport guidance forms the central link between these documents. It ensures that the gas stream leaving the capture system remains suitable for transport and that the gas stream arriving at the storage facility meets its acceptance criteria. The guidance also aligns with the PCS CCS methodology, which defines how net emission reductions are quantified, including transport-related emissions, losses, and energy use.
The document builds on internationally recognized standards such as ISO 27913, ISO 27916, ASME pipeline codes, DNV CO₂ transport frameworks, and relevant experience from natural gas and industrial gas pipeline operations. It does not replace national regulations but provides a harmonized technical basis for PCS verification across jurisdictions.
1.4 Objectives of CO₂ Transport Monitoring and Verification
Transport monitoring serves several key functions. It confirms that the mass of CO₂ entering the transport system matches, within reasonable accuracy and uncertainty, the mass delivered to the storage system. It ensures that any losses, venting events, or leakage are identified, quantified, and incorporated into project emissions accounting. Monitoring also verifies that CO₂ quality remains within acceptable thresholds during transport, ensuring compatibility with transport equipment and storage reservoir requirements.
Verification by VVBs relies heavily on transport monitoring data, including flow measurements, purity records, pressure and temperature logs, and maintenance documentation. This guidance defines the expectations for measurement methods, calibration procedures, data handling, uncertainty quantification, and reporting practices that allow transport performance to be verified consistently and confidently.
1.5 Key Characteristics of CO₂ Transport That Influence Monitoring
CO₂ transport differs from conventional natural gas transport because CO₂ behaves uniquely under pressure and temperature variations. Its phase can change rapidly, affecting density, compressibility, and flow behavior. Moisture and impurities can increase corrosion risk or form solids and hydrates that affect pipeline safety. Transport systems may involve compression stations, dehydration units, pressure letdown valves, and safety relief systems that create operational points where CO₂ could be lost.
Ship transport introduces additional dynamics related to cryogenic temperatures, tank pressure management, boil-off gas handling, and loading/unloading operations. Road and rail systems involve discrete batch movements, transfer points, and portable tanks with venting requirements.
All these characteristics require monitoring systems designed to capture the physical behavior of CO₂ as well as operational events that may influence loss accounting, mass balance, and data quality.
1.6 Transport System Boundary Definition Under PCS
Under PCS, the transport boundary begins at the point where CO₂ leaves the capture system’s measurement/control point and enters the transport network. The boundary ends at the custody transfer point where CO₂ enters the injection system or storage facility. For ship or tanker transport, the boundary includes loading terminals, bulk CO₂ tanks, voyage conditions, and unloading systems.
Defining the boundary ensures that emissions, losses, and energy consumption associated with transport are properly accounted for. It also ensures continuity between the upstream and downstream parts of the CCS chain. Operators must clearly describe the boundary in the Project Design Document and must identify all metering points, intermediate storage, potential leakage points, and energy-consuming equipment.
1.7 Structure of This Document
The remainder of this guidance is organized into chapters that describe:
transport modes and their operating principles;
engineering integrity requirements for pipelines, ships, and tankers;
monitoring and measurement systems;
loss accounting and venting quantification;
risk assessment and safety considerations;
data quality and calibration expectations; and
reporting obligations for verification.
Each chapter explains what operators must demonstrate to meet PCS requirements, while annexes provide technical tables, equipment specifications, and calculation examples.
1.8 Foundational Principles for PCS Transport Guidance
Transport under PCS must adhere to four core principles:
Accuracy — CO₂ quantities must be measured using calibrated, suitable instruments at both the inlet and outlet of the transport boundary.
Containment — systems must maintain CO₂ integrity and prevent avoidable losses, leaks, or venting.
Compatibility — CO₂ delivered to the storage facility must meet purity, moisture, and phase criteria required for safe injection and containment.
Transparency — all data, incidents, maintenance events, and deviations must be fully documented and available for validation and verification.
These principles ensure that transport performance is reliable, safe, and aligned with the environmental objectives of the Planetary Carbon Standard.
Chapter 2 — Overview Of CO₂ Transport Modes
2.1 Purpose of This Chapter
CO₂ may be transported through pipelines, by ship, or via road or rail tanker systems depending on project scale, geographic constraints, storage site location, and commercial considerations. Each transport mode has distinct physical, operational, and monitoring characteristics that influence the way CO₂ must be measured, conditioned, and controlled under the Planetary Carbon Standard (PCS).
This chapter provides an overview of these transport modes, the principles governing their operation, and the implications for monitoring and verification. Understanding these characteristics is essential before defining the engineering, safety, and MRV requirements that appear in later chapters.
2.2 Pipeline Transport of CO₂
Pipeline transport is the most widely used and technically mature mode for conveying CO₂ at industrial scale. Pipelines typically operate with CO₂ in a dense-phase or supercritical state, which provides high transport efficiency and reduces compressibility effects. The ability to maintain CO₂ above its critical pressure ensures stable flow, predictable phase behavior, and minimal energy losses.
Pipeline systems include compression stations, block valves, pressure control systems, monitoring points, and occasionally intermediate pumping stations. The physical behavior of CO₂ requires careful management of temperature and pressure to avoid phase transitions that could lead to vibrations, cavitation, or hydrate formation. Corrosion control is essential, especially when moisture or impurities such as oxygen or sulfur compounds are present.
For PCS purposes, pipelines require inlet and outlet metering, pressure and temperature monitoring, leak detection systems, and documentation of operational conditions. Pipelines may serve a single project or operate as part of a multi-user network, in which case mass balance reconciliation and custody transfer procedures become critical.
2.3 Ship-Based CO₂ Transport
Ship transport is increasingly used where storage sites are located offshore or where transport distance makes pipelines impractical. Ships carry CO₂ either as refrigerated liquid at low temperature and moderate pressure, or in pressurized tanks, depending on the vessel design.
Refrigerated CO₂ transport typically maintains temperatures around −50°C and pressures between 6 and 8 bar, keeping CO₂ in a dense liquid state. Pressurized CO₂ transport maintains higher pressures without deep refrigeration. In both cases, tank integrity, insulation, cooling systems, and pressure management are essential to prevent venting or boil-off losses.
Ship transport involves measurement at loading terminals, custody transfer, onboard monitoring during voyage, and measurement at unloading terminals. Losses may occur through boil-off or safety venting mechanisms, and these must be quantified. Monitoring systems must account for temperature gradients, tank pressure behavior, and mass reconciliation between loading and unloading.
The flexibility of shipping enables regional CO₂ transport hubs and cross-border storage, supporting decarbonization pathways in areas without suitable geological storage formations.
2.4 Road Tanker Transport
Road tanker transport is used primarily for small-scale CO₂ movement, temporary operations, pilot projects, or facilities with limited capture volumes. Tankers typically transport CO₂ as a refrigerated liquid under moderate pressure. Due to their smaller capacity and batch nature, road tankers require careful reconciliation of loaded and delivered quantities.
Monitoring includes mass measurement during loading, verification of tank conditions during transport, and measurement during unloading. Operators must maintain logs documenting pressure, temperature, and any venting events, particularly during periods of parking, idling, or unloading under warm conditions.
While road tankers are not cost-effective for large volumes, they provide operational flexibility and serve niche transport needs, especially during early project phases.
2.5 Rail-Based CO₂ Transport
Rail transport offers an intermediate option between road tankers and pipelines or shipping. Rail tank cars can transport larger volumes than road tankers and can serve industrial regions with established rail infrastructure.
Like road tankers, rail systems typically transport CO₂ in refrigerated or pressurized tanks. Monitoring focuses on custody transfer, temperature and pressure stability, venting control, and reconciliation of batch volumes. Because rail systems may involve long journey durations, environmental exposure and thermal fluctuations must be monitored and managed.
Rail transport is particularly suited to continental transport networks or regions where pipeline permitting presents challenges.
2.6 Intermediate Storage and Terminal Facilities
Transport modes often require intermediate storage, such as:
buffer tanks at pipeline inlets;
receiving tanks at pipeline outlets;
port terminals for ship loading and unloading;
bulk storage at industrial hubs;
temporary storage for DAC or small capture plants.
Intermediate storage introduces additional points where CO₂ may undergo pressure, temperature, or phase changes. Tanks must maintain CO₂ within defined stability conditions, and boil-off or pressure relief events must be monitored and quantified.
For PCS MRV, each storage unit becomes part of the transport boundary unless explicitly excluded by design. Measurement before and after intermediate storage is necessary to determine whether losses occurred.
2.7 CO₂ Conditioning Requirements for Transport
Before entering a transport system, CO₂ must be conditioned to meet its phase and purity requirements. Conditioning may include:
final dehydration;
impurity removal;
pressure and temperature stabilization;
filtration to remove particulates;
refrigeration (for ship or tanker transport).
Transport systems require CO₂ to remain within specific operational windows to avoid corrosion, freezing, hydrate formation, or mechanical instability. Deviations from these requirements may necessitate venting or cause equipment limitations, making conditioning a key determinant of transport safety and reliability.
2.8 Comparison of Transport Modes
Although all transport modes move CO₂ from capture to storage, they differ significantly in scale, energy requirements, operational risks, and monitoring needs.
Pipeline transport provides continuous flow and is suited for large volumes but requires precise phase management and integrity controls. Ship transport accommodates international movement and enables regional CO₂ hubs but introduces refrigerant systems and boil-off management. Road and rail transport provide flexibility but are batch-based and more susceptible to thermal variations and venting dependencies.
These differences influence the design of monitoring programs and the type of data needed for verification. Operators must select instruments and procedures appropriate for the chosen transport mode and ensure consistency with PCS requirements.
2.9 Role of Transport in the Overall CCS Chain
Transport systems act as the central conduit connecting capture and storage. Their reliability influences the entire CCS value chain. If transport systems fail to deliver CO₂ at the correct purity, pressure, or temperature, injection operations may be disrupted or compromised. If transport losses are not measured or reported, the environmental integrity of the project is weakened.
By presenting a structured overview of transport modes, this chapter prepares developers and VVBs for the detailed engineering, monitoring, loss accounting, and reporting requirements presented in the chapters that follow.
Chapter 3 — Engineering Requirements For CO₂ Transport Systems
3.1 Purpose of Engineering Requirements
Engineering requirements ensure that CO₂ transport systems operate safely, maintain containment integrity, and preserve the physical and chemical properties of CO₂ as it moves toward the storage site. Transport systems must withstand variable pressures, environmental conditions, and operational stresses. They must also manage phase behavior, corrosion risks, and loading/unloading operations with high reliability.
This chapter sets out the engineering principles that must be incorporated into the design and operation of CO₂ transport infrastructure under PCS. These principles apply across all transport modes and support consistent monitoring, verification, and reporting.
3.2 CO₂ Pipeline Engineering Requirements
Pipeline systems form the backbone of large-scale CO₂ transport. Their engineering requirements are determined by pressure, temperature, CO₂ composition, terrain, and safety considerations. Pipelines must be constructed using materials compatible with CO₂-rich streams. Steel grades must be selected based on expected operating pressures, fracture resistance, susceptibility to corrosion, and potential for embrittlement.
Pipeline design must ensure that CO₂ remains in a stable phase, typically dense-phase or supercritical. Operating pressures must be maintained above the minimum pressure required to avoid two-phase flow. Pressure control stations, block valves, and temperature management systems are essential components of pipeline integrity.
Corrosion control is particularly important because CO₂ mixed with moisture can form carbonic acid, which accelerates metal degradation. Trace impurities such as H₂S, SO₂, and O₂ can intensify corrosion risk. Engineering measures such as dehydration units, corrosion-resistant alloys, coatings, and continuous monitoring of moisture and impurity levels must be incorporated into pipeline design.
3.3 Compression and Pressure Management
Transporting CO₂ via pipeline requires the maintenance of adequate pressure levels along the route. Compression stations may be needed at intervals to compensate for pressure decline due to frictional losses. Compressors must be designed for CO₂ service, with materials and seals capable of handling dense-phase conditions. Vibration control, surge protection, and lubrication management are essential for maintaining mechanical integrity.
Pressure management systems must include relief valves, surge tanks, and automated shutoff mechanisms to prevent overpressure events. Temperature fluctuations associated with pressure changes must also be considered, as Joule–Thomson effects can result in cooling that may produce hydrates if moisture is present.
These engineering measures ensure predictable system performance and protect both equipment and personnel.
3.4 Pipeline Integrity Management
Pipeline integrity management requires continuous attention to the physical condition of the line. Operators must perform regular inspections, which may include in-line inspection tools, pressure tests, corrosion probes, and external monitoring systems. Integrity risks such as corrosion, mechanical damage, axial strain, geotechnical movement, or fatigue must be evaluated and addressed.
Pipeline coatings, cathodic protection systems, and monitoring of wall thickness contribute to long-term integrity. Operators must maintain detailed records of inspection results, maintenance actions, and any anomalies encountered. These records support PCS verification by demonstrating that the transport system has remained within safe and reliable operating limits.
3.5 Engineering Requirements for Ship-Based CO₂ Transport
Ship transport involves moving CO₂ in either refrigerated or pressurized liquid form. Refrigerated ships maintain CO₂ at low temperatures using onboard refrigeration systems and insulated tanks. These tanks must be designed to withstand thermal contraction, pressure buildup, and marine environmental stresses. Materials must remain ductile at cryogenic temperatures to avoid fracture risk.
In pressurized ships, CO₂ is kept above its vapor pressure through mechanical pressurization. Tanks must be engineered to withstand internal pressure fluctuations caused by ambient temperature changes and handling operations.
All ships require systems to manage boil-off gas. Boil-off may be reliquefied, compressed for storage, or safely vented during emergency conditions. Operators must design piping, pressure control systems, valves, and monitoring equipment to manage these dynamics and ensure safe containment throughout the voyage.
Ship engineering also includes loading and unloading systems at port terminals. These terminals must include transfer lines with pressure and temperature regulation, measurement systems for custody transfer, surge protection, and emergency shutdown mechanisms.
3.6 Engineering Requirements for Road and Rail Tanker Transport
Road and rail tankers typically transport CO₂ as a refrigerated or pressurized liquid. Tanks must be engineered for thermal insulation, structural integrity, and pressure containment. They must also incorporate safety valves, emergency venting mechanisms, and temperature monitoring systems to prevent accidental overpressure during warm weather or extended idle periods.
For rail transport, tank cars must comply with weight limits, shock resistance requirements, and coupling standards. Both road and rail systems require robust loading and unloading infrastructure that includes pressure-regulated hoses, protective couplings, transfer pumps, and accurate weighing or flow measurement systems.
Because road and rail transport involve batch deliveries, engineering design must support precise reconciliation of loaded and delivered volumes.
3.7 Intermediate Storage and Terminal Facility Design
Intermediate storage tanks serve as buffers between capture facilities, transport systems, and injection operations. These tanks must be engineered to maintain CO₂ within stable pressure and temperature ranges. They must include insulation, refrigeration or cooling systems when required, relief valves, and automated monitoring systems for liquid level, pressure, and temperature.
Terminals at ports or pipeline junctions must integrate safe loading and unloading zones, spill containment systems, emergency shutdown controls, and appropriate ventilation for enclosed spaces. Terminal design must support accurate metering and sample collection to ensure high-quality custody transfer records.
3.8 CO₂ Composition and Materials Compatibility
CO₂ containing impurities or moisture presents specific material compatibility challenges. Carbonic acid formation can corrode steels, while hydrogen sulfide and sulfur dioxide may cause localized corrosion. Oxygen and water can promote internal oxidation. Engineers must select materials that resist these mechanisms, including carbon steel with corrosion allowances, stainless steels, nickel alloys, or liners when required.
Temperature variations, particularly in ship or pipeline transport, may cause embrittlement or fatigue in unsuitable materials. Engineering procedures must assess material performance under expected operating temperatures, pressures, and impurity concentrations.
3.9 Hydrate Formation and Phase Stability
Hydrate formation poses a major operational risk, particularly in pipelines and ship storage systems. Hydrates are crystalline structures formed when CO₂ and water coexist under low-temperature, high-pressure conditions. They can block valves, restrict flow, damage pipelines, and create hazardous pressure buildups.
Maintaining CO₂ below moisture thresholds and above critical temperature or pressure is essential. Hydrate inhibitors, insulation, active heating, or controlled decompression may be used to mitigate risks. Operators must demonstrate an understanding of their hydrate formation envelope and incorporate mitigation strategies into both design and monitoring programs.
3.10 Safety Systems and Emergency Shutdown Requirements
Transport systems must incorporate safety devices that prevent catastrophic failure, protect personnel, and preserve system integrity. These devices may include emergency shutdown valves, rupture discs, fire suppression systems, gas detection units, vent stacks, pressure relief valves, and monitoring alarms.
Emergency shutdown procedures must be designed to isolate CO₂ flow, relieve excess pressure, and prevent uncontrolled releases. All safety systems must be tested regularly, and results must be documented. Operators must also develop emergency response plans tailored to transport mode and location.
3.11 Documentation of Engineering Design and Operational Boundaries
For PCS verification, operators must maintain a comprehensive description of the engineering design, operational boundaries, and equipment specifications of the transport system. Documentation must include pipeline or tank design pressure, maximum allowable operating pressure, material specifications, corrosion control strategies, insulation systems, pressure and temperature envelopes, and installation diagrams.
This documentation provides the basis for assessing whether the transport system is physically capable of maintaining CO₂ integrity and meeting monitoring expectations.
Chapter 4 — CO₂ Quality Requirements During Transport
4.1 Purpose of CO₂ Quality Requirements
The quality of CO₂ transported from capture facilities to storage sites determines both operational safety and system reliability. During transport, CO₂ must remain within specific purity, moisture, and compositional limits to prevent corrosion, hydrate formation, flow instability, and injection failures. Ensuring consistent CO₂ quality safeguards the integrity of pipelines, shipping systems, terminals, and storage reservoirs.
This chapter describes the technical expectations for CO₂ quality under PCS. These requirements apply to all transport modes and must be incorporated into design, monitoring, and operational procedures.
4.2 Importance of Purity Control in Transport
Purity determines the percentage of CO₂ relative to other gases such as nitrogen, oxygen, argon, hydrogen, or hydrocarbons. Variations in purity influence CO₂ density, compressibility, energy use, and phase behavior. High levels of non-condensable gases can disrupt compression and cause oscillations in pipeline flow or instability in ship tanks. Purity also affects the injectivity of storage reservoirs and may influence long-term geochemical interactions.
CO₂ entering the transport system must meet the purity specifications agreed upon by the storage operator or pipeline owner. These specifications ensure that the CO₂ stream behaves predictably under pressure and temperature variations and does not compromise material integrity.
PCS requires purity monitoring at the entry point to transport and recommends additional checks at intermediate storage or custody transfer points.
4.3 Moisture Limits and Corrosion Risk
Moisture is one of the most critical impurities affecting CO₂ transport. Even trace amounts of water can form carbonic acid when mixed with CO₂, accelerating corrosion of steel pipelines, valves, fittings, and pressure vessels. Moisture can also contribute to hydrate formation under certain temperature and pressure conditions.
To minimize these risks, CO₂ must be dehydrated before entering the transport system. Moisture concentrations must remain below defined thresholds, typically expressed in parts per million by volume (ppmv). These limits are based on the hydrate formation envelope, corrosion resistance of materials, and operational considerations.
Moisture must be measured downstream of any dehydration system and close to the transport inlet meter to ensure accuracy. Any deviations from moisture thresholds must be addressed immediately and documented in monitoring reports.
4.4 Impurities and Their Operational Impacts
CO₂ streams may contain impurities such as oxygen, nitrogen, sulfur species, hydrocarbons, or trace solvents (for example, amine remnants). These impurities can influence corrosion potential, phase behavior, environmental safety, and storage facility acceptance.
Oxygen may increase corrosion rates and promote chemical degradation in storage reservoirs. Nitrogen and argon can change compressibility and reduce transport efficiency. Sulfur species such as SO₂ and H₂S are highly corrosive and may render CO₂ unsuitable for injection without treatment. Hydrocarbons may affect flow regimes and introduce flammability concerns.
PCS requires that impurity levels remain within the tolerance limits defined by transport and storage operators. Operators must document expected impurity profiles and provide evidence that CO₂ conditioning processes adequately control concentrations.
4.5 Phase Behavior and Stability Requirements
CO₂ must remain within a stable phase throughout transport. For pipelines, the preferred state is dense-phase or supercritical, which ensures predictable flow and efficient compression. If CO₂ pressure falls below the critical threshold or if temperature rises unexpectedly, phase changes may occur, resulting in two-phase flow or gas breakout. These conditions increase measurement uncertainty and may damage equipment.
In ship-based transport, CO₂ is maintained in a refrigerated liquid state. Temperature excursions or pressure increases can result in vapor formation, increasing tank pressure and requiring controlled management.
Operators must understand the phase envelope of the CO₂ mixture they are transporting and must design systems capable of maintaining conditions safely within that envelope. Monitoring systems must track pressure and temperature continuously to detect deviations.
4.6 Requirements for CO₂ Conditioning Prior to Transport
Before CO₂ enters the transport system, further conditioning may be required to align with transport specifications. Conditioning steps may include:
moisture removal
removal of sulfur compounds
oxygen reduction
temperature stabilization
filtration to remove particulates
pressure stabilization
The conditioning steps must be matched to the transport mode. For example, ship-based systems require refrigeration to maintain liquid phase, while pipelines require dehydration and impurity control.
Conditioning systems must be reliable, monitored continuously, and included within the PCS monitoring boundary when they influence CO₂ quality.
4.7 Acceptance Criteria for CO₂ Entering the Transport System
Transport operators may set acceptance criteria based on:
maximum moisture content
minimum CO₂ purity
maximum allowable concentrations of impurities
temperature and pressure ranges
phase stability requirements
PCS requires that project developers obtain documented acceptance criteria from the transport operator and maintain records showing that CO₂ quality met these criteria throughout the monitoring period. Deviations from acceptance limits must be recorded, explained, and incorporated into MRV calculations.
4.8 Monitoring of CO₂ Quality During Transport
Monitoring must occur at the inlet to the transport system and, when appropriate, at intermediate or outlet points. Sampling must be representative, and analytical procedures must be validated. For pipelines, periodic sampling may suffice, while ships and tankers may require additional onboard measurements due to pressure and temperature variability.
Operators must document the monitoring schedule, methods, and instruments used. All results must be included in monitoring reports.
4.9 Handling of Off-Specification CO₂
If CO₂ entering or circulating within the transport system falls outside required specifications, the operator must prevent it from compromising system integrity. Off-spec CO₂ may require reconditioning, temporary diversion, or controlled venting. Any venting or disposal must be quantified and reported.
Repeated off-spec incidents may indicate deficiencies in upstream capture or conditioning systems and must be addressed accordingly.
4.10 Documentation and Reporting of CO₂ Quality
Documentation must include:
sampling records
purity and impurity analyses
moisture measurements
phase stability assessments
deviations and corrective actions
The documentation must be comprehensive enough for VVBs to confirm that CO₂ remained within the acceptable quality envelope during transport.
Chapter 5 — Measurement, Monitoring, And Verification Requirements For CO₂ Transport
5.1 Purpose of Transport Monitoring and Verification
Accurate monitoring and verification of CO₂ transport ensure that the mass of CO₂ delivered to the storage system is consistent with what was captured upstream. Transport monitoring also identifies losses, detects operational deviations, ensures compliance with CO₂ quality requirements, and provides a basis for calculating transport-related emissions. Since transport serves as the central conduit between capture and storage, reliable monitoring is essential for maintaining environmental integrity throughout the CCS chain.
This chapter establishes the measurement and monitoring expectations that apply to all CO₂ transport systems under PCS.
5.2 Definition of Metering Points in Transport Systems
Transport monitoring begins at the custody transfer point where CO₂ leaves the capture system. This point marks the official entry into the transport boundary. From there, CO₂ may pass through intermediate compression stations, booster units, terminals, or storage tanks before reaching the final injection system. At the point where CO₂ leaves the transport system and enters the storage facility, a second custody transfer measurement must occur.
Monitoring must therefore include at least two required metering points:
The transport inlet meter
The transport outlet meter
When transport involves multiple modes (such as pipeline to ship transfer), additional custody transfer meters must be installed at loading and unloading points.
These metering points form the backbone of transport MRV and allow verification of mass balance across the transport system.
5.3 Flow Measurement Requirements
Flow meters must be capable of providing accurate, continuous measurement under transport conditions. Preferred instruments include ultrasonic meters for pipelines and Coriolis meters for custody transfer at terminals or ship loading arms.
For pipelines, meters must be installed at locations where CO₂ flow is stable, single-phase, and free from vibrations or pressure pulsations. For ship and tanker loading operations, meters must be installed on lines with predictable flow rates and minimal cavitation risk.
Measurement systems must include:
temperature sensors
pressure sensors
density calculations using validated equations of state
These parameters are necessary for converting volumetric flow to mass flow. Flow measurement must be recorded at a frequency sufficient to capture operational variations, and timestamps must be synchronized across all instruments.
5.4 Pressure and Temperature Monitoring
CO₂ pressure and temperature must be monitored continuously throughout transport because these variables determine phase stability, density, and flow behavior. Pressure and temperature sensors must be installed:
immediately upstream and downstream of flow meters
along pipeline sections where phase changes are possible
in ship tanks and tanker vessels at representative points
at terminal storage tanks and loading/unloading lines
Monitoring must account for Joule–Thomson cooling effects during pressure reduction, ambient thermal effects on aboveground pipelines, and thermal cycling on ships or tankers.
All pressure and temperature sensors must be calibrated regularly and must have accuracy suitable for density calculations. The data must be logged digitally and retained for verification.
5.5 Sampling and CO₂ Quality Monitoring
Sampling ports must be located at custody transfer points and intermediate tanks where CO₂ composition is likely to change. Sampling must be designed to avoid condensation, contamination, or phase instability. Representative samples must support measurement of:
CO₂ purity
moisture
oxygen, nitrogen, and other non-condensable gases
sulfur species
hydrocarbons
Sampling frequency depends on transport mode. Pipelines with stable upstream quality may require periodic sampling, whereas ship tanks may require monitoring before loading, during transport, and at unloading due to temperature-related changes.
All analytical instruments used for impurity analysis must be traceably calibrated, and results must be included in the monitoring report.
5.6 Metering Requirements for Pipeline Transport
Pipeline transport requires continuous measurement at both the inlet and outlet to determine any mass changes. Metering must be supported by pressure and temperature measurements that allow density corrections.
Pipeline operators must maintain:
inlet meter data
outlet meter data
pressure and temperature trends
any operational events that influenced flow
Mass balance reconciliation must compare inlet and outlet quantities. Small discrepancies may arise due to measurement uncertainty, but any unexplained differences beyond acceptable tolerance must be investigated and documented.
5.7 Metering Requirements for Ship-Based Transport
Ship transport introduces batch-based custody transfer. Measurement occurs at:
Loading terminal
Ship tank conditions during voyage
Unloading terminal
At loading, mass is determined either by:
Coriolis meters in loading lines, or
weighing/level measurement in ship tanks
During voyage, tank pressure, temperature, and fill level must be monitored to allow estimation of boil-off or pressure relief losses. At unloading, mass delivered must be measured using:
metering on discharge lines, and/or
adjusted tank volume based on final temperature and pressure
The difference between loaded mass and delivered mass must be quantified and attributed to:
boil-off
venting
measurement uncertainty
All ship transport data must be included in the monitoring report.
5.8 Metering Requirements for Road and Rail Tankers
Road and rail tankers transport CO₂ in discrete batches. Measurement typically relies on:
weighing the tanker before and after loading (preferred), or
using Coriolis meters during loading and unloading
Temperature and pressure inside the tanker must be monitored for stability. Any venting—especially during unloading or in warm weather—must be recorded and quantified.
Batch reconciliation must show:
mass loaded
mass delivered
losses or gains attributable to venting or measurement error
Operators must maintain logs for each tanker trip and include them in the monitoring report.
5.9 Mass Balance Requirements for Multi-User Transport Networks
Shared pipelines or terminals may transport CO₂ from multiple sources to multiple injection points. MRV in such systems requires a mass balance approach that considers:
total CO₂ entering the network
total CO₂ delivered to all users
total CO₂ injected
network losses
Operators must implement data-sharing arrangements and ensure that measurement systems for all users meet PCS requirements. VVBs must have access to network-wide data to verify the accuracy of individual project contributions.
5.10 Leak Detection and Monitoring Expectations
Transport systems must incorporate leak detection mechanisms appropriate to the transport mode. Pipelines may use:
pressure drop analysis
acoustic monitoring
fiber-optic sensing
aerial surveys
surface and subsurface gas detection
Ships and tankers must monitor for tank overpressure, insulation failures, and vent activation events.
Any suspected leak must trigger an investigation, documented findings, and corrective actions. Quantification of loss must be included in monitoring reports.
5.11 Calibration and Instrument Quality Requirements
All measurement instruments must be calibrated at intervals suitable for maintaining accuracy. Calibration must follow recognized standards, and records must include:
calibration certificates
zero and span checks
adjustments applied
dates and responsible personnel
VVBs will examine calibration logs as part of verification.
5.12 Data Management and Traceability
Transport monitoring data must be:
recorded digitally
time-synchronized
backed up securely
stored for the required retention period
Operators must maintain clear traceability from raw data to calculated mass and CO₂ quality metrics. Any manual adjustments or corrections must be documented and justified.
5.13 Reporting of Transport Monitoring
Monitoring data must be summarized in the Transport Monitoring Report and must include:
inlet and outlet quantities
intermediate custody transfers
impurity and moisture analyses
venting events
losses and uncertainty values
calibration and maintenance activities
The report must allow VVBs to reconstruct the transport period and verify the accuracy of the reported quantities.
Chapter 6 — Transport Losses, Venting, And Emission Accounting
6.1 Purpose of Transport Loss Accounting
Transport systems are designed to contain CO₂, but operational realities such as pressure control, temperature variations, mechanical failures, or custody transfer processes may cause CO₂ to be released to the atmosphere. These releases are considered transport losses and must be measured, estimated, and reported under PCS. Transport losses affect the net quantity of CO₂ available for storage and therefore influence the climate benefit of the project. The purpose of this chapter is to ensure that all such losses—whether intentional or unintentional—are identified and incorporated into emission accounting with full transparency.
6.2 Types of Losses in CO₂ Transport
Losses during transport generally arise from three mechanisms: vapor releases related to thermodynamic behavior, mechanical leaks or failures, and operational activities that require temporary pressure reduction or venting.
In pipelines, losses may occur through small leaks at valves, flanges, seals, or pipe wall defects. Blowdown events during maintenance or emergency depressurization may also release CO₂. In ship transport, boil-off may occur when tank temperatures rise above design conditions, causing vapor formation that must be either reliquefied, compressed and stored, or released through controlled venting. Road and rail tankers experience losses when ambient heat causes tank pressure to increase, leading to relief valve activation or minor venting during unloading.
Each transport mode has a distinct profile of losses, but all must be quantified and reported.
6.3 Pipeline Losses and Their Characterization
Pipeline losses are typically low under normal operation but may become significant during maintenance or equipment failure. Losses can arise from minor leaks that persist over time, or from discrete events such as blowdowns. Pipeline operators must track any depressurization events, the volume of CO₂ released, the reason for the event, and the equipment involved. Even minor valve or seal leaks must be evaluated, documented, and, where quantification is possible, included in MRV calculations.
Pressure and flow anomalies detected by pipeline monitoring systems may also indicate unobserved leakage. Operators must investigate anomalies promptly and update mass balance calculations to reflect any confirmed losses.
6.4 Boil-Off and Venting in Ship-Based Transport
Ship transport introduces a unique category of losses caused by thermal behavior of CO₂ stored in refrigerated or pressurized tanks. When tanks absorb heat through insulation or from external conditions, liquid CO₂ may begin to vaporize. Pressure rises within the tank and must be managed through the ship’s refrigeration system or pressure-control equipment.
Boil-off that cannot be reliquefied or stored must be released through controlled venting. This venting must be recorded with estimates of mass based on tank conditions, pressure changes, and thermodynamic properties. The monitoring records for ship transport must include tank temperatures, internal pressures, refrigeration performance, and any pressure relief activations.
Losses during loading and unloading must also be recorded, as transient conditions can lead to small but measurable losses.
6.5 Losses in Road and Rail Tank Transport
Road and rail tankers carry smaller CO₂ loads but are more exposed to ambient conditions, resulting in greater sensitivity to heat gain. Small increases in temperature can elevate tank pressure, occasionally triggering safety vents or requiring manual venting before unloading. Operators must document tank conditions throughout transit and record any pressure relief valve activations.
Losses during connection or disconnection of hoses, during transfer pump operation, and when tanks equalize pressure with receiving systems must also be documented. Because tanker transport is batch-based, each transport cycle must be reconciled by comparing loaded mass with delivered mass.
6.6 Losses at Intermediate Storage or Terminals
Intermediate storage facilities, including port terminals or pipeline buffer tanks, may experience losses from venting, boil-off, or transfer operations. Tanks may undergo pressure changes due to environmental conditions, filling patterns, or equipment shutdowns. Any release that occurs at these facilities must be recorded, including the cause, estimated mass, and operational context.
Because terminals often handle multiple batches or ship loads, mass balance reconciliation must be maintained for each discrete transfer period.
6.7 Quantification of Transport Losses
Quantification of losses depends on the nature of the transport mode and the type of event. When losses occur through venting in pipelines, the released mass may be estimated using pressure-volume relationships, blowdown modeling, or line segment depressurization calculations. Ship venting losses may be estimated using tank pressure and temperature trends along with established CO₂ liquid-vapor equilibrium models. Tanker losses may be calculated using differences between mass loaded and delivered, corrected for measurement uncertainty.
All quantification methods must be documented and must rely on engineering principles or validated thermodynamic calculations. Conservative assumptions should be used when uncertainty is high.
6.8 Integration of Losses Into Net CO₂ Accounting
All losses occurring within the transport boundary must be subtracted from the mass of CO₂ that entered the system to determine the net mass delivered to storage. This value forms the basis for the transport component of PCS MRV. The capture system’s net captured amount feeds into transport, and the transport system’s net delivered amount feeds into storage. Losses therefore influence the entire CCS chain and must be treated with precision.
Monitoring reports must show a clear reconciliation of quantities entering the transport system, quantities delivered, total measured or estimated losses, and the resulting net CO₂ delivered.
6.9 Documentation Requirements for Losses
Operators must maintain logs for all events that caused or may have caused CO₂ losses. Each log entry should include the time of occurrence, operating conditions, cause of the event, corrective actions taken, and the method used to quantify the release. For ships or tankers, voyage logs, loading and unloading records, and tank condition trends must support loss calculations.
VVBs require sufficient documentation to verify that losses were properly identified, quantified, and incorporated into project emissions accounting.
6.10 Verification of Loss Accounting
VVBs will examine all transport loss records, compare mass balances, review operational logs, and assess whether quantification methods are appropriate and conservatively applied. They must confirm that all potential loss mechanisms have been considered and that no material losses have been excluded from MRV calculations.
Any inconsistencies, unexplained discrepancies, or missing documentation may result in non-conformities and require corrective action before verification can be completed.
Chapter 7 — Risk Assessment For CO₂ Transport Systems
7.1 Purpose of Transport Risk Assessment
Transporting CO₂ involves unique physical and operational risks that differ from those associated with conventional gases. The behavior of CO₂ under pressure, its susceptibility to rapid phase transitions, the possibility of fracture propagation in pipelines, the presence of cryogenic temperatures in ships, and the dynamic nature of tanker operations all create conditions that must be assessed systematically. The purpose of risk assessment under PCS is to ensure that transport systems remain safe, stable, and predictable throughout their operating life, and that any risks to personnel, the environment, or system integrity are minimized.
Risk assessment is not limited to initial design. It must be revisited periodically and updated as operating conditions evolve, equipment ages, or new information becomes available.
7.2 Risk Categories in CO₂ Transport
Risk in transport systems can be grouped into three general categories: physical risks related to CO₂ properties and system pressures, mechanical risks related to equipment or infrastructure integrity, and operational risks arising from human factors or unexpected events. Together, these risks influence the reliability of CO₂ delivery and the potential for accidental releases.
CO₂ presents unique hazards because it can transition rapidly between phases, expand violently if released from high pressure, and form dense vapor clouds that can accumulate in low-lying areas. These characteristics make transport systems technically demanding and require robust engineering controls.
7.3 Pipeline Transport Risk Considerations
Pipelines must be designed to withstand internal pressure, external forces, and environmental conditions. Key pipeline risks include rupture, corrosion, hydrate formation, embrittlement, and mechanical damage from excavation or ground movement. CO₂ pipelines may experience running fractures if crack propagation is not controlled. The selection of pipe material, wall thickness, and fracture control measures must reflect the operating pressure and CO₂ composition.
Corrosion poses a significant risk when moisture or corrosive impurities are present. Even trace water can form carbonic acid, leading to internal corrosion. Operators must monitor moisture content and implement corrosion management strategies that include coatings, cathodic protection, and periodic inspection.
Temperature variations can also influence pipeline integrity. CO₂ decompression produces cooling, which may lead to embrittlement in susceptible materials. Operators must consider thermal stresses and ensure that pipeline components remain within safe operating limits.
7.4 Ship Transport Risk Considerations
Ships transporting CO₂ face risks arising from cryogenic conditions, pressure fluctuations, marine weather, and ship handling. Refrigerated CO₂ tanks must remain at extremely low temperatures to avoid excessive vapor formation. Any failure of insulation or refrigeration systems can result in rapid pressure increase inside tanks. Pressure relief systems must function reliably to prevent tank overpressure.
Structural risks include the effect of low temperatures on tank material ductility, vibration and sloshing during rough seas, and fatigue from repeated thermal cycling. Operational risks include errors during loading or unloading, hose failures, and misalignment of custody transfer systems.
Environmental risks such as collision, grounding, or fire must be incorporated into the risk assessment. Emergency response procedures must account for large-volume CO₂ releases in marine environments.
7.5 Road and Rail Transport Risk Considerations
Road and rail tankers are exposed to ambient temperatures, physical shocks, and transport-related hazards such as collisions or derailments. Tanks must be engineered to withstand pressure fluctuations and mechanical impact. Relief valves and venting mechanisms must function reliably to prevent catastrophic overpressure, especially in warm environments.
Operational risks arise during loading and unloading, where connection failures, valve mis-operation, or pressure mismatches may result in CO₂ release. Transport routes must consider population density, emergency access, and compliance with hazardous material regulations.
Rail systems introduce additional risks related to coupling forces, vibration, and longer transit durations, which require monitoring of temperature and pressure throughout the journey.
7.6 Risks Associated With Intermediate Storage and Terminals
Terminals experience dynamic operations, including multiple transfers, tank fills, and pressure adjustments. Temperature or pressure changes can cause venting events. Tanks may experience fatigue or corrosion over time, especially when subject to frequent thermal or pressure cycling.
Terminal equipment such as loading arms, hoses, transfer pumps, and vapor recovery units must be maintained and inspected regularly. Failures in transfer lines can result in acute CO₂ releases, presenting risks to personnel and environmental safety.
Operators must identify risks specific to their terminal layout, equipment configuration, and local environmental conditions.
7.7 Material Compatibility and Corrosion Risks
CO₂ streams containing moisture or corrosive impurities pose particular challenges for material durability. Carbon steel may corrode rapidly when exposed to carbonic acid, sulfur compounds, or oxygen. Stainless steels and nickel alloys offer better resistance but may not be economically feasible for long pipeline sections.
Operators must ensure that materials used in pipelines, ships, tanks, and terminals are compatible with expected CO₂ composition. Detailed corrosion assessments must inform material selection, protective coatings, and maintenance schedules.
7.8 Phase Behavior Risks
Phase transitions represent one of the most critical technical risks in CO₂ transport. A sudden drop in pressure can cause CO₂ to transition from a dense-phase liquid to a gas-solid mixture, leading to line vibration, flow instability, erosive wear, and hydrate formation. Ship tanks face risks of spontaneous vaporization if temperature control is lost. Tankers may experience sudden pressure surges as CO₂ warms during transit.
Operators must understand the phase envelope of their CO₂ stream and design systems to avoid operating near unstable regions. Pressure relief systems, insulation, heating systems, and careful pressure control are essential safeguards.
7.9 Operational Risks and Human Factors
Operational risks often arise from incorrect procedures, insufficient training, communication errors, or failure to follow established protocols. CO₂ transport systems require precise coordination during loading and unloading, compression start-up, depressurization, and transfer operations.
Human error can lead to events such as misaligned valves, incorrect pressure settings, premature venting, or improper hose connection. Operators must establish robust training programs, operational checklists, and incident reporting systems to minimize such risks.
7.10 Emergency Response and Incident Preparedness
Transport operators must maintain emergency response plans tailored to the specific risks of pipelines, ships, or tank transport. These plans must include procedures for isolating the system, managing releases, protecting personnel, and notifying relevant authorities. Emergency drills and equipment testing must be performed regularly, and lessons learned must inform future risk assessments.
For pipelines, rapid shutdown valves and real-time monitoring may be necessary. Ships must maintain emergency venting and inerting systems. Tankers must have protocols for unexpected pressure rise or valve malfunction.
7.11 Documentation and Verification of Risk Management
PCS requires comprehensive documentation of risk assessments, including the identified risks, mitigation measures, monitoring strategies, and emergency procedures. Operators must maintain records of inspections, maintenance activities, incident reports, and operational deviations.
During verification, VVBs will review these documents and may request additional evidence to confirm that risk assessments are updated and that mitigation measures are implemented effectively.
Chapter 8 — Data Quality, Calibration, And Uncertainty Management
8.1 Purpose of Data Quality Requirements
Reliable CO₂ transport monitoring depends on high-quality data generated through properly selected instruments, correct installation, regular calibration, and disciplined data management. Transport systems may experience fluctuations in flow, pressure, temperature, and phase conditions that directly affect the accuracy of mass measurements. Data quality requirements ensure that CO₂ quantities transported are reported with sufficient precision and are traceable through verifiable methods.
This chapter defines the standards for data accuracy, calibration, uncertainty management, and recordkeeping that apply to all transport modes.
8.2 Minimum Data Quality Standards for Transport Systems
Transport monitoring must produce data that are accurate, consistent, and representative of actual operating conditions. Instruments must meet the minimum accuracy thresholds suitable for CO₂ custody transfer. Data must be recorded at a frequency that captures operational variability and enables verification of losses or anomalies.
The minimum PCS data quality principles include:
accuracy and precision appropriate for custody transfer;
continuous, traceable data logging;
calibration performed at regular intervals;
transparent documentation of any data gaps;
conservative treatment of uncertainty.
Table 8-1 summarizes the minimum accuracy requirements for transport monitoring instruments.
Table 8-1 — Minimum Accuracy Requirements for Key Transport Instruments
Ultrasonic flow meter
±0.5% of reading
Pipeline inlet/outlet metering
Coriolis flow meter
±0.1–0.2%
Ship loading/unloading, tanker transfer
Pressure transmitter
±0.1% full scale
Density calculation, leak detection
Temperature sensor (RTD)
±0.1°C
Density calculation
Tank level gauge (ship/tanker)
±0.2% of full scale
Voyage mass estimate
Weighbridge
±0.5%
Road/rail tanker mass determination
8.3 Instrument Calibration Requirements
Calibration ensures that instrumentation used in transport continuously performs within acceptable accuracy limits. Calibration must follow manufacturer recommendations or recognized international standards, whichever is more stringent.
Calibration frequency depends on instrument type, operational conditions, and susceptibility to drift. Table 8-2 summarizes expected calibration intervals under PCS.
Table 8-2 — Minimum Calibration Frequencies for Transport Instrumentation
Ultrasonic flow meter
Annually
Verify signal quality and straight-run requirements
Coriolis meter
Annually
Verify zero stability and density accuracy
Pressure transmitter
Annually
Check against calibrated reference gauge
Temperature sensor (RTD)
Annually
Confirm immersion and drift
Tank level gauge (ship)
Every 2–3 years
Use certified tank calibration tables
Weighbridge
Quarterly
Legal-for-trade calibration standard
GC purity analyzer
Monthly or per drift
Traceable calibration gases required
Moisture analyzer
Quarterly
Sensor aging check
Calibration records must include the method, reference standard, results, any corrections applied, and personnel responsible. If drift exceeds acceptable limits, historical data must be reviewed for potential recalculation.
8.4 Data Logging, Synchronization, and Record Retention
Transport monitoring must rely on digital data acquisition systems capable of:
continuous logging
timestamp synchronization across all instruments
secure storage and backup
audit trail visibility
Time synchronization is essential because mass flow, pressure, and temperature readings must align to calculate density correctly. Ships and tankers must synchronize onboard logs with terminal clocks to ensure consistency during custody transfer.
Transport operators must retain all data—raw and processed—for the duration specified by PCS, including calibration certificates, maintenance logs, sampling records, and event logs.
8.5 Handling Missing or Invalid Data
Data gaps may occur due to instrument malfunction, maintenance, communication issues, or unexpected shutdowns. PCS requires that all missing or invalid data be flagged and explained in monitoring reports.
If missing data cover a short period and surrounding data remain stable, conservative estimation may be allowed using engineering calculations, mass balance interpolation, or redundant measurement sources. When gaps significantly impact the ability to estimate transported CO₂ reliably, operators must notify PCS and may need to undertake additional verification steps.
All gap-filling methods must be transparent, justified, and traceable.
8.6 Uncertainty Quantification for Transport Measurement
Uncertainty arises from instrument accuracy limits, environmental variations, sampling variability, and data processing. The PCS approach requires that uncertainty be evaluated for each key measurement component and combined using accepted engineering or statistical methods.
Major contributors to uncertainty include:
flow meter accuracy
density calculation (pressure and temperature)
purity and moisture measurements
tank level and volume calculations for ships
weighbridge uncertainty for tankers
Table 8-3 provides a simplified illustration of how uncertainty components may contribute to total transport uncertainty.
Table 8-3 — Example Uncertainty Components
Flow meter accuracy
±0.5%
Pressure sensor
±0.1%
Temperature sensor
±0.1%
Density equation
±0.05%
Purity measurement
±0.3%
Total combined (RSS)
±0.6%
Uncertainty that exceeds acceptable thresholds must prompt investigation into instrument performance, data quality, or operational practices.
8.7 Data Validation Through Mass and Energy Balances
Mass balance remains the primary method for validating transport measurement accuracy. Operators must reconcile inlet mass with outlet mass, accounting for any losses and measurement uncertainty. A significant unexplained mass imbalance suggests a measurement error, unreported leak, calibration issue, or operational anomaly.
Energy balance applies primarily to ship transport, where refrigeration or pressurization energy may indicate unexpected boil-off or tank warming.
Mass and energy balance results must be included in monitoring reports and made available for verification.
8.8 Verification of Data Quality and Calibration Procedures
During verification, VVBs will evaluate whether:
instruments meet PCS accuracy requirements
calibration was performed on schedule
calibration results show acceptable drift
sampling methods produce representative CO₂ quality data
data synchronization is maintained
uncertainty calculations are reasonable and transparent
VVBs may request additional checks, recalculations, or supporting documents if discrepancies or inconsistencies are found.
8.9 Documentation Requirements
All data quality and calibration practices must be documented in the Transport Monitoring Report. Required documentation includes:
calibration certificates
instrument specifications
maintenance logs
sampling results
uncertainty evaluations
explanations of anomalies or missing data
mass balance tables
Documentation must allow an independent reviewer to trace each reported value to its underlying source.
8.10 Data Integrity and System Reliability
Transport systems must operate with a high degree of data integrity and reliability. Operators must implement redundancy for critical measurements where feasible, maintain cybersecurity on data acquisition systems, and ensure continuity of monitoring during operational transitions.
If a critical instrument fails, operators must act promptly to restore monitoring capability and ensure data continuity.
Chapter 9 — Reporting Requirements For Transport Operators
9.1 Purpose of Transport Reporting
Reporting ensures that monitoring results, operational events, and transport system performance are communicated clearly and transparently to the PCS Secretariat and Validation and Verification Bodies (VVBs). While monitoring generates data, reporting transforms that data into verifiable evidence. The Transport Monitoring Report must demonstrate, in a structured and traceable manner, how CO₂ was moved, under what conditions, in what quantities, and with what losses or deviations.
Transport reporting is critical because it provides the only formal record of CO₂ movement between the capture system and the storage facility, and it enables verification of mass balance across the CCS chain.
9.2 Role of the Transport Monitoring Report
The Transport Monitoring Report (TMR) serves as the central document summarizing transport activities during each monitoring period. It must present both quantitative measurements and qualitative descriptions of operating conditions, system stability, and any events that influenced CO₂ movement or measurement accuracy.
The TMR must be sufficiently detailed for VVBs to reconstruct the transport system’s operation without relying on external explanations. It must also demonstrate that all PCS monitoring requirements were met, including calibration, sampling, and loss accounting.
9.3 Required Components of the Transport Monitoring Report
A complete TMR must include a comprehensive set of elements that allow accurate verification. These elements ensure alignment with PCS methodology and technical guidance.
Table 9-1 — Required Sections of the Transport Monitoring Report
System description
Summary of transport mode, boundaries, metering points, diagrams
CO₂ quantities
Inlet, outlet, intermediate transfers, batch deliveries
Transport conditions
Pressure, temperature, phase behavior throughout period
CO₂ quality data
Purity, moisture, impurities at key points
Transport losses
Venting, boil-off, leaks, measured or estimated
Mass balance
Reconciliation of inlet vs. outlet with uncertainty
Calibration and QA/QC
Details of instrument calibration, corrections applied
Operational events
Maintenance, shutdowns, anomalies, corrective actions
Incident and safety log
Any abnormal occurrences or system alerts
Documentation annex
Supporting logs, certificates, sampling results
Each section must be presented clearly and supported by verifiable evidence.
9.4 Reporting of CO₂ Quantities Transported
The TMR must include a complete record of all quantities moved through the transport system. This includes total CO₂ entering the system, total CO₂ exiting, and any intermediate storage transfers. For multi-modal transport, such as pipeline-to-ship integration, quantities must be reported separately for each segment and then reconciled.
For pipeline systems, continuous flow data should be summarized into daily or monthly aggregates, with explanations for fluctuations. For ship transport, each voyage must be reported individually, showing loaded and delivered mass, boil-off events, and custody transfer records. For tankers, each batch must be reported separately.
9.5 Reporting of CO₂ Quality Data
The report must include all purity, moisture, and impurity analyses conducted during the monitoring period. Each result must be traceable to a sampling event, analytical method, and calibration record. Any deviations from required CO₂ quality thresholds must be documented, including the response taken and whether storage operators accepted or rejected the shipment.
If conditioning steps were used to adjust CO₂ quality before transport, the TMR must describe the method and demonstrate its effectiveness.
9.6 Reporting of Transport Losses and Venting
All forms of CO₂ loss must be fully disclosed. This includes pipeline blowdowns, relief valve activations, boil-off from ships, tanker venting, intermediate storage losses, and confirmed pipeline or hose leaks. For each loss, the report must explain the cause, estimate the mass released, and document the calculation method.
A summary table must accompany narrative explanations.
Table 9-2 — Example Transport Loss Reporting Format
This ensures clear traceability of all losses.
9.7 Mass Balance Presentation
The TMR must present a mass balance comparison showing:
total CO₂ entering transport
total CO₂ delivered
total measured and estimated losses
resulting net CO₂ delivered
Uncertainty values for each component must be included. If discrepancies exceed acceptable thresholds, the operator must provide explanations and evidence of investigation.
Table 9-3 — Example Mass Balance Summary
CO₂ at inlet
Metered value
CO₂ delivered
Metered value
CO₂ losses
Sum of events
Measurement uncertainty
Combined from instruments
Net delivered CO₂
Inlet minus losses
9.8 Reporting of Calibration Activities
The TMR must summarize all calibration activities for flow meters, pressure and temperature sensors, tank gauges, weighbridges, and analytical instruments. The summary must indicate calibration dates, results, corrections applied, and any instances where instrument drift required data adjustment.
Calibration evidence (certificates, logs, and reference gas documentation) must be included in the annex to the report.
9.9 Reporting of Operational Events and Deviations
Transport systems may experience planned or unplanned events such as maintenance shutdowns, pump or compressor failures, power outages, marine delays, or temperature excursions in tanks. Each event must be described in the report with details about the duration, influence on monitoring, and any operational adjustments required.
For mechanical failures or safety incidents, the report must document corrective actions and confirm whether any CO₂ losses occurred.
9.10 Documentation of Safety Incidents and Emergency Events
Any safety-related occurrences such as pressure relief valve activation, unexpected venting, pipeline alarms, or ship tank overpressure events must be logged and reported. Operators must describe the root cause, safety response, and mitigation measures taken to prevent recurrence.
VVBs will examine incident logs closely to verify that losses were fully captured and that no unreported emissions occurred.
9.11 Data Integrity, Traceability, and Archiving Requirements
Operators must ensure that all data used for reporting are archived securely, with clear traceability from raw measurements to reported quantities. This includes:
raw data files
processed datasets
calibration logs
maintenance records
control room logs
ship or tanker voyage logs
pressure and temperature trends
Transport records must be retained for the duration required by PCS, ensuring availability for future verification or project reviews.
9.12 Submission and Verification of the Transport Monitoring Report
The completed TMR must be submitted to the PCS Registry within the timeline defined by the methodology. Once submitted, the VVB will conduct verification, including document review, data checks, interviews with transport personnel, and examination of operational systems.
Only after VVB approval can the transport component be integrated into the full CCS monitoring cycle that leads to issuance.
Annex A — CO₂ Physical Properties And Phase Behavior References
A.1 Purpose
Transporting CO₂ safely and efficiently requires a clear understanding of its thermodynamic properties. CO₂ behaves differently from most gases commonly transported through pipelines or stored in tanks. It transitions rapidly between phases, exhibits high density in supercritical form, and forms hydrates under certain pressure–temperature combinations.
Annex A provides the physical data and phase behavior information needed to design, operate, and monitor CO₂ transport systems in accordance with PCS requirements. These data support decisions about pressure control, temperature management, instrumentation selection, and hydrate mitigation.
A.2 Fundamental Physical Properties of CO₂
CO₂ exhibits distinct behavior depending on temperature and pressure. Table A-1 summarizes key physical constants relevant to transport.
Table A-1 — Key Physical Properties of CO₂
Molecular weight
44.01 g/mol
Used in mass and density calculations
Triple point temperature
−56.6°C
CO₂ exists as solid/liquid/vapor in equilibrium
Triple point pressure
5.18 bar
Below this pressure, liquid CO₂ cannot exist
Critical temperature
31.1°C
Above this, CO₂ cannot liquefy regardless of pressure
Critical pressure
73.8 bar
Required to achieve supercritical state
Critical density
468 kg/m³
Important for dense-phase pipeline design
Gas constant (R)
0.1889 kJ/kg·K
Useful for thermodynamic equations
These values form the basis for understanding the phase envelope of CO₂.
A.3 CO₂ Phase Behavior: Operational Relevance
During transport, CO₂ may exist in gaseous, liquid, dense-phase, supercritical, or solid–gas states depending on pressure and temperature. Transport systems must be designed to avoid unstable conditions such as two-phase flow or solid formation.
Pipelines generally maintain CO₂ in dense-phase or supercritical state to ensure consistent flow and predictable behavior. Ships store CO₂ as refrigerated liquid, where temperature control is critical. Tankers and terminals must avoid conditions where CO₂ may flash, vaporize rapidly, or form dry ice.
Phase control is therefore central to transport engineering, metering accuracy, and loss prevention.
A.4 CO₂ Phase Envelope Reference Table
Table A-2 summarizes indicative CO₂ phase states under representative temperature and pressure combinations. These values are approximate and provided for operational reference; exact values depend on impurities.
Table A-2 — Approximate CO₂ Phase States Under Common Conditions
−60°C
6 bar
Solid + vapor
Below usable range for transport
−50°C
7 bar
Liquid
Typical refrigerated ship storage
−20°C
20 bar
Liquid
Stable for pressurized tanks
0°C
35 bar
Liquid–dense boundary
Sensitive to flashing
20°C
60 bar
Dense-phase
Common for pipelines
30°C
75 bar
Supercritical
Pipeline operating region
40°C
80 bar
Supercritical
Must monitor for heat gain
Above 31°C
Above 74 bar
Supercritical
No liquid possible
Transport operators must understand where their systems operate relative to this envelope.
A.5 Density Reference Table for CO₂ (Pipeline-Relevant Conditions)
The mass of CO₂ transported depends on density, which varies strongly with pressure and temperature. Operators must use validated equations of state (e.g., Peng–Robinson, Span–Wagner), but the table below provides indicative reference values.
Table A-3 — Approximate CO₂ Density in the Dense-Phase Region
0°C
60 bar
~850
10°C
70 bar
~770
20°C
75 bar
~720
30°C
80 bar
~680
35°C
85 bar
~650
40°C
90 bar
~620
Density decreases significantly as temperature increases, which influences mass flow calculations and compressor load.
A.6 Vapor Pressure and Boil-Off Behavior for Ships and Tankers
Ship and road/rail tank systems depend on maintaining CO₂ in liquid form. Table A-4 shows approximate vapor pressures at key temperatures.
Table A-4 — CO₂ Vapor Pressure at Representative Temperatures
−40°C
~ 14 bar
Stable liquid; low boil-off
−30°C
~ 22 bar
Ship storage range
−20°C
~ 35 bar
High-pressure tanker range
−10°C
~ 48 bar
Approaches tank safety limits
0°C
~ 60 bar
Risk of flashing; pressure relief activation likely
Understanding vapor pressure helps operators predict boil-off and venting risks.
A.7 Hydrate Formation Conditions
Hydrates can form when water and CO₂ coexist at high pressure and low temperature. Hydrates can plug pipelines, valves, or loading lines, posing significant operational risks.
Table A-5 — Approximate Hydrate Formation Thresholds
20 bar
~ 6°C
40 bar
~ 11°C
60 bar
~ 15°C
80 bar
~ 18°C
Hydrate prevention requires maintaining CO₂ temperatures above these thresholds or ensuring moisture is below acceptable limits.
A.8 Influence of Impurities on CO₂ Phase Behavior
Impurities influence CO₂ behavior by altering freezing points, vapor pressures, and critical properties. For example:
Nitrogen and oxygen shift the phase boundary upward, making flashing more likely.
Sulfur compounds increase corrosion risk and may influence certain phase transitions.
Water dramatically increases hydrate formation risk.
Hydrocarbons may introduce flammability considerations in tanker environments.
Operators must understand how the actual CO₂ composition deviates from pure CO₂ behavior and must use appropriate equations of state for mixed gases.
A.9 Use of Phase Diagrams in Operational Control
Transport operators must maintain pressure and temperature within the stable regions of the CO₂ phase diagram. Pipelines must remain above critical pressure during operation, while ships must maintain refrigeration to prevent rapid vaporization. Operators must reference validated phase diagrams during:
design of pressure control systems
evaluation of hydrate risk
assessment of loss mechanisms
emergency response planning
density calculation for custody transfer
Phase diagrams for project-specific CO₂ mixtures must be included in engineering documentation.
A.10 Reference Standards and Sources
This annex aligns with international references including:
ISO 27913 (CO₂ transport systems)
ISO 27916 (CO₂ quantification and verification)
DNV recommended practices for CO₂ pipelines and ship transport
IPCC and IEAGHG thermodynamic property reports
Span–Wagner and Peng–Robinson equations of state
ASME and API gas transport standards
Operators must use validated sources for all thermodynamic calculations referenced in monitoring and verification.
Annex B — Transport Metering And Instrument Specification Tables
B.1 Purpose
Transport monitoring requires reliable, accurate instrumentation capable of measuring CO₂ mass flow, pressure, temperature, and tank conditions under pipeline, maritime, or tanker environments. Annex B establishes the minimum specifications for instruments used in PCS transport MRV, ensuring consistency and verification readiness across all transport modes.
Tables in this annex provide operators and VVBs with clear reference standards for instrument selection, installation, calibration, and performance requirements.
B.2 Flow Measurement Instruments
Flow measurement forms the basis of CO₂ quantity determination during transport. Instruments must provide stable performance under fluctuating pressure, temperature, and flow conditions.
Table B-1 — Flow Measurement Devices for CO₂ Transport
Ultrasonic flow meter
±0.5%
Dense or gaseous CO₂; wide diameter range
Pipeline inlet/outlet
Preferred for pipeline custody transfer
Coriolis meter
±0.1–0.2%
Single-phase liquid or dense-phase
Ship loading/unloading; tanker transfers
High accuracy; sensitive to vibration
Turbine meter
±1%
Clean gas/liquid
Limited pipeline applications
Only acceptable with justification
Differential pressure meter
±1–3%
Requires stable flow
Backup or redundancy
Must include P & T correction
Tank level gauge (ship)
±0.2% volume
Cryogenic or pressurized tanks
Voyage monitoring
Requires certified tank calibration tables
B.3 Pressure and Temperature Instruments
Accurate pressure and temperature measurements ensure correct density calculations and phase stability assessment.
Table B-2 — Pressure and Temperature Instrumentation Requirements
Pressure transmitter
±0.1% full scale
Mounted close to meter; avoid vibration and dead legs
Key for density correction
Temperature sensor (RTD)
±0.1°C
Installed in thermowell with sufficient immersion
Must be synchronized with pressure sensor
Ship tank temperature probe
±0.2°C
Multiple vertical positions in tank
Required for boil-off quantification
Tanker temperature probe
±0.2°C
Shielded from ambient heat
Confirms pressure buildup risk
B.4 CO₂ Quality and Sampling Instruments
Transport systems require periodic verification of CO₂ composition to ensure compatibility with pipeline materials and storage reservoirs.
Table B-3 — CO₂ Quality Monitoring Instruments
CO₂ purity
Gas chromatograph
±0.1–0.2%
Must use calibration gases
Moisture
Chilled mirror hygrometer
ppm level
Preferred for custody transfer
Moisture (alternate)
Aluminum oxide sensor
ppm level
Suitable for continuous monitoring
Oxygen
Electrochemical sensor / GC
ppm–%
Indicates corrosion potential
Non-condensables (N₂, Ar)
GC
ppm–%
Influences phase behavior
Sulfur species (SO₂, H₂S)
GC with sulfur detector
ppm
Required if impurities expected
B.5 Ship and Tanker Instrumentation Requirements
Ship and tank transport require instruments designed to operate under cryogenic or high-pressure conditions.
Table B-4 — Ship and Tanker Instrument Specifications
Tank level gauge
Certified geometric calibration
Determines loaded and delivered CO₂ mass
Tank pressure sensor
±0.1% accuracy; rated for full pressure range
Monitors boil-off and safety limits
Tank temperature sensors
Multi-depth array; ±0.2°C
Required for density estimation
Gas detection sensors
CO₂-specific; alarm triggers
Personnel safety during loading/unloading
Vent flow recorder (if used)
Traceable measurement or estimation capability
Quantifies boil-off releases
B.6 Pipeline Integrity and Leak Detection Instrumentation
While not used for custody transfer, integrity monitoring instruments support verification of losses and system safety.
Table B-5 — Pipeline Integrity Monitoring Instruments
Pressure/flow transient monitors
Detect anomalies suggesting leaks
Essential for long-distance pipelines
Fiber-optic acoustic sensing
Detects external interference or rupture
Used in high-risk areas
Corrosion probes
Monitor corrosion rate in real time
Useful for impurity-rich CO₂
Inline inspection (ILI) tools
Detect wall thinning, cracks, deformation
Periodic integrity checks
B.7 Calibration Requirements for Transport Instruments
Calibration ensures accuracy and traceability. Instruments must follow the minimum calibration frequencies specified in PCS requirements.
Table B-6 — Minimum Calibration Intervals
Ultrasonic flow meter
Annual
Calibration certificate
Coriolis flow meter
Annual
Zero stability verification
Pressure transmitters
Annual
Reference gauge comparison
Temperature sensors
Annual
Sensor drift test
GC analyzer
Monthly or per drift
Calibration gas records
Moisture analyzer
Quarterly
Sensor health verification
Weighbridge
Quarterly
Legal metrology certificate
B.8 Installation Considerations
Instrument performance depends heavily on installation quality. Pipes must provide sufficient straight-run length for ultrasonic meters, tanks must include certified level measurement tables, and sensors must be protected from external heat and vibration. Sampling ports must avoid moisture condensation or multiphase conditions, as these distort purity measurements.
Installation requirements must be documented in the engineering design file and made available during verification.
B.9 Data Output and Integration Requirements
All instruments must produce digital outputs suitable for integration into SCADA or equivalent data logging systems. Time synchronization between flow, pressure, temperature, and purity data is essential for accurate density and mass calculations. Redundant data pathways are recommended for critical custody transfer instruments.
Operators must ensure that data interfaces are stable, backed up, and protected from accidental or unauthorized modification.
Annex C — Transport Loss Calculation Examples And Standardized Templates
C.1 Purpose
Transport losses must be quantified accurately to ensure integrity of PCS MRV. Losses may arise from pipeline blowdowns, pressure-relief events, ship boil-off, tanker venting, intermediate storage depressurization, or small leaks. Annex C provides standardized calculation examples and templates that operators and VVBs can apply across different transport modes.
These examples illustrate acceptable PCS approaches for estimating CO₂ loss, documenting events, and completing mass balance reconciliations.
C.2 Example Calculations
C.2.1 Example Pipeline Blowdown Calculation
When a pipeline segment is depressurized for maintenance, the CO₂ released must be estimated using its initial pressure, final pressure, volume, and temperature.
Assume:
Pipeline internal volume: 120 m³
Initial pressure: 85 bar
Final pressure: 10 bar
Temperature: 25°C
Using a simplified real-gas equation:
Density at 85 bar, 25°C ≈ 700 kg/m³
Density at 10 bar, 25°C ≈ 18 kg/m³
Mass released ≈ (700 − 18) × 120 = 682 × 120 = 81,840 kg CO₂
This value must be recorded in the Transport Monitoring Report, along with the reason for blowdown.
C.2.2 Example Ship Boil-Off Calculation
Ship tanks experience boil-off when heat enters the tank, increasing temperature and vapor pressure.
Assume:
Tank volume: 1,200 m³
Initial liquid temperature: −48°C
Final liquid temperature: −46°C
Vapor pressure increase: 1.2 bar
Vapor density at −46°C: ~40 kg/m³
Vapor space volume: 150 m³
Estimated boil-off mass released ≈ 40 kg/m³ × 150 m³ × (pressure rise proportion)
If the pressure rise corresponds to release of 20% vapor volume:
Mass released ≈ 40 × 150 × 0.20 = 1,200 kg CO₂
This approach must be backed by validated vapor–liquid equilibrium (VLE) data.
C.2.3 Tanker Venting Example
Assume a road tanker experiences heat gain during a 3-hour idle period:
Tank pressure increased from 18 bar to 21 bar
Relief valve activated briefly, releasing enough vapor to return pressure to 20 bar
Using vapor density at 20 bar and 0°C ≈ 38 kg/m³
Estimated vent volume: 5 m³
Loss = 38 × 5 = 190 kg CO₂
All such events must be recorded with timestamps and cause descriptions.
C.2.4 Mass Balance Example for a Pipeline System
Assume:
Inlet metered mass: 150,000 tonnes
Outlet metered mass: 149,300 tonnes
Blowdown losses: 200 tonnes
Estimated leaks: 150 tonnes
Net delivered = 149,300 tonnes
Total loss = 700 tonnes
Discrepancy = 150,000 − (149,300 + 700) = 0 tonnes
Mass balance closes successfully. If discrepancy > uncertainty threshold, investigation is required.
C.3 Standardized PCS Templates
C.3.1 Transport Loss Log Template
Table C-1 — Loss Event Log
C.3.2 Ship Transport Voyage Record Template
Table C-2 — Ship Load/Unload Record
Operators should attach tank pressure/temperature graphs for each voyage.
C.3.3 Tanker Delivery Reconciliation Template
Table C-3 — Road/Rail Tanker Batch Reconciliation
C.3.4 Pipeline Mass Balance Template
Table C-4 — Pipeline Mass Balance Summary
Inlet mass
Continuous flow meter
Outlet mass
Continuous flow meter
Blowdown losses
Logged events
Estimated fugitive losses
Engineering estimate
Total losses
Sum
Net delivered mass
Outlet mass
Balance discrepancy
Should be <= uncertainty
C.3.5 CO₂ Quality Summary Template (Transport Mode Neutral)
Table C-5 — CO₂ Quality Reporting Template
CO₂ purity
GC
Inlet/outlet
Moisture
Hygrometer
Inlet/outlet
Oxygen
GC or electrochemical
Inlet/outlet
Nitrogen
GC
Inlet/outlet
Sulfur species
GC
As required
C.4 Guidance For Using Templates
All templates in this annex serve as standardized starting points for PCS reporting. Transport operators may expand them to reflect system-specific features, but the core data fields must remain intact. Each table must be accompanied by:
traceable measurement sources
calculation methods
supporting logs or calibration certificates
explanations for deviations or anomalies
Templates form a critical component of the Transport Monitoring Report and support consistent, efficient verification.
Annex D — Glossary And Technical References For CO₂ Transport Systems
D.1 Purpose
Annex D standardizes terminology and provides authoritative reference sources that underpin the engineering and monitoring expectations for CO₂ transport under PCS. Because transport involves multiple modes (pipeline, ship, tanker) and complex thermodynamic behavior, the glossary clarifies terms used throughout the guidance. The reference section ensures that PCS requirements remain aligned with globally recognized standards and scientific literature.
D.2 Glossary Of Transport-Related Terms
Acoustic Leak Detection — A technique that identifies leaks through sound or vibration signatures in pipelines.
Batch Transport — Discrete transport operations where CO₂ is moved in individual loads, such as road or rail tankers.
Blowdown — The rapid depressurization of a pipeline or vessel for maintenance or safety reasons, resulting in CO₂ release.
Boil-Off — Vapor generated in a CO₂ tank (typically on ships or tankers) due to heat transfer into the liquid.
Bulk Storage Tank — A large, fixed or mobile tank used to hold CO₂ before loading, after unloading, or between transport stages.
CO₂ Conditioning — Processes used to prepare CO₂ for transport, including dehydration, cooling, impurity removal, and pressure stabilization.
Critical Point — The temperature and pressure above which CO₂ cannot exist as a liquid (31.1°C, 73.8 bar for pure CO₂).
Custody Transfer — The formal transfer of responsibility for CO₂ from one party to another, requiring accurate metering and documentation.
Dense-Phase CO₂ — CO₂ at high pressure where it behaves as a liquid-like fluid with high density and low compressibility.
Depressurization — Controlled reduction of pressure in pipelines or tanks, typically performed during maintenance or emergency response.
Fugitive Emissions — Unintentional CO₂ releases from valves, seals, fittings, or material defects.
Hydrate — Ice-like crystalline compound formed when CO₂ and water are present under specific pressure–temperature conditions.
Inlet Meter — The instrumented point where CO₂ enters the transport boundary.
Intermediate Storage — Temporary storage facilities (buffer tanks, terminals) used between transport stages.
Leak Detection System — Integrated technology designed to detect pressure anomalies, flow deviations, or acoustic signals that indicate leakage.
Level Gauge — Instrument used to measure liquid height in tanks, enabling mass estimation in ships and tankers.
Mass Balance — A reconciliation of CO₂ entering and exiting a transport system, including losses.
Non-Condensable Gases — Gases such as nitrogen or oxygen that remain gaseous under transport conditions and influence phase behavior.
Outlet Meter — The instrumented point where CO₂ leaves the transport boundary and enters the storage system.
Phase Envelope — A diagram that shows the temperature–pressure boundaries within which CO₂ exists as solid, liquid, gas, or supercritical.
Pipeline Right-of-Way — Designated land area where pipelines are installed and maintenance and safety protocols apply.
Pressure Relief Valve — A safety device that releases CO₂ when internal pressure exceeds design limits.
Refrigerated CO₂ — Liquid CO₂ stored at low temperatures and moderate pressures, common in ship transport.
Relief Event — A release of CO₂ due to activation of a pressure relief valve or system.
Running Fracture — A propagating crack in a pipeline that may continue to grow after initial failure if not controlled.
SCADA — Supervisory Control and Data Acquisition system used for real-time transport monitoring.
Supercritical CO₂ — CO₂ above its critical temperature and pressure, exhibiting both liquid and gas characteristics.
Tank Calibration Table — Certified reference chart that correlates tank level measurements with liquid volume.
Thermal Cycling — Repeated temperature changes that may weaken tank or pipeline materials over time.
Two-Phase Flow — Flow where CO₂ simultaneously exists as more than one phase (gas + liquid), often undesirable in pipelines.
Vapor Pressure — The pressure at which CO₂ liquid and vapor coexist at a given temperature.
Venting — Intentional release of CO₂ to the atmosphere due to safety or operational requirements.
Voyage Log — A record maintained during ship transport that includes tank levels, temperatures, pressures, and venting events.
D.3 Technical References
This section identifies authoritative sources used in defining PCS transport requirements. Operators and VVBs should rely on these documents when designing, operating, or verifying CO₂ transport systems.
ISO Standards
ISO 27913:2016 - Carbon dioxide capture, transportation and geological storage — Pipeline transportation systems.
ISO 27916:2019 - Carbon dioxide capture, transportation and geological storage — Quantification and verification.
DNV Recommended Practices
DNV-RP-F104 — Design and Operation of Carbon Dioxide Pipelines.
DNV-RP-F103 — Submarine Pipeline Systems.
DNV-RP-F101 — Corroded Pipelines.
IPCC and IEAGHG Documents
IPCC Special Report on Carbon Dioxide Capture and Storage (2005).
IEAGHG Technical Reports on CO₂ pipeline transport, ship transport systems, and thermodynamic behavior.
API and ASME Standards
API MPMS (Manual of Petroleum Measurement Standards) for flow measurement.
ASME B31.4 and ASME B31.8 for pipeline design considerations (adapted for CO₂ where applicable).
Thermodynamic References
Span–Wagner Equation of State for CO₂.
Peng–Robinson Equation of State for CO₂ mixtures.
NIST REFPROP database: reference thermophysical properties of CO₂.
Maritime Transport Guidelines
IMO International Gas Carrier (IGC) Code.
Ship Classification Society requirements for CO₂ carriers (ABS, DNV, Lloyd’s Register).
Safety and Hazard Standards
OSHA CO₂ exposure guidelines.
NFPA standards for gas handling and emergency response.
D.4 Use of Glossary and References in PCS Verification
The glossary ensures consistent terminology among all parties, reducing ambiguity during monitoring, reporting, and verification. The reference set provides VVBs and operators with an authoritative scientific and engineering foundation for evaluating measurement systems, equipment performance, and operational safety.
PCS expects all CO₂ transport projects to reference appropriate standards from Annex D when developing monitoring plans, designing transport infrastructure, or justifying technical decisions.