ISO/DIS 6338-5:2026(en)
ISO/TC 67/SC 9
Secretariat: AFNOR
Date:2025-12-12
Calculations of greenhouse gas (GHG) emissions throughout the liquefied natural gas (LNG) chain —
Part 5:
Regasification
Calcul des émissions de gaz à effet de serre (GES) dans la chaîne gaz naturel liquéfié (GNL) —
Partie 5: Regazéification
© ISO 2026
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Contents
6 Quantification of GHG emissions 2
6.2 Identification of GHG sources and quantification approach 3
6.2.2 Emissions from fuel combustion 3
6.2.3 Emissions from flaring and venting 4
6.2.5 Emissions associated with imported energy, utilities, and consumables 5
6.3 Calculation of GHG emissions 5
7 GHG inventory quality management 6
Foreword
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This document was prepared by Technical Committee ISO/TC 67, Oil and gas industries including lower carbon energy, Subcommittee SC 9, Production, transport and storage facilities for cryogenic liquefied gases.
A list of all parts in the ISO 6338 series can be found on the ISO website.
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Introduction
Natural gas will play a key role in the energy transition (e.g. by replacing coal to produce electricity) and the use of liquefied natural gas (LNG) to transport natural gas is expected to increase. The process of liquefying natural gas is energy-intensive. Gas producers are increasingly accountable for their greenhouse gas (GHG) emissions and the ambition to reduce them. Furthermore, there is an emerging marketing demand for GHG data to enable commercial mechanisms such as offsetting to be utilized.
There is no standardized and auditable methodology to calculate the carbon footprint of the whole LNG chain (including but not limited to the well, upstream treatment, transportation, liquefaction, shipping, regasification and end user distribution). Various standards indicate possible approaches but are inconsistent in their results or not easily applicable.
The ISO 6338 series covers each part of the LNG chain and enables a consistent GHG inventory.
The KPIs and related requirements to access to key international initiatives, agreements and reporting/accounting standards on climate ambitions and zero carbon emission strategies are given in ISO 6338-1:2024, Annex B.
Attention should be paid to activities that can occur in different parts (e.g. gas treatment and distribution upstream of the liquefaction plant).
NOTE It is not possible to make like-for-like comparisons, or define a certification scheme, for one block only.
Calculations of greenhouse gas (GHG) emissions throughout the liquefied natural gas (LNG) chain —
Part 5:
Regasification
1.0 Scope
This document provides the part of the method to calculate the GHG emissions throughout the LNG chain specific to regasification. It covers activities from the inlet to the outlet of the regasification plant.
The general requirements are covered in ISO 6338-1.
2.0 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 6338‑1, Calculations of greenhouse gas (GHG) emissions throughout the liquefied natural gas (LNG) chain — Part 1: General
ISO 14044, Environmental management — Life cycle assessment — Requirements and guidelines
ISO 14064‑1, Greenhouse gases — Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals
3.0 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14064-1 and ISO 6338-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
4.0 Principles
The principles given in ISO 6338-1 shall be followed.
5.0 GHG inventory boundaries
The GHG report for regasification of LNG shall cover all associated facilities. The list in Table 1 is not exhaustive.
Table 1 — List of facilities within the scope of this document
LNG Regasification Facility | In scope | Out of scope |
|---|---|---|
LNG Carrier |
| X (ISO 6338-4) |
Marine Facilities (e.g. LNG unloading arms) | X |
|
LNG Storage | X |
|
Regasification Unit (e.g. high- and low-pressure pumps, vaporisers, boil off gas system, metering) | X |
|
Utilities (e.g. nitrogen, instrument air) | X |
|
Onsite power Generation | X |
|
Imported Utilities (e.g. power) | X |
|
Floating Storage and Regasification Unit (FSRU) (including ship utilities) | X |
|
Injection in gas grid | X |
|
Loading of Road/Rail Tankers | X |
|
Distribution of LNG by Road/Rail |
| X |
Gas Transmission Grid |
| X |
The organization having financial and/or operational control over the facilities shall report all GHG emissions and removals within the reporting boundaries at least on an annual average basis.
Injection in gas grid is considered as done by the plant operator.
6.0 Quantification of GHG emissions
6.1 General
A typical regasification plant is shown in Figure 1 from GIIGNL.
Key
1 unloading arms
2 berth/jetty
3 LNG carrier
4 submerged LP pumps
5 ship gas return compressor
6 flare
7 boil-off gas compressors
8 BOG recondenser
9 open rack vaporizer
10 fuel gas
11 submerged combustion vaporizer
12 THT
13 odorization
14 metering
15 pipeline
16 to sea
17 from sea
18 HP pumps
Figure 1 — Typical regasification plant
ISO 20257-1 and ISO 20257-2 provide information on FSRU.
6.1.1 Identification of GHG sources and quantification approach
6.1.2 General
The general approach is given in ISO 6338-1. Emissions estimation guidance for LNG value chain can be found in the API Consistent Methodology for Estimating Greenhouse Gas Emissions from Liquified Natural Gas (LNG) Operations (2015)[26].
6.1.3 Emissions from fuel combustion
The quantification approaches for emissions from fuel combustion are described in Table 2.
Table 2 — Emissions from fuel combustion
Source | Examples | Quantification approach |
|---|---|---|
Gas turbine drivers | Primary gas compression drivers, power generation drivers, other refrigeration drivers (e.g. fractionation), CO2 sequestration compressor drivers | Typically, primary data are recorded to enable GHG quantification. As a minimum, fuel gas consumption and composition shall be measured (noting that fuel composition at an LNG plant can vary widely depending on operating mode). |
Diesel drivers | Firewater pumps, power generation, boiler feed water pumps | Operator may report typical annual diesel consumption and include resulting annual emissions as a nominal allowance in the GHG calculation. |
Boilers | Steam for turbine drivers, steam for process heating | Typically, primary data are recorded to enable GHG quantification for major fuel consumers (contributing >5 % of the total GHG emissions.) As a minimum, fuel gas consumption and composition shall be measured. |
Fired heaters | Regeneration gas heater, heating medium heater, direct fired reboilers | If fuel measurements are available, operator should record total fuel gas consumption and composition. If direct fuel measurements are not available, a calculation may be used on operating duty and efficiency. |
Incinerators | Acid gas vent incinerator, thermal oxidizers, catalytic oxidizers, waste disposal | As above. |
Unburned hydrocarbons (for example methane slip from combustion engines) in general shall be taken into account in all sections. If fuel measurements are available, operator should record total fuel gas consumption combined with combustion efficiency data for the fired equipment used. Ideally, combustion efficiency should be validated with measured emission data. | ||
6.1.4 Emissions from flaring and venting
The quantification approaches for emissions from flaring and venting are described in Table 3.
Table 3 — Emissions from flaring and venting
Source | Examples | Quantification approach |
|---|---|---|
Atmospheric venting of unburned hydrocarbon | Feed gas pipeline blowdown, storage tank venting and pressure protection, loading arm blowdown, compressor blowdown, flare operation with failed ignition, venting from gas chromatographs and calorimeters, venting from seals of compression units | Typically, primary data are recorded for significant venting events, such as pipeline blowdown. Primary data are recorded to enable GHG quantification contributing =>5 % of the site’s total GHG emissions. The primary data may be calculated for smaller individual sources. |
Flares | Process plant pressure protection, depressuring, storage tank pressure protection, boil-off gas management, refrigerant composition management, purge gas and pilots | Typically, primary data are recorded to enable GHG quantification from flaring contributing >5 % of the site’s total GHG emissions. The primary data may be calculated for smaller individual sources. |
Nitrogen vents from NRU | Nitrogen vents from nitrogen rejection units can contain methane, and are generally routed to atmosphere | If primary data are not available, a calculated allowance using licensor composition data may be used. |
Unburned hydrocarbons (for example methane slip from combustion engines) in general shall be taken into account in all sections. Operator should record total flare gas, combined with combustion efficiency data for the flare tip used. Ideally, combustion efficiency should be validated with measured emission data. For more information, see [16] | ||
6.1.5 Fugitive emissions
The quantification approaches for fugitive emissions are described given in Table 4.
Table 4 — Fugitive emissions
Source | Examples | Quantification approach |
|---|---|---|
Permeation | Emissions through porous materials | Can be calculated with emissions factors for different materials. |
Gas leaks | Leaks from pipes and fittings, rotating equipment seals, storage tank seals | Typically done via calculation using equipment count and standard leakage factors. Measured leakage data from atmospheric monitoring may be used to adjust the leakage factors applied. |
There might also be emissions from refrigerants.
6.1.6 Emissions associated with imported energy, utilities, and consumables
Emissions associated with imports require data from the exporter. Contractual relationship with the exporter should include a requirement to provide emissions data. In the absence of reliable GHG data for imports, the calculation shall account for the complete supply chain for the imported commodity. The cut-off criteria for reporting shall be defined in accordance with ISO 14044.
The quantification approaches for emissions associated with imported energy are described in Table 5 and emissions from other utilities and consumables are described in Table 6.
Table 5 — Emissions associated with imported energy
Source | Examples | Quantification approach |
|---|---|---|
Electric power | Power from third party fossil fuel combustion, power from grid | Primary data are recorded for total power consumed. GHG quantification requires intensity data from the supplier. In case of supply from a grid, the average intensity from all suppliers to the grid shall be used. |
Heat or steam | Steam or heating medium from third party | Primary data are recorded for total imported heating utility. GHG quantification requires intensity data from the supplier. In case of heat generated from waste heat externally, emissions from primary fuel use should be considered. |
Table 6 — Emissions from other utilities and imported consumables
Source | Examples | Quantification approach |
|---|---|---|
Other utilities | Cooling, air, nitrogen, water | Primary data are recorded for total imported utility. GHG quantification requires intensity data from the supplier. Secondary data may be used if primary data are not available. |
Imported consumables | Refrigerant not produced on site | Primary data are recorded for quantities consumed. GHG quantification from consumables requires intensity data from the supplier. Secondary data may be used if primary data are not available. |
6.2 Calculation of GHG emissions
The calculation of GHG emissions is given in ISO 6338-1.
6.2.1 Preferred units
The preferred units are given in ISO 6338-1. A list of unit conversion factors is provided in ISO 6338-1:2024, Annex A.
6.2.2 Allocation
The principles and methodology are given in ISO 6338-1.
All emissions associated with gas regasification processes shall be also allocated to the types and quantities of energy used and produced in the process (heat/cold/electricity).
If products/services are sold downstream of the plant, allocation methods shall be defined (energy/mass based).
6.2.3 Carbon capture
The opportunities for carbon capture and the quantification of carbon capture benefit are described in ISO 6338-1.
7.0 GHG inventory quality management
The quality management of the GHG inventory is given in ISO 6338-1.
8.0 GHG reporting
The reporting of GHG emissions is given in ISO 6338-1.
9.0 Independent review
The independent review of the quantification of the GHG emissions is given in ISO 6338-1.
Bibliography
[1] ISO 6338, Method to calculate GHG emissions at LNG plant
[2] ISO 14020, Environmental statements and programmes for products — Principles and general requirements
[3] ISO 14064‑2, Greenhouse gases — Part 2: Specification with guidance at the project level for quantification, monitoring and reporting of greenhouse gas emission reductions or removal enhancements
[4] ISO 14064‑3, Greenhouse gases — Part 3: Specification with guidance for the verification and validation of greenhouse gas statements
[5] ISO 14065, General principles and requirements for bodies validating and verifying environmental information
[6] ISO 14066, Environmental information — Competence requirements for teams validating and verifying environmental information
[7] ISO 14067, Greenhouse gases — Carbon footprint of products — Requirements and guidelines for quantification
[8] ISO 20257‑1, Installation and equipment for liquefied natural gas — Design of floating LNG installations — Part 1: General requirements
[9] ISO 20257‑2, Installation and equipment for liquefied natural gas — Design of floating LNG installations — Part 2: Specific FSRU issues
[10] CEN/TS 17874, Methodology for methane emissions quantification for gas transmission, distribution and storage systems and LNG terminals
[11] PAS 2060, Specification for the demonstration of carbon neutrality
[12] EPA AP-42, Compilation of Air Emission Factors
[13] EPA Method-21, Determination of Volatile Organic Compound Leaks
[14] Marcogaz, Recommendations on LDAR campaigns
[15] Methane Guiding Principles, Reducing Methane Emissions: Best Practice Guide Equipment Leaks
[16] API, compendium on GHG methodology
[17] GHG Protocol, Scope 2 guidance
[18] IEA, Yearly report Emission factors
[19] IPCC, Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories
[20] IPPC, 6th assessment report
[21] IOGP report 2.59-197 Method for estimating atmospheric emissions from E&P operations
[22] IPIECA Petroleum industry guideline for reporting GHG
[23] World Business Council for Sustainable Development (WBCSD)/World Resources Institute (WRI). Greenhouse Gas Protocol, Corporate Accounting and Reporting Standard, April 2004
[24] EFFAS THE EUROPEAN FEDERATION OF FINANCIAL ANALYSTS SOCIETIES, Key Performance Indicators for Environmental, Social & Governance Issues
[25] United Nations, Global indicator framework for the Sustainable Development Goals and targets of the 2030 Agenda for Sustainable Development
[26] API Consistent Methodology for Estimating Greenhouse Gas Emissions from Liquefied Natural Gas (LNG) Operations
