oSIST prEN ISO 6338-1:2026

Calculations of greenhouse gas (GHG) emissions throughout the liquefied natural gas (LNG) chain - Part 1: General (ISO 6338-1:2024)

This document:
—     provides the general part of the method to calculate the greenhouse gas (GHG) emissions throughout the liquefied natural gas (LNG) chain, a means to determine their carbon footprint;
—     defines preferred units of measurement and necessary conversions;
—     recommends instrumentation and estimation methods to monitor and report GHG emissions. Some emissions are measured; and some are estimated.
This document covers all facilities in the LNG chain. The facilities are considered “under operation”, including emissions associated with initial start-up, maintenance, turnaround and restarts after maintenance or upset. The construction, commissioning, extension and decommissioning phases are excluded from this document but can be assessed separately.
This document covers all GHG emissions. These emissions spread across scope 1, scope 2 and scope 3 of the responsible organization. Scope 1, 2 and 3 are defined in this document. All emissions sources are covered including flaring, combustion, cold vents, process vents, fugitive leaks and emissions associated with imported energy.
This document describes the allocation of GHG emissions to LNG and other hydrocarbon products where other products are produced (e.g. LPG, domestic gas, condensates, sulfur).
This document does not cover specific requirements on natural gas production and transport to LNG plant, liquefaction, shipping and regasification.
This document is applicable to the LNG industry.

Berechnungsverfahren der Treibhausgasemissionen (THG) in der gesamten Flüssigerdgas-(LNG-)Kette - Teil 1: Allgemeines (ISO 6338-1:2024)

Calcul des émissions de gaz à effet de serre (GES) dans la chaîne gaz naturel liquéfié (GNL) - Partie 1: Généralités (ISO 6338-1:2024)

Le présent document:
—     fournit les généralités sur la méthode de calcul des émissions de gaz à effet de serre (GES) dans la chaîne gaz naturel liquéfié (GNL), un moyen de déterminer leur empreinte carbone;
—     définit les unités de mesure privilégiées et les conversions nécessaires;
—     recommande l'instrumentation et les méthodes d'estimation pour surveiller et déclarer les émissions de GES. Certaines émissions sont mesurées et d'autres estimées.
Le présent document couvre toutes les installations de la chaîne GNL. Les installations sont considérées comme étant «en exploitation», cela inclut les émissions associées à la mise en service, au démarrage initial, à la maintenance, à la révision et aux redémarrages après une maintenance ou perturbation. Les phases de construction, de mise en service, d'extension et d'abandon sont exclues, mais peuvent être évaluées séparément.
Le présent document couvre toutes les émissions de GES. Ces émissions se répartissent entre la catégorie 1, la catégorie 2 et la catégorie 3 de l'organisme responsable. Les catégories 1, 2 et 3 sont définies dans le présent document. Toutes les sources d'émission sont couvertes, y compris le torchage, la combustion, les évents froids, les évents de procédé, les fuites fugitives et les émissions associées à l'énergie importée.
Ce document décrit l'allocation des émissions de GES au GNL et aux autres produits d'hydrocarbures lorsque d'autres produits sont produits (par exemple, GPL, gaz domestique, condensats, soufre, etc.).
Ce document ne couvre pas les exigences spécifiques relatives à la production, au transport jusqu'à l'usine GNL, à la liquéfaction, au transport maritime et à la regazéification.
Ce document est applicable à l'industrie du GNL.

Izračuni emisij toplogrednih plinov v oskrbovalni verigi z utekočinjenim zemeljskim plinom (LNG) - 1. del: Splošno (ISO 6338-1:2024)

Ta dokument:
- zagotavlja splošni del metode za izračun emisij toplogrednih plinov (GHG) skozi celotno verigo utekočinjenega zemeljskega plina (LNG), kar omogoča določitev njihovega ogljičnega odtisa;
- opredeljuje prednostne merske enote in potrebne pretvorbe;
- priporoča instrumentacijo in metode ocenjevanja za spremljanje in poročanje o emisijah GHG. Nekatere emisije so merjene; nekatere so ocenjene.
Ta dokument zajema vse objekte v verigi LNG. Objekti se štejejo kot "v obratovanju", vključno z emisijami, povezanimi z začetnim zagonom, vzdrževanjem, prenovo in ponovnimi zagoni po vzdrževanju ali motnjah. Faze gradnje, zagona, širitve in razgradnje so izključene iz tega dokumenta, vendar se lahko ocenijo ločeno.
Ta dokument zajema vse emisije GHG. Te emisije se raztezajo čez obseg 1, obseg 2 in obseg 3 odgovorne organizacije. Obseg 1, 2 in 3 so opredeljeni v tem dokumentu. Zajeti so vsi viri emisij, vključno z baklami, zgorevanjem, hladnimi odzračevalniki, procesnimi odzračevalniki, uhajanjem in emisijami, povezanimi z uvoženo energijo.
Ta dokument opisuje dodelitev emisij GHG LNG-ju in drugim ogljikovodikovim proizvodom, kjer se proizvajajo drugi proizvodi (npr. LPG, domači plin, kondenzati, žveplo).
Ta dokument ne zajema posebnih zahtev glede proizvodnje zemeljskega plina in transporta do obrata LNG, utekočinjanja, ladijskega prevoza in reuplinjanja.
Ta dokument je uporaben za industrijo LNG.

General Information

• Status: Not Published
• Public Enquiry End Date: 01-Jun-2026
• ICS: 13.020.40 - Pollution, pollution control and conservation
• ICS: 75.020 - Extraction and processing of petroleum and natural gas
• Technical Committee: DPL - Gas supply
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 07-Apr-2026
• Due Date: 25-Aug-2026
• Ref Project: prEN ISO 6338-1 - Calculations of greenhouse gas (GHG) emissions throughout the liquefied natural gas (LNG) chain - Part 1: General (ISO 6338-1:2024)

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2026
Izračuni emisij toplogrednih plinov v oskrbovalni verigi z utekočinjenim
zemeljskim plinom (LNG) - 1. del: Splošno (ISO 6338-1:2024)
Calculations of greenhouse gas (GHG) emissions throughout the liquefied natural gas
(LNG) chain - Part 1: General (ISO 6338-1:2024)
Berechnungsverfahren der Treibhausgasemissionen (THG) in der gesamten
Flüssigerdgas-(LNG-)Kette - Teil 1: Allgemeines (ISO 6338-1:2024)
Calcul des émissions de gaz à effet de serre (GES) dans la chaîne gaz naturel liquéfié
(GNL) - Partie 1: Généralités (ISO 6338-1:2024)
Ta slovenski standard je istoveten z: prEN ISO 6338-1
ICS:
13.020.40 Onesnaževanje, nadzor nad Pollution, pollution control
onesnaževanjem in and conservation
ohranjanje
75.020 Pridobivanje in predelava Extraction and processing of
nafte in zemeljskega plina petroleum and natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

International
Standard
ISO 6338-1
First edition
Calculations of greenhouse gas
2024-01
(GHG) emissions throughout the
liquefied natural gas (LNG) chain —
Part 1:
General
Calcul des émissions de gaz à effet de serre (GES) dans la chaîne
gaz naturel liquéfié (GNL) —
Partie 1: Généralités
Reference number
ISO 6338-1:2024(en) © ISO 2024

ISO 6338-1:2024(en)
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 6338-1:2024(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principles . 3
4.1 General .3
4.2 Relevance .3
4.3 Completeness .3
4.4 Consistency .3
4.5 Transparency .3
4.6 Accuracy .3
4.7 Conservativeness.3
5 GHG inventory boundaries . 3
6 Quantification of GHG emissions . 4
6.1 Identification of GHG sources and quantification approach .4
6.1.1 General .4
6.1.2 Emissions from fuel combustion . .4
6.1.3 Emissions from flaring and venting .5
6.1.4 Fugitive emissions .6
6.1.5 Emissions associated with imported energy, utilities, and consumables .6
6.2 Calculation of GHG emissions .6
6.2.1 Requirements and guidance .6
6.2.2 GHG inventory . .7
6.2.3 GHG quantification methods for fuel combustion .9
6.2.4 GHG quantification methods for flaring and venting .9
6.2.5 GHG quantification methods for fugitive emissions .10
6.2.6 Quantification methods for emissions from imported energy, utilities, and
consumables .10
6.2.7 Relevant period and frequency .11
6.3 Preferred units .11
6.4 Allocation .11
6.4.1 Principles .11
6.4.2 Methodology . .11
6.5 Carbon capture . 12
6.5.1 Opportunities for carbon capture. 12
6.5.2 Quantification of carbon capture benefit . 13
7 GHG inventory quality management .13
7.1 General . 13
7.2 GHG emission calculation approach .14
7.3 Estimation of inventory uncertainties .14
7.4 Procedures for documentation and archiving .14
7.5 Quality control .14
7.6 Quality assurance . 15
8 GHG reporting .15
8.1 General . 15
8.2 Additional information. 15
8.3 GHG emission reduction .16
8.4 Carbon offset and emission trading . .16
9 Independent review . .16
Annex A (informative) Conversion factors for reference . 17

iii
ISO 6338-1:2024(en)
Annex B (informative) International initiatives on climate ambitions .18
Annex C (informative) Carbon footprint (CFP) of e-methane .20
Bibliography .22

iv
ISO 6338-1:2024(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
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.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
ISO 6338-1:2024(en)
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, starting with liquefaction.
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.
An example for e-methane is given in Annex C.

vi
International Standard ISO 6338-1:2024(en)
Calculations of greenhouse gas (GHG) emissions throughout
the liquefied natural gas (LNG) chain —
Part 1:
General
1 Scope
This document:
— provides the general part of the method to calculate the greenhouse gas (GHG) emissions throughout the
liquefied natural gas (LNG) chain, a means to determine their carbon footprint;
— defines preferred units of measurement and necessary conversions;
— recommends instrumentation and estimation methods to monitor and report GHG emissions. Some
emissions are measured; and some are estimated.
This document covers all facilities in the LNG chain. The facilities are considered “under operation”, including
emissions associated with initial start-up, maintenance, turnaround and restarts after maintenance or
upset. The construction, commissioning, extension and decommissioning phases are excluded from this
document but can be assessed separately.
This document covers all GHG emissions. These emissions spread across scope 1, scope 2 and scope 3 of the
responsible organization. Scope 1, 2 and 3 are defined in this document. All emissions sources are covered
including flaring, combustion, cold vents, process vents, fugitive leaks and emissions associated with
imported energy.
This document describes the allocation of GHG emissions to LNG and other hydrocarbon products where
other products are produced (e.g. LPG, domestic gas, condensates, sulfur).
This document does not cover specific requirements on natural gas production and transport to LNG plant,
liquefaction, shipping and regasification.
This document is applicable to the LNG industry.
2 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 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
API Consistent Methodology for Estimating Greenhouse Gas Emissions from Liquefied Natural Gas (LNG)
Operations
ISO 6338-1:2024(en)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14064-1 and the following 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/
3.1
global warming potential
GWP
ratio of the time-integrated radiative forcing (warming effect) from the instantaneous release of 1 kg of the
GHG relative to that from the release of 1 kg of CO
3.2
scope 1
direct greenhouse gas emissions
direct GHG emissions
emissions coming from sources that are owned or controlled by the facility
Note 1 to entry: This can be the emissions that are directly created by product fabrication or synthesis, for example,
combustion fumes from a refinery.
3.3
scope 2
indirect greenhouse gas emissions from purchased and consumed energy
indirect GHG emissions from purchased and consumed energy
emissions from the generation of imported electricity, steam, and heating/cooling consumed by the facility
Note 1 to entry: These emissions physically occur at the facility where electricity, steam and cooling or heating are
generated but as a user of the energy, the consuming party is still responsible for the greenhouse gas emissions that
are being created.
3.4
scope 3
other indirect greenhouse gas emissions
other indirect GHG emissions
emissions from sources that are not owned and not directly controlled by the facility
Note 1 to entry: However, they are related to the company’s activities. This is usually considered to be the supply chain
of the company, so emissions caused by vendors within the supply chain, outsourced activities, and employee travel
and commute. In many industries, these emissions account for the biggest amount of GHG emissions. This is due to
the fact that in today’s economy, many tasks are outsourced and few companies own the entire value chain of their
products.
3.5
quality assurance
QA
planned system of review procedures conducted by personnel not directly involved in the inventory
compilation/development process
3.6
quality control
QC
planned system of review procedures conducted by personnel not directly involved in the inventory
compilation/development process

ISO 6338-1:2024(en)
4 Principles
4.1 General
The application of the principles specified in 4.2 to 4.7 is fundamental to guaranteeing that GHG calculations
are a true and fair account.
4.2 Relevance
Use data, methods, criteria, and assumptions that are appropriate for the intended use of reported
information. The quantification and reporting of GHG emissions shall include only information that users –
both internal and external to the plant – need for their decision-making. This information shall thus fit the
intended purpose of the GHG project and meet the expectations or requirements of its users. Data, methods,
criteria, and assumptions that are misleading or that do not conform to this document are not relevant and
shall not be included.
4.3 Completeness
Consider all relevant information that can affect the accounting and quantification of GHG reductions, and
complete all requirements. All relevant information shall be included in the quantification of GHG emissions.
A GHG monitoring plan shall also specify how all data relevant to quantifying GHG reductions will be
collected.
4.4 Consistency
Use data, methods, criteria, and assumptions that allow meaningful and valid comparisons. The credible
quantification of GHG emissions requires that methods and procedures be always in the same manner,
that the same criteria and assumptions be used to evaluate significance and relevance, and that any data
collected and reported be compatible enough to allow meaningful comparisons over time.
4.5 Transparency
Provide clear and sufficient information for reviewers to assess the credibility and reliability of GHG
emissions claims. Transparency is critical for quantifying and reporting GHG reductions, particularly given
the flexibility and policy-relevance of many GHG accounting. GHG information shall be compiled, analysed,
and documented clearly and coherently so that reviewers can evaluate its credibility. Information relating
to the GHG assessment boundary and the estimation of baseline emissions should be sufficient to enable
reviewers to understand how all conclusions were reached.
4.6 Accuracy
Uncertainties with respect to GHG measurements, estimates, or calculations should be reduced as much as
is practical, and measurement and estimation methods shall avoid bias. Acceptable levels of uncertainty
depend on the objectives for implementing a GHG project and the intended use of quantified GHG reductions.
Where accuracy is sacrificed, data and estimates used to quantify GHG reductions shall be conservative.
4.7 Conservativeness
Where data and assumptions are uncertain and where the cost of measures to reduce uncertainty is not
worth the increase in accuracy, best endeavours should be made to use the most probable data, with an
analysis of the impact of likely uncertainty margins.
5 GHG inventory boundaries
Table 1 is a template for the reporting boundaries of the GHG report.

ISO 6338-1:2024(en)
Table 1 — List of facilities
In scope of Out of scope
Relevant part of ISO 6338 Comment
the report of the report
Facility A X
Facility B 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.
6 Quantification of GHG emissions
6.1 Identification of GHG sources and quantification approach
6.1.1 General
The main emission sources to consider derive from fuel combustion, flaring, releases to atmosphere
(including fugitive emissions) and emissions associated with imported energy or consumables. Tables 2 to 5
give an initial checklist of emission sources to consider, and an overview of typical quantification methods
suitable for different emission sources.
The chosen method of quantification per emissions source differs from one facility to another. Different
facilities have access to a varying number of flow meters, composition analysis equipment and level meters
available.
Operators shall develop a GHG quantification plan to map out how all emission sources can best be identified
in the facility, with a preference to obtain primary data for all major emission sources. The measurement
plan shall also include an assessment of data accuracy and impact on the total GHG emissions calculation.
This assessment allows the operator to assess if there is a need to further improve the amount or accuracy of
instruments available for the total assessment. Guidance on this assessment is detailed in ISO 14064-1:2018,
Annex C.
A list of activity data shall be defined based on reliability as primary and secondary data:
— primary data: quantified value of a process or an activity obtained from a direct measurement or a
calculation based on direct measurements;
— secondary data: data obtained from sources other than primary data.
Primary data shall be used. Only in the absence of primary data, secondary data may be used, which can
include estimated quantities and industry average emission factors.
Typically, primary data are recorded to enable GHG quantification contributing > 5 % of the site’s total
GHG emissions. For smaller individual sources a calculated approach is acceptable. CEN/TS 17874 defines
material and non-material methane emissions.
6.1.2 to 6.1.5 describe sources to consider and typical quantification approach for the main emissions
sources.
6.1.2 Emissions from fuel combustion
Table 2 is a template for describing the quantification approaches for emissions from fuel combustion.

ISO 6338-1:2024(en)
Table 2 — Emissions from fuel combustion
Source Examples Quantification approach
Gas turbine Primary liquefaction drivers, power genera- Typically, primary data are recorded to ena-
drivers tion drivers, other refrigeration drivers (e.g. ble GHG quantification. As a minimum, fuel gas
fractionation), CO sequestration compres- consumption and composition are required. (Fuel
sor drivers composition at an LNG plant can vary widely de-
pending on operating mode.)
Diesel drivers Firewater pumps, power generation, boiler Operator may report typical annual diesel con-
feed water pumps sumption and include resulting annual emissions
as a nominal allowance in the GHG calculation.
Boilers Steam for turbine drivers, steam for process Typically, primary data are recorded to enable
heating GHG quantification for major fuel consumers (con-
tributing >5 % of the total GHG emissions.) As a
minimum, fuel gas consumption and composition
shall be measured.
Fired heaters Regeneration gas heater, heating medium If fuel measurements are available, operator
heater, direct fired reboilers should record total fuel gas consumption and
composition. If direct fuel measurements are not
available, a calculation based on operating duty
and efficiency is acceptable.
Incinerators Acid gas vent incinerator, thermal oxidizers, As above.
catalytic oxidizers, waste disposal
Unburned hydrocarbons 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.
6.1.3 Emissions from flaring and venting
Table 3 is a template for describing the quantification approaches for emissions from flaring and venting.
Table 3 — Emissions from flaring and venting
Source Examples Quantification approach
Atmospheric waste Acid gas vent, sulfur plant tail gas Typically, primary data are recorded to enable
disposal from GHG quantification from venting contributing
treating units >5 % of the site’s total GHG emissions. For smaller
individual sources a calculated approach based
on heat and material balance data is acceptable.
As a minimum, fuel gas consumption and compo-
sition are required.
Atmospheric vent- Feed gas pipeline blowdown, storage tank Typically, primary data are recorded for signifi-
ing of unburned venting and pressure protection, loading cant venting events, such as pipeline blowdown.
hydrocarbon arm blowdown, compressor blowdown, flare A calculated approach is acceptable for venting
operation with failed ignition events contributing <5 % of total annual emis-
sions.
Flares Process plant pressure protection, depres- Typically, primary data are recorded to enable
surising, storage tank pressure protection, GHG quantification from flaring contributing
boil-off gas management, refrigerant compo- >5 % of the site’s total GHG emissions. For smaller
sition management, purge gas and pilots individual sources a calculated approach is ac-
ceptable.
Nitrogen vents Nitrogen vents from NRUs can contain meth- If primary data are not available, a calculated
from nitrogen ane and are generally routed to atmosphere allowance using licensor composition data may be
rejection units used.
(NRUs)
Unburned hydrocarbons 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 meas-
ured emission data.
ISO 6338-1:2024(en)
6.1.4 Fugitive emissions
Table 4 is a template for describing the quantification approaches for fugitive emissions.
Table 4 — Fugitive emissions
Source Examples Quantification approach
Permeation Emissions through porous materials Can be calculated with emissions factors for dif-
ferent materials.
Gas leaks Leaks from pipes and fittings, rotating Typically done via calculation using equipment
equipment seals, storage tank seals count and standard leakage factors. Measured
leakage data from atmospheric monitoring may
be used to adjust the leakage factors applied.
6.1.5 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.
Table 5 is a template for quantification approaches for emissions associated with imported energy, utilities
and consumables.
Table 5 — Emissions associated with imported energy, utilities, and consumables
Source Examples Quantification approach
Electric power Power from third party fossil fuel combus- Primary data are recorded for total power con-
tion, power from grid sumed. GHG quantification requires intensity
data from the supplier. In case of supply from a
grid, the average intensity from all suppliers to
the grid is required.
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, emissions from pri-
mary fuel use may be excluded, but supplemental
emissions such as pumping power, or back up
fired heaters or boilers shall be included.
Other utilities Cooling, air, nitrogen, water Primary data are recorded for total imported
utility. GHG quantification requires intensity data
from the supplier. Secondary data are acceptable
if primary data are not available.
Imported Refrigerant not produced on site Primary data are recorded for quantities con-
consumables sumed. GHG quantification from consumables
requires intensity data from the supplier. Second-
ary data are acceptable if primary data are not
available.
6.2 Calculation of GHG emissions
6.2.1 Requirements and guidance
This subclause provides requirements and guidance regarding the evaluation of activity data and emission
factors required to convert emission source data to GHG emissions. In some cases, emissions are measured
directly (e.g. in case of venting), but most commonly a calculation is required to convert measured data to
reported emissions (e.g. in case of fuel combustion).

ISO 6338-1:2024(en)
Emission calculations shall be performed in accordance with API Consistent Methodology for Estimating
Greenhouse Gas Emissions from Liquefied Natural Gas (LNG) Operations.
The key input data required to derive an emission factor are flowrate, composition, and combustion
efficiency.
For flowrate, measured data should be used. However, in the absence or failure of measurement
instrumentation, calculated approaches may be used, e.g. based on heat and material balances, or other data
such as pressure drop which may be used to estimate a flowrate.
For composition, measured data should also be used. However, in the absence of measured data, calculated
and estimated approaches may be used, e.g. based on periodic sampling or calculation from the heat and
material balance. For sources with predictable composition (e.g. diesel fuel) standard emission factors may
[14]
be used. See API GHG Compendium for emissions standards and approach.
For combustion efficiency, measured data should be used. However, in the absence of directly measured
data, the equipment vendor can supply efficiency data based on factory testing of their equipment or refer to
[14]
API GHG Compendium for typical values.
[7]
For methane emissions, CEN/TS 17874 defines that generic emission factors can only be used for non-
material emissions
Each time a GHG emission evaluation is reported, the calculation approach shall also be stated, recognising
that the quality of data available for this calculation impacts the accuracy of the results.
LNG plant GHG emissions are estimated using a combination of methodologies. Elements of the method
consists of:
— direct measurements including mass balance approaches;
— emission factors including those provided by equipment manufacturers;
— engineering calculations that are based on process knowledge.
6.2.2 GHG inventory
6.2.2.1 General
A GHG emissions inventory is comprised of measured, calculated and estimated emissions from individual
emission sources that are aggregated to produce the inventory, in accordance with the following steps.
— Define the purpose and content of the GHG inventory, GHG emissions sources and assessment boundary
and the reference base year.
— Select activity data and emission factors: provide sector-specific good practice guidance and references
for emission factors (see Clause 6).
— Select measuring technologies or calculation methods: describe different quantification methods
depending on the availability of site-specific activity data and emission factors.
— Define the data recording and reporting criteria, and related documentation.
GHG Inventory methodology and process shall include the following elements:
— base year;
— GHG emission sources;
— activity data inputs;
— GHG emission factors;
— Global warming potentials.
ISO 6338-1:2024(en)
The plant owner shall define requirements for the GHG inventory records, reports and documentation and
archive it in a consistent manner.
6.2.2.2 Base year definition
A meaningful and consistent comparison of emissions over time requires that companies set a performance
datum with which to compare current emissions. This performance datum is referred to as the base year
emissions. It describes an activity or a set of activities that result in GHG emissions against which current
activity emissions can be compared for the purpose of quantifying GHG reductions.
The selection of base year shall represent and be consistent to the following criteria:
— same boundary of activities;
— same technologies or practices;
— same plant configuration, deployment, implementation, operation;
— same type, quality, and similar quantity of product(s) or service(s) as the current year.
For consistent tracking of emissions overtime, the past base year emissions shall be recalculated, according
to the new reporting boundary, when significant structural changes occur for any of the above criteria
during the year of reporting.
6.2.2.3 GHG emission sources
The plant owner shall define a GHG assessment boundary through the following steps:
— identify the plant activities that comprise the GHG project;
— identifying the primary (major sources) and secondary (minor sources) effects associated with each
plant activity listed in 6.1;
— thoroughly analysing the secondary effects to determine which are significant for the purpose of
estimating and quantifying GHG reductions.
For complete, accurate and transparent quantification of GHG reductions, the GHG assessment boundary
shall be clearly defined and reported. The GHG assessment boundary shall include the primary and
significant secondary effects of all operational activities. Specific exclusions or inclusions shall be clearly
identified and justified/explained; and exclusions shall not exceed 5 % of the aggregate GHG emissions in
scope 1 and scope 2.
6.2.2.4 GHG emission factors
Different types of emission factors are used to convert activity data and upstream/downstream data into
GHG emissions data.
a) Material emission factors
1) Life cycle materials emission factors, which include emissions that occur at every stage of a
material/product’s life, from raw material acquisition or generation of natural resource to end of
life.
2) Cradle-to-gate (“upstream”) emission factors, which include all emissions that occur in the life cycle
of a material/product up to the point of sale by the producer.
b) Energy emission factors
1) Life cycle fuel emission factors, which include not only the emissions that occur from combusting
the fuel (Combustion emissions factors) but all other emissions that occur in the life cycle of the fuel
such as emissions from extraction, processing, and transportation of fuels (Well-to-tank emission
factors).
ISO 6338-1:2024(en)
2) Combustion emission factors, which include only the emissions that occur from combusting the
fuel.
c) Upstream and downstream transportation factors often included in specific international models such
as the GHG protocol.
Company shall define emission factors used to convert activity data and upstream/downstream data into
GHG emissions data, record and archive it in a consistent manner.
6.2.2.5 GHG global warming potentials
Each GHG has a unique atmospheric lifetime and heat-trapping potential. To express emissions based on
their global warming potential, the mass of emissions of each GHG is multiplied by its corresponding GWP.
The result is referred to as the CO -equivalent (CO -eq) emissions. Because the GWP of CO is always 1, the
2 2 2
mass emissions of CO and the CO -eq emissions are identical. Global warming potentials are calculated
2 2
over different time periods, typically ranging from 20 years to 500 years. The most common time period for
expressing GWPs is 100 years.
The reporting entity shall define GWP reference used to convert GHG data into GHG equivalent and record
and archive it in a consistent manner.
6.2.3 GHG quantification methods for fuel combustion
One of the features of LNG operations is that the carbon content of the fuel gas can vary throughout the
operations chain and can also vary in different operating modes. During liquefaction, the fuel gas used
typically has lower carbon content than the feed stream used for producing the LNG, since it consists mostly
of lower molecular weight boil-off gas and most of the inlet gas stream’s inert nitrogen.
6.2.4 GHG quantification methods for flaring and venting
6.2.4.1 General
GHG quantification shall follow the requirements and should follow the guidance in 6.2.1. Additional
considerations are given in 6.2.4.2 to 6.2.4.3.
6.2.4.2 Flaring
The flare system at LNG facilities operates as an emergency facility. It is a critical part of the safety system
and is designed to prevent escalation of accidents and dangerous situations. It is mainly used to eliminate
any discharge from the pressure relief system. Any waste gas sent to the flare (i.e. gas from the process
which is not recovered, such as dehydrator vents or compressor seal gas) is usually insignificant compared
with other industrial processes such as petrochemical or refining.
In principal, operators should avoid operational flaring, however it is possible that small quantities
of planned releases occur into the flare system, including fuel for pilots and purging, and exceptional
operational releases such as for defrosting or refrigerant composition management. In these cases, the
source gas entering the flare system should be known; and emissions factors may be derived.
In case of emergency flaring, an incident investigation should identify the source of a release; and this
information may be used to derive an emission factor to apply to the event.
Measurement-based methane destruction efficiency, destruction efficiency determined through the
application of correlations based on representative sampling, or in some cases process simulation and/
or engineering calculations may be used for emissions quantification at the flare. These emissions
quantifications shall be validated against relevant field data.
Measured combustion efficiency factors may also be used, recognizing they provide a conservative reported
value compared to destruction efficiency. More information can be found in API Consistent Methodology for
Estimating Greenhouse Gas Emissions from Liquefied Natural Gas (LNG) Operations, 2015.

ISO 6338-1:2024(en)
6.2.4.3 Venting
Venting from the acid gas removal unit is often a significant contributor to total LNG plant emissions. The
flowrate and composition of the vent gas are required to assess GHG emissions
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