2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

June 2023

2023 Government

Greenhouse Gas

Conversion Factors for

Company Reporting

Methodology Paper for Conversion Factors

Final Report

This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated.

To view this licence, visit www.nationalarchives.gov.uk/doc/open-government-licence/ or write to the Information

Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gsi.gov.uk.

Any enquiries regarding this publication should be sent to GreenhouseGas.Statistics@beis.gov.uk.

This document has been produced by Rebekah Bramwell, Peter Brown, Fabio Galatioto, Dom Ingledew, Eirini

Karagianni, Joanna MacCarthy, Paddy Mullen, Charles Walker, Dan Willis, Jason Wong (Ricardo Energy &

Environment) and Billy Harris (WRAP) for the Department for Energy Security & Net Zero.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Contents

Glossary ................................................................................................................................... 11

1. General Introduction ......................................................................................................... 14

Overview of major changes since the previous update ....................................................... 16

Conversion factors update frequency ................................................................................. 17

2. Fuel Emission Factors ...................................................................................................... 20

Section summary ................................................................................................................ 20

Summary of changes since the previous update ................................................................ 20

Direct Emissions ................................................................................................................. 21

Indirect/WTT Emissions from Fuels .................................................................................... 21

3. UK Electricity, Heat and Steam Emission Factors ............................................................ 27

Section summary ................................................................................................................ 27

Summary of changes since the previous update ................................................................ 27

Direct Emissions from UK Grid Electricity ........................................................................... 28

Indirect/WTT Emissions from UK Grid Electricity ................................................................ 37

Conversion factors for the Supply of Purchased Heat or Steam ......................................... 37

Summary of Method 1: 1/3: 2/3 Method (DUKES) .............................................................. 38

Calculation of CO

Emissions Factor for CHP Fuel Input, FuelMixCO

factor ..................... 38

Calculation of Non-CO

and Indirect/WTT Emissions Factor for Heat and Steam .............. 42

4. Refrigerant and Process Emission Factors ....................................................................... 44

Section summary ................................................................................................................ 44

Summary of changes since the previous update ................................................................ 44

Global Warming Potentials of Greenhouse Gases ............................................................. 44

Greenhouse Gases Listed in the Kyoto Protocol ................................................................ 44

Other Greenhouse Gases ................................................................................................... 45

5. Passenger Land Transport Emission Factors ................................................................... 46

Section summary ................................................................................................................ 46

Summary of changes since the previous update ................................................................ 46

Direct Emissions from Passenger Cars .............................................................................. 48

Conversion factors for Petrol and Diesel Passenger Cars by Engine Size ......................... 48

Hybrid, LPG and CNG Passenger Cars .............................................................................. 54

Plug-in Hybrid Electric and Battery Electric Passenger Cars (xEVs) .................................. 54

Conversion factors by Passenger Car Market Segments ................................................... 64

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Direct Emissions from Taxis ............................................................................................... 66

Direct Emissions from Vans/Light Goods Vehicles (LGVs) ................................................. 67

Plug-in Hybrid Electric and Battery Electric Vans (xEVs) .................................................... 69

Direct Emissions from Buses .............................................................................................. 71

Direct Emissions from Motorcycles ..................................................................................... 73

Direct Emissions from Passenger Rail ................................................................................ 74

International Rail (Eurostar) ................................................................................................ 74

National Rail ....................................................................................................................... 75

Light Rail ............................................................................................................................. 75

London Underground .......................................................................................................... 77

Indirect/WTT Emissions from Passenger Land Transport ................................................... 77

Cars, Vans, Motorcycles, Taxis, Buses and Ferries............................................................ 77

Rail ...................................................................................................................................... 77

6. Freight Land Transport Emission Factors ......................................................................... 78

Section summary ................................................................................................................ 78

Summary of changes since the previous update ................................................................ 78

Direct Emissions from Heavy Goods Vehicles (HGVs) ....................................................... 78

Direct Emissions from Vans/Light Goods Vehicles (LGVs) ................................................. 81

Direct Emissions from Rail Freight ...................................................................................... 83

Indirect/WTT Emissions from Freight Land Transport......................................................... 83

Vans and HGVs .................................................................................................................. 83

Rail ...................................................................................................................................... 84

7. Sea Transport Emission Factors ....................................................................................... 85

Section summary ................................................................................................................ 85

Summary of changes since the previous update ................................................................ 85

Direct Emissions from RoPax Ferry Passenger Transport and ........................................... 85

freight .................................................................................................................................. 85

Direct Emissions from Other Marine Freight Transport ....................................................... 87

Indirect/WTT Emissions from Sea Transport ...................................................................... 87

8. Air Transport Emission Factors ......................................................................................... 88

Section summary ................................................................................................................ 88

Summary of changes since the previous update ................................................................ 88

Passenger Air Transport Direct CO

Emission Factors ....................................................... 89

Allocating flights into short- and long-haul: ......................................................................... 92

Taking Account of Freight ................................................................................................... 94

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Taking Account of Seating Class Factors ........................................................................... 96

Freight Air Transport Direct CO

Emission Factors ............................................................. 97

Conversion factors for Dedicated Air Cargo Services ......................................................... 97

Conversion factors for Freight on Passenger Services ....................................................... 99

Average Conversion factors for All Air Freight Services ................................................... 100

Air Transport Direct Conversion factors for CH

and N

O ................................................. 100

Emissions of CH

.............................................................................................................. 101

Emissions of N

O .............................................................................................................. 101

Indirect/WTT Conversion factors from Air Transport ......................................................... 102

Other Factors for the Calculation of GHG Emissions ........................................................ 103

Great Circle Flight Distances ............................................................................................ 103

Non-CO

impacts and Radiative Forcing .......................................................................... 103

9. Bioenergy and Water ...................................................................................................... 108

Section summary .............................................................................................................. 108

Summary of changes since the previous update .............................................................. 108

General Methodology ........................................................................................................ 109

Water ................................................................................................................................ 109

Biofuels ............................................................................................................................. 109

Other biomass and biogas ................................................................................................ 111

10. Overseas Electricity Emission Factors ............................................................................ 113

Section summary .............................................................................................................. 113

Summary of changes since the previous update .............................................................. 113

Direct Emissions and Emissions resulting from Transmission and Distribution Losses from

Overseas Electricity Generation ....................................................................................... 113

Indirect/WTT Emissions from Overseas Electricity Generation ......................................... 114

11. Hotel Stay ....................................................................................................................... 116

Section summary .............................................................................................................. 116

Summary of changes since the previous update .............................................................. 116

Direct emissions from a hotel stay .................................................................................... 116

12. Material Consumption/Use and Waste Disposal ............................................................. 118

Section summary .............................................................................................................. 118

Summary of changes since the previous update .............................................................. 118

Emissions from Material Use and Waste Disposal............................................................ 119

Material Consumption/Use ................................................................................................ 119

Waste Disposal ................................................................................................................. 121

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

13. Fuel Properties ............................................................................................................... 123

Section summary .............................................................................................................. 123

Summary of changes since the previous update .............................................................. 123

General Methodology ........................................................................................................ 123

14. SECR kWh Conversion factors ....................................................................................... 125

Section summary .............................................................................................................. 125

Summary of changes since the previous update .............................................................. 126

General Methodology ........................................................................................................ 126

15. Homeworking .................................................................................................................. 127

Section summary .............................................................................................................. 127

General Methodology ........................................................................................................ 127

References ............................................................................................................................. 129

Appendix 1. Additional Methodological Information on the Material Consumption/Use and

Waste Disposal Factors ......................................................................................................... 136

1.1 Data Quality Requirements .................................................................................... 136

1.2 Data Sources ......................................................................................................... 137

1.3 Use of data below the set quality standard ............................................................ 137

Wood and Paper data ....................................................................................................... 138

Excluded Materials and Products ..................................................................................... 138

Greenhouse Gas Conversion factors ................................................................................ 143

Appendix 2. Updated full time series – Electricity and Heat and Steam Factors .................... 145

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Tables

Table 1: summary of conversion factors that are in AR4 or/and AR5 basis GWPs ........................ 18

Table 2: Related worksheets to the fuel conversion factors ........................................................... 20

Table 2: Liquid biofuels for transport consumption ......................................................................... 22

Table 3: Imports of LNG into the UK as a share of imports and net total natural gas supply .......... 24

Table 4: Basis of the indirect/WTT emissions factors for different fuels ......................................... 24

Table 5: Related worksheets to UK electricity and heat & steam emission factors ......................... 27

Table 6: Base electricity generation emissions data ...................................................................... 30

Table 7: Base electricity generation conversion factors (excluding imported electricity) ................. 33

Table 8: Base electricity generation emissions factors (including imported electricity) ................... 35

Table 9: Fuel types and associated emissions factors used in the determination of FuelMixCO

factor

...................................................................................................................................... 39

Table 10: Heat/Steam CO

emission factor for DUKES 1/3 2/3 method. ........................................ 41

Table 11: Related worksheets to passenger land transport emission factors ................................. 46

Table 13: DfT's Table BUS03a_km - Passenger kilometres on local bus services by metropolitan area

status and country: Great Britain ................................................................................... 47

Table 14: DfT's Table BUS03b - Average bus occupancy on local bus services by metropolitan area

status and country: Great Britain ................................................................................... 47

Table 12: Average CO

conversion factors and total registrations by engine size for 2005 to 2022 (based

on data sourced from SMMT) ........................................................................................ 49

Table 13: Average ‘real-world’ uplift for the UK applied to gCO

/km data ...................................... 50

Table 14: Summary of emissions reporting and tables for electric vehicle emission factors ........... 55

Table 15: xEV car models and their allocation to different market segments ................................. 56

Table 16: Summary of key data elements, sources and key assumptions used in the calculation of GHG

conversion factors for electric cars and vans ................................................................. 62

Table 17: Average car CO

conversion factors and total registrations by market segment for 2006 to

2022 (based on data sourced from SMMT) .................................................................... 65

Table 18: New conversion factors for vans for the 2023 GHG Conversion factors ......................... 69

Table 19: xEV van models and their allocation to different size categories .................................... 70

Table 20: Key assumptions used in the calculation of CO

emissions from Urea (aka ‘AdBlue’) use71

Table 21: Conversion factors for buses for the 2023 GHG Conversion factors .............................. 72

Table 22: Summary dataset on CO

emissions from motorcycles based on detailed data provided by

Clear (2008) .................................................................................................................. 73

Table 23: GHG emission factors, electricity consumption and passenger km for different tram and light

rail services ................................................................................................................... 76

Table 24 Related worksheets to freight land transport emission factors ........................................ 78

Table 25: Change in CO

emissions caused by +/- 50% change in load from the average loading factor

of 50% ........................................................................................................................... 79

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Table 26: Typical van freight capacities and estimated average payload ....................................... 82

Table 27: Utilisation of vehicle capacity by company-owned LGVs: annual average 2003 – 2005

(proportion of total vehicle kilometres travelled) ............................................................. 82

Table 28: Related worksheets to sea transport emission factors ................................................... 85

Table 29: Assumptions used in the calculation of ferry emission factors ........................................ 86

Table 30: Related worksheets to air transport emission factors ..................................................... 88

Table 31: Assumptions used in the calculation of revised average CO

conversion factors for passenger

flights for 2023 ............................................................................................................... 90

Table 32: Illustrative short- and long- haul flight distances from the UK ......................................... 93

Table 33: CO

conversion factors for alternative freight allocation options for passenger flights based on

2023 GHG Conversion factors ....................................................................................... 94

Table 34: Final average CO

conversion factors for passenger flights for 2023 GHG Conversion factors

(excluding distance and RF uplifts) ................................................................................ 95

Table 35: CO

conversion factors by seating class for passenger flights for 2023 GHG Conversion

factors (excluding distance and RF uplifts) .................................................................... 96

Table 36: Revised average CO

conversion factors for dedicated cargo flights for 2023 GHG Conversion

factors (excluding distance and RF uplifts) .................................................................... 97

Table 37: Assumptions used in the calculation of average CO

conversion factors for dedicated cargo

flights for the 2023 GHG Conversion factors .................................................................. 98

Table 38: Air freight CO

conversion factors for alternative freight allocation options for passenger flights

for 2023 GHG Conversion factors (excluding distance and RF uplifts) ......................... 100

Table 39: Final average CO

conversion factors for all air freight for 2023 GHG Conversion factors

(excluding distance and RF uplifts) .............................................................................. 100

Table 40: Total emissions of CO

, CH

and N

O for domestic and international aircraft from the UK GHG

inventory for 2021 ........................................................................................................ 101

Table 41: Final average CO

, CH

and N

O conversion factors for all air passenger transport for 2023

GHG Conversion factors (excluding distance and RF uplifts) ...................................... 101

Table 42: Final average CO

, CH

and N

O conversion factors for air freight transport for 2023 GHG

Conversion factors (excluding distance and RF uplifts)................................................ 102

Table 43: Impacts of radiative forcing according to Lee et al., (2021) .......................................... 104

Table 44: Aviation non-CO

emissions equivalence metrics for GWP, GTP and GWP* taken from Lee et

al. (2021) ..................................................................................................................... 105

Table 45: Related worksheets for bioenergy and water emission factors ..................................... 108

Table 46: Fuel lifecycle GHG Conversion factors for biofuels ...................................................... 110

Table 47: Fuel sources and properties used in the calculation of biomass and biogas emission factors

.................................................................................................................................... 112

Table 48: Distances and transportation types used in EF calculations ......................................... 121

Table 49: Distances used in the calculation of emission factors .................................................. 122

Table 50: Related worksheets to SECR kWh emissions factors .................................................. 125

Table 51: Base electricity generation emissions data – most recent datasets for time series ....... 145

Table 52: Base electricity generation conversion factors (excluding imported electricity) – fully consistent

time series dataset ...................................................................................................... 147

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Table 53: Base electricity generation emissions factors (including imported electricity) – fully consistent

time series dataset ...................................................................................................... 150

Table 54: Fully consistent time series for the heat/steam and supplied power carbon factors as

calculated using DUKES method ................................................................................. 152

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Figures

Figure 1: Time series of the mix of UK electricity generation by type ............................................. 29

Figure 2: Updated GCF 'Real world' uplift values for the UK based on (ICCT, 2017) ..................... 52

Figure 3: Comparison of 'Real world' uplift values from various sources (ICCT, 2017) .................. 53

Figure 4: Illustration of the relationship of electric range to average electric share of total km for PHEVs

assumed in the calculations ........................................................................................... 64

Figure 5: Boundary of material consumption data sets ................................................................ 120

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Glossary

Abbreviation Definition

ANPR Automatic Number Plate Recognition

BEV Battery electric vehicle

CAA Civil Aviation Authority

CBS National Bureau for Statistics in the Netherlands

CEF Carbon emission factor

Methane

CHP Combined Heat and Power

CHPQA Combined Heat and Power Quality Assurance

CNG Compressed natural gas

Carbon dioxide

DfT Department for Transport

DUKES Digest of UK Energy Statistics

EEA European Environment Agency

EF Emission factor

ETS Emissions Trading System

FAME Fatty Acid Methyl Ester

GCV Gross calorific value

GHG Greenhouse gas

GVW Gross vehicle weight

GWP Global Warming Potential

HGVs Heavy goods vehicles

IPCC Intergovernmental Panel on Climate Change

LCA Life cycle assessment

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

LGVs Light goods vehicles

LPG Liquefied petroleum gas

MTBE Methyl tert-butyl ether

NAEI National Atmospheric Emissions Inventory

NCV Net calorific value

NEDC New European Driving Cycle

O Nitrous oxide

ORR Office of Rail and Road

PHEV Plug-in hybrid electric vehicle

RF Radiative forcing

RoPax Roll on/roll off a passenger

RTE French transmission system operator

RTFO Renewable Transport Fuel Obligation

RW Real-world

SEAI Sustainable Energy Authority of Ireland

SECR Streamlined Energy and Carbon Reporting

SMMT Society of Motor Manufacturers and Traders

T&D Transmission & Distribution

TfL Transport for London

TTW Tank-To-Wheel (i.e. direct emissions at the point of use)

UK GHGI UK’s Greenhouse Gas Inventory

UNFCCC United Nations Framework Convention on Climate Change

WLTP Worldwide Harmonised Light Vehicle Test Procedure

WTT Well-To-Tank (i.e. upstream emissions from the production of fuel or electricity)

WTW Well-To-Wheel (= Well-To-Tank + Tank-To-Wheel)

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

xEV Generic term for battery electric vehicles (BEV), plug-in hybrid electric vehicles

(PHEV), range-extended electric vehicles (REEV) and fuel cell electric vehicles

(FCEV)

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

1. General Introduction

1.1. Greenhouse gases (GHG) can be measured by recording emissions at source,

by continuous emissions monitoring or by estimating the amount emitted using

activity data (such as the amount of fuel used) and applying relevant conversion

factors (e.g. calorific values, emission factors, etc.).

1.2. These conversion factors allow organisations and individuals to calculate GHG

emissions from a range of activities, including energy use, water consumption,

waste disposal and recycling, and transport activities. For instance, a conversion

factor can be used to calculate the amount of GHG emitted as a result of burning

a particular quantity of oil in a heating boiler.

1.3. Chapters 2 to 14 present the conversion factors for a single type of emissions-

releasing activity (for example, using electricity or driving a passenger vehicle).

These emissions-releasing activities are categorised into three groups known as

scopes. Each activity is listed as either Scope 1, Scope 2 or Scope 3.

a) Scope 1 (direct) emissions are those from activities owned or controlled by your

organisation. Examples of Scope 1 emissions include emissions from

combustion in owned or controlled boilers, furnaces and vehicles; and emissions

from chemical production in owned or controlled process equipment.

b) Scope 2 (energy indirect) emissions are those released into the atmosphere that

is associated with the consumption of purchased electricity, heat, steam and

cooling. These indirect emissions are a consequence of an organisation’s

energy use but occur at sources the organisation does not own or control.

c) Scope 3 (other indirect) emissions are a consequence of your actions that occur

at sources an organisation does not own or control and are not classed as

Scope 2 emissions. Examples of Scope 3 emissions are business travel by

means not owned or controlled by an organisation, waste disposal, materials or

fuels that an organisation purchases. Deciding if emissions from a vehicle, office

or factory that you use are Scope 1 or Scope 3 may depend on how

organisations define their operational boundaries. Scope 3 emissions can be

from activities that are upstream or downstream of an organisation. More

information on Scope 3 and other aspects of reporting can be found in the

Greenhouse Gas Protocol Corporate Standard

1.4. The 2023 UK Government Greenhouse Gas Conversion factors for Company

Reporting

(hereafter the 2023 UK GHG Conversion factors) represent the

current official set of UK government conversion factors. These factors are also

used in a number of different policies.

https://ghgprotocol.org/corporate-standard

Previously known as the ‘Guidelines to Defra/DECC’s GHG Conversion factors for Company Reporting’.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

1.5. The UK GHG Conversion Factors have been developed as part of the NAEI

(National Atmospheric Emissions Inventory) contract, managed by Ricardo

Energy & Environment, which includes the:

a) UK Air Quality Pollutant Inventory (AQPI)

b) UK Greenhouse Gas Inventory (GHGI)

1.6. The UK GHGI for 2021 (Ricardo Energy & Environment, 2023) is available at:

https://unfccc.int/documents/627789.

1.7. Values for the non-carbon dioxide (CO

) GHGs, methane (CH

) and nitrous

oxide (N

O), are presented as CO

equivalents (CO

e), using Global Warming

Potential (GWP) factors from the Intergovernmental Panel on Climate Change

(IPCC)’s fifth assessment report (IPCC, 2014)(GWP for CH

= 28, GWP for N

= 265). This is consistent with reporting under the United Nations Framework

Convention on Climate Change (UNFCCC) and consistent with the UK GHGI,

upon which the 2023 GHG Conversion Factors are based. Although the IPCC

has prepared a newer version, the methods have not yet been officially accepted

for use under the UNFCCC.

1.8. The 2023 GHG Conversion Factors are for use with activity data that falls

entirely or mostly within 2023. The factors will continue to be improved and

updated on an annual basis with the next publication in June 2024. Further

information about the 2023 GHG Conversion factors together with previous

methodology papers is available at:

https://www.gov.uk/government/collections/government-conversion-factors-for-

company-reporting.

1.9. It is important to note that the primary aim of this methodology paper is to

provide information on the methodology used in creating the UK Government

GHG Conversion factors for Company Reporting. This report provides the

methodological approach, the key data sources and the assumptions used to

define the conversion factors provided in the 2023 GHG Conversion factors. The

report aims to expand and complement the information already provided in the

data tables themselves. However, it is not intended to be an exhaustively

detailed explanation of every calculation performed (this is not

practical/possible), nor is it intended to provide guidance on the practicalities of

reporting for organisations. Rather, the intention is to provide an overview with

key information so that the basis of the conversion factors provided can be better

understood and assessed.

1.10. Detailed guidance on how the conversion factors provided should be used is

contained in the “Introduction” worksheet of the 2023 GHG Conversion factors

set. This guidance must be referred to before using the conversion factors and

provides important context for the description of the methodologies presented in

this report and in the table footnotes.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Overview of major changes since the previous update

1.11. Major changes and updates in terms of methodological approach from the 2023

update are summarised below. All other updates are essentially revisions of the

previous year's data based on new/improved data whilst using existing

calculation methodologies (i.e. using a similar methodological approach as for

the 2022 update):

a) In the 2023 update, factors for development petrol and diesel, and avtur

(renewable) have been added; new fuels are reported if they are contributing

more than 1% to the supply.

b) For the 2023 update for refrigerants, previously nominal estimated GWPs

presented in the 2014 EU F-gas regulations for some hydrocarbons have been

replaced with properly assessed IPCC assessment values.

c) The methodology for estimating the UK for water supply and water treatment

factors has been improved including additional data submitted by the UK water

suppliers. This has been done using actual volume of wastewater treated and

drinking water supplied by water companies together with data reported in the

water companies' Carbon Accounting Workbooks (CAW).

d) In the 2023 update, GWPs used in the calculation of CO

e are based on the

Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report

(AR5) over a 100-year period so that the Conversion Factors are consistent with

current national and international reporting requirements. For the direct

emissions factors, this simply involved converting the individual factors for CH

and N

O to use the AR5 GWPs rather than the AR4 values. For the indirect

emissions factors, in most cases they are based on CO

e values from studies

that encapsulate multiple GHGs. In cases where the data on the individual

GHGs were given in the studies, those values were converted to AR5 as per the

direct factors. In some cases, however, the individual gas data was not available

and as such these factors have been updated to AR5 by using other studies as

proxies. These details are covered in “summary of changes since the previous

update” in their sections.

e) The European Environment Agency (EEA) no longer provides new UK vehicle

data which was previously used in calculating the factors from LGVs and xEVs.

For the 2023 update, the 2021 new registrations numbers of UK LGVs and xEVs

by vehicle models have been obtained from the UK Department for Transport

(DfT). Vehicle models’ specific data such as CO

emission, mass, and capacity

for individual models were assumed to have remained the same since the

previous update, and these are obtained from the previous version of the EEA

database (EEA, 2021b), which is the latest year that contains UK data.

f) The UK GHG Conversion Factors cover also the period when national and

regional measures were introduced to prevent and reduce the global spread of

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

coronavirus (COVID-19). Transport trends have been affected by these

measures which can be seen in DfT's statistics used to derive these factors.

Passenger kilometres and thus occupancy levels for certain modes of transport

(buses, cars, vans, rail, air) have significantly dropped in 2020 and they didn't go

back to pre-COVID levels in 2021 too. Because for the aviation sector it will take

longer to recover to pre-COVID levels, it was decided to update the 2023 factors

using the actual 2021 load factors whereas for the rest transport sectors, it was

decided that pre-COVID occupancy levels would be retained for the years 2020

and 2021.

g) The multiplier that is applied to account for the non-CO

climate change effects

of aviation has been revised downwards to 1.7 In line with the latest scientific

evidence. Other changes to the aviation factors result primarily from the reduced

load factors (a consequence of the COVID-19 pandemic) rather that

methodological changes.

Conversion factors update frequency

1.12. The scope of the conversion factors has expanded over time (mainly due to the

addition of new factors and an increased QA burden). In light of this, a risk-based

approach has been adopted which focuses on delivering accurate conversion

factors for high-emitting UK sources that vary over time, and reflect changes in

key sources for most companies, including electricity, natural gas, waste

management, road transport fuels and fleet. However, less focus has been

invested on conversion factors for minor sources and minor pollutants, where no

or little new reference data exists and / or where there is little variation over time.

In these areas conversion factor update frequency reflects the level of risk

associated with retaining an historical value.

1.13. The conversion factors for high-emitting UK sources vary over time, reflect

changes in key sources for most companies and are therefore updated annually

or periodically. In this latest release, the Conversion Factors that are updated to

reflect latest UK evidence (for example on fuel mix, transport fleet, vehicle

utilisation) include:

• Fuels: Natural Gas, Diesel, Petrol, Coal, CNG and LNG

• Bioenergy

• Refrigerants

• Electricity use

• Heat and Steam

• Passenger vehicles, delivery vehicles, and business travel: Cars, HGVs, LGVs,

xEVs & Buses

• Aviation

Heat & Steam factors are scheduled to be updated in the 2023 and 2025 Conversion Factors publications.

Aviation factors are scheduled to be updated in the 2023 and 2025 Conversion Factors publications.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

• Water Supply and Water Treatment

• Waste management

• Outside of scopes

1.14. Conversion Factors that have been held constant from the 2022 release include:

• Homeworking (held constant but aligned with AR5 GWPs values)

• Hotel stay

1.15. Conversion Factors that have been held constant since the 2021 release (they

were in the AR4 basis) are now aligned with AR5 GWPs:

• All methane and nitrous oxide CFs, other than those associated with waste

management and aviation

• Fuels: butane, LPG, other petroleum gas, propane, aviation spirit, aviation

turbine fuel, burning oil, gas oil, fuel oil, lubricants, naphtha, processed fuel oils

- residual oil, processed fuel oils - distillate oil, refinery miscellaneous, waste

oils, marine gas oil, marine fuel oil, coking coal, petroleum coke

• Passenger vehicles, business travel - land, sea: taxis, motorcycles, rail,

shipping

• Well-to-Tank factors

1.16. The table below shows a summary of which factors are still in an AR4 basis and

which have been aligned to AR5 GWPs. These details are covered in “summary

of changes since the previous update” in their sections.

Table 1: summary of conversion factors that are in AR4 or/and AR5 basis GWPs

In AR4 basis In AR5 basis

Fuel



WTT Fuel



UK electricity



Transmission & Distribution



WTT UK electricity



WTT Transmission &

Distribution



Heat & Steam



WTT Heat & Steam



Water Supply & Water Treatment factors are to be updated only when new data is available. This year in 2023 the

factors are fully updated.

The UK electricity out of scopes factor remained constant from the 2022 release as part of the factors update

frequency arrangement.

WTT Bioenergy factors are still based on a AR4 basis.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

In AR4 basis In AR5 basis

Refrigerant and Processes



Passenger Land Transport



WTT Passenger Land

Transport



Freight Land Transport



WTT Freight Land Transport



Sea Transport



WTT Sea Transport



Air Transport



WTT Air Transport



Bioenergy



WTT Bioenergy



Water Supply & Treatment



Hotel Stay

 

Material Use



Waste Disposal



Homeworking



For Refrigerants & other process gases, almost all values have been updated to use AR5 GWPs (and where AR5

values were not available, but AR6 values were, AR6 GWPs were used).

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

2. Fuel Emission Factors

Section summary

2.1. The fuels conversion factors should be used for primary fuel sources combusted

at a site or in an asset owned or controlled by the reporting organisation. Well-to-

tank (WTT) factors should be used to account for the upstream Scope 3

emissions associated with extraction, refining and transportation of the raw fuel

sources to an organisation’s site (or asset), prior to their combustion.

2.2. The fuel properties can be used to determine the typical calorific values/densities

of the most common fuels. The fuel properties should be utilised to change units

of energy, mass, volume, etc. into alternative units; this is particularly useful

where an organisation is collecting data in units of measure that do not have a

fuel conversion factor that can be directly used to determine a carbon emission

total. where the related worksheets to fuel conversion factors are available in the

online spreadsheets of the UK GHG Conversion factors.

2.3. Table 1 shows where the related worksheets to fuel conversion factors are

available in the online spreadsheets of the UK GHG Conversion factors.

Table 2: Related worksheets to the fuel conversion factors

Worksheet name Full set Condensed set

Fuels Y Y

WTT – fuels Y N

Fuel properties Y Y

Conversions Y Y

Summary of changes since the previous update

2.4. In the 2023 update the direct and indirect conversion factors for fuels have been

updated to use the AR5 global warming potentials (GWPs). For the direct

factors, this simply involved converting the individual factors for CH

and N

O to

use the AR5 GWPs rather than the AR4 values. For the indirect factors, in most

cases they are based on CO

e values from studies that encapsulate multiple

GHGs. In cases where the data on the individual GHGs were given in the

studies, those values were converted to AR5 as per the direct factors. In many

cases however, the individual gas data was not available and as such these

factors have been updated to AR5 by using other studies as proxies. This

involved finding other studies that provide individual gas data and converting

those values to AR5 and using the change observed to scale the AR4 values

from the studies we previously used (the fuels scaled in this way are: Natural

Gas, CNG, LNG, Petrol, and Diesel).

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Direct Emissions

2.5. Fuel conversion factors for direct emissions presented in the 2023 GHG

Conversion factors are based on the conversion factors used in the UK GHGI for

2021 (Ricardo Energy & Environment, 2023).

2.6. The CO

emissions factors are based on the same factors used in the UK GHGI

and are essentially independent of application as they assume that all fuel is fully

oxidised and combusted. These factors have been updated for natural gas, coal,

petrol and diesel to be in line with the latest UK GHGI. Emissions of CH

and

O can vary to some degree for the same fuel depending on the use (e.g.

conversion factors for gas oil used in rail, shipping, non-road mobile machinery

or different scales/types of stationary combustion plants can all be different). The

figures for fuels in the 2023 GHG Conversion factors are based on an activity-

weighted average of all the different CH

and N

O conversion factors from the

2021 GHGI.

2.7. The majority of conversion factors from the GHGI are on a net energy basis

(t/TJ), and have been converted into different energy, volume and mass based

units using the information on Gross and Net Calorific Values (CV) (see definition

of Gross CV and Net CV in the footnote below

) used in the GHGI or for some

fuels, BEIS’s Digest of UK Energy Statistics (DUKES) (BEIS, 2022).

2.8. There are three tables in the 2023 GHG Conversion factors, the first of which

provides conversion factors for gaseous fuels, the second for liquid fuels and the

final table provides the conversion factors for solid fuels.

2.9. When making calculations based on energy use, it is important to check (e.g.

with your fuel supplier) whether these values were calculated on a Gross CV or

Net CV basis and use the appropriate factor. Natural gas consumption figures

quoted in kilowatt hours (kWh) by suppliers in the UK are generally calculated

(from the volume of gas used) on a Gross CV basis (National Grid, 2021).

Therefore, the emission factor for energy consumption on a Gross CV basis

should be used by default for calculation of emissions from natural gas in kWh,

unless your supplier specifically states they have used Net CV basis in their

calculations instead.

2.10. When using the direct conversion factor for aviation turbine fuel, applying a 1.7

multiplier to the CO

is applicable to account for the radiative forcing effects of

emissions at altitude. Further explanation of this is provide in section 8.41.

Indirect/WTT Emissions from Fuels

2.11. These fuel lifecycle emissions (also sometimes referred to as ‘Well-To-Tank’, or

simply WTT, emissions usually in the context of transport fuels) are the

emissions ‘upstream’ from the point of use of the fuel. They result from the

Gross CV or higher heating value (HHV) is the CV under laboratory conditions. Net CV or lower heating value (LHV)

is the useful calorific value in typical real-world conditions (e.g. boiler plant). The difference is essentially the latent

heat of the water vapour produced (which can be recovered in laboratory conditions).

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

extraction, transport, refining, purification or conversion of primary fuels to fuels

for direct use by end-users and the distribution of these fuels. They are classed

as Scope 3 according to the GHG Protocol.

2.12. For the upstream conversion factors relating to diesel, petrol, kerosene, natural

gas, CNG, and LNG, data are taken from a study by Exergia (Exergia et al.,

2015); please refer to Table 4 for definitions of acronyms. As the Exergia report

(Exergia et al., 2015) does not estimate upstream emissions for other fuels the

JEC Well-To-Wheels study is used for coal, LPG, and lubricants; data are taken

from (JEC WTW v5, 2020) as this is the most recent update for this source. Data

for naphtha is taken from an older version of the JEC report (JEC WTW v4a,

2014) because it is not present in the most recent update.

2.13. For fuels covered by the 2023 GHG Conversion factors where no fuel lifecycle

emission factor was available in either source, these were estimated based on

similar fuels, according to the assumptions in Table 4.

2.14. WTT emissions for petrol, diesel and kerosene in the Exergia study (Exergia et

al., 2015), used within the 2023 GHG Conversion factors set, are based on:

• Detailed modelling of upstream emissions associated with 35 crude oils used in

EU refining, which accounted for 88% of imported oil in 2012.

• Estimates of the emissions associated with the transport of these crude oils to

EU refineries by sea and pipeline, based on the location of ports and refineries.

• Emissions from refining, modelled on a country by country basis, based on the

specific refinery types in each country. An EU average is then calculated based

on the proportion of each crude oil going to each refinery type.

• An estimate of emissions associated with imported finished products from

Russia and the US.

2.15. Conversion factors are also calculated for diesel as supplied at public and

commercial refuelling stations, by factoring in the WTT component due to

biodiesel supplied in the UK as a proportion of the total supply of diesel and

biodiesel (4.92% by unit volume, 4.58% by unit energy – see Table 2). These

estimates have been made based on the Department for Transport Renewable

Fuel Statistics (DfT, 2023).

2.16. Conversion factors are also calculated for petrol as supplied at public and

commercial refuelling stations, by factoring in the bioethanol supplied in the UK

as a proportion of the total supply of petrol and bioethanol (7.62% by unit

volume, 5.03% by unit energy – see Table 2). These estimates have also been

made based on Department for Transport Renewable Fuel Statistics (DfT, 2023).

Table 3: Liquid biofuels for transport consumption

Total Sales, millions of litres Biofuel % Total Sales

Biofuel Conventional Fuel

per unit

mass

per unit

volume

per unit

of energy

Diesel/Biodiesel 1,279 24,691 5.26% 4.92% 4.58%

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Total Sales, millions of litres Biofuel % Total Sales

Biofuel Conventional Fuel

per unit

mass

per unit

volume

per unit

of energy

Petrol/Bioethanol 1,093 13,243 8.10% 7.62% 5.03%

Source: Department for Transport, Table RTFO 01. Data used here is from the Renewable fuel statistics 2022 Third provisional

tables

2.17. Emissions for natural gas, LNG and CNG, used within the 2023 GHG

Conversion factors, are based on (Exergia et al., 2015):

a) Estimates of emissions associated with supply in major gas producing

countries supplying the EU. These include both countries supplying piped gas

and countries supplying LNG.

b) The pattern of gas supply for each Member State (based on IEA data for

natural gas supply in 2012).

c) Combining the information on emissions associated with sources of gas, with

the data on the pattern of gas supply for each Member State, including the

proportion of LNG that is imported.

d) For parts of the natural gas supply chain which occur in the UK (transmission

and distribution and dispensing of CNG), data from DUKES (BEIS, 2022) is

used to update the emissions for these activities estimated in Exergia.

2.18. The methodology developed allows for the value calculated for gas supply in the

UK to be updated annually This allows changes in the sources of imported gas,

particularly LNG, to be reflected in the emissions value.

2.19. Information on quantities and source of imported gas are available annually from

DUKES

(BEIS, 2022a) and can be used to calculate the proportion of gas in

UK supply coming from each source. These can then be combined with the

emissions factors for gas from each source from the EU study (Exergia et al.,

2015), to calculate a weighted emissions factor for UK supply.

2.20. The methodology for calculating the WTT conversion factors for natural gas and

CNG is different to the other fuels as it considers the increasing share of UK gas

supplied via imports of LNG (which have a higher WTT emission factor than

conventionally sourced natural gas) in recent years. Table 3 provides a summary

of the information on UK imports of LNG and their significance compared to other

sources of natural gas used in the UK grid. Small quantities of imported LNG are

now re-exported, so a value for net imports is used in the methodology. The

figures in Table 3 have been used to calculate the revised figures for Natural

Gas and CNG WTT conversion factors provided in Table 4 below.

From Table 4.1 Commodity balances for natural gas and Table 4.5 Natural gas imports and exports, DUKES 2022

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Table 4: Imports of LNG into the UK as a share of imports and net total natural gas supply

Year

LNG % of total natural

gas imports

(1)

Net Imports as % total

supply of natural

gas

(2)

LNG Imports as %

total UK supply of

natural gas

2011 46.0% 43.7% 29.5%

2012 27.1% 49.2% 17.5%

2013 19.1% 51.7% 12.1%

2014 26.0% 46.3% 15.9%

2015 30.2% 43.4% 18.8%

2016 21.4% 48.2% 12.7%

2017 13.5% 46.7% 8.0%

2018 14.8% 48.0% 8.6%

2019 38.0% 49.1% 22.7%

2020 41.8% 45.6% 24.7%

2021 28.5% 57.5% 18.8%

Source: DUKES 2022, (1) Table 4.5 - Natural gas imports and exports; (BEIS, 2022) and (2) Table 4.1 - Commodity balances

2.21. The final combined conversion factors, presented as kilograms of carbon dioxide

equivalents per gigajoule on a net calorific value basis (kgCO

e/GJ, Net CV

basis), are listed in Table 4. These include WTT emissions of CO

, N

O and CH

These are converted into other units of energy (e.g. kWh, Therms) and to units of

volume and mass using the default Fuel Properties and Unit Conversion factors

also provided in the 2023 GHG Conversion factors alongside the emission factor

data tables.

Table 5: Basis of the indirect/WTT emissions factors for different fuels

Fuel

Indirect/WTT EF

(kgCO

e/GJ, Net CV

basis)

Source of

Indirect/WTT

Emission Factor

Assumptions

Aviation Spirit 18.28 Estimate Similar to petrol

Aviation turbine fuel 15.07

Exergia, EM Lab and

COWI, 2015

Emission factor for

kerosene

Burning oil 15.07 Estimate

Same as Kerosene,

as above

Butane 7.60 Estimate Same as LPG

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Fuel Indirect/WTT EF

(kgCO

e/GJ, Net CV

basis)

Source of

Indirect/WTT

Emission Factor

Assumptions

CNG 11.66

Exergia, EM Lab and

COWI, 2015

Factors in UK %

share LNG imports

Coal (domestic) 16.46 JEC WTW v5 (2020)

Emission factor for

coal

Coal (electricity

generation)

16.46 JEC WTW v5 (2020)

Emission factor for

coal

Coal (industrial) 16.46 JEC WTW v5 (2020)

Emission factor for

coal

Coal (electricity

generation - home

produced coal only)

16.46 JEC WTW v5 (2020)

Emission factor for

coal

Coking coal 16.46 Estimate

Assume same as

factor for coal

Diesel (100% mineral

diesel)

17.47

Exergia, EM Lab and

COWI, 2015

Fuel oil 17.47 Estimate

Assume same as

factor for diesel

Gas oil 17.47 Estimate

Assume same as

factor for diesel

LPG 7.60 JEC WTW v5 (2020)

LNG 20.04

Exergia, EM Lab and

COWI, 2015

Lubricants 27.30 JEC WTW v5 (2020)

Marine fuel oil 17.47 Estimate

Assume same as

factor for fuel oil

Marine gas oil 17.47 Estimate

Assume same as

factor for gas oil

Naphtha 14.10

JEC WTW v4a

(2014)

Natural gas 9.30

Exergia, EM Lab and

COWI, 2015

Factors in UK %

share LNG imports

Other petroleum gas 6.50 Estimate

Based on LPG figure,

scaled relative to

direct emissions ratio

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Fuel Indirect/WTT EF

(kgCO

e/GJ, Net CV

basis)

Source of

Indirect/WTT

Emission Factor

Assumptions

Petrol (100% mineral

petrol)

18.28

Exergia, EM Lab and

COWI, 2015

Petroleum coke 11.85 Estimate

Based on LPG figure,

scaled relative to

direct emissions ratio

Processed fuel oils -

distillate oil

26.39 Estimate

Based on lubricants

figure

Processed fuel oils -

residual oil

26.45 Estimate

Based on lubricants

figure

Propane 7.60 Estimate Same as LPG

Refinery

miscellaneous

8.55 Estimate

Based on LPG figure,

scaled relative to

direct emissions ratio

Waste oils

26.46

Estimate

Based on lubricants

figure

Notes:

(1) Burning oil is also known as kerosene or paraffin used for heating systems. Aviation Turbine fuel is a similar kerosene fuel

specifically refined to a higher quality for aviation.

(2) CNG = Compressed Natural Gas is usually stored at 200 bar in the UK for use as an alternative transport fuel.

(3) Fuel oil is used for stationary power generation. Also, use this emission factor for similar marine fuel oils.

(4) Gas oil is used for stationary power generation and 'diesel' rail in the UK. Also, use this emission factor for similar marine

diesel oil and marine gas oil fuels.

(5) LNG = Liquefied Natural Gas, usually shipped into the UK by tankers. LNG is usually used within the UK gas grid; however,

it can also be used as an alternative transport fuel.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

3. UK Electricity, Heat and Steam Emission

Factors

Section summary

3.1. UK electricity conversion factors should be used to report on electricity used by

an organisation at sites owned or controlled by them. This is reported as a Scope

2 (indirect) emission. The conversion factors for electricity are for the electricity

supplied to the grid that organisations purchase – i.e. not including the emissions

associated with the transmission and distribution of electricity. Conversion

factors for transmission and distribution losses (the energy loss that occurs in

getting the electricity from the power plant to the organisations that purchase it)

are available separately and should be used to report the Scope 3 emissions

associated with grid losses. WTT conversion factors for the UK and overseas

electricity should be used to report the Scope 3 emissions of extraction, refining

and transportation of primary fuels before their use in the generation of

electricity.

3.2. Heat and steam conversion factors should be used to report emissions within

organisations that purchase heat or steam energy for heating purposes or for the

use in specific industrial processes. District heat and steam factors are also

available. WTT heat and steam conversion factors should be used to report

emissions from the extraction, refinement and transportation of primary fuels that

generate the heat and steam organisations purchase.

3.3. Table 5 shows where the related worksheets to UK electricity and heat & steam

conversion factors are available in the online spreadsheets of the UK GHG

Conversion factors set.

Table 6: Related worksheets to UK electricity and heat & steam emission factors

Worksheet name Full set Condensed set

UK electricity Y Y

Transmission and distribution Y Y

WTT – UK & overseas Electricity Y N

Heat and steam Y N

WTT – heat and steam Y N

Summary of changes since the previous update

3.4. The Combined Heat and Power (CHP) methodologies depend upon the DUKES

CHP fuel mix, which varies from year to year, and CH

and N

O emission factor

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

data from the UK GHGI, which are also subject to inter-annual variations or

revisions to assumptions (see Section 2 of this report). There have not been any

method changes for the heat and steam conversion factors described in this

chapter.

3.5. In the 2023 update, the direct and indirect conversion factors for UK electricity

have been updated to use AR5 global warming potentials (GWPs). For the direct

factor and the transmission and distribution factor, this was done by simply using

the AR5 GWPs for CH

and N

O rather than the AR4 values used previously. For

the indirect factors, the indirect factors for each fuel used in electricity generation

was updated to AR5 as described in the Fuels section. However, the indirect

factors for the biofuels have not been updated to AR5 as the data sources used

were not able to be converted to the latest GWPs as of the time of the 2023

update, see the Bioenergy and Water section for more details.

Direct Emissions from UK Grid Electricity

3.6. The electricity conversion factors given represent the average CO

emission

from the UK national grid per kWh of electricity generated, classed as Scope 2 of

the GHG Protocol and separately for electricity transmission and distribution

losses, classed as Scope 3. The calculations also factor in net imports of

electricity via the interconnectors with Ireland, the Netherlands, France, Belgium,

and Norway. These factors include only direct CO

, CH

and N

O emissions at

UK power stations and from autogenerators, plus those from the proportion of

imported electricity. They do not include emissions resulting from production and

delivery of fuel to these power stations (i.e. from gas rigs, refineries and

collieries, etc.).

3.7. The UK grid electricity factor changes from year to year as the fuel mix

consumed in UK power stations (and autogenerators) changes, and as the

proportion of net imported electricity also changes. These annual changes can

be large as they depend very heavily on the relative prices of coal and natural

gas as well as fluctuations in peak demand and renewables. There has been a

sustained decline in the amount of coal used for electricity generation over the

past few years, largely driven by the increase in the carbon floor price from £9

per tonne of CO

to £15 in 2015 (BEIS, 2022). The annual variability, and the

recent trends in coal use, in UK electricity generation mix is illustrated in Figure 1

below.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Figure 1: Time series of the mix of UK electricity generation by type

Notes: The chart presents data for actual years; the emissions factors for a given GHG Conversion Factor update year

correspond to the data for the actual year 2 years behind, i.e. the 2023 conversion factors are based on 2021 data.

3.8. The UK electricity conversion factors provided in the 2023 GHG Conversion

factors are based on emissions from IPPC sectors 1A1ai (power stations) and

1A2b/1A2gviii (autogenerators) in the UK Greenhouse Gas Inventory (GHGI) for

2021 (Ricardo Energy & Environment, 2023). These emissions from the GHGI

only include autogeneration from coal and natural gas, and do not include

emissions for electricity generated and supplied by autogenerators using oil or

other thermal non-renewable fuels

. Estimates of the emissions arising from

other fuels used for autogeneration have been made using standard GHGI

emission factors, information from DUKES (BEIS, 2022) Table 5.6, and BEIS’s

DUKES team on the total fuel use (and shares by fuel type). The method also

accounts for the share of autogeneration electricity that is exported to the grid

(~25.5% for the 2023 data year), which varies significantly from year-to-year.

3.9. The UK is a net importer of electricity from the interconnectors with France, the

Netherlands, Belgium, and Norway, and a net exporter of electricity to Ireland

according to DUKES (BEIS, 2022). For the 2023 GHG Conversion factors the

total net electricity imports were calculated from DUKES Table 5.1.2 (Electricity

supply, availability and consumption 1970 to 2021). The net shares of imported

electricity over the interconnectors are calculated from data from DUKES Table

5A (Net Imports via interconnectors, GWh).

3.10. An average imported electricity emission factor is calculated from the individual

factors for the relevant countries (CBS, 2023), (RTE, 2022), (SEAI, 2023), (AIB,

2023) weighted by their respective share of net imports. This average electricity

emission factor – including losses – is used to account for the net import of

electricity, as it will also have gone through the relevant countries’ distribution

systems. Note that this method effectively reduces the UK’s electricity conversion

factors as the resulting average net imported electricity emission factor is lower

than that for the UK. This is largely because France’s electricity generation is

Other thermal non-renewable fuels include the following (with ~2023 update % share): blast furnace gas (~28%),

chemical waste (~7%), coke oven gas (~3%) and municipal solid waste (MSW, ~61%)

20%

40%

60%

80%

100%

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

Share of GWh electricity

supplied

GWh electricity supplied

Coal Oil Gas Thermal renewables Other thermal sources Nuclear and other renewables

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

much less carbon-intensive than that of the UK, and accounts for the largest

share of the net imports.

3.11. The source data and calculated emissions factors are summarised in Table 6,

Table 7 and Table 8. Time series source data and conversion factors are

fixed/locked from the 2023 GHG Conversion Factor update and for earlier years

have been highlighted in light grey. The tables provide the data and conversion

factors against the relevant data year. Table 6 also provides a comparison of

how the data year reads across to the GHG conversion factors update/reporting

year to which the data and conversion factors are applied, which is two years

ahead of the data year. For example, the most recent emission factor for the

2023 GHG Conversion factors is based on the data year 2021.

3.12. Earlier years (those prior to the current update) are based on data reported in

previous versions of DUKES and following the convention set from 2016 data

year, historic time series factors/data have not been updated. Time series data in

light grey is locked/fixed for the purposes of company reporting and has not been

updated in the database in the 2023 GHG Conversion factors update.

3.13. A full-time series of data using the most recently available GHGI and DUKES

datasets for all years is provided in Appendix 2 of this report. This is provided for

purposes other than company reporting, where a fully consistent data time series

is desirable, e.g. for policy impact analysis. This dataset also reflects the

changes in the methodological approach implemented for the 2016 update and is

applied across the whole time series.

Table 7: Base electricity generation emissions data

Data

Year

Applied to

Reporting Year

Electricity

Generation

(1)

GWh

Total Grid

Losses

(2)

UK electricity generation

emissions

(3)

, ktonne

1990 1992 290,666 8.08% 204,614 2.671 5.409

1991 1993 293,743 8.27% 201,213 2.499 5.342

1992 1994 291,692 7.55% 189,327 2.426 5.024

1993 1995 294,935 7.17% 172,927 2.496 4.265

1994 1996 299,889 9.57% 168,551 2.658 4.061

1995 1997 310,333 9.07% 165,700 2.781 3.902

1996 1998 324,724 8.40% 164,875 2.812 3.612

1997 1999 324,412 7.79% 152,439 2.754 3.103

1998 2000 335,035 8.40% 157,171 2.978 3.199

1999 2001 340,218 8.25% 149,036 3.037 2.772

2000 2002 349,263 8.38% 160,927 3.254 3.108

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Data

Year

Applied to

Reporting Year

Electricity

Generation

(1)

GWh

Total Grid

Losses

(2)

UK electricity generation

emissions

(3)

, ktonne

2001 2003 358,185 8.56% 171,470 3.504 3.422

2002 2004 360,496 8.26% 166,751 3.49 3.223

2003 2005 370,639 8.47% 177,044 3.686 3.536

2004 2006 367,883 8.71% 175,963 3.654 3.414

2005 2007 370,977 7.25% 175,086 3.904 3.55

2006 2008 368,314 7.21% 184,517 4.003 3.893

2007 2009 365,252 7.34% 181,256 4.15 3.614

2008 2010 356,887 7.45% 176,418 4.444 3.38

2009 2011 343,418 7.87% 155,261 4.45 2.913

2010 2012 348,812 7.32% 160,385 4.647 3.028

2011 2013 330,128 7.88% 148,153 4.611 3.039

2012 2014

320,470 8.04% 161,903 5.258 3.934

2013 2015

308,955 7.63% 146,852 4.468 3.595

2014 2016

297,897 8.30% 126,358 4.769 2.166

2015 2017

296,959 8.55% 106,209 7.567 2.136

2016 2018 297,203 7.85% 84,007 7.856 1.532

2017 2019

294,086 7.83% 74,386 7.588 1.353

2018 2020

289,120 7.92% 68,046 8.443 1.368

2019 2021

282,282 8.13% 60,504 9.158 1.321

2020 2022

269,804 8.39% 52,654 9.267 1.323

2021 2023

269,343 7.96% 57,803 9.808 1.396

Notes:

(1) From 1990-2013 (data year): Based upon calculated total for centralised electricity generation (GWh supplied) from DUKES

Table 5.5 Electricity fuel use, generation and supply for the year 1990 to 2014. The total is consistent with UNFCCC emissions

reporting categories 1A1ai+1A2d includes (according to Table 5.5 categories) GWh supplied (gross) from all ‘Major power

producers’; plus, GWh supplied from thermal renewables + coal and gas thermal sources, hydro-natural flow and other non-

thermal sources from ‘Other generators’.

From 2014 (data year) onwards: based on the total for all electricity generation (GWh supplied) from DUKES Table 5.6,

with a reduction of the total for autogenerators based on unpublished data from the BEIS DUKES team on the share of this

that is actually exported to the grid (~18% in 2019).

(2) Based upon calculated net grid losses from data in DUKES Table 5.1.2 (long term trends, only available online).

(3) From 1990-2013 (data year): Emissions from UK centralised power generation (including Crown Dependencies only) listed

under UNFCCC reporting category 1A1a and autogeneration - exported to the grid (UK Only) listed under UNFCCC reporting

category 1A2f from the UK Greenhouse Gas Inventory for 2012 (Ricardo-AEA, 2014) for data years 1990-2012, and for 2013

(Ricardo Energy & Environment, 2015) for the 2013 data year.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

From 2014 (data year) onwards: Excludes emissions from Crown Dependencies and also includes an accounting (estimate)

for autogeneration emissions not specifically split out in the UK GHGI, consistent with the inclusion of the GWh supply for

these elements also from 2014 onwards. Data is from the GHGI (Ricardo Energy & Environment, 2023) for the 2021 data

year.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Table 8: Base electricity generation conversion factors (excluding imported electricity)

Data

Year

Emission Factor, kgCO

e / kWh

% Net

Electricity

Imports

For electricity GENERATED

(supplied to the grid)

Due to grid transmission

/distribution LOSSES

For electricity CONSUMED

(includes grid losses)

Total

Total TOTAL

1990 0.70395 0.00019 0.00577 0.70991 0.05061 0.00001 0.00042 0.05104 0.76580 0.00021 0.00628 0.77229 3.85%

1991 0.68500 0.00018 0.00564 0.69081 0.04318 0.00001 0.00033 0.04352 0.74675 0.00019 0.00615 0.75309 5.18%

1992 0.64907 0.00017 0.00534 0.65458 0.05678 0.00002 0.00042 0.05722 0.70205 0.00019 0.00578 0.70801 5.29%

1993 0.58632 0.00018 0.00448 0.59098 0.05101 0.00002 0.00037 0.05140 0.63160 0.00019 0.00483 0.63662 5.25%

1994 0.56204 0.00019 0.00420 0.56643 0.04471 0.00002 0.00030 0.04502 0.62154 0.00021 0.00464 0.62639 5.22%

1995 0.53394 0.00019 0.00390 0.53803 0.03813 0.00001 0.00024 0.03839 0.58721 0.00021 0.00429 0.59170 4.97%

1996 0.50774 0.00018 0.00345 0.51137 0.04182 0.00002 0.00026 0.04210 0.55432 0.00020 0.00376 0.55828 4.80%

1997 0.46989 0.00018 0.00297 0.47304 0.03816 0.00002 0.00022 0.03840 0.50961 0.00019 0.00322 0.51302 4.76%

1998 0.46912 0.00019 0.00296 0.47226 0.04084 0.00002 0.00024 0.04111 0.51211 0.00020 0.00323 0.51555 3.51%

1999 0.43806 0.00019 0.00253 0.44077 0.04375 0.00002 0.00027 0.04404 0.47745 0.00020 0.00275 0.48041 3.94%

2000 0.46076 0.00020 0.00276 0.46372 0.04083 0.00002 0.00024 0.04109 0.50293 0.00021 0.00301 0.50616 3.82%

2001 0.47872 0.00021 0.00296 0.48189 0.04398 0.00002 0.00027 0.04427 0.52354 0.00022 0.00324 0.52701 2.78%

2002 0.46256 0.00020 0.00277 0.46554 0.04487 0.00002 0.00027 0.04516 0.50418 0.00022 0.00302 0.50742 2.24%

2003 0.47767 0.00021 0.00296 0.48084 0.03621 0.00002 0.00023 0.03646 0.52187 0.00023 0.00323 0.52533 0.57%

2004 0.47831 0.00021 0.00288 0.48140 0.03831 0.00002 0.00025 0.03857 0.52395 0.00023 0.00315 0.52733 1.97%

2005 0.47196 0.00022 0.00297 0.47515 0.03884 0.00002 0.00024 0.03910 0.50883 0.00024 0.00320 0.51226 2.16%

2006 0.50098 0.00023 0.00328 0.50448 0.03883 0.00002 0.00023 0.03908 0.53993 0.00025 0.00353 0.54371 1.97%

2007 0.49625 0.00024 0.00307 0.49956 0.03838 0.00002 0.00022 0.03863 0.53555 0.00026 0.00331 0.53911 1.37%

2008 0.49433 0.00026 0.00294 0.49752 0.03611 0.00002 0.00021 0.03634 0.53414 0.00028 0.00317 0.53759 2.91%

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Data

Year

Emission Factor, kgCO

e / kWh

% Net

Electricity

Imports

For electricity GENERATED

(supplied to the grid)

Due to grid transmission

/distribution LOSSES

For electricity CONSUMED

(includes grid losses)

Total

Total TOTAL

2009 0.45211 0.00027 0.00263 0.45501 0.03783 0.00002 0.00024 0.03809 0.49074 0.00030 0.00285 0.49389 0.80%

2010 0.45980 0.00028 0.00269 0.46277 0.05061 0.00001 0.00042 0.05104 0.49613 0.00030 0.00290 0.49933 0.73%

2011 0.44877 0.00029 0.00285 0.45192 0.04318 0.00001 0.00033 0.04352 0.48715 0.00032 0.00310 0.49056 1.76%

2012 0.50520 0.00034 0.00381 0.50935 0.04418 0.00003 0.00033 0.04454 0.54938 0.00037 0.00414 0.55389 3.40%

2013 0.47532 0.00036 0.00347 0.47915 0.03925 0.00003 0.00029 0.03956 0.51457 0.00039 0.00375 0.51871 4.10%

2014 0.42417 0.00040 0.00217 0.42673 0.03837 0.00004 0.00020 0.03860 0.46254 0.00044 0.00236 0.46534 6.44%

2015 0.35766 0.00064 0.00214 0.36044 0.03343 0.00006 0.00020 0.03369 0.39108 0.00070 0.00234 0.39412 6.59%

2016 0.28266 0.00066 0.00154 0.28486 0.02409 0.00006 0.00013 0.02428 0.30675 0.00072 0.00167 0.30913 5.57%

2017 0.25294 0.00065 0.00137 0.25496 0.02148 0.00005 0.00012 0.02165 0.27442 0.00070 0.00149 0.27660 4.78%

2018 0.23536 0.00073 0.00141 0.23750 0.02024 0.00006 0.00012 0.02042 0.25559 0.00079 0.00153 0.25792 6.20%

2019 0.21434 0.00081 0.00139 0.21654 0.01897 0.00007 0.00012 0.01917 0.23331 0.00088 0.00152 0.23571 6.98%

2020 0.19516 0.00086 0.00146 0.19748 0.01786 0.00008 0.00013 0.01808 0.21302 0.00094 0.00160 0.21555 6.22%

2021 0.21461 0.00091 0.00154 0.21706 0.01856 0.00008 0.00013 0.01877 0.23317 0.00099 0.00168 0.23583 8.36%

Notes: * From 1990-2013 the emission factor used was for French electricity only and is as published in previous methodology papers. The methodology was updated from 2014

onwards with new data on the contribution of electricity from the other interconnects, hence these figures are based on a weighted average emission factor of the conversion factors for

France, the Netherlands and Ireland, based on the % share supplied.

Emission Factor (Electricity CONSUMED) = Emission Factor (Electricity GENERATED) / (1 - %Electricity Total Grid LOSSES)

Emission Factor (Electricity LOSSES) = Emission Factor (Electricity CONSUMED) - Emission Factor (Electricity GENERATED)

⇒ Emission Factor (Electricity CONSUMED) = Emission Factor (Electricity GENERATED) + Emission Factor (Electricity LOSSES),

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Table 9: Base electricity generation emissions factors (including imported electricity)

Data Year

Emission Factor, kgCO2e / kWh

% Net Elec

Imports

For electricity GENERATED (supplied

to the grid, plus imports)

Due to grid

transmission/distribution LOSSES

For electricity CONSUMED

(includes grid losses)

O Total CO

O Total Total

1990 0.6812 0.00019 0.00558 0.68697 0.05985

0.00002 0.00049

0.06036 0.74106

0.0002 0.00607

0.74733 3.85%

1991 0.65616 0.00017 0.0054 0.66174 0.05915

0.00002 0.00049

0.05966 0.71532

0.00019 0.00589

0.72139 5.18%

1992 0.62005 0.00017 0.0051 0.62532 0.05061

0.00001 0.00042

0.05104 0.67066

0.00018 0.00552

0.67636 5.29%

1993 0.55913 0.00017 0.00428 0.56358 0.04318

0.00001 0.00033

0.04352 0.60232

0.00018 0.00461

0.6071 5.25%

1994 0.53633 0.00018 0.00401 0.54051 0.05678

0.00002 0.00042

0.05722 0.59311

0.0002 0.00443

0.59773 5.22%

1995 0.5113 0.00018 0.00373 0.51521 0.05101

0.00002 0.00037

0.0514 0.56231

0.0002 0.0041 0.56661 4.97%

1996 0.48731 0.00017 0.00331 0.4908 0.04471

0.00002 0.0003 0.04502 0.53202

0.00019 0.00361

0.53582 4.80%

1997 0.45112 0.00017 0.00285 0.45414 0.03813

0.00001 0.00024

0.03839 0.48925

0.00019 0.00309

0.49253 4.76%

1998 0.45633 0.00018 0.00288 0.45939 0.04182

0.00002 0.00026

0.0421 0.49816

0.0002 0.00314

0.5015 3.51%

1999 0.42438 0.00018 0.00245 0.427 0.03816

0.00002 0.00022

0.0384 0.46254

0.0002 0.00267

0.46541 3.94%

2000 0.44628 0.00019 0.00267 0.44914 0.04084

0.00002 0.00024

0.04111 0.48712

0.00021 0.00292

0.49024 3.82%

2001 0.46725 0.0002 0.00289 0.47034 0.04375

0.00002 0.00027

0.04404 0.511 0.00022 0.00316

0.51438 2.78%

2002 0.45378 0.0002 0.00272 0.4567 0.04083

0.00002 0.00024

0.04109 0.49461

0.00022 0.00296

0.49779 2.24%

2003 0.47537 0.00021 0.00294 0.47853 0.04398

0.00002 0.00027

0.04427 0.51936

0.00023 0.00322

0.5228 0.57%

2004 0.47033 0.00021 0.00283 0.47337 0.04487

0.00002 0.00027

0.04516 0.51521

0.00022 0.0031 0.51853 1.97%

2005 0.46359 0.00022 0.00291 0.46673 0.03621

0.00002 0.00023

0.03646 0.49981

0.00023 0.00314

0.50318 2.16%

2006 0.49263 0.00022 0.00322 0.49608 0.03831

0.00002 0.00025

0.03857 0.53094

0.00024 0.00347

0.53465 1.97%

2007 0.49054 0.00024 0.00303 0.49381 0.03884

0.00002 0.00024

0.0391 0.52939

0.00025 0.00327

0.53291 1.37%

2008 0.48219 0.00026 0.00286 0.48531 0.03883

0.00002 0.00023

0.03908 0.52102

0.00028 0.00309

0.52439 2.91%

2009 0.44917 0.00027 0.00261 0.45205 0.03838

0.00002 0.00022

0.03863 0.48755

0.00029 0.00284

0.49068 0.80%

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Data Year

Emission Factor, kgCO2e / kWh

% Net Elec

Imports

For electricity GENERATED (supplied

to the grid, plus imports)

Due to grid

transmission/distribution LOSSES

For electricity CONSUMED

(includes grid losses)

O Total CO

O Total Total

2010 0.45706 0.00028 0.00267 0.46002 0.03611

0.00002 0.00021

0.03634 0.49317

0.0003 0.00289

0.49636 0.73%

2011 0.44238 0.00029 0.00281 0.44548 0.03783

0.00002 0.00024

0.03809 0.4802 0.00031 0.00305

0.48357 1.76%

2012 0.49023 0.00033 0.00369 0.49426 0.04287

0.00003 0.00032

0.04322 0.5331 0.00036 0.00402

0.53748 3.40%

2013 0.4585 0.00035 0.00334 0.46219 0.03786

0.00003 0.00028

0.03816 0.49636

0.00038 0.00362

0.50035 4.10%

2014 0.40957 0.00039 0.00209 0.41205 0.03705

0.00003 0.00019

0.03727 0.44662

0.00042 0.00228

0.44932 6.44%

2015 0.34885 0.00062 0.00209 0.35156 0.03261

0.00006 0.0002 0.03287 0.38146

0.00068 0.00229

0.38443 6.59%

2016 0.28088 0.00066 0.00153 0.28307 0.02394

0.00006 0.00013

0.02413 0.30482

0.00072 0.00166

0.3072 5.57%

2017 0.25358 0.00065 0.00137 0.2556 0.02153

0.00005 0.00012

0.0217 0.27511

0.0007 0.00149

0.2773 4.78%

2018 0.23104 0.00072 0.00138 0.23314 0.01987

0.00006 0.00012

0.02005 0.25091

0.00078 0.0015 0.25319 6.20%

2019 0.21016 0.0008 0.00137 0.21233 0.0186 0.00007 0.00012

0.01879 0.22876

0.00087 0.00149

0.23112 6.98%

2020 0.19121 0.00084 0.00143 0.19348 0.0175 0.00008 0.00013

0.01771 0.20871

0.00092 0.00156

0.21119 6.22%

2021 0.20496 0.00087 0.00147 0.20730 0.01773

0.00008 0.00013

0.01794 0.22269

0.00095 0.00160

0.22524 8.36%

Notes: * From 1990-2013 the emission factor used was for French electricity only. The methodology was updated from 2014 onwards with new data on the contribution of electricity

from the other interconnects, hence these figures are based on a weighted average emission factor of the conversion factors for France, the Netherlands, Ireland, Belgium, and

Norway, based on the % share supplied.

Emission Factor (Electricity CONSUMED) = Emission Factor (Electricity GENERATED) / (1 - %Electricity Total Grid LOSSES)

Emission Factor (Electricity LOSSES) = Emission Factor (Electricity CONSUMED) - Emission Factor (Electricity GENERATED)

⇒ Emission Factor (Electricity CONSUMED) = Emission Factor (Electricity GENERATED) + Emission Factor (Electricity LOSSES)

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Indirect/WTT Emissions from UK Grid Electricity

3.14. In addition to the GHG emissions resulting directly from the generation of

electricity, there are also indirect/WTT emissions resulting from the production,

transport and distribution of the fuels used in electricity generation (i.e.

indirect/WTT/-fuel lifecycle emissions as included in the Fuels WTT tables). The

average fuel lifecycle emissions per unit of electricity generated will be a result of

the mix of different sources of fuel/primary energy used in electricity generation.

3.15. The WTT conversion factor for electricity has been calculated using the

corresponding fuels WTT conversion factors and data on the total fuel

consumption by type of generation from Table 5.6 and Table 6.6, DUKES 2021

(BEIS, 2022).

3.16. As the WTT factor for UK Grid Electricity is no longer annually updated as part of

the conversion factors, the data for these calculations are no longer presented

here.

Conversion factors for the Supply of Purchased Heat or Steam

3.17. The conversion factors for the supply of purchased heat or steam represent the

average emission from the heat and steam supplied by the UK Combined Heat

and Power Quality Assurance (CHPQA) scheme (BEIS, 2019a) operators for a

given year. This factor changes from year to year, as the fuel mix consumed

changes and is therefore updated annually. No statistics are available that would

allow the calculation of UK national average conversion factors for the supply of

heat and steam from non-CHP (Combined Heat and Power) operations.

3.18. CHP simultaneously produces both heat and electricity, and there are several

conventions used to allocate emissions between these products. At the

extremes, emissions could be allocated wholly to heat or wholly to electricity, or

in various proportions in-between.

3.19. To determine the amount of fuel attributed to CHP heat (qualifying heat output,

or ‘QHO’), it is necessary to apportion the total fuel to the CHP scheme to the

separate heat and electricity outputs. This then enables the fuel, and therefore

emissions, associated with the QHO to be determined. There are three possible

methodologies for apportioning fuel to heat and power:

a) Method 1: 1/3 : 2/3 Method (DUKES)

b) Method 2: Boiler Displacement Method

c) Method 3: Power Station Displacement Method

3.20. The GHG Conversion factors use the 1/3 : 2/3 DUKES method (Method 1) to

determine emissions from heat and therefore only this method is described

below.

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Summary of Method 1: 1/3: 2/3 Method (DUKES)

3.21. Under the UK’s Climate Change Agreements (CCAs)

(Environment Agency,

2020), this method, which is used to apportion fuel use to heat and power,

assumes that twice as many units of fuel are required to generate each unit of

electricity than are required to generate each unit of heat. This follows from the

observation that the efficiency of the generation of electricity (at electricity only

generating plant) varies from as little as 25% to 50%, while the efficiency of the

generation of heat in fired boilers ranges from 50% to about 90%.

3.22. Mathematically, Method 1 can be represented as follows:

Where:

• ‘Total Fuel Input (TFI)’ is the total fuel to the prime mover.

• ‘Heat Output’ is the useful heat generated by the prime mover.

• ‘Electricity Output’ is the electricity (or the electrical equivalent of mechanical

power) generated by the prime mover.

• ‘Heat Energy’ is the fuel to the prime mover apportioned to the heat generated.

• ‘Electricity Energy’ is the fuel to the prime mover apportioned to the electricity

generated.

3.23. This method is used only in the UK for accounting for primary energy inputs to

CHP where the CHP generated heat and electricity is used within a facility with a

CCA.

Calculation of CO

Emissions Factor for CHP Fuel Input, FuelMixCO

factor

3.24. The value FuelMixCO

factor referred to above is the carbon emission factor per

unit fuel input to a CHP scheme. This factor is determined using fuel input data

provided by CHP scheme operators to the CHPQA programme, which is held in

confidence.

The value for FuelMixCO

factor is determined using the following expression:

Where:

Climate Change Agreements (CCAs) are agreements between UK energy intensive industries and UK

Government, whereby industry undertakes to make challenging, but achievable, improvements in energy efficiency

in exchange for a reduction in the Climate Change Levy (CCL).

( )

OutputHeat

OutputHeatOutputyElectricit

InputFuelTotal

EnergyHeat _

__2

_ ×













+×

( )

OutputyElectricit

OutputHeatOutputyElectricit

InputFuelTotal

EnergyyElectricit _

__2

_ ×













+×

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

• FuelMixCO

factor is the composite emissions factor (in tCO

/MWh thermal

fuel input) for a scheme

• Fuel Input is the fuel input (in MWh thermal, MWh

) for a single fuel

supplied to the prime mover

• Fuel CO

Emissions factor is the CO

emissions factor (in tCO

/MWh

) for

the fuel considered.

• TFI is total fuel input (in MWh thermal) for all fuels supplied to the prime

mover.

3.25. Fuel inputs and emissions factors are evaluated on a Gross Calorific Value

(Higher Heating Value) basis. The following Table 9 provides the individual fuel

types considered under the CHPQA scheme and their associated emissions

factors, consistent with other reporting; fuel mix varies every year and thus there

are zero entries for specific fuel types.

Table 10: Fuel types and associated emissions factors used in the determination of

FuelMixCO

factor

Fuel

Emissions Factor

(kgCO

/kWh

)

Biodiesel, bioethanol etc

Biomass (such as woodchips, chicken litter etc)

Blast furnace gas

0.93

Butane

0.21

Coal and lignite

0.32

Coke oven gas

0.14

Coke, and semi-coke

0.34

Domestic refuse (raw)

0.16

Ethane

0.18

Fuel oil

0.27

Gas oil

0.25

Hydrogen

Landfill gas

Methane

0.18

Mixed refinery gases

0.25

Natural gas

0.18

Other

0.18

Other Biogas (e.g. gasified woodchips)

Other gaseous waste

0.18

Other liquid waste (non-renewable)

0.25

Other liquid waste (renewable)

Other oils

0.25

Other solid waste

0.16

Petroleum coke

0.34

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Fuel

Emissions Factor

(kgCO

/kWh

)

Petroleum gas

0.21

Propane

0.21

Refuse-derived Fuels (RDF)

0.16

Sewage gas

Unknown process gas

0.18

Uranium

VOC's

Waste exhaust heat from high temperature processes

Waste heat from exothermic chemical reactions

Other waste heat

Wood Fuels (woodchips, logs, wood pellets etc)

Fuel cells

0.18

Syngas / Other Biogas (e.g. gasified woodchips)

Pentane

Other Industrial By-Product gases

0.18

Hospital waste

0.16

Hydrogen (as a by-product)

Hydrogen (as a primary fuel)

Oil shale

0.27

Bituminous or asphaltic substance

0.27

Carbon Monoxide

0.18

Agricultural residues

Arboricultural & Forestry residues

Biogas produced by an AD plant

Branches and prunings

Building and demolition materials

Distillers grain

Dried wood chips

Fatty Acid Methyl Esters (biodiesel)

Gases otherwise produced from AD of biological

materials

Industrial waste

0.16

Milling residues

Municipal solid waste

0.16

Organic waste material such as manure, chicken litter,

food waste

Other commercial renewable oils

Other Waste Woods

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Fuel

Emissions Factor

(kgCO

/kWh

)

Other wood fuels

Paper sludge

Rapeseed oil

Refinery asphaltic oil

0.27

Refuse derived fuel

0.16

Roundwood

Spent solvents

0.25

Straw

Syngas from Wood Chips

Tallow

Undried woodchips

Used cooking oil

Visibly Clean Waste Wood (grade A of PAS 111)

Wood pellets

Sources: GHG Conversion factors for Company Reporting (2023 update) and UK GHGI (Ricardo Energy & Environment, 2023).

Note: For waste derived fuels, the emission factor can vary significantly according to the waste mix. Therefore, if you have site-

specific data, it is recommended that you use that instead of the waste derived fuel emissions factors in this table.

3.26. The 1/3 : 2/3 method (Method 1) was used to calculate the new heat/steam

conversion factors provided in the Heat and Steam tables of the 2023 GHG

Conversion factors. This is shown in Table 10. It is important to note that the

conversion factors update year is two years ahead of the data year. For

example, the most recent emission factor for the 2023 GHG Conversion factors

is based on the data year of 2021 in the Table 10.

3.27. While not used in the 2023 GHG conversion factors, the factor for heat from CHP

and power from CHP has also been calculated using the other two CHP methods

and the DUKES power method. These are: 0.25791 CO

/kWh heat (Boiler

displacement), 0.22293 CO

/kWh heat (Power station displacement), 0.33813

/kWh power (DUKES method), 0.36609 CO

/kWh power (Boiler

displacement), 0.42826 CO

/kWh power (power station displacement).

Table 11: Heat/Steam CO

emission factor for DUKES 1/3 2/3 method.

Data Year

kgCO

/kWh supplied heat/steam

Method 1 (DUKES: 2/3rd - 1/3rd)

2001 0.23770

2002 0.22970

2003 0.23393

2004 0.22750

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Data Year

kgCO

/kWh supplied heat/steam

Method 1 (DUKES: 2/3rd - 1/3rd)

2005 0.22105

2006 0.23072

2007 0.23118

2008 0.22441

2009 0.22196

2010 0.21859

2011 0.21518

2012 0.20539

2013 0.20763

2014 0.20245

2015 0.19564

2016 0.18618

2017 0.17447

2018 0.17102

2019 0.17150

2020 0.17574

2021 0.17791

Calculation of Non-CO

and Indirect/WTT Emissions Factor for Heat and Steam

3.28. CH

and N

O emissions have been estimated relative to the CO

emissions,

based upon activity weighted average values for each CHP fuel used (using

relevant average fuel conversion factors from the UK GHGI). Where fuels are not

included in the UK GHGI, the value for the most similar alternative fuel was used.

3.29. Indirect/WTT GHG conversion factors have been estimated relative to the CO

emissions, based upon activity weighted average indirect/WTT GHG emission

factor values for each CHP fuel used (see “Indirect/WTT Emissions from Fuels”

section for more information). Where fuels are not included in the set of

indirect/WTT GHG conversion factors provided in the 2023 GHG Conversion

factors, the value for the most similar alternative fuel was used.

3.30. The final conversion factors for supplied heat or steam utilised are presented in

the ‘Heat and Steam’ tables of the 2023 GHG Conversion factors and are

counted as Scope 2 emissions under the GHG Protocol.

3.31. For district heating systems, the location of use of the heat will often be some

distance from the point of production and therefore there are distribution energy

losses. These losses are typically around 5%, which need to be factored into the

calculation of overall GHG emissions where relevant and are counted as Scope

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

3 emissions under the GHG Protocol (similar to the treatment of transmission

and distribution losses for electricity).

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

4. Refrigerant and Process Emission

Factors

Section summary

4.1. Refrigerant and process conversion factors should be used for reporting leakage

from air-conditioning and refrigeration units or the release to the atmosphere of

other substances that have a global warming potential.

4.2. This section of the methodology paper relates to the “Refrigerant & other”

worksheet available in both the full and condensed set of the 2023 UK GHG

Conversion factors set.

Summary of changes since the previous update

4.3. Almost all values have been updated to use AR5 GWPs (and where AR5 values

were not available, but AR6 values were, AR6 GWPs have been used). Almost

all changes are less than 20%, however, given the wide range of substances

considered here, and the limited science for some of the more niche products,

updates to GWPs can be substantial for some individual substances. Most

significantly, previously nominal estimated GWPs presented in the 2014 EU F-

gas regulations for some hydrocarbons have been replaced with properly

assessed IPCC assessment values, and in those cases changes, and typically

these have been revised from between 3 and 6 to less than 0.2.

Global Warming Potentials of Greenhouse Gases

4.4. The GWP values have been updated to those published by the IPCC in the Fifth

Assessment Report (IPCC, 2014). There are a small number of refrigerants that

are not included in the Fifth Assessment Report. In these cases, we have

adopted values from either IPCC Sixth Assessment Report (IPCC, 2023), , the

IPCC Fourth Assessment Report (IPCC, 2007), or Annex IV of the EU F gas

regulation (517/2014)

Greenhouse Gases Listed in the Kyoto Protocol

4.5. Mixed/Blended gases: GWP values for refrigerant blends are calculated on the

basis of the percentage blend composition (e.g. the GWP for R404a that

comprises of 44% HFC125

, 52% HFC143a and 4% HFC134a is [3170 x 0.44]

+ [4800 x 0.52] + [1300x 0.04] = 3943). A limited selection of common blends is

presented in the Refrigerant tables. This calculation is done separately for Kyoto

components and non-Kyoto components, so that users of blends which include

both can distinguish what proportion of the GWP relates specifically to Kyoto

components while also presenting the total GWP.

HFC: Hydrofluorocarbon

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Other Greenhouse Gases

4.6. CFCs and HCFCs

: While these products typically have high GWPs, they were

excluded from Kyoto Protocol reporting due to already being controlled under the

Montreal Protocol due to them being Ozone Depleting Substances (ODS). Most

use of ODS are now banned in the UK, so these are unlikely to be relevant to UK

users unless they have a legacy system and/or are using the product for specific

exempted end-uses.

4.7. Other substances which are neither controlled under the Kyoto Protocol or

Montreal protocol. Many non-ODS substances which have comparatively low

GWPs (typically <10) or are not widely used are not included under the Kyoto

Protocol or Montreal protocol but are included in domestic F-gas regulations.

These are included here for completeness, and it also means that the GWP

values for blends should closely align with the calculations required for labelling

F-gas equipment.

CFCs: Chlorofluorocarbons; HCFCs: Hydrochlorofluorocarbons

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

5. Passenger Land Transport Emission

Factors

Section summary

5.1. Conversion factors for passenger land transport are included in this section of

the methodology paper. This section includes vehicles owned by the reporting

organisation (Scope 1), business travel in other vehicles (e.g. employee own car

for business use, hire car, public transport (Scope 3)), and electric vehicles (EVs)

(Scope 2). Other Scope 3 conversion factors included here are for transmission

and distribution losses for electricity used for electric vehicles, WTT for

passenger transport (vehicles owned by reporting organisation) and other

business travel.

5.2. Motorcycles, methane and nitrous oxide conversion factors remain constant

since the 2021 GHG Conversion factors but have been updated from AR4 to

AR5 GWP values. WTT conversion factors also remain constant and have been

updated from AR4 to AR5 GWP values.

5.3. Note that passenger land transport factors should only be used in the absence of

data for fuel or electricity consumption for the vehicles in question.

5.4. Table 11 shows where the related worksheets to the passenger land transport

conversion factors are available in the online spreadsheets of the UK GHG

Conversion factors.

Table 12: Related worksheets to passenger land transport emission factors

Worksheet name Full set Condensed set

Passenger vehicles Y Y

UK Electricity for Electric Vehicles (EVs) Y Y

UK Electricity T&D for EVs Y Y

Business travel – land* Y Y

WTT – pass vehicles & travel – land* Y N

* cars and motorbikes only

Summary of changes since the previous update

5.5. For xEVs cars, the European Environment Agency (EEA) no longer provides

new UK vehicle data which was previously used in calculating the factors for

xEVs cars. In the 2023 update, the number of new registrations of xEVs cars in

UK in 2021 have been obtained from the UK Department for Transport (DfT).

2023 Government greenhouse gas conversion factors for company reporting: Methodology paper

Vehicle model specific CO

emissions and energy consumption for individual

models are assumed to have remained the same since the previous year and

derived from the previous version of the EEA database (EEA, 2021b). For new

xEVs models that were not included in previous version of EEA database, their

vehicle model specific CO

emissions and energy consumption were assumed to

be the same as those values from the same vehicle models in seven other EEA

countries (France, Germany, Ireland, Belgium, Netherlands, Spain, and Portugal)

in the latest EEA database (EEA, 2022).

5.6. The UK GHG Conversion Factors cover also the period when national and