UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 3 This is the United Kingdom’s National Inventory Report (NIR) submitted in 2023 to the United Nations Framework Convention on Climate Change (UNFCCC). It contains national greenhouse gas emission estimates for the period 1990-2021, and descriptions of the methods used to produce the estimates. The greenhouse gas inventory (GHGI) is based on the same datasets used by the UK in the National Atmospheric Emissions Inventory (NAEI) for reporting atmospheric emissions under other international agreements. The GH GI is therefore consistent with these other air emissions inventories where they overlap. The greenhouse gas inventory is compiled on behalf of the UK Department for Energy Security and Net Zero (DESNZ) for the Science and Innovation for Climate and Energy (SICE) Directorate, by Ricardo Energy & Environment. We acknowledge the positive support and advice from DESNZ throughout the work, and we are grateful for the help of all those who have contributed to this NIR. A list of the contributors can be found in Chapter 18. The GHGI is compiled according to the Intergovernmental Panel on Climate Change (IPCC ) 2006 Guidelines (IPCC, 2006). Each year the inventory is updated to include the latest data available. Improvements to the methodology are backdated as necessary to ensure a consistent time series. Methodological changes are made to take account of new data sources, or new guidance from IPCC, and new research, sponsored by DESNZ or otherwise. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 4 Emissions of greenhouse gases presented in this report are normally given in Gigagrams (Gg), Million tonnes (Mt) and Teragrams (Tg). Global Warming Potential (GWP) weighted emissions are also provided. To convert between the units of emissions, use the conversion factors given Prefixes and multiplication factors Multiplication factor Abbreviation Prefix Symbol 1,000,000,000,000,000 1015 peta P 1 kilotonne (kt) = 103 tonnes = 1,000 tonnes 1 Mega tonne (Mt) = 106 tonnes = 1,000,000 tonnes Conversion of carbon emitted to carbon dioxide emitted To convert emissions expressed in weight of carbon, to emissions in weight of carbon dioxide, Conversion of Gg of greenhouse gas emitted into Gg CO2 equivalent Gg (of GHG) * GWP = Gg CO2 equivalent. The GWP is the Global Warming Potential of the greenhouse gas. The GWPs of greenhouse

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 5 Abbreviations for Greenhouse Gases and Chemical Direct HFCs Hydrofluorocarbons Direct NF3 Nitrogen trifluoride Direct SF6 Sulphur hexafluoride Indirect NMVOC Non-methane volatile organic compound Indirect NOx Nitrogen oxides (reported as nitrogen dioxide) Indirect SO2 Sulphur oxides (reported as sulphur dioxide) HFCs, PFCs, NF3 and SF6 are collectively known as the ‘F-gases’. IPCC Category Source Description 1A1a Public Electricity and Heat Production 1A1c Manufacture of Solid Fuels and Other Energy Industries 1A1ci Manufacture of solid fuels 1A1ciii Other energy industries 1A2 Manufacturing Industries and Construction 1A2e Food Processing, Beverages and Tobacco 1A2gvii Off-road vehicles and other machinery 1A3biii Heavy duty trucks and buses 1A3e Other Transportation (to be specified)

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 6 IPCC Category Source Description 1A4a Commercial / Institutional 1A4bii Off-road vehicles and other machinery 1A4c Agriculture / Forestry / Fishing 1A4cii Off-road vehicles and other machinery 1A5 Other (not elsewhere specified) 1A5a Other, Stationary (including Military) 1A5b Other, Mobile (including military) 1B Fugitive Emissions from Fuels 1B1a1ii Post-Mining Activities 1B1a1iii Abandoned Underground Mines 1B1a2ii Post-Mining Activities 1B1b Solid fuel transformation 1B2a5 Distribution of Oil Products 1B2b4 Transmission and storage 2A4 Other Process uses of Carbonates

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 7 IPCC Category Source Description 2A4c Non-metallurgical Magnesium Production 2B4 Caprolactam, Glyoxal and Glyoxylic Acid Production 2B6 Titanium Dioxide Production 2B8 Petrochemical and Carbon Black Production 2B8c Ethylene Dichloride and Vinyl Chloride Monomer 2C3c F-gases used in foundries 2D Non-energy Products from Fuels and Solvent Use 2E1 Integrated Circuit or Semiconductor

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 8 IPCC Category Source Description 2F Product Uses as Substitutes for ODS 2F1 Refrigeration and Air Conditioning 2F1f Stationary Air-Conditioning 2G Other Product Manufacture and Use 2G2 SF6 and PFCs from Other Product Use 2H2 Food and beverages industry

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 9 IPCC Category Source Description 3D1 Direct N2O Emissions From Managed Soils 3D12a Animal Manure Applied to Soils 3D12b Sewage Sludge Applied to Soils 3D12c Other Organic Fertilizers Applied to Soils 3D13 Urine and Dung Deposited by Grazing Animals 3D15 Mineralization/Immobilization Associated with Loss/Gain of Soil Organic 3D16 Cultivation of Organic Soils 3D2 Indirect N2O Emissions From Managed Soils 3D22 Nitrogen Leaching and Run-off 3E Prescribed Burning of Savannas 3F Field Burning of Agricultural Wastes 3I Other Carbon-containing Fertilisers 4 Land-use, land-use change and forestry 4A1 Forest Land Remaining Forest Land 4A2 Land Converted to Forest Land 4B1 Cropland Remaining Cropland 4B2 Land Converted to Cropland 4C1 Grassland Remaining Grassland 4C2 Land Converted to Grassland 4D1 Wetlands Remaining Wetlands 4D2 Land Converted to Wetlands 4E1 Settlements Remaining Settlements 4E2 Land Converted to Settlements 4F1 Other Land Remaining Other Land 4F2 Land Converted to Other Land

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 10 IPCC Category Source Description 5A1 Managed Waste Disposal Sites 5A2 Unmanaged Waste Disposal Sites 5A3 Uncategorized Waste Disposal Sites 5B Biological Treatment of Solid Waste 5B2 Anaerobic Digestion at Biogas Facilities 5C Incineration and Open Burning of Waste 5D Wastewater Treatment and Discharge

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 27 International Flights from UK Airports, 1990-2018 172 Includes cold start emissions 182

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 28 CO2 emissions from carbonate use 247

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 29 semiconductor manufacture sector (kg per kg input gas) 321 UK, Isle of Man, Falkland Islands, all other crown dependencies and all other area is 25 763.4 kha ) (GBR - UK, 3 CDs, 4 OTs) 393

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 30 UNFCCC Review Findings 2021/2022 510 UNFCCC Review Findings 2022 534

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 31 between selected years by sector 103 between selected years by gas 105 between selected years by sub-sector for Energy 107 between selected years by sub-sector for Industrial Processes and Product between selected years by sub-sector for Agriculture41 118

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 32 between selected years by sub-sector for Waste 122 overall N application rate to crops 341 contribution to total fertiliser use 342 nitrate contribution to total fertiliser use 342 arable, other soils, to emissions and losses 344 nitrous oxide (N2O) from agriculture 366

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 34 The Climate Change Act became UK Law on 26 November 2008. This legislation introduced a legally binding target for the UK to reduce GHG emissions to 80% below base year by 2050, with legally binding five -year GHG budgets. The independent Climate Change Com mittee (CCC) was set up to provide independent advice the UK Government on the setting and meeting of UK carbon budgets, as well as monitoring progress against them. In June 2019, the UK government furthered this by setting a legally binding target to achi eve net zero greenhouse gas emissions across the UK economy by 2050. The UK was the first major economy in the world to legislate for a net zero target. Reporting under the Paris Agreement is expected to start in 2024, and therefore this report (for the 2023 submission) does not yet include any reporting specifically related to the Paris Countries that have signed and ratified the Kyoto Protocol were legally bound to reduce their greenhouse gas emissions by an agreed amount. The first commitment period of the Kyoto Protocol was from 2008 to 2012. A single European Union (EU) Kyoto Protocol reduction target for greenhouse gas emissions of -8% compared to base-year levels was negotiated for the first commitment period, and a Burden Sharing Agreement allocated the target between Member States of the European Union. Under this agreement, the UK reduction target was - The second commitment period of the Kyoto Protocol was for 2013 to 2020 inclusive. For this second commitment period, the EU, the Member States and Iceland communicated an independent quantified economy -wide emission reduction target of a 20 percent emission reduction by 2020 compared with 1990 levels (base year) (“the EU2020 target”). The EU2020 target was based on the understanding that it would be fulfilled jointly by the European Union, the Member States, the UK and Iceland.
Under the terms of the Withdrawal Agreement, the UK remain ed committed to its shared target and reporting with the EU under the Kyot o Protocol, including any further requirements for the conclusion of the true up period . The EU2020 target is unconditional and supported by EU legislation in place since 2009 (The EU Climate and Energy Package). This Kyoto target included the UK, and the relevant Crown Dependencies (CDs) and Overseas Territories (OTs) for whom the ratification is extended. Further information on Kyoto Protocol reporting can be found in the final submission relating to the 2nd commitment period in the 2022 submission1. Further information on the UK Devolved Administrations (DAs) action to tackle climate change can be found on the CCC’s website2. Information on climate adaptation can be found on the 1 The 2022 submission of the NIR can be found here 2 The Climate Change Act 2008 (2050 Target Amendment) Order 2019. 3 Climate change adaptation Guidance and regulation,

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 35 ES 1.2 Greenhouse Gas Inventories The UK ratified the United Nations Framework Convention on Climate Change (UNFCCC) in December 1993, and the Convention came into force in March 1994. Parties to the Convention are committed to develop, publish, and regularly update national emission inventories of This is the United Kingdom’s National Inventory Report (NIR) submitted in 2023 to the UNFCCC. It contains national greenhouse gas emission estimates for the period 1990-2021, and the descriptions of the methods used to produce the estimates. The report is prepared in accordance with decision 24/CP.19 4. Note that decision 24/CP.19 paragraph 2 dictates that AR4 Global Warming Potentials (GWPs) should be used “until a further decision is adopted”, and decision 7/CP.275 is a further decision that adopts AR5 GWPs for reporting under the Paris Agreement, and hence AR5 GWPs are used in this report. The UK Greenhouse Gas Inventory is compiled and maintained by a consortium led by Ricardo Energy & Environment – the Inventory Agency – under contract to DESNZ. Ricardo Energy & Environment is directly responsible for producing the emissions estimates for CRF categories Energy (CRF sector 1), Industrial Processes and Product Use (CRF Sector 2), and Waste (CRF Sector 5). Ricardo Energy & Enviro nment is also responsible for inventory planning, data collection, QA/QC and inventory management and archiving. Aether, a member within the consortium, is responsible for compiling emissions from railways and for the UK’s OTs and CDs. Ray Gluckman (Gluckman Consulting) advises on F-gas emissions. Forestry emissions and removals in the Land -Use, Land-Use Change and Forestry sector (CRF sector 4) are calculated by Forest Research and the remainder of the sector is calculated and compiled by the UK Centre for Ecology and Hydrology (UKCEH), both partners within the consortium. Agricultural sector emissions estimates (CRF sector 3) are produced by a consortium led by Rothamsted Research, under contract to the UK Department for Environment, Food and Rural Affairs (Defra). DESNZ, Defra and the DAs also fund research contracts to provide improved emissions estimates for certain sources such as fluorinated gases, landfill methane, enteric fermentation, and shipping. Information from these programmes is fed into the inventory via the National Inventory System (Section 1.2.1.1). 'The inventory covers the seven direct greenhouse gases in the UNFCCC reporting guidelines on annual inventories for Parties included in Annex I to the Convention. These are as • Sulphur hexafluoride (SF6); and These gases contribute directly to climate change owing to their positive radiative forcing effect. Also reported are four indirect greenhouse 4 FCCC Decision 24/CP.19. Revision of the UNFCCC reporting guidelines on annual inventories for Parties included in Annex I to the Convention 5 FCCC Decision 7/CP.27. Common metrics used to calculate the carbon dioxide equivalence of anthropogenic greenhouse gas emissions by sources and removals by sinks

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 36 • Non-Methane Volatile Organic Compounds (NMVOC); and • Sulphur oxides (reported as SO2). Emissions of indirect N 2O from emissions of NO x and NH3 are estimated as a memo item. These emissions are not included in the national total. Unless otherwise indicated, percentage contributions and changes quoted refer to net emissions (i.e. emissions minus removals), based on the full coverage of UK emissio ns including all relevant Overseas Territories and Crown Dependencies, consistent with the UK’s The UK inventory provides data to assess progress towards the UK Government’s own Carbon Budgets and to meet commitments as a Party to the UNFCCC. Geographical coverage for these two purposes differs to some extent, because of the 1) UNFCCC coverage (the ‘GBR’ submission). The UK’s ratification of the UNFCCC has been extended to Bermuda, the Cayman Islands, the Falkland Islands, Gibraltar, Guernsey, the Isle of Man and Jersey and the UK reports an inventory on this basis. 2) The UK Government Carbon Budgets apply to the UK only, and exclude all emissions from the UK’s Crown Dependencies and Overseas Territories. Emissions data for th e first geographical coverage (Coverage 1) is used for the data in the show CO 2 and the direct greenhouse gases, disaggregated by gas and by sect or for geographical Coverage 2. Coverage 2 are reported for information and to facilitate comparison detail of how emissions between scopes compare. 6

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 37 Crown Dependencies and relevant Overseas Territories, 1990-2021. (Mt CO2 Equivalent) 1990 1995 2000 2005 2010 2015 2018 2019 2020 2021 % change CO2 (Inc. net LULUCF) 607.3 569.2 569.7 568.4 508.6 417.9 375.1 361.7 321.4 342.6 -44% CO2 (Exc. net LULUCF) 603.7 567.7 570.5 572.1 513.8 423.8 380.6 366.9 327.2 348.4 -42% CH4 (Inc. net LULUCF) 150.9 144.2 124.3 101.3 75.7 63.0 60.9 60.4 58.0 57.4 -62% CH4 (Exc. net LULUCF) 145.3 138.6 118.8 95.7 70.1 57.3 55.2 54.7 52.3 51.7 -64% N2O (Inc. net LULUCF) 44.4 35.7 26.9 23.3 20.7 20.1 19.8 19.9 18.7 19.2 -57% N2O (Exc.
net LULUCF) 42.5 33.9 25.2 21.7 19.3 18.7 18.5 18.6 17.4 17.9 -58% HFCs 12.1 15.6 7.0 8.7 11.5 13.3 13.0 12.3 11.5 10.8 -10% PFCs 1.5 0.5 0.5 0.4 0.3 0.3 0.1 0.2 0.2 0.2 -87% Total (Inc. net LULUCF) 817.5 766.5 730.2 703.1 617.5 515.0 469.4 455.1 410.2 430.7 -47% Total (Exc. net LULUCF) 806.3 757.6 723.9 699.6 615.7 513.9 467.9 453.2 409.0 429.5 -47% 1. One Mt equals one Tg, which is 1012 g (1,000,000,000,000 g) or one million tonnes 2. Net Emissions are reported in the Common Reporting Format

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 38 net emissions from LULUCF. The largest contribution to total emissions is CO 2, which contributed 80% to total net emissions in 2021. Methane emissions account for the next largest share (13%), and N 2O emissions make up a further 4%. Emissions of all these gases have decreased since 1990, contributing to an overall decrease of 47%. estimated GHG emissions from the Crown Dependencies and selected relevant Overseas Territories (Mt CO2 equivalent) Source Category 1990 1995 2000 2005 2010 2015 2018 2019 2020 2021 1. Energy 602.9 558.6 553.8 550.3 498.9 404.7 366.9 352.7 312.9 335.0 and Product Use 80.0 73.6 53.4 49.7 41.0 43.1 36.1 35.7 34.1 32.3 3. Agriculture 50.8 49.9 48.6 46.4 43.8 44.4 43.6 43.8 42.5 43.1 5. Waste 72.5 75.6 68.2 53.2 31.9 21.7 21.3 21.0 19.5 19.1 Total (net emissions) 817.5 766.5 730.2 703.1 617.5 515.0 469.4 455.1 410.2 430.7 which are included in the scope of the UK’s ratification of the UNFCCC The largest contribution to greenhouse gas emissions is from the energy sector. In 20 21 this contributed 78% to the total net emissions. Emissions of CO2, CH4 and N2O all arise from this sector, but CO2 is the dominant gas consisting of 97% of emissions. Since 1990, emissions from the energy sector have declined by 44%. The second largest source of greenhouse gases is the agricultural sector, contributing 10% in 2021. Emissions from this sector are mostl y CH 4 and N 2O, contributing 6 5% and 3 2% respectively. Only a small amount of CO2 is emitted in comparison. Since 1990, emissions from this sector have declined by 15%. Industrial processes and product use make up the third largest sector for greenhouse gas emissions in the UK, contributing 8% to the national total in 2021. Emissions of all seven direct greenhouse gases occur from this sector. Since 1990, emissions from this sector have Land-Use, Land -Use Change, and Forestry contains sinks as well as sources of CO 2 emissions. LULUCF was a net sink in 2021. Emissions from this sector occur for CO 2, N2O The remaining sector that contributes to direct greenhouse gas totals is waste. In 20 21 this contributed 4% to the national total. This sector leads to emissions of CO2, CH4 and N2O, with emissions occurring from waste incineration, solid waste disposal on land and wastewater handling. CH4 is the dominant gas consisting of 90% of all emissions. Emissions from this sector have declined and in 2021 were 74% below 1990 levels. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 39 estimates. Nitrogen oxides, carbon monoxide and NMVOCs are included in the inventory because they can result in an incre ase in tropospheric ozone concentration, increasing radiative forcing. Sulphur oxides are included because they contribute to aerosol formation. Gas 1990 1995 2000 2005 2010 2015 2018 2019 2020 2021 NOx 2861 2467 1984 1752 1251 1020 848 794 685 689 that are included in the UK’s ratification of the UNFCCC. Since 1990, emissions of all indirect gases have decreased. The largest source of emissions for NOx, CO and SO2 is the energy sector, with 80% of emissions or more arising from activities within this sector. For NMVOC, 58% of emissions are from the industrial processes and product use sector, with other significant contributions from the energy sector. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 40 This work is delivered for the Department for Energy Security and Net Zero . The Land-Use Change and Forestry estimates were provided by the UK Centre for Ecology and Hydrology (UKCEH) in Edinburgh with the support of Forest Research. Rothamsted Research provide the estimates of agricultural emissions. Department for Energy Security and Net Zero tom.forrest@beis.gov.uk Technical enquiries should be directed The Gemini Building, Fermi Avenue peter.brown@ricardo.com A copy of this report and related data may be found on the website maintained by Ricardo Energy & Environment for Defra and

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 41 This is the UK’s 2023 National Inventory Report (NIR). The NIR is one element of the annual greenhouse gas inventory (GHGI) that is compulsory to submit to the UNFCCC by signatories to the Convention on 15 April of each year. The NIR is compiled in accordance with the revised UNFCCC reporting guide lines, see decision 24/CP.19 7. Note that decision 24/CP.19 paragraph 2 dictates that AR4 Global Warming Potentials (GWPs) should be used “until a further decision is adopted”, and decision 7/CP.27 8 is a further decision that adopts AR5 GWPs for reporting under the Paris Agreement, and hence AR5 GWPs are used in this report. The other elements of this submission include the reporting of GHG emissions by sources and removals by sinks in the Common Reporting Format (CRF) tables, and any other additional information in support of this submission. The UK is a signatory to the Convention and is also a Party to the Kyoto Protocol. Under the Kyoto Protocol, the UK has been obliged to report supplementary information required under Article 7, paragraph 1, of the Ky oto Protocol 9 for each year of both commitment periods , alongside the inventory submission due under the Convention, in accordance with paragraph 3(a) of decision 15/CMP.1.
This edition of the NIR is no longer within the Kyoto Protocol reporting period, as such elements relating to the Kyoto Protocol are not included in this Background Information on Climate Change The Climate Change Act 10 became UK Law on the 26 November 2008. This legislation introduced a new, more ambitious, and legally binding target for the UK to reduce GHG emissions to 80% below base year by 2050, with legally binding five-year GHG budgets. The independent Climate Change Committee (CCC) was set up to advise the UK Government on setting and meeting of UK carbon budgets , as well as monitoring progress against them. In June 2019, the UK Government furthered this ambition by setting a legally binding target to achieve net-zero greenhouse gas emissions across the UK economy by 205011. The UK was the first major economy in the world to legislate for a net-zero target. 7 24/CP.19 Revision of the UNFCCC reporting guidelines on annual inventories for Parties included in Annex I to the Convention 8 FCCC Decision 7/CP.27. Common metrics used to calculate the carbon dioxide equivalence of anthropogenic greenhouse gas emissions by sources and removals by sinks 9 Kyoto Protocol to the United Nations Framework Convention on Climate Change. 11 The Climate Change Act 2008 (2050 Target Amendment) Order 2019. Available

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 42 Further information on the UK’s action to tackle climate change can be found on the Department for Energy Security and Net Zero’s website12. Information about climate adaptation can be found on the UK Government’s topic page13. Countries that signed and ratified the Kyoto Protocol were legally bound to reduce their GHG emissions by an agreed amount. A single European Union Kyoto Protocol reduction target for GHG emissions of -8% compared to base-year levels was negotiated for the first commitment period, and a Burden Sharing Agreement allocated the target between Member States of the European Union. Under this agreement, the UK reduction targ et was 12.5% relative to the base year. The first commitment period of the Kyoto Protocol was from 2008 to 2012. The second commitment period of the Kyoto Protocol (the Doha Amendment) ran for eight years, from 2013 to 2020 inclusive. For this second commitment period, alongside the EU and its Member States, the UK communicated an independent quantified economy-wide emission reduction target of a 20% emission reduction by 2020 compared with 1990 levels (base year). The target for the European Union, its Me mber States and Iceland is based on the understanding that it will be fulfilled jointly with the European Union, its Member States and Iceland. The 20% emission reduction target by 2020 is unconditional and supported by legislation in place since 2009 (Climate and Energy Package). This Kyoto target covered the UK, and the relevant Crown Dependencies and Overseas Territories to whom ratification was extended. The UK and the EU formally ratified the Doha Amendment on 17 November 2017, and 21 December 2017, re spectively. The Doha Amendment entered into force on 31 December 2020. Under the terms of the Withdrawal Agreement, the UK remained committed to its shared target with the EU under the Kyoto Protocol. Background Information on Greenhouse Gas Inventories 1.1.2.1 Reporting of the UK Greenhouse Gas Inventory The UK ratified the UNFCCC in December 1993 and the Convention came into force in March 1994. Parties to the Convention are committed to develop, publish, and regularly update national emission inventories of GHGs. The UK’s NIR is prepared in accordance with Decision 24/CP.19 14. In addition, the UK also reports GHG emissions by sources and removals by sinks in the CRF tables. The estimates are consistent with the IPCC 2006 Guidelines. The UK Greenhouse Gas Inventor y is compiled and maintained by a consortium led by Ricardo Energy & Environment – the Inventory Agency – under contract to the Science and Innovation for Climate and Energy Directorate in the Department for Energy Security and Net Zero (DESNZ). Full detai ls of the institutional arrangements for the preparation of the GHG inventory are explained in Section 1.1. This report and corresponding CRF tables provide annual emission estimates submitted by the UK to the UNFCCC for the period 1990 to 2021. The geographical coverage of this 1. UNFCCC Coverage I ncludes UK, Crown Dependencies (Jersey, G uernsey, Isle of Man) and the Overseas Territories (Bermuda, Cayman Islands, Falkland Islands, 12 Department for Energy Security and Net Zero, available 13 Climate change adaptation, available 14 FCCC Decision 24/CP.19. Revision of the UNFCCC reporting guidelines on annual inventories for Parties included in Annex I to the Convention

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 43 The main section of this report presents GHG emissions for the years 1990 -2021, discusses the reasons for the trends , and documents any changes in t he estimates due to revisions made since the last inventory submission. The Annexes provide supplementary detail regarding the methodology of the estimates and include sections on the estimation of uncertainties and atmospheric verification of the inventory. Full time series of emission factors and other background data are included on the NAEI website 15 and are uploaded as part of The CRF consists of a series of detailed spreadsheets, with one set for each year. A copy of the CRF accompanies this report and is available on the NAEI website15. 1.1.2.2 Geographical coverage of UK emissions For the 2023 submission, the UK is reporting only one set of CRF tables. The tables previously reported (under the KP, and for the EU) are no longer necessary. From 2024, the UK will need to report under the Paris Agreement, which may necessitate a second set of CRF tables going A major source of acti vity data (AD) for the UK inventory is provided through the publication DUKES is the United Kingdom (BEIS, 2022).
Shipments to the Channel Islands and the Isle of Man from the United Kingdom are not classed as exports and supplies of solid fuel and petroleum to these islands are therefore includ ed as part of the United Kingdom inland The definition of the UK used for DUKES accords with that of the "economic territory of the United Kingdom" used by the UK Office for National Statistics (ONS), which in turn accords with the definition required to be used under the European System of Accounts (ESA95). Depending on the required reporting framework, the geographical coverage of the UK inventory presented in this NIR includes emissions from territories associated with the UK.
The Crown Dependencies are the Isle of Man and the Channel Islands (Jersey and Guernsey). They are not part of the United Kingdom and are largely self -governing with their own legislative assemblies and systems of la w. The British Government, however, is responsible for their defence and international relations.
• Overseas Territories (OTs) (formerly called Dependent Territories) The relevant Overseas Territories are the Cayman Islands, Bermuda, Falkland Islands, and Gibraltar. Other Overseas Territories have not signed up to the UNFCCC and are not included in the NIR.
Overseas Territories are constitutionally not part of the United Kingdom and have separate constitutions, and most have elected governments with varying degrees of responsibilities for domestic matters. The Governor, who is appointed by, and represents, His Majesty the King, retains responsibility for external affairs, internal security, defence, and in most cases the public service. Activity data estimates for individual OTs and CDs are provided by their respective government departments, through direct communications with the Inventory Agency. These data are used to supplement UK national statistics (such as DUKES) to compile and report a complete inventory for all territories. 15 UK NAEI - National Atmospheric Emissions Inventory, available

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 44 1.1.2.3 Greenhouse Gases Reported in the UK Inventory The greenhouse gases reported ▪ Sulphur hexafluoride (SF6); and, ▪ Nitrogen trifluoride (NF3). ▪ Nitrogen oxides (NOx, as NO2); ▪ Non-Methane Volatile Organic Compounds (NMVOCs); and, ▪ Sulphur oxides (reported as SO2). Indirect greenhouse gases have indirect effects on radiative forcing and estimates are requested by the UNFCCC guidelines. In addition to the gases listed above, Part ies may also report indirect emissions of N 2O resulting from NO x and NH 3 emissions, from sources other than agriculture. These are included in the UK’s inventory report and are reported as a memo item. Emissions estimates are made using methodologies corre sponding mostly to the detailed sectoral Tier 2 or Tier 3 methods in the IPCC Guidelines. Most sources are reported in the detail required by the CRF. The main exceptions are the emissions from certain F -gas categories which are also considered commerciall y sensitive. Consequently, emissions data have been aggregated to protect this information. Appropriate steps to weight emission factors have been taken prior to aggregation, hence retaining the completeness of the UK inventory. 1.1.2.4 Global Warming Potentials (GWPs) of the Greenhouse Gases The direct greenhouse gases have different effectiveness in radiative forcing. The GWP is a means of providing a simple measure of the relative radiative effects of the emissions of the various gases. The index is defined as t he cumulative radiative forcing between the present and a future time horizon caused by a unit mass of gas emitted now, expressed relative to that of CO2. It is necessary to define a time horizon because the gases have different lifetimes in carbon feedback, according to the Fifth Assessment Report (IPCC, 2014). These are the GWP values that are required for reporting under the Paris Agreement and the UNFCCC from 2024. The UK has adopted these from the 2023 submission. By weighting the emission of a gas with its GWP it is possible to estimate the total contribution to g lobal warming of UK greenhouse Sulphur hexafluoride SF6 23,500 Nitrogen trifluoride NF3 16,100

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 45 HFC-43-10mee CF3CHFCHFCF2CF3 1,650 Perfluoromethane PFC-14 -CF4 6,630 Perfluoroethane PFC-116 - C2F6 11,100 Perfluoropropane PFC-218 - C3F8 8,900 Perfluorobutane PFC-3-1-10 - C4F10 9,200 Perfluorocyclobutane PFC-318 - c-C4F8 9,540 Perfluouropentane PFC-4-1-12 - C5F12 8,550 Perfluorohexane PFC-5-1-14 - C6F14 7,910 Perfluorodecalin PFC-9-1-18b - C10F18 >7,190 Perfluorocyclopropane c-C3F6 >9,200 Institutional, Legal and Procedural Arrangements for The UK greenhouse gas inventory is compiled and maintained by a consortium led by Ricardo Energy & Environment – the Inventory Agency – under contract to the SICE Directorate i n DESNZ (formerly BEIS) . Ricardo Energy & Environment is responsible for producing the emissions estimates for CRF categories of Energy (CRF sector 1), Industrial Processes and Product Use (CRF sector 2), and Waste (CRF sector 5). Land -Use, Land-Use Change and Forestry emissions (CRF sector 4) are calculated by the UK Centre for Ecology and Hydrology (UKCEH) with the support of Forest Research. Ricardo Energy & Environment is also responsible for inventory planning, data collection, QA/QC and inventory mana gement and Agricultural sector emissions (CRF sector 3) are produced by Rothamsted Research, under contract to the Department for Environment, Food & Rural Affairs (Defra). UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 46 1.2.1.1 The UK Greenhouse Gas National Inventory System (UK NIS) (NIS) and Section 1.2.2 includes further detailed information on the roles and responsibilities of each of the key organisations. BEIS) is the Single National Entity responsible for submitting the UK's GHGI to the UNFCCC. The Inventory Agency compiles the GHGI on behalf of DESNZ and produces disaggregated estimates for the Devolved Administrations (DAs) within the UK. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 47 The National Inventory Steering Committee (NISC) is formed of two groups, the Advisory Body and the Executive Body. Both groups meet twice per year, in Ap ril and November. The Advisory Body brings together technical experts on the inventory while the Executive Body membership consists of government stakeholders and end users of inventory data. The purpose of the Advisory Body is to advise on how proposed ch anges to the inventory should be prioritised and delivered, discussing any risks to the data supply chain as well as reviewing the inventory to identify any potential issues. The Executive Body reviews and discusses modifications to the inventory methodolo gy and resulting recalculations, making recommendations as to whether these modifications should be accepted. It also advises the DESNZ Greenhouse Gas Inventory Team on how improvements to the inventory should be prioritised. The Executive Body aims to ens ure that a rigorous science and evidence base remains central to decision-making on the future of the inventory, and stakeholders remain up to date with any significant risks to the Inventory. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 48 The UK GHGI has been reported annually since 19 94, and historically the acquisition of the data required has been based on a combination of existing environmental and energy legislation and informal arrangements with industry contacts and trade associations.
The legislation relied upon has been set up for other purposes, such • Integrated Pollution Prevention and Control (IPPC) regulations (industrial point source emission data from UK environmental regulatory agencies); and, • Statistics of Trade Act (UK energy statistics from DESNZ, formerly BEIS). To meet the standards required under the K yoto Protocol, the UK introduced legislation specifically for national inventory purposes which took effect from November 2005 16. These standards are maintained beyond the end of the KP commitment periods. This legislation makes provision for DESNZ’s Secretary of State to issue a notice in the event that information required for the inventory that has been sought volun tarily is not provided. The UK values voluntary participation and this legislation is inten ded as a last resort once all other avenues to elicit the required data, in the format and to the timing specified, have failed. To ensure that the system works most effectively and to minimise the need for legislative action, DESNZ establishes data supply agreements (DSAs) with relevant organisations to build upon existing relationships with data supply organisations. These agreements formalise the acquisition of data and clarify the main requirements of quality, format, security, and timely delivery of data for the national inventory. This process is on -going, through the NISC (see Section 1.2.2.4 There are currently DSAs in place with the Sc ottish Government, the Scottish Environment Protection Agency, the Northern Ireland Environment Agency, Natural Resources Wales and Overview of Inventory Planning As summarised in Section 1.1, the UK has designated authorities with clear roles and responsibilities. The following sections summarise the roles and responsibilities of key stakeholders in the UK’s National Inventory System (NIS). 1.2.2.1 Single National Entity – DESNZ In 2016, BEIS was created from the Department of Energy and Climate Change (DECC) and the Department for Business, Innovation and Skills (BIS) and became the Single National Entity for the UK. This has been confirmed in writi ng to the UNFCCC Executive Secretary. BEIS has overall responsibility for the UK Greenhouse Gas Inventory and the UK National System and carries out this function on behalf of His Majesty’s Government and the Devolved Administrations (Das) (Wales, Scotland, and Northern Ireland). At the time of preparing this report, a new government department – the Department for Energy Security and Net Zero (DESNZ) has been formed, which will take on the Single National Entity role. This will be communicated to the UNFCCC Executive Secretary once the legal transition is completed. DESNZ (formerly BEIS) is responsible for the institutional, legal, and procedural arrangements for the national system and for the strategic development of the 16 Greenhouse Gas Emissions Trading Scheme (Amendment) and National Emissions Inventory Regulations 2005

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 49 Within DESNZ, the Science and Innovation for Climate and Energy (SICE) Directorate administers this responsibility. The SICE Directorate coordinates expertise from across Government and manages research contracts to ensure that the UK Greenhouse Gas Inventory meets international standards set out in the UNFCCC reporting guidelines, and the As the designated Single National Entity for the UK GHG NIS, DESNZ has the following roles • National Inventory System management and planning ▪ Overall control of the NIS development and function; ▪ Management of contracts and delivery of the GHG inventory; and, ▪ Definition of performance criteria for NIS key organisations. • Development of legal and contractual infrastructure ▪ Review of legal and organisational structure; and, ▪ Implementation of legal instruments and contractual developments as required The contact point for the Single National Entity is provided on the Contacts page of the NIR. 1.2.2.2 Inventory Agency – Ricardo Energy & Environment Consortium A 4-year contract was established for the Inventory Agency in 2020 following a competitive tendering exercise. Ricardo Energy & Environment leads the consortium responsible for compiling the inventory, under contract to DESNZ (form erly BEIS). Ricardo Energy & Environment is responsible for all aspects of national inventory preparation, reporting and quality management. The current consortium consists • Ricardo Energy & Environment – lead contractor; • UKCEH – overall responsibility for the LULUCF estimates. • Forest Research – responsible for forestland estimates that feed into the LULUCF • Aether – responsible for estimates from railways and the OTs and CDs; and DA • Ray Gluckman Consulting – contributions to the F-gas inventory. Ricardo Energy & Environment together with the project partners prepares the NAEI which is the core air emissions database from which the GHGI is extracted. This arrangement ensures consistency in reporting across all air emissions for diff erent reporting purposes (UNFCCC, United Nations Economic Commission for Europe etc.). Activities collecting and processing data from a wide range of sources; selecting appropriate emission factors and estimation methods according to IPCC guidance; compiling the inventory; managing inventory QA/QC including QC of raw and processed data and data management tools, documentation and archiving, prioritisation of methodology and data improvements; carrying out uncertainty assessments; delivering the NIR (including CRF tables) by deadlines set to the UNFCCC on As the designated Inventory Agency for the UK GHG National Inventory System, Ricardo Energy & Environment has the following roles and • Co-ordination with DESNZ to deliver the NIS; • Review of current NIS performance and assessment of required development action; • Scheduling of tasks and responsibilities to deliver GHG inventory and NIS. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 50 • Drafting of agreements with key data providers; and, • Review of source data and identification of developments required to improve GHG • Documentation and archiving; • Dissemination of information regarding NIS to Key Data Providers; and, • Management of inventory QA/QC plans, programmes, and activities. • Data acquisition, processing, and reporting; and, • Delivery of NIR (including associated CRF tables) to time and quality. The Inventory Agency has formal systems in place to ensure that staff working on the inventory are well trained and able to carry out their duties effectively and efficiently.
The technical competence of the staff is facilitated through a combination of th e formal Ricardo Energy & Environment and inventory -specific staff management and training systems. Roles and responsibilities for all inventory team members are clearly defined, and a comprehensive system of QA/QC is in place. Section 1.6 sets out the QA/QC plan in detail. Ricardo Energy & Environment systems ensure subcontractors are managed actively and deliver inputs to the inventory on time and to the specified quality. The contact point for the Inventory Agency is provided on the Contacts page of the NIR. The Rothamsted Research Consortium, under contract to Defra, is responsible for the preparation and development of the agriculture inventory. The Rothamsted Rese arch Consortium conducts specific research in the agriculture sector and provides finalised GHG emissions data to Ricardo Energy & Environment for inclusion within the UK GHGI, is directly responsible for compiling the agriculture sections of the CRF, and for maintaining documentation and archiving of their models and processes. Ricardo Energy & Environment are responsible for checking consistency between outputs. The Rothamsted Research consortium • Rothamsted Research – lead contractor, dairy, pig, poultry and other livestock • ADAS – Modelling and database management, Sheep and grassland estimates; • Cranfield University – Beef and arable estimates • UKCEH - sector-wide data analysis and high resolution mapping • Ricardo Energy & Environment – QA/QC support 1.2.2.3 Key Data Providers and Reference Sources The organisations that provide the raw data to the UK GHGI include a wide range of government departments, non-departmental public bodies and government agencies, private companies, and industrial trade associations. Within the UK GHG National Inventory System, organisations that are Key Data Providers have the following roles and

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 51 Data quality, Format, Timeliness, Security • delivery of source data in the appropriate format and in time for inventory compilation, allowing for completion of required QA/QC procedures; • assessment of their data acquisition, processing and reporting systems, having regard • identification of any required org anisational or legal development and resources to meet more stringent NIS data requirements, notably the security of data provision in • communication with DESNZ, Ricardo Energy & Environment and their peers or members to help to disseminate information regarding the GHG inventory and National Energy statistics required for compilation of the GHGI are obtained from DUKES, which is compiled and published annually by a team of energy statisticians within DESNZ (formerly Information on industrial processes is provided either directly to the Inventory Agency by the individual plant operators or • The Environment Agency's (EA) Pollution Inventory for England (PI); • Natural Resources Wales’s (NRW) Emissions Inventory for Wales (WEI); • The Scottish Environment Protection Agency’s (SEPA) Scottish Pollutant Release • The Northern Ireland Environment Agency’s (NIEA) Northern Ireland Pollution • The DESNZ Offshore Petroleum Regulator for Environment & Decommissioning (DESNZ OPRED) Environmental and Emissions Monitoring System (EEMS) Reporting to these UK inventories for the purposes of environmental regulation is a statutory requirement for industries under the Environmental Permitting Regulations (EPR) . The data from these inventory sources is also used to quality check data provided voluntarily by companies directly to Ricardo Energy & Environment. In addition, the Inventory Agency receives energy, fuel compositional data and emission estimates from all UK installations that operate within the UK Emissions Trading System (UK ETS), from detailed annual operator returns to the UK regulators of UK ETS (EA, SEPA, NRW, NIEA, DESNZ OPRED) 17. These data are used by the Inventory Agency and the DESNZ energy statistics team to improve the UK energy balance and emission estimates for high - emitting source categories in the Energy and IPPU sectors (see Annex 7 for further details). The UK Centre for Ecology and Hydrology (UKCEH) compiles estimates of emissions and removals from LULUCF as part of the Ricardo Energy & Environment consortium using land- use data and information on forestry from the Forestry Commission Research Agency (an executive agency of the Forestry Commission, known as Forest Research), Government Departments, DAs and from other sources. 17 The UK Emissions Trading Scheme (UK ETS) replaced the UK’s participation in the EU ETS on 1 January 2021. UK based operators (except for electricity generators in Northern Ireland, who will remain in EU ETS in accordance with the terms of the Northern Ireland Protocol (or Protocol on Ireland/Northern Ireland to the Withdrawal Agreement, depending on how formal the publication is)) will now report their emissions under the UK ETS. For the purposes of calculating UK emissions statistics, teams should use EU ETS data for emissions arising up to December 31st, 2020, and use UK ETS data for emissions emitted from 1st January 2021. As the UK ETS was initially designed to provide a smooth transition for relevant sectors from the EU to the UK scheme, the two data sets will be compatible. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 52 Rothamsted Research compiles the inventory for agricultural emissions using agricultural statistics from Defra and the Northern Ireland Department of Agriculture, Environment and 1.2.2.4 The National Inventory Steering Committee, pre-Submission Review and To meet the detailed requirements of a National System and to ensure the UK efficiently and effectively works towards implementing best practices, a formal cross-Government body, the National Inventory Steering Committee (NISC) was formed in 2006. The NISC is tasked with the official consideration and approval of the national inventory prior to submission to the UNFCCC.
This pre-submission review is achieved at a NISC meeting prior to the finalisation of the inventory, and any recalculations to the inventory are presented and discussed at this One of the main roles of the committee is to assist the DESNZ GHG inventory management team to manage and to prioritise the ove r-arching inventory QA and facilitate review and improvement and better communication between inventory stakeholders across government Members of the Steering Committee include the Inventory Agency team at Ricardo Energy & Environment, other contractors, plus appropriate sector, legal and economic experts. These experts are responsible for reviewing methodologies, activity data, emission factors and emission estimates at a sectoral level and report their findings and recommendation s to the Steering Committee on a regular basis. The committee is responsible for ensuring that the inventory meets international standards of quality, accuracy, and completeness, and is delivered on time each year to the UNFCCC. The NISC is responsible for agreeing the priorities for the UK GHGI improvement programme. Where inventory improvement research is commissioned by the NISC, the research reports are reviewed and approved for use within the UK GHGI compilation by members of the NISC, managed by DESNZ , as part of the pre- Following the NISC meeting in the autumn, any changes to the inventory methodology are signed off by the Director of Science and Innovation for Climate and Energy (SICE), who is the Senior Responsible Officer in DESNZ. Final technical sign -off of inventory outputs rests with the Inventory Agency, as part of the governance procedures agreed with DESNZ as Single National • Any outputs relating to financial mechanisms are signed off by the Senior Responsible Officer at the Inventory Agency, as evidence that all quality control has been conducted on these outputs • National inventory outputs and technical delivery sign-off (e.g. on improvement projects) are signed off by either the inventory Senior Analyst or Technical Director at their roles and responsibilities in relation to the preparation and develo pment of the national inventory. These tables include organisations from the following categories, many of which are classed as key data • UK government departments – including DESNZ, the Department for Environment, Food and Rural Affairs (Defra), and Department for Transport (DfT) • DAs in Scotland, Wales, and Northern Ireland • Inventory contractors (who compile data for the Inventory among other tasks) • Government agencies (e.g. environmental regulators)

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 53 • Industry bodies or associations • Consultants and invited experts The development of the inventory is driven through the NISC, which meets twice a year to discuss the outcomes of recent peer, internal and expert reviews and to agree the prioritisation, funding, implementation, and review of items on the UK inventory improvement programme. The Key Category Analysis and the uncertainty analysis, qualitative analysis from Inventory Agency experts as well as recommendations from reviews of the UK GHGI are used as guidance to help the members of the NISC make decisions on which improvements are the most important. Key categories with high uncertainty are given priority over non-key categories or categories with a low uncertainty. The annual inventory review feedback from the UNFCCC and outcomes from QA/QC checks, as well as sector-specific peer- or bilateral review findings are also considered to guide decisions on UK GHGI improvement priorities. A qualitative uncertainty analysis of the invent ory is implemented by the Inventory Agency. This qualitative uncertainty analysis supports the Key Category Analysis and helps determine the highest priority emission sources in the UK where methodological improvements could be applied to improve the accur acy of emission estimates, or more detailed reporting used to improve transparency. This qualitative assessment is conducted by experts of the inventory team within the inventory cycle, including through a post -submission review of data sources, methods and feedback from the UNFCCC ERTs. In spring each year, DESNZ and the Inventory Agency hold a review meeting, at which the findings of the UN reviews, other peer reviews commissioned by DESNZ, internal post - submission review and qualitative analysis of sourc e categories are discussed in order to develop a comprehensive list of inventory improvement items for discussion, prioritisation and

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 54 Organisation Role in relation to NISC Key NISC responsibilities • Administer functions of Single National Entity for the UK National • Overall responsibility for inventory development, compilation, and • Manage GHG inventory research contracts • Ensure that UK GHGI conforms to UN international standards and Defra – Air Quality & Industrial • Air quality (AQ) inventory manager • Manager of AQ research contracts • Ensure that UK AQ inventory conforms to UN international standards • Overall responsibility for AQ inventory development, compilation, and • With DESNZ, ensure coordinated approach to improvements across GHG and AQ inventories, where relevant.
Defra • Liaison between Defra and NISC • Provide an analytical overview of all relevant Defra sectors • Provide link with Defra climate change mitigation team • Inform NISC of UK programme developments • Explore links between inventory and carbon budgets and potential • UK Emissions Trading System (UK • Provide UK ETS fuel use and fuel characterisation datasets for determining industrial fuel use statistics and GHG emission from • Improve links between UK ETS registry and GHG inventory • Feed international emissions inventory expectations back to the NISC to ensure the UK complies and develops the inventory accordingly • Provide information on future international developments and changes • Provide advice on the implications of domestic changes to the inventory in an international arena

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 55 Organisation Role in relation to NISC Key NISC responsibilities • LULUCF Inventory manager • Provide LULUCF inventory data that conforms to UNFCCC international standards and requirements • Work with the NISC to ensure highest quality data • Agriculture Inventory Manager • Providing agriculture inventory data that conforms to UN international • Work with the NISC to ensure highest quality data Defra – Waste • Waste • To provide waste policy expertise to the inventory, including landfill • To assist in improving landfill waste data quality • Energy statistics • Annual publication of Digest of UK Energy Statistics (DUKES) • Providing energy statistics to inform the UK inventory • Management, compilation, QA/QC and reporting of pollutant emission inventories/registers under Intergovernmental Panel on Climate Change (IPCC) regulations, and EU ETS annual emission reporting • Ensure that the pollutant emission inventories for industrial processes regulated under IPC/IPCC (PI, SPRI, ISR) are presented in the required format and timescale for inventory estimation and reporting • Collate information in annual emission reports for UK ETS • Offshore oil and gas regulator • Providing offshore oil and gas industry annual activity and emission data to inform the UK inventory • Regulation of the offshore oil and gas industry, including management of the Environmental and Emissions Monitoring System (EEMS) of environmental emissions from that sector • Transport • Publication of transport statistics each year • Providing transport statistics to inform the UK inventory Devolved Administrations • Inventories for Devolved • General review function for completeness and accuracy of UK inventory from a devolved perspective, including ensuring the integration of local datasets and specific research where appropriate. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 56 Organisation Role in relation to NISC Key NISC responsibilities • Devolved administration climate change legislation and statutory • Aid NISC in understanding the implications of the UK inventory for the devolved administration inventories, legislation, GHG targets and other • Contractor responsible for the UK GHG inventory; activity data, methods, emission factors, emissions estimation, reporting and • Compile the annual National Inventory Report (NIR) and Common Reporting Format (CRF) submission to the UN • Participate in sectoral expert panels as required • Contractor responsible for emissions from railways, and from Overseas Territories and Crown Dependencies • Joint role in managing the inventory improvement programme and development of QA/QC procedures • Contractor responsible for LULUCF inventory, activity data, methods, emission factors and removals estimation • Prepare and develop LULUCF inventory of emissions and removals and deliver on time for incorporation into the national inventory • Participate in sectoral expert panels as required • Contractor responsible for forestry elements of the LULUCF inventory • Participate in sectoral expert panels as required • Agriculture Inventory compilation • Contractor responsible for agriculture inventory; activity data, methods, emission factors and emission estimation • Prepare and develop agriculture inventory and deliver on time for incorporation into national inventory • Participate in sectoral expert panels as required • Energy modelling and projections • Produce UK CO2 projections • F-gases • To provide F-gas policy expertise to the inventory • To assist in improving F-gas data quality

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 57 Organisation Role in relation to NISC Key NISC responsibilities • Atmospheric measurements and interpretation at Mace Head, Ireland, and other tall tower sites. • Provide atmospheric measurements and interpretation of these data collected at Mace Head, for use in inventory data verification • Prepare comparison between estimated and observed emissions for the NIR External reviewers • Representation of industries, industry organisations and independent experts in the development of the national • Other experts or representatives may be asked to participate in sectoral expert panels or to review key sources or sources where significant changes to methods, activity data or emission factors have occurred e.g. ONS, UKPIA, Offshore Energies UK, Tata Steel, Electricity Supply Industry, international

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 58 1.2.2.5 UK Inventory Improvement Programme Each year the inventory is updated to include the latest data available. Improvements to the methodology are made and are backdated to ensure a consistent time series. Methodological changes are made to take account of new research and data sources, any new guidance from IPCC, relevant work, or emission f actors from sources such as EMEP – the European Monitoring and Evaluation Programme, which sits under the Convention on Long Range Transboundary Air Pollution (CLRTAP), the European Environment Agency (EEA) and the US Environmental Protection Agency (EPA), or from specific research programmes sponsored by DESNZ and other UK Departments. The UK NIS has a formal Inventory Improvement Programme, overseen by the NISC. This achieves the dual aims of (i) progressing research to improve the UK GHGI data quality, a nd (ii) developing inter departmental/agency working relationships to integrate inventory -related information from across Government. The NISC helps prioritise improvements across the inventory. These improvements are designed to improve the transparency, accuracy, consistency, comparability, and completeness of the inventory18. Incremental improvements are made routinely to ensure the inventory uses the most accurate activity data and emission factors. A detailed and prioritised list of larger inventory im provement tasks is maintained by the Inventory Agency.
The list is kept under review continually and is formally reviewed annually at a NISC meeting. This list is prioritised by taking into account the Key Category Analysis (see Section 1.5), the quantitative uncertainty analysis, sector and pollutant expert judgements, and the future obligations of the inventory. The timing of the improvements and re sourcing of the work are important considerations for the NISC. The Single National Entity takes the final decision on timing and implementation of improvements to the inventory. 1.2.2.6 Agriculture inventory improvements The UK GHG agricultural inventory has rece ntly undergone a major improvement program resulting in the adoption of a new coded (C#) inventory model with finer spatial, temporal, and sectoral resolution in underlying calculations, implementation of several country -specific emission factors and improvements to activity data. Further planned improvements are more modest, but 1. Review UK livestock feed data and revise inventory parameters according to outcomes 2. Continue to review the scientific literature to revise and r efine UK-specific emission factors as relevant data arise. Overview of Inventory Preparation and Management For details of inventory preparation, see Section 1.2. The Environment Agency was appointed as the UK Registry Administrator for the Kyoto Registry and EU ETS (until the UK left the latter scheme at the end of the transition period on 31 December 2020) by BEIS. The Environment Agency remains th e administrator for the UK ETS and the KP registry. The UK for this purpose comprises England, Wales, Scotland, Northern Ireland, offshore oil and gas installations and Gibraltar. The Environment Agency is 18 As detailed in chapter 6.5 of the 2006 IPCC Guidelines. Available nggip.iges.or.jp/public/2006gl/pdf/1_Volume1/V1_6_Ch6_QA_QC.pdf

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 59 Responsibilities of the Environment Agency are • Manage the contractors responsible for maintaining the computer systems (Siemens for software/hosting the Registry and Trustis for digital certificates); • Conform to the Kyoto Protocol and the COP/ Meeting of the Parties (MOP) decisions • Conform to the EU Registries Regulations as amended from time to time; • Allow access for authorised users19. • Act on instructions from Competent Authorities to manage accounts; and, The present UK GHG inventory for the period 1990-2021 was compiled in accordance with the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC, 2006). As discussed in paragraph 12 (a) in the fifty-second to fifty-fifth session of the UNFCCC Subsidiary Body for Scientific and Technological Advice20, while the IPCC have since published a refinement to the 2006 IPCC guidelines (IPCC, 2019), these are yet to be adopted for use in historic inventory reporting under the UNFCCC, but can be used in some cases if specifically justified. Data collection, processing, and storage The data acquisition task provides the fundamental activity data from which the GHG I is constructed. The process starts in June with the annual reques ts for data. A database which contains a list of contacts and datasets is used to track progress of the data acquired. The following activities are carried out each year, in order, as the inventory is Improvements to calculatio n methods are implemented before the inventory is compiled. These improvements are in part based on recommendations of UNFCCC reviews, European Commission reviews, peer reviews, bilateral reviews and relevant research sponsored by DESNZ, Defra or other organisations. Requests for activity data and background data are issued to a wide range of data suppliers. Each request is issued with a unique code, and a database is used to track the request and the data supplied from that request. Activity data received are examined. Anomalies are investigated, such as time series discrepancies, or large changes in values from the previous to the current inventory year. Data are prepared to allow emissions of direct and indirect GHG to be estimated. 19 Terms and Conditions at 20

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 60 Provisional emissions are estimated using the most recent activity data available. A series of internal reviews are carried out to detect anomalies in the estimates (time series variations and year to year changes). Errors and omissions are then rectified. Emissions reporting (including background data) Estimates of emissions are prepared for the various reporting formats (e.g. IPCC, UNECE etc. including differing geographical coverages). Draft reports are written to satisfy the reporting criteria of the various agencies, e.g. the The reports are reviewed internally, by external contributing agencies, and by DESNZ. Errors and omissions are then rectified. Final reports and data sets are then submitted via approved reporting routes, published in print and made available on publicly accessible web sites. At the end of each inventory cycle, all data, spreadsheets, databases and reports are archived, allowing all data to remain traceable, should it be needed in future years. The system outlined above complies with the QA/QC procedures outlined in Volume 1, Rothamsted Research and UKCEH, who are the sector experts for agriculture and LULUCF, respectively, have their own systems in place for data collection. As the Inventory Agency responsible for compiling the overall inventory estimates, Ricardo Energy & Environment receives completed emission estima tes from these organisations as part of the annual data Ricardo Energy & Environment has work programmes in place with UKCEH and Rothamsted to help harmonise the quality systems used with those Ricardo Energy & Environment use in Quality assurance/quality control (QA/QC) procedures and extensive review of GHG inventory The QA/QC plan for the UK inventory is explained in Section 1.6. Additional details of QA/QC in the LULUCF and Agriculture sectors can be found in Chapter 6, Section 6.11 and Chapter

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 61 The methods used to estimate emissions are described in detail in the relevant sections of this report. The direct and indirect GHGs reported are estimated using methodologies which mostly correspond to the detailed sectoral Tier 2/3 methods in the IPCC Guidelines. are described in more detail in the subsequent Chapters and Appendices.
CRF sector Comments on methods 1A • Basic combustion module (fuel use * emission factor); • Transport models (see MS 6 to MS 10); and, • Carbon balance approach (See MS 4). 1B • Carbon Balance approach (See MS 4); • BEIS EEMS inventory (See Annex 3.1.2.2); and, • Gas leakage data from network operators (See MS 19). 2A • Cement IPCC Tier 2 approach (see Section 4.2.2); • Lime Approach is comparable to IPCC Tier 2, although the Tier 1 default factor is used in the reporting of emissions; • IPCC Tier 2 approach, UK-specific factors from UK and EU ETS; • IPCC Tier 2 approach, UK-specific factors from UK and EU • Other carbonates – Tier 1 approach for earlier part of time-series, Tier 2 for years covered by UK and EU ETS. 2B • Emissions calculated based on emissions data from industry, UK and EU ETS, and the environmental regulators’ inventories, except • Use of EU and other MS statistics to estimate methanol manufactured in the • Use of IPCC default factors for CH4 from ethylene oxide, acrylonitrile, carbon black in years where no environmental regulators’ inventories data available; • Use of IPCC default factor for CO2 from ethylene dichloride across full time- 2C • Iron and Steel - 2 stage carbon balance and UK and EU ETS/operator carbon factors for carbonate use and arc furnaces (see MS 4); • Spreadsheet model and operator reported emissions for aluminium and • Tier 1 approach for non-ferrous metal production. 2D • Emissions calculated based on IPCC defaults for non-energy use of fuels; • IPCC method based as a proportion of the amount of fuel consumed for urea consumption in road transport. 2E, 2F • Spreadsheet models to estimate emissions of F-gases. 2G • Spreadsheet models to estimate emissions of F-gases; • NHS research into anaesthetic use; • Pollution inventory data for other uses of N2O; and, • Statistics on cream consumption and Danish inventory assumptions for N2O as a propellant for whipped cream. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 62 CRF sector Comments on methods 3A • Emissions calculated based on animal population data and appropriate EFs. 3B • Emissions calculated based on animal population data and appropriate EFs. 3D • Emissions calculated based on animal population data, fertilizer data and 3F • Emissions calculated based on IPCC methodologies and USEPA EFs. 3G • Tier 1 approach for liming. 4 • Mathematical models used to estimate emissions and removals from Land- • CARBINE model used to estimate emissions and removals from Forestry, 5A • The Methane Emissions from Landfill model (MELmod). 5B • UK waste activity data and IPCC default emission factors. 5C • Country specific emission factors, partially based on Pollution Inventory data and IPCC default/other literature emission factors. 5D • IPCC default method using country specific activity data for all N2O and CH4 from private waste-water management systems and industrial waste-water • Data from operator returns to the regulator for water company waste-water The sources of data used are documented in the relevant sections of this NIR. Much of the Relevant activity data contained in the source Digest of UK Energy Statistics (UK Department for Energy Security and Net Zero, formerly Department for Business, Energy, and Industrial • Energy statistics for the UK (imports, exports, production, consumption, demand) of liquid, solid • Calorific values of fuels and conversion factors. (UK ETS regulatory agencies in the UK; data supplied via UK Department for Business, Energy, and Industrial • Emissions from installations and characteristics of • Energy data are aggregated by sector and used to inform inventory estimates; and, • Fuel quality data are used to derive up to date carbon emission factors for major fuels in energy • The UK was part of the EU ETS up until 2020, and from 2021 onwards formed the UK ETS. Both

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 63 Relevant activity data contained in the source sources are used across the time series within the inventory, and therefore there are references to • Vehicle km according to vehicle type and road type; • Vehicle licensing statistics (split in vehicle km by • Selected domestic and international civil aviation Northern Ireland Inventory of Statutory Releases, transport data (NI Department of Agriculture, the Environment and Rural Affairs, NI Department for Regional Development) • Traffic count and vehicle km data for Northern • Information on regulated processes in NI. • Detailed domestic and international civil aviation (Environment Agency and Natural • Information on emissions from regulated processes Scottish Pollutant Release Inventory (Scottish Environment Protection • Information on regulated processes in Scotland. United Kingdom Petroleum Industry • Lead and sulphur contents of fuels, benzene content of petrol, RVP of petrol. Environmental Emissions Monitoring • Detailed inventory of oil and gas emissions. UK Iron and Steel Industry Annual (International Steel Statistics Bureau) • Energy production and consumption in the Iron and • Other statistics regarding the Iron and Steel United Kingdom Minerals Yearbook • Statistical data on minerals production,

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 64 Relevant activity data contained in the source • Automatic Number Plate Recognition (ANPR) data used to help define fleet composition on different Key data sources within the Energy sector are further elaborated in Annex 3. These include the annually updated data sets EEMS, the PI, SPRI and ISR listed above, and other one -off studies that are used across several source categories (Baggott et al., 2004 and Scarborough et al., 2017). DUKES is described in more detail in Annex 4. Key categories are defined as the sources of emissions that have a significant influence on the year, derived from the IPCC Approach 1 and 2 key category analyses. Tables are included for the analysis with and without LULUCF and for the base year and most recent year estimated. Details of the key source category analysis are given in Annex 1.
A trend cannot be calculated for the base year alone, and so the tables for the base year only contain key source categories categories within the energy sector. The Key Category Analysis (KCA) ranking system is an additional tool that the UK has developed to aid in the prioritisation of improvement work. The KCA ranking system works by allocating a score based on how high categories rank in the base year and most recent year level assessments and the trend assessment for the approach 1 KCA including LULUCF. For example, if CO2 from road transport liquid fuel use is the 4th hi ghest by the base year level assessment, 3rd highest by the most recent year level assessment and has the 5th highest trend assessment then its score would be 4+3+5=12. The categories are then ranked from lowest score to highest, with draws in score resolved by the most recent year level assessment. The assessments excluding LULUCF are ignored for this exercise, as the LULUCF sectors would only be included in half of the assessments and would therefore give an Following IPCC good practice, a qualitative analysis of the inventory has been made to identify key categories. Details of this analysis are given in Annex 1. This has not identified any further categories that are not already identified as part of the Approach 1 or Approach 2 analyses. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 65 1A (Stationary) Oil CO2 L2, T2 1A1 Energy solid fuels CO2 L1, T1 1A1 Energy liquid fuels CO2 L1, T1 1A1 Energy gaseous fuels CO2 L1, T1 1A1 Energy other fuels CO2 L1, T1 1A2 Manufacturing industries and solid 1A2 Manufacturing industries and 1A2 Manufacturing industries and 1A3b Road liquid fuels CO2 L1, T1 1A3d Domestic liquid fuels CO2 L1, L2 1A4 Other solid fuels CO2 L1, T1 1A4 Other liquid fuels CO2 L1, T1 1A4 Other gaseous fuels CO2 L1, T1 1A5 liquid fuels CO2 L1, T1 1B1 Coal mining and handling CH4 T1, T2

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 66 1B2 Oil and gas extraction CO2 L1 1B2 Oil and gas extraction CH4 L1, T1 1B2 Natural Gas Transmission CH4 T2 2B Chemical industries HFCs T2 2B2 Nitric acid production N2O T1 2B3 Adipic acid production N2O T1 2B8 Petrochemical and carbon black production CO2 L1, T1 2B9 Fluorochemical production HFCs, PFCs, 2C1 Iron and steel production CO2 L1, T1 2F Product Uses as Substitutes for ODS HFCs L2, T2 2F1 Refrigeration and air conditioning HFCs, PFCs, 2G Other Product Manufacture and Use N2O L2, T2 3A Enteric Fermentation CH4 L2, T2 3A1 Enteric fermentation from Cattle CH4 L1, T1 3A2 Enteric fermentation from Sheep CH4 L1, T1 3B1 Manure management from Cattle CH4 L1, T1 3B2 Manure management from Sheep N2O L1 3D Agricultural soils N2O L2, T2, L1, T1 4A Forest land CO2 L2, T2, L1, T1 4B Cropland CO2 L2, T2, L1, T1

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 67 4C Grassland CH4 L2, T2, L1, T1 4C Grassland CH4 L1, T1, L2, T2 4D Wetlands CH4 L1, T1, L2, T2 4E Settlements CO2 L2, T2, L1 4G Harvested wood products CO2 L1, T1 5A Solid waste disposal CH4 L2, T2, L1, T1 5B Biological treatment of solid waste CH4 T1, L2, T2 5B Biological treatment of solid waste N2O T2 5C Waste Incineration CO2 L2, T2 5D Wastewater Handling N2O L2, T2 1A1 Energy solid fuels CO2 L1 1A1 Energy liquid fuels CO2 L1 1A1 Energy gaseous fuels CO2 L1 1A2 Manufacturing industries and 1A2 Manufacturing industries and

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 68 1A2 Manufacturing industries and 1A3b Road liquid fuels CO2 L1 1A3d Domestic liquid fuels CO2 L1, L2 1A4 Other solid fuels CO2 L1 1A4 Other liquid fuels CO2 L1 1A4 Other gaseous fuels CO2 L1 1A5 liquid fuels CO2 L1 1B1 Coal mining and handling CH4 L1, L2 1B2 Oil and gas extraction CH4 L1 1B2 Oil and gas extraction CO2 L1 1B2 Natural Gas Transmission CH4 L2 2B Chemical industries HFCs L2 2B2 Nitric acid production N2O L1 2B3 Adipic acid production N2O L1 2B8 Petrochemical and carbon black production CO2 L1 2B9 Fluorochemical production HFCs, PFCs, 2C1 Iron and steel production CO2 L1 2G Other Product Manufacture and Use N2O L2

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 69 3A Enteric Fermentation CH4 L2 3A1 Enteric fermentation from Cattle CH4 L1 3A2 Enteric fermentation from Sheep CH4 L1 3B1 Manure management from Cattle CH4 L1 3B2 Manure management from Sheep N2O L1 3D Agricultural soils N2O L1, L2 5A Solid waste disposal CH4 L1, L2 1A (Stationary) Oil CO2 L2, T2 1A1 Energy solid fuels CO2 L1, T1 1A1 Energy liquid fuels CO2 L1, T1 1A1 Energy gaseous fuels CO2 L1, T1 1A1 Energy other fuels CO2 L1, T1

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 70 1A2 Manufacturing industries and 1A2 Manufacturing industries and 1A2 Manufacturing industries and 1A3b Road liquid fuels CO2 L1, T1 1A3d Domestic liquid fuels CO2 L1 1A4 Other solid fuels CO2 L1, T1 1A4 Other liquid fuels CO2 L1, T1 1A4 Other gaseous fuels CO2 L1, T1 1A5 liquid fuels CO2 L1, T1 1B1 Coal mining and handling CH4 T1, T2 1B2 Oil and gas extraction CO2 L1 1B2 Oil and gas extraction CH4 L1, T1 1B2 Natural Gas Transmission CH4 L2, T2 2B Chemical industries HFCs T2

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 71 2B2 Nitric acid production N2O T1 2B3 Adipic acid production N2O T1 2B8 Petrochemical and carbon black production CO2 L1 2B9 Fluorochemical production HFCs, PFCs, 2C1 Iron and steel production CO2 L1, T1 2F Product Uses as Substitutes for ODS HFCs L2, T2 2F1 Refrigeration and air conditioning HFCs, PFCs, 2G Other Product Manufacture and Use N2O L2, T2 3A Enteric Fermentation CH4 L2, T2 3A1 Enteric fermentation from Cattle CH4 L1, T1 3A2 Enteric fermentation from Sheep CH4 L1, T1 3B1 Manure management from Cattle CH4 L1, T1 3B2 Manure management from Sheep N2O L1 3D Agricultural soils N2O L2, T2, L1, T1 5A Solid waste disposal CH4 L2, T2, L1, T1 5B Biological treatment of solid waste CH4 T1, L2, T2 5B Biological treatment of solid waste N2O L2, T2 5C Waste Incineration CO2 L2, T2 5D Wastewater Handling CH4 L1, L2 5D Wastewater Handling N2O L2, T2

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 72 1A1 Energy solid fuels CO2 L1 1A1 Energy liquid fuels CO2 L1 1A1 Energy gaseous fuels CO2 L1 1A2 Manufacturing industries and 1A2 Manufacturing industries and 1A2 Manufacturing industries and 1A3b Road liquid fuels CO2 L1 1A3d Domestic liquid fuels CO2 L1, L2 1A4 Other solid fuels CO2 L1 1A4 Other liquid fuels CO2 L1 1A4 Other gaseous fuels CO2 L1 1A5 liquid fuels CO2 L1 1B1 Coal mining and handling CH4 L1, L2 1B2 Oil and gas extraction CO2 L1 1B2 Oil and gas extraction CH4 L1 1B2 Natural Gas Transmission CH4 L2

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 73 2B Chemical industries HFCs L2 2B3 Adipic acid production N2O L1 2B8 Petrochemical and carbon black production CO2 L1 2B9 Fluorochemical production HFCs, PFCs, 2C1 Iron and steel production CO2 L1 2G Other Product Manufacture and Use N2O L2 3A Enteric Fermentation CH4 L2 3A1 Enteric fermentation from Cattle CH4 L1 3A2 Enteric fermentation from Sheep CH4 L1 3B1 Manure management from Cattle CH4 L1 3D Agricultural soils N2O L2, L1 5A Solid waste disposal CH4 L2, L1 This section presents the QA/QC system for the UK greenhouse gas inventory (GHGI), including the approaches used for verification and treatment of confidentiality issues.
QA/QC • Quality Control (e.g. raw data checks, calculation checks, output checks) to minimise the risk of errors within the available resources to deliver the inventory; • Quality Assurance (e.g.
peer reviews, bilateral reviews, expert reviews) whereby independent experts periodically review all or part of the inventory to identify potential • Verification where alternate independent datasets are available to compare against The current system complies with the Tier 1 procedures outlined in the IPCC Good Practice Guidance (IPCC, 2006) and also includes a range of bespoke sector specific QA/QC activities that comply with Tier 2. Ricardo Energy & Environment, the Inventory Agency, is also fully accredited to ISO 9001:2015 and ISO 14001: 2015 (see Box 1.1).
This accreditation provides additional institutional standards which the Inventory Agency is required to apply to all projects

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 74 and ensures that the wider company conforms to good practice in project management and Description of the current QA/QC system The NAEI and the UK Greenhouse Gas Inventory are compiled and maintained together by Ricardo Energy & Environment (the Inventory Agency), on behalf of the UK Depa rtment for Energy Security and Net Zero (DESNZ) and the Department for Environment, Food and Rural Affairs (Defra). Ricardo Energy & Environment prepares the GHG submission to the UNFCCC.
The data compilation for some source sectors of the UK inventory are performed by other • Rothamsted Research manages the compilation of emission estimates for the agriculture sector under contract to Defra, working with a team of contractors that are agriculture sector experts from several other ADAS, Cranfield University, the Centre for Ecology and Hydrology (UKCEH) and Scotland’s Rural College (SRUC). • The Centre for Ecology and Hydrology ( UKCEH) and Forest Research (FR) together compile the Land Use, Land -Use Change and Forestry (LULUCF) sector, both under sub-contract to Ricardo Energy & Environment.
Many of the statistical datasets received by Ricardo Energy & Environment, UKCEH, FR and Rothamsted Research for the UK GHGI compilation come from data provider organisations that are UK government departments, agencies, research establishments or consultants working on behalf of the UK Government or for trade associations. Several of these data provider organisations (e.g.
DESNZ, the Department for Transport, Defra, the Office of National Statistics and British Geological Survey) qualify as UK National Statistical Agencies (as defined in UN Guidance21) and abide by strict statistical QA/QC standards. Other organisations (e.g.
the UK environmental regulatory agencies that provide installation - level emissions data) supply important datasets for the UK inventory and have their own QA/QC systems that govern data quality. Regulatory agencies for industry and commerce have developed data QA/QC systems to support their specific regulatory functions, includ ing to regulate operator environmental performance (such as to underpin atmospheric emissions reporting under UK ETS or the Environmental Permitting Regulations (EPR)) and to regulate other activity performance that is relevant for the national inventory (such as annual reporting against industry performance standards for water companies, gas suppliers, electricity suppliers).
In some cases, data for the national inventory are provided by individual companies or organisations (e.g. trade associations) and i n those instances the Inventory Agency requests information annually regarding QA/QC systems that underpin the data, as well as seeking information on estimated uncertainties of the data provided.
Ricardo Energy & Environment is responsible for co -ordinating inventory -wide QA/QC activities relating to inventory submissions, across all inventory stakeholders. In addition, Ricardo Energy & Environment works with organisations supplying data to the GHG inventory to encourage them to demonstrate their own leve ls of QA/QC that comply with either 2006 IPCC Guidelines or the UK’s National Statistics standards, through stakeholder consultation meetings, annual information requests, and via the National Inventory Steering Committee The UK inventory QA/QC system encompasses a wide range of activities to 21

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 75 • inventory planning tasks, review of historic data and methods, identification of improvement priorities, data and method selection, inventory team training and • inventory compilation and reporting tasks, management and documentation of data flows from raw data through calculation of emission estimates to reporting, input data requests/acquisition, management of compilation processes and quality checking systems, documentation of data, methods and assumptions, assessment of key source categories and uncertainties, reporting of inventory outputs; • inventory checking tasks, raw data checks, inventory model / calculation checks, source -specific and cross-cutting output checks, checking reasons for changes compared to previous inventory estimates, emission trend checks, emission • inventory QA review tasks, pre -submission reviews, post -submission reviews, peer reviews, bilateral reviews, expert reviews.
1.6.1.1 Overview of the UK QA/QC system inventory QA/QC system includes three core 1. The QA/QC Plan is a document maintained by the GHGI’s QA/QC manager (at Ricardo Energy & Environment) and defines the specific quality objectives and QA/QC activities required in undertaking the compilation and reporting of GHG estimates.
The plan sets out source -specific and general (cross -cutting) activities to ensure that quality objectives are met within the required inventory reporting timeframe. The QA/QC plan also assigns roles and responsibilities for the Inventory Agency team and records the key outcomes from inventory QA activities in order to underpin a programme of 2.
QA/QC Implementation includes the physical undertaking of the QA/QC activities throughout the data gathering, co mpilation and reporting phases of the annual inventory cycle and in accordance with the QA/QC plan. 3.
Documentation and Archiving. Documentation is embedded within the UK’s compilation tools.
The NIR transparently describes the data sources, methods, assumptions and QA/QC implementation used in producing the GHG inventory including records of activities undertaken, findings/issue logs, recommendations and any necessary actions taken or planned . Archiving ensures a complete backup and storage of all mat erial used for the compilation of the estimates.
UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 76

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 77 Box 1.2: ISO 9001:2015 and ISO 14001:2015 Accreditation In addition to the UK’s GHGI -specific QA/QC system, through Ricardo Energy & Environment, the Inventory has been subject to ISO 9000 since 1994 and is now subject to ISO 9001:2015 , t he international standard that specifie s requirements for a quality management system. It is audited by Lloyds Register Quality Assurance (LRQA) and the Ricardo Energy & Environment internal QA auditors.
The NAEI has been audited favourably by LRQA on five occasions in the last 1 5 years. The emphasis of these audits was on authorisation of personnel to work on inventories, document control, data tracking and spreadsheet checking, and project management.
As part of the Inventory management structure there is a nominated officer responsible for the QA/QC system – the QA/QC Co- ordinator. As part of the Ricardo Group certification, Ricardo Energy & Environment is currently accredited to ISO 9001:2015 .
Lloyds Register Quality Assurance carried out a three-yearly recertification audit of Ricardo Energy & Environment which was completed in October 2022. Ricardo Energy & Environment successfully passed the recertification, with no major non-compliances, and a new Ricardo Group certificate was issued in February 2023.
Under the Ricardo Group certification, Ricardo Energy & Environment is currently certificated for the Quality Assurance ISO 9001:2015, Environmental Management System ISO 14001: 2015 and Health & Safety ISO 4500:2018 standards. Specific details of the QA/QC plan, implementation, documentation and archiving are provided 1.6.1.2 Scope of the QA/QC plan The scope of the QA/QC plan 1.
Calculation of greenhouse gas estimates and reporting to UNFCCC (including emissions and removals from all sources and gases) 2. Calculation of air pollutant estimates and reporting to UNECE (including emissions from all sources and pollutants) 3.
Calculation of estimates and reporting to UK National Statistics 4. Identification and phased implementation of incremental improvements to the QA/QC Improvements to the QA/QC System The QA/QC plan and procedures are subject to continuous review and improvement.
In 2014, BEIS and Defra commissioned an independent review of the NAEI QA architecture, through a series of audits on 15 of the NAEI models. The review was conduc ted by Hartley McMaster (HM) and was aimed at assessing the NAEI QA systems against the requirements of IPCC guidance, BEIS model QA guidance and the wider Government guidelines for model integrity (HM Treasury Aqua Book22).
Further to this review, BEIS commissioned in late 2016 a review of a further sample of NAEI models by Cambridge Architectural Research (CAR). During 2016, HM also reviewed a representative sample of the models operated by Forest Research (FR) and UKCEH to generate the LULUCF estimates, and during 2017 HM reviewed a sample of models used to process point source data for the national inventory.
In 2020 HM undertook a quality review of the Power Station model. The findings of these reviews have underpinned QA system improvements over recent submission cycles; further model -specific QA improvements may be implemented in future, subject to priorities and resources available .
In 2021, Det Norske Veritas (DNV) were awarded the contract to provide independent QA/QC of 22 The Aqua guidance on producing quality analysis for government (2015), available

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 78 the NAEI. As part of their contract, DNV has reviewed two batches of models that underpin the inventory.
These reviews have not found any errors in the inventory, but have concluded that there are changes that could be made to the models to improve transparency and reduce the Improvements made to the inventory QA/QC system during the 202 3 submission cycle • Completion of data logs for the inventory compilation workbooks to improve documentation and transparency. • Completion of assumption logs for the inventory compilation workbooks, to help identify • Removal of hard coded values within calculations in the inventory compilation workbooks, to reduce the risk of errors and improve transparency.
• Continued roll out of the NAEI Data Portal to facilitate pollutant -specific and activity data checking, building up the data set on known trend changes as well as facilitating checks. The new NAEI Data Portal also allows more focussed checking with the more significant changes more easily identified.
• Implementation of the new road transport model • Improvements to the NRMM model to apply best practice digital principles, largely around documentation and reproducibility of the code. The key objectives of the QA/QC plan a re to ensure that the estimates in the GHG and air pollutant inventories are of a suitably high quality and will meet the methodological and reporting requirements for UK submissions to the United Nations Economic Commission for Europe (UNECE) and UNFCCC, as set out within national inventory reporting guidance from the IPCC23 and CLRTAP24.
The inventory data quality objectives are to achieve the principles of Transparency, Completeness, Consistency, Comparability and Accuracy (TCCCA): • The description of methods, assumptions, data sources used to compile estimates in internal (spreadsheets and other calculation tools) and published material (e.g. the NIR) and on the inclusion of national and assumptions (e.g.
source category detail and the split between UK ETS and non-UK ETS sources, implementation of policies and measures, carbon contents of fuels, site specific estimates, national statistics such as population, GDP, energy prices, carbon prices etc.). • The documentation of QA/QC activities and their implementation using internal checklists and summarised in relevant public material (e.g.
NIR). • and include all relevant (anthropogenic) emission/removal activities, using representative data for the national territory for socio -economic assumptions and policies and measures for all required years, categories, gases and scenarios.
• across trends in emissions/removals for all years (especially where applicable between the historic and projected estimates) and that there is internal consistency in aggregation of emissions/removals. Where possible, the same methodologies are used for the base year and all subsequent years and consistent data sets are used to estimate emissions or removals from sources or sinks.
23 2006 IPCC Guidelines for National Greenhouse Gas 24 Guidelines for reporting emissions and projections data under the Convention (2013 EB ECE/EB.AIR/122/Add.1, 2013/3 and 2013/4):

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 79 • with other reported emission/re moval estimates through use of the latest reporting templates and nomenclature consistent with reporting requirements. Using the correct IPCC category level and consistent units for expressing mass of emissions/removals by gas, split between UK ETS and non -UK ETS sources, scenarios, units for parameters and of input parameters (e.g.
energy prices, carbon price, population etc.). • ensuring the most accurate methods are used in the application of methods, minimising the uncertainty in assumptions and in use of data sources used for the estimates and inclusion of national and assumptions.
The overall aim of the inventory QA/QC system is to meet the above objectives, and to minimise the risk of errors in the UK inventory data such that emission estim ates are not knowingly over- or under-estimated as far as can reasonably be judged. The inventory QA/QC system also reflects that quality is one of three often competing attributes for a given project quality, time, and resources.
Noting that the c omplete set of UK GHGI and Air Pollutant Inventory (API) estimates contain many large and small contributors to emissions/removals, key category analysis is used to prioritise the most important categories (i.e. the highest-emitting source categories in the UK and/or the most uncertain sources).
More resources and time are typically directed towards method development, compilation, reporting and associated QA/QC activities for these key source categories, with simpler methods and less rigorous approaches ty pically applied to lower emitting / more certain (non -key) source 1.6.2.2 Roles and Responsibilities The QA/QC plan sets out specific responsibilities for the different QA (review) and QC (data controls, checking) activities and to different roles within the inventory compilation and reporting team. These are embedded within compilation and processing spr eadsheets and databases.
Training and project management communication across the Inventory Agency ensures that these responsibilities are clear, with specific tasks and checks signed -off at appropriate stages throughout the inventory process. The following responsibilities are outlined • QA/QC Manager (“Senior Analyst”): Coordinates all QA/QC activities and manages the contributions from data suppliers, sector experts and independent experts and undertakes cross cutting QA/QC activities .
Maintains the QA/QC plan, co -ordinates action across the team set quality objectives, communicate and implement QA/QC activities, identify training and development needs (individual, systematic); • Knowledge Lead the technical development and implementation of the NAEI programme, supporting the QA manager and project management team in delivering the project to meet technical requirements of international reporting as well as UK - specific and other output quality expectations. Manage periodic revie w and perform final checking activities on data and report submissions.
• Project Lead all key management activities including management of the project finances, commercial issues, liaison with DESNZ and Defra, manage and attend project meetings, communicating project tasks and requirements to the team and oversee the day-to-day running of the project. Manage team resources and support the QA Manager, Technical Director and Knowledge Leaders in identifying and resolving resource limitations (e.g.
skills gaps, continuity planning); • Task Managers/Sector Task managers (or sector experts) are responsible for the maintenance of task documentation (e.g. compiler manual, scope documents, quality checking records and correspondence) and task QA Pla n to definition of checking requirements; timeline delivery of work; coordination of task sign -off;

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 80 identification of team training requirements and risk management.
They perform sector specific review and checking activities and report to the QA/ QC Manager . Sector Experts also collaborate with data suppliers and other key stakeholders to review data quality (input data and outputs), perform quality checks on supplied information, assess and report on uncertainties associated with NAEI outputs.
Ide ntify improvement requirements for their tasks/sectors and promote/ implement cross cutting QA /QC improvements by sharing best practice and engaging in team communication activities. • External Review Provide expert/peer review of emissions and projections for specific sectors, identify key findings and inventory improvement recommendations, and report to the QA/QC Manager.
The QA/QC plan sets out a detailed timeline for QA/QC checks. The timeline is designed to fit in with compilation a nd reporting requirements for all UK GHG and Air Pollutant reporting 1.6.2.4 Quality Control and Documentation The UK’s GHGI Quality Control (checking, documentation and archiving) occurs throughout checks used within the UK greenhouse gas inventory .
The horizontal bars symbolise ‘gates’ through which data does not pass until it meets the quality criteria and the appropriate checks have been performed. The key activities that are undertaken and documented to check the 1.
Checking of input data for scope, completeness, consistency with data for recent years and (where available) verification against other independent datasets . Compilers check the incoming data from data providers to assess whether the data are complete and consistent with data for recent years.
In some cases, checks are performed to compare data between individual operators (e.g. gas composition data from multiple UK gas transporters) and between different reporting mechanisms (such as comparisons of operator-reported activity and emissions data between EPR and UK ETS).
For severa l sources, production-based emission estimates can be compared with other data (e.g. sales data, plant capacity data) to check that the trends and values are reasonable.
2. Analysis of internal inventory energy and mass balances and other statistics assumptions against National Statistics input data (e.g.
DUKES and ONS). Mass or energy balances are performed for each major fuel in the UK economy and any deviations from UK energy statistics are checked and documented.
Several sector methods for key categories also have Tier 2 checks to assess internal consistency, such as carbon balance checks for the carbon flows through integrated iron and steel works. 3.
Completeness checks. The database is checked for completeness and consistency of entry across the different p ollutants and gases.
For example, combustion sources are checked for inclusion of all relevant pollutants and the database checked for any missing estimates and appropriate use of notation keys. 4.
Recalculation checks. The latest inventory dataset is compare d against the previous inventory submission.
Any recalculations are documented by inventory compilers and signed off by checkers. Reasons for the recalculations are documented, e.g.
method improvements, revisions to input data or assumptions. These recalcu lation notes are referenced within the inventory database to facilitate reporting and transparency of

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 81 5.
Time series checks and benchmarking checks . The time series of emissions are checked for step changes, trends, and any outlier data (e.g.
outlier EFs or peaks/dips in activity data trends). Any unusual features are checked and explained, with reasons for significant trends and outliers documented in the method sections of the NIR.
Implied Emission Factors (IEFs) are checked against previous estimates and for key categories against defaults (from IPCC guidance) to identify any notable UK-specific EF outliers. 6.
Method implementation checks . A range of common checks are performed across inventory calculation models, such checking that units are correct for input parameters; checking that selection of NCVs or default EFs is consistent across years/pollutants; checking for either new emission estimates (e.g.
due to new UK data or new methodological guidance or new EFs within the IPCC guidance) or for any missing emission sources compared to previous submissions. 7.
Reporting checks. Inventory submissions are checked to ensure correct allocation into the CRF categories.
Emission totals at national and sub-category level are checked against the “master” dataset derived from the UK inventory database outputs, to minimise risks of data transcription errors into reporting templates. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 82 Checking and documentation is facilitated by specific custom data storage and handling systems and procedures developed for the GHGI compilation that 1.
A database of contacts containing uniquely referenced data on suppliers, data users, detailed data requirement specifications (including requirements for supplier QA/QC and uncertainty information) and data supplied to and delivered from the inventory. This

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 83 database tracks all data sources and suppliers used for the estimation of emissions/removals with unique references that are used to tag datasets through the inventory compilation process.
The contacts database also tracks all outputs from the GHGI including formal submissions and data supplied in response to informal and ad- 2. Individual data processing tools are used to prepare the majority of source data into suitable AD and EF s for UK emissions estimates .
These data processing tools (spreadsheets and database models) are uniquely identified and i nclude QC procedures, summaries and source data referencing and documentation within them. QC procedures are embedded in the tools which provide sector specific checks (e.g.
energy/mass balance) and implied emission factor checking for default and country specific emission factors . The QC procedures within each tool/spreadsheet include calculation input/output checking cells and flags to identify calculation errors.
The QC summary sheets in each tool/spreadsheet include links to QC activities that need to be performed, flags for the QC activities, their status and sign off; details of source data; key assumptions, methods, data processing activities and progress; the scope of activities, gases and years included; relationships with other models (where inter - dependencies exist); records of authorship; version control and checking . All relevant cells in the data processing spreadsheets are colour coded for ease of reference indicating whether the cells are calculation cells, output cells, checking cells or data input cells.
All input data are referenced to the unique data source and data supplier held in the contacts database so all source data can be traced back to its originator and date of supply. All spreadsheets are subject to second person checking prior t o data uploading to the NAEI database.
3. A core database (NAEI database) of AD and EFs with embedded tier 1 QC routines and data source and data processing referencing .
The database provides the quality assured dataset of UK emissions and removals used for UNFCCC reporting (including CRF population), responding to ad-hoc queries or deriving other downstream estimates (e.g. emissions by Devolved Administration and emissions by Local Authority) .
The detailed Activity Data and Emission Factor components for each source or sink category estimate are held within the NAEI database and include all sources, activities, gases/pollutants (GHGI and A QPI), territories and years. The majority of data in the database are imported directly from the individual data processing models ( as described above).
To ensure data source transparency, all data points in the database carry a reference to either the upstream data processing tools used to derive the data, the external data source and supplier or both . It also includes details of the date entered, the person uploading the data, its units (to ensure correct calculation), and a revision or recalculation code (which ensures that recalculations of historic data can be easily traced and summarised in reports) .
Automated data import routines used to populate the database minimise transcription errors and errors resulting from importing data that has not been properly checked . This process extracts output data from the upstream data processing models and can be controlled by the Inventory Agency via a data import dashboard.
The automated system ensures that data is only uploaded to the database once it meets specified QA/QC criteria of data checking, completion and consistency. Several detailed QC checking queries are embedded within the database that facilitate annual QC activities, as defined in the QA/QC Plan, a.
Checks with previous submissions for changes due to recalculations or errors at a detailed level, by source-activity-pollutants (a designated auditor identifies

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 84 sources where there have been significant changes or new sources. Inventory compilers are then required to explain these changes to satisfy the auditor)25; b.
Assessment of trends and time series consistency for selected key sources , including QC of activity data and emissions of high priority pollutants; c. Mass balance checks for all major fuels to ensure that the total fuel consumptions in the GHG inventory are in accordance with those published in energy National Statistics from BEIS, and that any exceptions or deviations are d. Input-output checks for key UK models to conduct “implementation” checks on the processing of data from upstream models for LULUCF, agriculture and F - e. Industry-specific checks, to compare UK inventory output data against operator- reported data via other mechanisms, such as the UK ETS and Environmental Permitting Regulations (EPR). These checks enable high -level checks on the data consistency for high -emitting source categories (e.g.
power station s, refineries, cement kilns, iron and steel works) for priority pollutants (e.g. CO 2, f. Other activity data checks (e.g.
production and consumption with National g. Implied Emission Factor checks (assessing trends in IEF and comparison with h. A consistency check between IPCC output and NFR 2020 formatted output. 4.
Data extraction checking routines and Data exported from the NAEI database and entered into reporting tools (e.g. the CRF Reporter tool) are finally checked against the direct database output totals to ensure that any inconsistencies are identified and rectified prior to submission.
This includes interrogating the output xml from the CRF software and comparing this against a series of queries from the NAEI database to compare both emissions and activity data. 5.
Official annual reports to UNFCCC and UNECE provide full documentation of inventory estimation methodologies, data sources and assumptions by source sector, key data sources and significant revisions to methods and historic data, where appropriate. In addition, the annual report to the UNFCCC includes details of planned prioritising improvements identified by the Inventory Agency and agreed by the National Inventory Steering Committee, and from Expert and Peer Reviews.
Any data presented in reports are checked against accompanying submission datasets and the NAEI 6. At the end of each reporting cycle, all the database files, spreadsheets, online manuals, electronic source data, records of communications, paper source data, output files representing all calculations for the whole time series are frozen and archived on a central server.
Electronic information is stored on secure and separately located servers (with one acting purely as back-up) that are regularly backed up. Paper information is archived in a Roller Racking system with a simple electronic database of all items referenced in the archive.
• The agriculture inventory (compiled by Rothamsted Research in North Wyke) is backed up daily on their network storage system . This system is mirrored with the Rothamsted Research Harpenden site, comprising an offsite backup.
• At UKCEH, all data and information relating to the LULUCF inventory is stored on a networked drive (accessible only by the project team) which is backed up daily by disaggregated source sectors used in the NAEI database. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 85 UKCEH computer support.
There is a separate folder for each inventory year and at the end of an inventory cycle the final versions of all datasets remain unchanged for back reference if r equired. In addition to this , the model code used within UKCEH for inventory compilation is stored in a subversion repository to ensure a clear record of all amendments and iterations.
1.6.2.5 Quality Assurance and Verification Quality Assurance and verification a ctivities provide an objective, independent review of inventory source data, methods and assumptions. These activities are primarily conducted to assess compliance with reporting requirements (e.g.
comparing UK inventory methods against international guide lines) and to identify areas for future inventory improvement. QA and verification activities 1.
Assessment of improvements against recommendations and the Inventory Improvement Programme lists of required improvements. 2.
Official annual review of changes to estimates and trends, prior to submission, by stakeholders supplying key datasets and by UK government departments responsible 3. Peer/Expert review of methods, assumptions, and data sources for new/revised estimates and on a periodic basis for key categories to determine whether methods should be improved due to the availability of new datasets and assumptions (focussing 4.
Documentation of recalculations and changes to the estimates. 5.
Verification analysis (e.g. comparison of trends with trends in ambient measurements).
Annually, and prior to submission, the National Inventory Steering Committee (NISC) reviews the emissions inventory datasets. The NISC i s tasked with the official consideration and approval of the national inventory prior to submission to the UNFCCC .
The NISC comprises key stakeholders, including the Single National Entity (DESNZ) (see Institutional Arrangements section), who understand the GHG estimates and input data sources. 1.6.2.5.2 Stakeholder Consultation with Key Data Providers The Inventory Agency consults with a wide range of stakeholders to ensure that the UK inventory uses the best available data and research, interprets information from data providers correctly and improves outputs to address user requirements.
The Inventory Agency plans and participates in a series of one -to-one meetings and engagement activities each year. Stakeholder consultation activities completed during the compil ation of the 1990 -2021 Department for Energy Security and Net Zero • The Inventory Agency are part of the stakeholder group for UK Energy statistics, which includes regular meetings with the DUKES team.
The stakeholder group w orks to provide independent QA/QC of energy stats updates, feedback our requirements as users of energy stats, and ensure that any revisions in the DUKES data are reflected appropriately in the inventory. Other engagement happens throughout the year based on need, for example, so that time series recalculations are made in consultation with the DUKES team.
This year there was some specific engagement with the DUKES team to support in the revisions to the gas oil reconciliation process for the inventory. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 86 • Consultation with OPRED to request clarifications on the scope and completeness of Environmental and Emissions Monitoring System (EEMS) reported data for several individual installations, to ensure correct interpretation of the available data.
• Meetings, teleconferences and emails with sector experts and emission inventory analysts from the environmental regulatory agencies in the UK (Environment Agency - EA, National Resources Wales - NRW, Scottish Environment Protection Agency - SEPA and Northern Ireland Environment Agency - NIEA) and plant operators. These were undertaken to address source -specific emission factor uncertainties and obtain up-to-date information regarding site -specific activities, abatement and changes to plant design or scope o f reporting.
In some instances, this has led to corrections to • Consultation with industry regulators such as OFGEM and UREGNI has helped to improve the quality of data used for gas use and fugitive emission estimates from the • Consultation with industry regulators to understand outliers in reported electrical gas • Ongoing consultation with TechWorks provided qualitative information on trends the fed into the new upgraded semiconductor model. • Ongoing consultation with Water UK and Ofwat to improve the quality of data supply.
• Consultation with MoD to provide updated AWACS data. • Consultation with the Iron and Steel Statistics Bureau (ISSB) to access more detailed statistics than are available through publications and to confirm the reporting of energy • Consultation with the Department for Transport (DfT) to discuss the potential use of MOT data for improving the relative mileage with age assumption for road transport and to discuss the methodological approach applied for the analysis of ANPR data to develop the fleet composition; • Discussion with the Environmental Analysis team at DfT about fleet modelling • Chemical Industries Association (chemicals manufacture), British Coatings Federation (manufacture of paints and inks), Euromonitor (non -aerosol personal care and household products) British Aerosol Manufacturers Association (BAMA) and the European Solvents Industry Group (sol vent manufacture and use) .
New data from these trade bodies led to revisions mainly to the UK NMVOC inventory. 1.6.2.5.3 Expert, Peer and Bilateral Reviews The UK’s programme of bilateral and external peer reviews is managed by the NISC as part of the improvement programme.
Bilateral reviews are initiated with other countries as a means to learn from good practice in other countries as well as to provide independent expertise to review estimates. The UK has participated in a number of bilateral exchanges, with the mo st Since 2002, the UK has implemented a programme of peer reviews by experts outside of the organisation responsible for the estimates.
External Peer review is applied in two 1) When new methods have been developed for important source categories. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 87 2) On a rolling programme to determine whether methods should be improved due to the availability of new datasets and assumptions (focussing on key categories).
In addition, the UK participates in the annual UNFCCC and EU review processes. DESNZ (then BEIS) commissioned a team of international experts to conduct a rapid review of the Energy and IPPU categories, with a focus on future requirements as well as consideration of the current methods and data.
The outcomes from this review will feed into the improvement programme. An individual review of the annual submission of the United Kingdom of Great Britain and Northern Ireland submitted in 202 2.
The ARR has been publ ished and the actions planned or taken as a result of these findings is set out in A 2021 annual review of national greenhouse gas inventory data by the European Environment Agency. The review considered the transparency, accuracy, consistency, comparability and completeness of the national GHG inventory.
Reviewers raised a number of issues, all of which were clarified and resolved. No recommendations were made.
An individual review of the annual submission of the United Kingdom of Great Britain and Northern Ireland submitted in 2021 was undertaken by the UNFCCC review team, and the findings have fed into the improvement programme. A 2020 comprehensive ESD review by the European Environment Agency.
The review considered the transparency, accuracy, consistency, comparability and completeness of the national GHG inventory. Reviewers raised a number of issues and provided recommendations for 4 of these, which the UK accepted.
These have fed though to the 2021 submission. Annual review by the UNFCCC expert review team.
Reviews highlight reporting issues of transparency, completeness, consistency, comparability or accuracy that need to be resolved by the UK. A list of the current issues and their status are provided in Chapter 10.
No annual review was carried out by the UNFCCC in 2015 due to delays in reporting, nor in 2018 due to limited UNFCCC funds for conducting reviews. In October 2019, the UK hosted an In-Country Review.
The UK and German inventory experts for the agriculture sector met in Germany during May 2019 to conduct a review of the new K methods and

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 88 documentation. The findings of the review have fed into the inventory improvement plan for the sector.
The UK hosted the French lead on LULUCF for a bilateral review in London during autumn 2018. The findings of the review will feed into plans for improvements for the 2020 submission.
In the absence of a formal UNFCCC review during 2018, and noting that a major change in the UK methodology for most agriculture sources was implemented in the 2018 submission to move to higher -tier methods, the UK invited an experienced UNFCCC reviewer to conduct a focussed expert review of the new UK methods. This was conducted during autumn 2018 and the findings from the review fed into the inventory improvement plan.
A full review was conducted for all Member states. Reviews highlight reporting issues of transparency, completeness, consistency, comparability, or accuracy that need to be resolved by the UK.
Although a full review for all Member Sta tes was not conducted, the UK volunteered for the second stage of the review to consider any potentially significant issues. None were found with the UK submission.
Bilateral review with Denmark, focusing on energy, and industrial processes and product use. Also considered the changes made to the UK NIR for the 2015 submission, in the absence of a formal UNFCCC review.
The findings of the review fed into the compilation of the 2016 inventory submission. The UK participated in a multi -lateral review workshop hosted by the German UBA inventory team, to consider the IPCC 2006 Guidelines on QA/QC and review implementation across all participating countries to exchange best practice, identify any areas of ambiguity and/or difference in Member State approach to QA implementation.
The findings fed into a paper submitted by UBA to the EU Working Group 1 for inventory agencies. Preparatory review to the UNFCCC assessment of UK KP reporting.
Bilateral review with Germany, focusing on the energy balance, iron and steel, refineries, the chemical industry and waste and biofuels. The recommendations from this review fed into the UK inventory improvement programme.
The review focussed on non -LULUCF sectors and provided a report for each Member State (including the UK) highlighting recommendations for improvements as well as documentation of any revised estimates as a result of the review. The UK made 3 minor (in total ~ 0.1%) revisions as recommended

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 89 by this review for lime production and burning of biomass for energy to address underestimates, and for dairy cattle to address an overestimate.
The object of the review was to share methods, experiences and potential data sources across the three teams and to provide recommendations on how to improve each of the inventories for these sectors. The recommendations for the UK were added to the UK GHGI improvement programme for consideration by Assumptions about leakage rates and the mix of HFC fluids in each sub-sector were peer reviewed, by a workshop of experts in 2008.
Losses during manufacture/initial charging and at decommissioning in the original refrigeration sector model were generally based on factors recommended by the IPCC or the recommendations from this workshop. The model was again peer reviewed by SKM Enviros in 2010 and has since been replaced by new research in 2011.
BEIS funded an external peer review of the research programme that provides LULUCF emissions estimates to the Greenhouse Gas Inventory in 2009. In addition, in 2009 the LULUCF inventory project was audited by an independent UKCEH team to confirm compliance with the Joint Code of Practice, where the project was praised for its high standards.
The objectives of the review were to develop emissions inventory capacity in collaboration wit h France, and to provide elements of expert peer review to meet quality assurance requirements under national inventory systems e.g. Article 5, paragraph 1, of the Kyoto Protocol and European Union Monitoring Mechanism (Regulation MMR) e.g.
280/2004/EC. Specific activities undertaken included sharing good practice between the UK and France and the development of ideas for efficient future technical collaboration.
1.6.2.5.4 Capacity building and knowledge sharing The UK actively participates in capacity building and knowledge sharing activities with other countries. These initiatives are usually led by the NISC but also include some projects led by Ricardo Energy & Environment (the Inventory Agency).
In the past, some were funded by the EU and EEA through the European Topic Centre on Air and Climate Mitigation. The list below highlights some recent examples of these activities.
1. UKCEH participation in annual yearly knowledge sharing with European LULUCF inventory compilers at EU Joint Research Council LULUCF meetings.
2. Knowledge sharing with the Vietnam inventory team.
3. Capacity building workshop with Balkan EU accession countries on National System 4.
Study visit by delegation from the Chinese National Centre for Climate Change Strategy and International Cooperation (NCSC) as part of their week -long visit to the UK arranged by BEIS. Ricardo hosted representatives from NCSC, BEIS and Welsh Government, presenting on compilation and usage of national, devolved, local and city

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 90 5.
Knowledge sharing between UKCEH LULUCF inventory compilers and Maltese LULUCF inventory compilers in 2016. 6.
In 2018 the UK inventory team collaborated with peers from the EU Working Group 1 to draft a note for circulation to all M ember States regarding the fossil carbon content of road transport biofuels, based on our research with the UK fuel supply chain. 7.
The UK experts on inventory verification and the InTEM (Inversion Technique for Emission Modelling) model, from BEIS and the M et Office, have engaged with verification experts from other countries and across other research institutes through the IG3IS symposium and user summit in November 2018 in Geneva, Switzerland. This was in order to share knowledge and experience from the UK programme and explore options for further development of these techniques to underpin emissions inventory verification at a range of spatial scales, and/or targeted at specific industries / sources.
8. NAEI experts provided capacity building project in the K yrgyz Republic funded by the World Bank in 2018 (Ricardo with UKCEH).
9. The UK Partnering for Accelerated Climate Transitions (UK PACT) programme.
UK The inventory team has several staff on the programmes roster of experts. Eligible countries can request sup port on GHG inventories via the British Embassy or High Commission in their country, as described at Skill -Shares and Secondments 10.
The DESNZ team and the Inventory Agency attended the most recent IG3IS summit on verification Geneva in February 2023 DESNZ has a research programme that derives independent emission estimates for the UK using in-situ high-precision high-frequency atmospheric observations of the UNFCCC gases and a range of other trace gases at the Mace Head Atmospheric Research Station on the west coast of the Republic of Ireland and a network of tall tower sites around the UK. The UK Met Office employs the Lagrangian dispersion model NAME (Numerical Atmospheric dispersion Modelling Environment) to sort the observations made at Mace Head into those that represent northern hemisphere baseline air masses and those that represent regionally polluted air masses arriving from Europe.
The Met Office inversion modelling system, InTEM, is then used to estimate the magnitude and spatial distribution of the UK and European emissions that best support the observations and provide a fully independent estimate of annual emission trends for the UK. The technique has been applied to 3 year rolling subsets of the data.
The work was exte nded to three sites across the UK, at Angus (north of Dundee , decommissioned in 2015), Talcolneston (Norfolk), and Ridge Hill (Herefordshire), to create the UK DECC (Deriving Emissions linked to Climate Change) Network. Two additional stations, Heathfield (HFD) in Southern England and Bilsdale (BSD) in North Yorkshire, were established through the NERC GAUGE (Greenhouse Gas UK and Global Emissions) programme.
BSD replaced TTA in 2015 in the UK DECC network and is funded by BEIS. A fire at BSD in August 2021 destroyed the tower and measurements have therefore been discontinued until a replacement tower is available.
HFD is supported by the National Physical Laboratory (NPL). The data from these additional sites have resulted in significant increases in the sp atial and temporal resolution of the InTEM emission estimates, and hence, an improvement in the UK estimates.
The uncertainties associated with the UK emission estimates have also decreased. Most recently a comparison of inventory estimates of HFC-134a with those modelled through the InTEM system has suggested that the inventory may be overestimating its HFC -134a

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 91 emissions.
Further analysis of the mobile air conditioning sector of the inventory, the main UK source of HFC-134a, has suggested several parameters with high uncertainty that may be the source of the difference . Revisions to the refrigeration and air conditioning model (to review assumptions following the implementation of the EU F-gas regulations) have been made, and this comparison is now in better agreement.
The complete results of the verification using the atmospheric observations and a more detailed description of the modelling method used are given in Annex 6 of the UK NIR and NAEI input data from some sources are subject to commercial confidentiality, notably where the production data and/or activity data for a specific installation or company are identifiable. For example, there are confidential data indicating the plant production capacity for sp ecific industrial plant (e.g.
cement kilns, chemical plant), annual sales data of specific commodities (e.g. sporting goods) and also details of fuel use for specific installations (e.g.
plant-level data from UK ETS-regulated installations). It is important therefore that in the management of these data within the NAEI system, and in the publication of emission estimates (and other data) relating to these data sources, that the NAEI does not disclose such commercially sensitive information.
There are several mechanisms that the Inventory Agency, Ricardo Energy & Environment, and the wider inventory compilation teams (e.g. Rothamsted Research) deploy to ensure that disclosure of confidential data does not • The provision of sensitive raw data to the Inventory Agency, if not through direct communication with the data source organisations, is managed via Defra or DESNZ using file encryption with password protection; • Confidential data, such as the UK ETS dataset, is managed by the Inventory Agency on a password-protected secure server which has limited access rights, i.e.
access is limited to the relevant compilers and checkers only; • Within the NAEI database tables, there are specific data fields to identify confidential data. These are applied to cover all the associated data, such as emissions, AD and EFs, to minimise the risk of mistakenly releasing sufficient information that the confidential data can be inferred.
These database data fields then enable ease of identification of risk of data disclosure in any NAEI database output (e.g. data at different spatial scales, such as for a specific Local Authority or in mapping outputs); • Confidential data assignations are periodically reviewed, and in every routine data request for input data for the NAEI the organisation providing the data is given an opportunity to identify confidential data; • Where data outputs use the confidential data, the data are reported at an aggregated level – either with other sources (e.g.
in the case of sporting goods), or over a larger geographical area (e.g. in the case of emissions mapping outputs which are usually at 1km x 1km resolution, data for some sources are aggregated and smeared over a larger area, typically 10km x 10km).
This may mean that the UK cannot report exactly 26

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 92 in line with the expected level of sectoral resolution as defined in the CRF reporting format for GHGs, but this is considered an acceptable trade-off that is necessary to The UK National Inventory Reports f rom the 1999 NIR onwards, and estimates of emissions of GHGs, are all publicly available on the NAEI website27. The UK GHG inventory estimates uncertainties using both Approach 1 (error propagation) and Approach 2 (Monte Carlo simulation) described by the IPCC.
Approach 1 provides estimates of uncertainty by GHG according to IPCC sector. Approach 2 considers the correlations between sources and provides estimates of uncertainty according to GHG in 1990 and the latest reporting year, and by IPCC sector.
Approach 2 (Monte Carlo simulation) suggests that the uncertainty in the combined GWP weighted emissions of all the greenhouse gases is 5.0% in 1990 and 2.5% in 2021. The trend in the total GWP weighted emissions ex pressed as the fall between 1990 and 2021 is -47%, with a 95% confidence interval of between -53% and -43%.
A full description of the uncertainty analysis is presented in Annex 2. The UK GHG inventory aims to include all anthropogenic sources of GHGs.
This section discusses sources of greenhouse gases not currently included in reporting. Sources Reported as ‘Not Estimated’ their expected level of emissions would be relative to the national total, and the UK’s justification for not estimating these sources.
Section 37(b) of the UNFCCC reporting guidelines on annual greenhouse gas inventories stipulates that Parties may report emissions as not estimated if an activity occurs in the Party, and • The 2006 IPCC Guidelines do not provide methodologies to estimate the • A disproportionate amount of effort would be required to collect data for a gas from a specific category that would be insignificant in terms of the overall level and trend in • Where an emission should only be considered insignificant if the likely level of emissions is below 0.05 per cent of the national total GHG emissions, a nd does not The total national aggregate of estimated emissions for all gases and categories considered insignificant shall remain below 0.1 per cent of the national total GHG emissions. The below expected level of emissions would be relative to the national total.
UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 93 Explanation for not estimating Estimate TRUE It is estimated that the decomposition of 1 t FK 5-1-12 generates about 400 t CO2 eq PFCs. As this product is used only at one small magnesium production plant and has been trialled at one larger plant, total emissions in the United Kingdom due to the decomposition of FK 5-1-12 could be up to about 2 kt CO2 eq per year since 2012 and zero before 2012.
Based on consultation with the small number of magnesium manufacturers in the UK. When deriving an estimate of emissions based on the IPCC default methodology and using the largest of the 2003-5 UK IPCC guidelines the estimate of emissions is smaller than the thresholds (both as a percentage of national emissions and as an absolute value of emissions) to be considered insignificant.
Consultation with industry has indicated that current UK Based on data for 2003-5, no other data When deriving an estimate of emissions based on the IPCC default methodology and using the 2003 UK production capacity estimate of emissions is 3 orders of magnitude smaller than the thresholds (both as a percentage of national emissions and as an absolute value of emissions) to be considered insignificant. Consultation with industry has indicated that current UK production capacity is smaller than in 2003, and the limited remaining production processes do not require any F-Gases Based on data for 2004, no other data identified Very small quantities of PFCs are sold in the UK market for this application, but it is believed that these are sold exclusively for hermetically sealed applications and products that are sold on to This is a conservative assumption that the upper limit of PFC sales to the UK is entirely used and emitted within the UK for heat transfer fluids, although our understanding is that the majority of this PFC is emitted outside 28 Where IE means “included elsewhere” 29 Specifically the lowest national total annual emissions excluding LULUCF since 1990

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 94 Explanation for not estimating Estimate TRUE Not estimated due to insufficient data.
Emissions are expected No suitable data identified to generate even an Data on Overseas Territory activity for this source are not Estimate is made by applying the highest annual UK emissions from this source to the ratio of UK and OT and CD cropland areas. Data on Overseas Territory activity for this source are not Estimate is made by applying the highest annual UK emissions from this source to the ratio of UK and OT and CD cropland areas.
Data on Overseas Territory activity for this source are not Estimate is made by applying the highest annual UK emissions from this source to the ratio of UK and OT and CD cropland areas. Insufficient information for reporting.
The UK is developing an approach to estimating emissions from this source, but do not currently have suitable data to present. Insufficient activity data for reporting.
The UK is developing an approach to estimating emissions from this source, but do not currently have suitable data to present. TRUE There are no data available on CO2 content of coal mine methane in the UK, and therefore we have considered the 2006 Guidelines, section 4.1.2: "The following sections focus on methane emissions, as this gas is the most important fugitive emission for coal mining.
CO2 emissions should also be included in the inventory where data are available". CO2 from combustion of coal mine methane is included in the UK GHGI under 1A1c This is the highest value since 1990 when estimated by assuming that colliery methane has a similar CO2 content to natural gas.
UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 95 Explanation for not estimating Estimate TRUE Indirect CO2 emissions from the oxidation of VOCs are not mandatory for reporting under the UNFCCC reporting Estimate of emissions due to abatement of NMVOC by oxidation presented. This estimate is based on the differences in emissions of NMVOC reported for 2017 for each source category within 2D3 compared with emissions reported for 1990 (when solvent emissions will not have been abated).
For almost all source categories, NMVOC emissions are lower in 2017 than in 1990 and expert judgement was applied as to what proportion of the reductions in each category was driven by sector decline, reformulation of products, changes in practices to minimise solvent requirement, recovery or Emissions from oxidation of solvents may have been higher in some years in the past but only from the late nineties onwards (since most processes did not abate emissions before then). Since total emissions were also significantly higher in the past, we believe that it is likely that emissions from abatement of NMVOC would represent a similar % of total emissions in those earlier years.
UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 96 Explanation for not estimating Estimate TRUE No appropriate data available Use of CO2 by-products from industrial processes (e.g. ammonia production) in the food and drink industry (e.g.
carbonated drinks). For simplicity, the UK currently includes all CO2 by-product from UK ammonia production in the national total, but this estimate is not necessarily the same as UK final consumption of products containing CO2 by-product.
In order to generate an accurate and complete estimate of UK emissions of CO2 from by-products we would need to estimate the imports and exports of CO2 by-product and imports and exports of products containing by- There are also sources of CO2 of biogenic origin in this source, but these would not contribute to the national total, so have not Assumed to be replaced by re-growth within the year. Assumed to be replaced by re-growth within the year.
No evidence of wildfires on permanent TRUE Emissions of CO2 are biogenic and therefore are excluded. As sources of non-LULUCF CO2 of biogenic origin are not included in the national total, the impact on the national total is 0.
This summary confirmed that there are no sources for which emissions are not estimated which would be expected to be above 0.05% of the UK national total in any year, and that the sum of the sources is estimated to be under 0.1%. Note that many of the sources included are reported as

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 97 “NE” due to there not being a suitable methodology to generate an estimate, when including only sources for which are not rep orted due to insignificance, the likely proportion of emissions omitted is much lower than 0.1% of the UK national total in any year.
Therefore, the UK inventory’s use of ‘NE’ in the CRF is compliant with section 37(b) of the UNFCCC reporting guidelines on annual greenhouse gas inventories. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 98 Sources Outside the Scope of the National Total The following sections discuss sources of emissions relating to UK activities relevant to climate change which are excluded from the national total due to being outside of the scope of greenhouse gas inventory reporting requirements.
1.8.2.1 International Aviation and Shipping International shipping and aviation refer to emissions associated with travel from a location within the geographic scope of the inventory to a location outside that scope. The approach adopted by the UNFCCC is that combustion emissions from these journeys are to be reported as ‘memo items’ but not included in Party’s national totals.
The UNFCCC separately engages with the Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO) Emissions from processes other than fuel combustion can occur on these international journeys (e.g. fugitive emissions of HFCs used in refrigeration or air conditioning in shipping), however these emissions are comparatively small, and many of these source are likely to be indirectly captured by territorial emissions estimates for those sources.
In accordance with UNFCCC reporting requirements, the UK GHGI reports emissions and activity relating to due to fuel combustion in international aviation and shipping as a ‘memo item’ in CRF Table1.D, and the methodology is presented in MS 7 and MS 13, but these are not included in national totals. The UK does not make specific estimates of, or report emissions of sources that occur on international journeys other than fuel combustion and lubricant use.
1.8.2.2 Aviation-Induced Radiative Forcing Almost all anthropogenic emissions occur at or near ground level, and therefore emissions are reported using Global Warming Potentials (GWPs) that reflect how pollutants contribute to global warming when released at ground level. Howe ver, emissions that are emitted at high altitudes (i.e.
fuel combustion emissions from the cruise stage of flights) contribute to atmospheric chemistry differently to ground level emissions due to contrails and their impact on cloud formation, although precisely how strong this effect is sensitive to a number of factors, The UK GHGI reports emissions and activity from emissions due to aviation cruise in CRF Table1.A(a)s3 and Table1.D and the methodology is presented in MS 7 . However, these emissions reported do not account for the aviation-specific impact as there is no approach to account for this in the 2006 IPCC guidelines and it is not fac ilitated in the reporting mechanisms adopted by the UNFCCC.
1.8.2.3 Carbon Dioxide of Biogenic Origin Carbon dioxide contributes to the greenhouse gas effect independently of whether originating from a mineral (e.g. fossil fuels) or biogenic (e.g.
wood burning) or igin. The main difference between mineral and biogenic carbon is that without anthropogenic intervention, mineral carbon generally remains stored in a solid form and does not interact with atmospheric chemistry, whereas without anthropogenic intervention, biogenic carbon is part of a natural cycle where some is released to the atmosphere as CO 2, and CO 2 is absorbed from the atmosphere to be stored in organic matter.
Because of this, anthropogenic activity contributes to higher levels of CO2 from these sources differently; i.e. anthropogenic mineral CO2 sources are effectively increasing the total carbon in circulation, whereas anthropogenic contribution 30 31

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 99 of biogenic CO2 are a shifting of the split in the carbon cycle to have a higher proportion in the One approach to estimate the net change to carbon in the atmosphere is to estimate the changes in carbon stored in vegetation, soils and other organic matter.
This approach accounts for emissions of CO2 by assuming that carbon in vegetation removed i s eventually emitted via combustion, animal consumption and respiration, or decomposition, and simultaneously accounts for CO 2 sequestered and stored by vegetation. The 2006 IPCC guidelines sets out a methodology to account for carbon stock changes in this way, and the UNFCCC agreed that this method should be used, the net carbon stock change reported against Land Use, Land Use Change and Forestry (LULUCF) and included in Party’s national The approach for accounting for carbon stock changes in land means that including estimates of emissions of CO 2 from fuels of biogenic origin at the point of release would be a double count of this carbon stock approach, and therefore estimates of CO2 of biogenic origin at the point of release is excluded from national totals, but can be reported as a ‘memo item’.
The UK uses the UNFCCC agreed LULUCF approach for accounting for CO 2 of biogenic origin, which is reported in CRF Table4 to Table4(IV) and the methodology is discussed in Section 6. The UK also reported CO2 of biogenic origin from fuel use or incineration against the various sectors in which they are combusted as ‘memo items’ the total of which is presented in CRF Table10s1, but these values are not included in the national total.
1.8.2.4 Ozone Depleting Substances (ODS) regulated under the Montreal Protocol These substances are explicitly excluded from requirements to report under UNFCCC. As stated at climate-change-transparency/methodological-issues-relating-to-fluorinated-gases: • "The UNFCCC agreed that all Parties shall develop national inventories of anthropogenic emissions by sources and removals by sinks of all greenhouse gases (GHGs) not controlled by the Montreal Protocol..."; and, Where the Montreal Protocol is a UN agreement for the control of ODS.
Many ODS are additionally potent greenhouse gases, for which we estimate peak emissions in the 90s to be over 20Mt CO 2e. Almost all emissive uses of O DS have been discontinued, many using HFCs as a substitute (also potent greenhouse gases, but with zero ozone ODS emissions are not reported in the UK Greenhouse Gas inventory, but some ODS use is modelled as part of understanding emissions of ODS-substitutes.
1.8.2.5 Other Substances with Non-Zero GWPs These substances are not included in the products required to be reported under UNFCCC or otherwise. Most of these products are believed to be only used in small quantities, have modest GWPs, or both.
For example, key substitutes for high GWP HFCs include hydrofluoroolefins, or hydrocarbons, which typically have GWPs two orders of magnitude smaller than the HFC being replaced. It is estimated that in recent years total emissions from these pollutants exceed 0.1 Mt CO2e.
Emissions of these products are not reported in the UK Greenhouse Gas inventory, but some use is modelled as part of understanding emissions of products they are used to substitute. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 100 Water vapour is abundant in the atmosphere, significantly contributes to the Earth’s Greenhouse effect, and there are anthropogenic sources of water vapour (e.g.
from the combustion of most fossil fuels). However, it is believed that atmospheric concentrations of water vapour are pri marily driven by temperature (warmer air can maintain higher humidity, and warmer water evaporates at a greater rate) 32, and anthropogenic emissions do not contribute significantly 33.
Because of this, water vapour is key to understand for climate modelling, including how water vapour can contribute to a warming feedback loop, but not important for estimating anthropogenic emissions in greenhouse gas inventories. Therefore, no estimate is made or reported for water vapour emissions in the UK GHGI.
1.8.2.7 Indirect Greenhouse Gases In addition to the direct GHGs, scientists also consider the effects of indirect GHGs on the radiative forcing of the atmosphere. Although they are not included in GWP weighted greenhouse gas emissions totals, these indirect GHGs affect the overall radiative balance of the atmosphere.
There are four indirect GHGs which must be reported under the UNFCCC, and estimates of their emissions are reported in across the CRF tables, and the NIR against the various sources where these pollutants arise. They • Non-Methane Volatile Organic Compounds (NMVOC) • Sulphur oxides (reported as SO2).
The effects of these gases on radiative forcing are complex. CO, NOX and NMVOC control in part the abundance of ozone ( O3) and the oxidising capacity (OH) of part of the upper atmosphere called the troposphere.
These pollutants act as indirect greenhouse gases through their influence on atmospheric chemistry; for example, through the formation of tropospheric O3 or changing the lifetime of CH4. The emissions of NOx and CO are dominated by human activities34.
Sulphate aerosols, formed from releases of SO2 which because of their small size are effective scatterers of sunlight and have long lifetimes, are responsible for radiative forcing. Volcanic eruptions that inject substantial amounts of SO 2 gas into the stratosphere are the dominant natural cause of externally forced climate change on annual and multi-decadal time scales35.
A reduction in SO2 emissions leads to more warming. NOX emission control has both a cooling (through reducing of tropospheric ozone) and a warming effect (due to its impact on methane lifetime and aerosol production)35.
1.8.2.8 Other Climate Forcing Pollutants Particulate matter also plays a part in radiative forcing. The colour or reflectivity of the particles is important and the effects on forcing are complicated.
Air pollution control measures to limit the levels of particulate matter emitted in turn will affect the emissions and atmospheric 32 33 IPCC FAQs, Q1-2-3 at 34 “Atmospheric Chemistry and Greenhouse Gases” Executive 35 Chapter 8 Anthropogenic and Natural Radiative Forcing. Section 8.4.2 Volcanic Radiative Forcing.
FAQ 8.2 | Do Improvements in Air Quality Have an Effect on

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 101 concentrations of several pollutants, NO X, NMVOCs, ammonia, black carbon, organic carbon, and SO2. In some cases, this can result in both heating and cooling effects.
Aerosol cooling occurs through aerosol –radiation, and, aerosol –cloud interactions. On the other hand, black carbon (BC) or soot, absorbs heat in the atmosphere leading to radiative forcing.
When BC is deposited on snow, it reduces its or ability to reflect sunlight. Reductions of BC emissions can therefore have a cooling effect, but the additional interaction of black carbon with clouds is uncertain and could lead to some counteracting warming.
Some couplings between the air quality pollutant e missions and climate are still poorly understood or identified, including the effects of air pollutants on precipitation patterns, making it difficult to fully quantify these consequences35. Particulate emission and black carbon are not included in the GHGI, but are reported in the UK submissions under the Convention on Long-range Transboundary Air Pollution (CLRTAP).
1.8.2.9 Carbon fluxes from underwater terrain Currently, carbon dioxide fluxes (i.e. sequestration or emissions) from sea, lake and river beds (also referred to as ‘blue carbon’) are not included in the UK national atmospheric emissions inventory.
This is primarily driven by the omission of a methodology for estimating these in the IPCC guidelines (the methodological guidance for national inventory reports adopted by the UNFCCC), where the omission of the methodology means that national inventories are not required to generate an estimate. Countries would have to go out of their way to develop the evidence based upon which to make an estimate if they wanted to include it.
The UK can and does estimate emissions and sinks from sources not included in the IPCC guidelines where suitable data and methodologies are identified, and in some cases conduct research to develop those data and methodologies. In this case, our understanding is that doing so for underwater terrain would be complicated a) the high uncertainty in estimates for CO2 fluxes (e.g.
the chemistry is fundamentally different to above water fluxes, as water absorbs atmospheric CO 2, so the location in the water column would impact the quantity eventually released to the atmosphere, but it would also indirectly impact the atmospheric CO2 which can be absorbed by b) the challenge in understanding what proportion of these fluxes are anthropogenic (we consider all on land fluxes in the UK to be anthropogenic as the entirety of the UK is populated, but this is less clear for underwater terrain); c) the question of territorial boundaries, noting that UK fishing vessels operate outside UK waters, and non-UK fishing vessels operate within UK waters; and, d) the reporting systems for inventory reporting do not provide a fra mework for reporting such fluxes (it would most naturally fit with Land Use, Land Use Change and Forestry, but there are no reporting categories for non-land). Some of these are less of an issue for coastal wetlands, and therefore inclusion of these is more likely that other underwater terrain fluxes.
Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 102 1 Population and GDP figures from ONS

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 103 trends between selected years by sector38 representatively present in this format. 38 ‘Base year’ refers to 1990 for CO2, CH4 and N2O, or 1995 for F-gases.
F-gases are fluorine containing compounds which are potent greenhouse gases, Sulphur Hexafluoride (SF6), Nitrogen Trifluoride (NF3), Perfluorocarbons (PFCs) and

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 104 emissions from the energy sector – particularly from power stations The increase between 2020 and 2021 is due to the increase in activity following the restrictions caused by the COVID- 19 pandemic. Total emissions are dominated by the energy sector across the time series.
Emissions from all sectors have declined, with the larg est decline in percentage terms from Unless otherwise indicated, percentages quoted relate to net emissions (i.e. accounting for carbon sinks in the LULUCF sector).
The geographical coverage of the inventory is the UK and the Crown Dependencies and Overseas Territories to whom the UK’s ratification of the The percentage changes presented in this chapter are calculated from original emission estimates within the inventory database. They may, therefore, differ slightly from those that could be calculated from rounded figures in this report.
A summary of the contribution of each GHG to the emission trends is provided below. The subsequent sections of this chapter provide an interpretation of emission trends, pri marily focusing on the trends by source sector.
39 F-gases are fluorine containing compounds which are potent greenhouse gases, Sulphur Hexafluoride (SF6), Nitrogen Trifluoride (NF3), Perfluorocarbons (PFCs) and Hydrofluorocarbons (HFCs). Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 105 trends between selected years by gas • Emissions of CO2 are by far the largest component of total GHG emissions, of which the largest sources are power generation and road transport.
Emissions have reduced across the time series due to fuel switching, structural change, and improvements in end-use efficiency. The strong link between power generation and CO2 emissions means that short term trends can be dominated by UK t emperatures.
In cold years like 1996 and 2010 there was an increase in demand for power for heating and in warm years like 2011 and 2014 there was a decrease. • The second most important source of greenhouse gases is methane (CH4).
Annual emissions of CH4 have reduced by over half since 1990. The main sources of CH4 are agriculture, waste disposal, leakage from the gas distribution system and coal mining.
Reductions in CH 4 emissions in the UK are driven by the increased utilisation of methane from landfills, a large decline in UK coal mining, investment in improvements to the natural gas supply infrastructure to reduce leakage and a reduction in livestock • Emissions of nitrous oxide (N2O) have also reduced by over half since 1990. Most N2O emissions a re generated from the agriculture sector , Agriculture sector N 2O emissions have decreased primarily due to reduced emissions from synthetic fertiliser application.
N2O is also released during the production of nitric and adipic acid, a significant source in 1990 contributing to approximately half of all N2O emissions. Due to a decline in production together with the installation of abatement equipment, the Industrial Processes and Other Product Use (IPPU) sector now only contribute around • The smallest percentage reduction in emissions across the time series is for the F- HFCs, PFCs, NF3 and SF6.
All F-gas emissions are accounted for under the IPPU sector. F-gas emissions have decreased since 1995, due mainly to the fall in F- gas manufacture in the UK and the installation of abatement equipment at two of the

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 106 three UK manufacturers.
These emission reductions have been to some extent offset by the increases in the use of HFCs as substitutes for ozone depleting substances, particularly in refrigeration and air conditioning. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 107 between selected years by sub-sector for Energy The energy sector GHG emissions are primarily CO2 from fossil fuel combustion in power generation, transport, manufacturing and construction, and other stationary and mobile fuel combustion.
The supply of fossil fuels also leads to significant emissions of CH4 from fugitive emission sources, such as from coal mining, oil and gas extraction and from the natural gas transmission and distribution system. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 108 reductions are due primarily to improvements in energy efficiency, and economy -wide fuel- switching from carbon-intensive fossil fuels such as coal, to greater proportional use of natural gas, nuclear power, and renewables.
There have also been large reductions in fugitive CH 4 emissions due to a large decline in coal mining, with the last large UK deep mine closing in 2015, and the reduction in leakage from the natural gas distribution network through a UK - wide programme of infrastructure improvements. Emission trends in Energy sub-sectors 2.1.2.1 Electricity generation There are several reasons for the decline in emissions from the power generation sector since • The UK power sector fuel mix has shifted towards use of Combined Cycle Gas Turbine (CCGT) stations rather than conventional steam stations burning coal or oil.
CCGT stations operate at a higher thermal efficiency, for example in 201 8 they operated on average at 48.9% efficiency, whilst coal-fired stations operated on average at 34.1% • The shift in fuel mix away from more carbon -intensive fuels such as coal and oils, to less carbon-intensive fuels such as natural gas; the calorific value of natural gas per unit mass carbon is higher than that of coal and oil; • There has been an increase in electricity gener ated from non -fossil fuel energy sources, due to increased use of wastes and renewable energy sources. 2.1.2.2 Manufacturing Industries and Construction Since 1990, emissions from Manufacturing Industries and Construction fuel combustion have declined, with lower fuel use and emissions reported across all sub-sectors iron and steel, non-ferrous metals, chemicals, food and drink, paper and pulp, minerals and from mobile

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 109 machinery.
This reflects the general decline in UK manufacturing output (e.g. of steel , aluminium) as well as a shift away from carbon-intensive fuels such as coal and oils to greater use of natural gas, as well as waste-derived and renewable fuels.
Reductions in emissions from unclassified industrial combustion also made a large contribution to the overall trend in emissions from the Manufacturing Industries and Construction sector. Emissions have declined by over 40% since 1990.
This is largely a result of reduced consumption of gas oil, fuel oil, coal, and natural gas, partly offset by increases in burning oil and LPG within the sector. Emissions from the Transport sector are dominated by road transport, which peaked in 2007, but have declined since 2007, and by 2019 were just below 1990 levels.
Emissions increased in 2021 after a large decrease in 2020 due to the COVID -19 pandemic. This trend prior to 2020 was driven by a number of factors, • Increases in vehicle kilometres in most years, except for a few years after 2007; • Improvements in the fuel efficiency of engines in the UK fleet; • Increases in the typical weight of passenger cars, increasing the energy needed to • Increase in energy requirement for additional applications, like air conditioning; • Fuel switching from petrol to diesel, improving fuel efficiency, but in some cases resulting in higher N2O emissions due to NOX abatement technology; • Increasing sizes of heavy goods vehicles; and, • The increasing displacement of fossil fuels by biofuels across the time series, since 2002, as CO2 emissions from the consumption of biofuels are not included in the UK 40 Carbon of biogenic origin are accounted for in the carbon stock calculations in the Land Use, Land-Use Change and Forestry

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 110 Emissions from domestic aviation increased between 1990 and 2005 but have subsequently decreased to levels comparable to 1990 by 2019.
This is because of a move to use more fuel- efficient aircraft in 2006 and a lower number of air miles being flown. There was an increase in emissions from domestic aviation in 2021 after a large reduction in air travel in 2020 due to Shipping emissions in the UK peaked in the late 1990s and have decreased since then.
The reductions are driven by lower shipping activity in several key sectors, notably the support vessels to the offshore oil and gas sector and oil tanker movements. Shipping emissions increased in 2021 after a notable drop in 2020 due to the COVID-19 pandemic.
2.1.2.4 Domestic, Commercial and Agriculture Emissions from domestic fuel combustion dominate emissions from the Domestic, Commercial and Agriculture sector. Emissions from this sector changed little between 1990 and 2009 but have declined more recently.
The effect of annual temperatures can produce large inter-annual variations. Fuel consumption data since 1990 indicates a general trend in fuel switching in these sectors, away from more carbon-intensive fuels such as coal, coke, fuel oil and gas oil, towards natural gas.
This shift has partly been driven by fuel prices but also through the growth of the UK gas supply network. 2.1.2.5 Fugitives (Energy exploration, production, and distribution) Fugitive energy sector emissions mostly consist of methane released from coal mining, oil and gas extraction and natural gas distribution.
In 1990, the majority of these emissions came from the production of solid fuels; however, these emissions have decreased significantly, due to the closure of all UK deep coal mines (by 2015). Another notable trend arises from the reductions in leakage of methane from the natural gas distribution network.
Over the time series, the UK gas transporters have invested significantly in replenishment of the gas pipeline infrastructure, replacing leakier cast iron pipework with low -leakage plastic pipelines. The fugitive emissions from upstream oil and gas exploration and production have tracked UK production, declining since a peak in 2004.
Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 111 41 Other includes 2D – Non-energy Products from Fuels and Solvent Use, 2E – Electronics Industry, and 2G – Other Product

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 112 sub-sector, relative to 199042 trends between selected years by sub-sector for Industrial Processes 42 Emissions from sector 2F are dominated by F-gas emissions, whose base year is 1995. See Section 2.1.2.1 for information

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 113 The Industrial Processes and Product Use (IPPU) sector accounts for all GHG emissions from industrial sources43 and product use including solvents.
Just under half of IPPU emissions are now CO2, although this only contributes to small proportion of total CO2 emissions. All F-gas emissions are generated from IPPU sources, and there are small quantities of CH4 and N2O partly due to the closure of numerous UK installations, including several integrated steelworks, primary aluminium works, chemical production sites and cement kilns, as well as the installation of abatement equipment, for example at adipic and nitric acid plant and by F -gas manufacturers.
The declining trend in emissions is also a reflection of decreasing production of many industrial materials in the UK, most notably in the chemicals and steel sectors. A large number of closures in the period 2007-2009 were due to decreased demand for many products as a result of the general economic situation in the UK and elsewhere, with falling demand for steel, cement, bricks, and aluminium, for example, leading to plant closures.
The large step- change in chemical sector emissions in 1998 -1999 was due to the fitting of N 2O abatement equipment at a major adipic acid manufacturing facility, which has subsequently closed. Emission trends in IPPU sub-sectors 2.2.2.1 Refrigeration, Air-Conditioning and Heat Pumps (RACHP) Until the early 1990s, Ozone Depleting Substances (ODS) were used a s refrigerants for RACHP applications, but in response to the Montreal Protocol these products were phased out in the UK in favour of products with no ozone depleting potential. The main substitutes for ODS were hydrofluorocarbons (HFCs), which has similar properties, but are still potent greenhouse gases. As a result of this there is a steep increase in HFC use since the mid-90s, plateauing in recent years as almost all ODS-based systems are thought to have been retired Since 2008 an increasing number of applications have been restricted from using higher GWP HFCs by EU regulation of F-gases. EU regulation has also become more stringent regarding the management of HFCs and HFC -using systems, and since 2015 a quota system was introduced, limiting the total HFC (on a GWP basis) allowed to be sold on the EU market. All of these actions are believed to have contributed to the plateaux in HFC emissions and subsequent downturn in recent years. Further discussion of these trends , including how they compare to atmospheric measurements, and other European countries subject to HFC-quota systems can be found in 43 Note that emissions from fuel combustion for energy is allocated to the energy sector (1A2). For more information,

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 114 Annual CO2 emissions from cement manufacture comprised 69% of total mineral sector CO2 emissions in 2021 but have fallen by 42% since 1990 due to the closure of many kilns and decreasing UK clinker production. Emissions fell to a low point of 3.7 MtCO 2 in 2009 due to the impact of the recession in 2008 -2009, and then increased again and hav e stabilised in recent years at around 4.0 to 4.5 MtCO2. Other mineral source categories don’t have a significant impact on the UK GHG trends; lime production and CO 2 emissions has reduced by around 18% since 1990, glass production emissions are down by around 17%; brick manufacturing emissions are down by 62%. 44 Merchant refers to sites selling lime and emitting CO2, captive refers to sites using lime and CO2 in-situ so in theory no FGD is an abbreviation of Flue Gas Desulphurisation Excludes very small glassworks producing lead crystal glass, frits etc. Some early site numbers are estimates

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 115 Emissions from adipic acid manufacture were reduced significantly in 1999, approximately half of the total fall in chemical sector emissions in that year, due to the retrofitting of an emissions abatement system to the only adipic acid plant in the UK, which subsequently closed in April By-product emissions from the manufact ure of HFCs and HCFCs have decreased to zero since 1990, due to plant closures and the installation of abatement equipment. Approximately half of the fall in chemical sector emissions in 1999 emissions was due to the installation of a thermal oxidiser at t he UK’s only HCFC -22 plant in that year, with emissions in 2000 falling again due to a full year of operation with the new abatement technology. Due to the phase out of HCFC-22 for many applications, production and emissions at this site has fallen and aft er a closure and reopening in 2010 and 2013 respectively, the plant permanently closed in 2016 ending emissions from this process. N2O emissions from nitric acid manufacture show falls due to the closure of 4 plants between 2000 and 2008 and due to the ins tallation of abatement technology in the larger of the Aside from these specific examples of emissions abatement, there has also been an underlying shrinkage in the UK chemical production sector over the time series, with many chemical and petrochemical installations closing since the 1990s. For example, all UK manufacturing of methanol ceased in 2001, whilst the installations producing carbon black and ethylene oxide closed in 2009. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 116 GHG emissions from across the UK metal production sector have fallen by around 61% since 1990, with every sector showing a marked reduction in production levels and emissions over the time series. The largest contributor to the UK trends is the closure of several large integrated steelworks and a decline in UK steel output, leading to Iron & Steel (I&S) sector IPPU CO2 emissions decreasing by 55% (across 2C1a-2C1d), which accounts for 88% of the total UK metal production sector CO2 reductions since 1990. Emission trends in the sector in recent years reflect the volatility of UK steel production since the economic down -turn from 2008, including a 27% reduction in CO2 emissions in 2008-2009 followed by several years of uncertainty regarding plant investments and possible closures; the sector increased production and emissions during 2013 to 2015 but the closure of the Redcar steelworks in 2015 and closures of coke ovens and lower production across UK sites led to a 31% decline in CO 2 emissions in 2015 -2016, with total I&S IPPU emissions (2c1a -2C1d) thereafter stabilizing at around 10 to 11 MtCO2. The production of primary aluminium has also dec lined significantly across the time series, with CO 2 emissions down by 87% and only one smelter now remaining in operation in Lochaber, Scotland.
In recent years a large step-down in emissions in 2011-2012 reflects the closure of the large Lynemouth smelter in March 2012, with sector emissions relatively stable There are no other primary non-ferrous metal processes in the UK since the closure of a large zinc and lead smelter complex in 2003; this one site closure accounts for 9% of total metal sector IPPU CO 2 emission reductions in the UK since 1990. A number of secondary lead processes are in operation but these merely recover lead from batteries and clean scrap and there is no evidence of any process emissions of CO2 from any of them. 45‘Other non-ferrous’ includes primary production of non-ferrous metals other than aluminium, or large-scale secondary smelting

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 117 46 ‘Other’ refers to the following IPCC Field Burning of Agricultural Wastes (3F), Liming (3G), Urea Application (3H), and Overseas Territory and Crown Dependency Agriculture Emissions (3J)

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 118 trends between selected years by sub-sector for Agriculture46 In the UK, the Agriculture sector is dominated by CH4 emissions from livestock generated through enteric fermentation (animal digestion processes) and N2O emissions from manure management and fertiliser application. The emissions from this sector have shown an overall decrease since 1990, reflecting trends in livestock numbers and emissions from fertiliser Emission trends in Agriculture sub-sectors 2.3.2.1 Enteric fermentation and Manure Management Emissions from livestock have declined over the time series primarily due to a decline in emissions from enteric fermentation (CH4) (3A) and manure (N2O) (3B) from cattle. This is, in turn, due to decreased cattle numbers. Annual emissions from fertiliser use (3H) have declined by 14% since 1990, this is driven by a reduction in synthetic fertiliser application, particularly to grasslands. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 119 47 Some of these are trends in the size of the net removals rather than net emissions. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 120 The Land Use, Land-Use Change and Forestry (LULUCF) sector is the only sector within the national GHG inventory which reports both emissions and removals. Removals are from carbon stock gains in above- and below-ground biomass, soils and harvested wood products, emissions are from carbon stock losses and GHG emissions from LULUCF activities. The sector is currently a net source across the time series. The LULUCF sector covers emissions and removals of direct GHGs under six categories, of which Forest Land and Harvested Wood Products are net sinks, and Cropland, Grassland, the whole LULUCF sector The UK does not report any emissions or removals from the Other Land category. Emissions from the LULUCF sector have shown an ov erall decrease since 1990, largely driven by an increase in the Forest Land net sink and a reduction in the Cropland, Grassland and Settlement net sources. Annual removals from Forest land increased significantly by 43% between 1990 and 2009 but have levelled off to around 30% above the 1990 level since 2012. The variation in the net sink is driven by afforestation in earlier decades and the effect on the age structure of the present forest area, particularly conifer plantations. High levels of conifer afforestation between 1950 and 1990 resulted in increasing carbon stocks (and CO 2 removals) up to 2009 but these forests are now reaching harvesting age, with associated carbon losses and transfer to the Harvested Wood Products category. Harvested areas are replanted but young trees have much lower rates of carbon sequestration than the mature trees they have replaced. As a result, there is a progressively decreasing stock in tree biomass and litter, offset by an increasing carbon stock in soils (BE IS 2019). Afforestation rates have reduced substantially since 1990 but have started to increase in recent years. 2.4.1.2 Cropland, grassland and settlements Annual emissions from Cropland have decreased by 12% since 1990. Net emissions from the Grassland category decreased between 1990 and 1998, returned to 1990 levels 2000 -2001, and have decreased steadily since then to 11% of 1990 net emissions. Annual emissions from Settlements have decreased by 30% relative to 1990. The changes in these categories are due to lower rates of land use conversion since 2000, compared to rates of conversion before The Wetlands category is stable until 2015, when it shows spikes in 2015 and 2018-19. These result from emissions associated with felling of forests for peatland habitat restoration and 2.4.1.4 Harvested wood products Annual removals due to harvested wood products (HWP) are variable over time. This is due to increased harvesting rates as the substant ial areas of afforestation reach the age to be removals in 2012 is an artefact of the modelling approach and is small in absolute terms. The carbon gains in the HWP pools are consistent with the carbon losses from Forest Land. Both are estimated using the CARBINE model with tree carbon losses on harvest transferred to the HWP, litter and deadwood pools and modelled accordingly. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 121

Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 122 trends between selected years by sub-sector for Waste The Waste sector accounts for all emissions generated from waste treatment and disposal. Emissions generated from energy recovery from waste are accounted for in the Energy sector. In the UK, emissions from the waste sector are dominated by CH4 emissions from landfill sites. Overall, annual emissions from the waste sector have decreased significantly since 1990 but Emission trends in Waste sub-sectors Almost all of the reduction in UK GHG emissions across the Waste sector is due to a decline in CH4 emissions from landfill.
Emissions estimates from landfill are derived from the amount of biodegradable wastes disposed of to landfill, and the method takes account of the recovery of landfill gas for energy generation or in flares Since 1990, CH4 emissions from landfill have declined significantly due to the implementation of landfill gas recovery systems, flares and also due to the reduction in biodegradable wastes disposed to UK landfills through greater regulation and an increase in recycling a nd composting rates. Landfill gas capture rates have plateaued in recent years, which is a key driver of the recent flattening out of emissions from waste. The UK activity and GHG emissions from industrial waste water treatment (5D2) shows no significant trend across the time series. For municipal waste water treatment (5D1), however, a major change in regulation, with the introduction of the EU Urban Waste Water Treatment Directive, led to a ban on disposal of untreated sewage to the waterways. This led to the step- change in estimated emissions between 2000 and 2001. Since then, there has been a slight decline in emissions, but in recent years the emission estimates have levelled off. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 123 Waste incineration is a minor source of GHG emissions in the UK. The emissions from clinical and chemical waste incineration show a gradual decline across the time series, partly driven by the decline in the UK chemical industry, and partly through improvements in waste The most notable impact on the UK GHGI trend arises from the ban on the incineration of MSW without energy recovery in 1996; this regulatory change led to all UK MSW incinerators either closing or retrofitting boilers to raise electricity, and therefore fr om 1997 onwards all “energy from waste” plant emissions from the incineration of MSW are reported in the power generation sector of the inventory, in 1A1a. 2.5.2.4 Biological treatment of solid waste Since 1990 emissions from the biological treatment of waste sec tor has sharply grown from almost exclusively small -scale composting to a widespread and large -scale alternative practice for the treatment of biodegradable wastes, the generation of energy and the efficient generation of biogas as an alternative fuel. The continued increase in emissions from this source is part of the reason why emissions from the waste sector have flattened out in recent The indirect greenhouse gases in the UK consist of Carbon Monoxide (CO), Nitrogen Oxides (NOx), Non-Methane Volatile Organic Compounds (NMVOC) and Sulphur dioxide (SO 2). Of these, NO x, CO and NMVOC can increase tropospheric ozone concentration and hence radiative forcing. SO2 contributes to aerosol formation in t he atmosphere. This is believed to have a negative net radiative forcing effect, tending to cool the surface. Emission trends for GHGs and SO2 have occurred since 1990. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 124 Annual emissions of CO have decreased by 83% since 1990. In 2021 80% of UK emissions of CO were from the energy sector, with 20% of emissions in this sector from transport. Since 1990, annual emissions from transport have decreased by 96%. This is mainly because of the increased use of three-way catalysts, although a proportion is a consequence of fuel switching in moving from petrol to diesel cars. Another large source of CO emissions in the UK is from manufacturing and construction which contributed 32% of total CO emissions in 2021. Emissions from within this category mostly come from biomass combustion and off -road vehicles used in manufacturing and construction. Annual emissions of NOx have decreased by 76% since 1990. In 2021, 94% of NOx emissions in the UK came from the energy sector with the greatest contribution from road transport. The reduction in NOx emissions is primarily due to abatement measures on power stations, three- way catalysts fitted to cars and stricter emission regulations on heavy duty vehicles. Emissions from the energy industries contributed 20% of total NO x emissions in the UK in 2021. Since 1990, annual emissions from this sector have decreased by 84% mainly due to a decrease in emissions from public electricity and heat production. Since 1998 the electricity generators adopted a programme of progressively fitting low NO x burners to their 500 MWe coal fired units. Since 1990, further changes in the electricity sup ply industry such as the increased use of nuclear generation and the introduction of CCGT plant have resulted in additional reduction in NOx emissions. Emissions from Manufacturing, Industry and Construction have fallen by 61% since 1990. Over this period, the industrial sector has seen a move away from the use of coal, coke and fuel oil towards natural gas and gas oil usage. Trends in Greenhouse Gas Emissions 2 UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 125 Non-Methane Volatile Organic Compounds Annual emissions of NMVOCs have decreased by 72% since 1990. In 2021, 58% of emissions were from industrial processes and other product use. Around 70% of emissions in this sector were from the Non-energy Products from Fuels and Solvent Use sector whose emissions have halved since 1990.Most of the remaining NMVOC emissions in the industrial process es and other product use sector are from the food and drink and chemicals industries. In 2021, 24% of NMVOC emissions originated from the energy sector. Of these, the largest contribution arose from the fugitive emissions of oil and natural gas which comprised 54% of NMVOC emissions from the sector. Fugitive emissions of oil and natural gas includes emissions from gas leakage along with the transportation, refining, and storage of oil Since 1990, total annual emissions of SO 2 have decreased by 96%. In 2021, 88% of SO 2 emissions originated from the energy sector, with the greatest contribution from Domestic, Commercial and Agriculture. Since 1990, emissions from power stations have declined by almost 100%.
This decline has been due to the incr ease in the proportion of electricity generated CCGT stations, other gas fired plants, the increase in the proportion of electricity generated in nuclear plants, and the application of Flue Gas Desulphurisation abatement equipment on several of the largest coal-fired power stations in the UK. CCGTs run on natural gas and are more efficient than conventional coal and oil stations and have negligible SO 2 Emissions from Manufacturing, Industry and Construction were responsible for 25% of UK SO2 emissions in 2021. Since 1990, emissions from this category have declined by 92%. This decline is due to the reduction in the use of coal and oil in favour of natural gas, and also some improvement in energy efficiency. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 126 combines the KCAs, and gives an indication o f which categories contain or are a Key Category. Smaller numbers relate to a higher ranking. More detail on how they’re derived estimate has been taken from Monte Carlo analysis. Emission trends are presented for 1990-2021 and 2020-2021. A description of the trends and the main drivers behind these can be found in Chapter 2 Total Energy 335 -44% 7% 0% 0% 1. Energy industries 80 -67% 4% 0% 0% heat production 3, 5, 7, 29 3% 56 -73% 9% 0% 0% MS 1 b. Petroleum refining 3, 5, 7, 29 14% 11 -38% 0% 0% 0% MS 1 industries and construction 44 -42% 7% 3% -2% a. Iron and steel 6, 8, 10 5% 1 -68% 7% 17% 2% MS 4 b. Non-ferrous metals 6, 8, 10 5% 1 -84% 8% 0% 1% MS 3 c. Chemicals 6, 8, 10 5% 5 -59% -5% 8% 2% MS 3 d. Pulp, paper and print 6, 8, 10 6% 1 -72% -1% 1% 1% MS 3 beverages and tobacco 6, 8, 10 5% 4 -48% 4% -1% 3% MS 3 f. Non-metallic minerals 6, 8, 10 11% 3 -62% 8% 1% 0% MS 3 specify) 6, 8, 10 5% 29 -20% 11% 3% -7% MS 3, MS 6 3. Transport 108 -12% 10% 1% 0% a. Domestic aviation 32 20% 1 -52% 28% 2% 0% MS 7 b. Road transportation 1 2% 101 -10% 11% 1% 1% MS 8 c. Railways 16% 2 6% 9% 0% 0% MS 9 d. Domestic navigation 20 18% 5 -36% 2% 0% 0% MS 10, MS e. Other transportation 16% 0 32% -16% -72% -56% MS 6 4. Other sectors 94 -18% 7% -2% 2%

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 127 Commercial/institutional 2, 12, 15 3% 19 -33% 7% -3% 13% MS 5 b. Residential 2, 12, 15 4% 69 -15% 7% -2% 0% MS 5, MS 6 Agriculture/forestry/fishing 2, 12, 15 31% a. Stationary N/A N/A IE N/A N/A N/A N/A b. Mobile 25 7% 2 -70% 14% -2% 0% MS 15, MS 1. Solid fuels 13% 1 -97% -1% 0% 0% handling 18 1 -98% -3% 0% 0% MS 17 transformation 18 0 -88% 3% 0% 0% MS 4, MS 20 a. Oil 17, 23 0 -90% -1% -4% 0% MS 5 b. Natural gas 17, 23 4 -67% -4% 2% 0% MS 5, MS 20 c. Venting and flaring 17, 23 3 -45% -17% 0% 0% MS 5 storage N/A N/A NO N/A N/A N/A N/A 1. Transport of CO2 N/A N/A NO N/A N/A N/A N/A 2. Injection and storage N/A N/A NO N/A N/A N/A N/A 3. Other N/A N/A NO N/A N/A N/A N/A Memo N/A N/A 22 -10% -6% -4% 6% International bunkers N/A N/A 22 -10% -6% -4% 6% Aviation N/A N/A 13 -15% -11% -5% 7% MS 7 Navigation N/A N/A 9 -1% 2% -4% 5% MS 14 Multilateral operations N/A N/A NE N/A N/A N/A N/A biomass N/A N/A 48 842% 4% -32% -51% MS 1, MS 3, CO2 captured N/A N/A NO N/A N/A N/A N/A

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 128 Comparison of Sectoral and Reference Approaches The UK compares its Sectoral Approach (SA) and Reference Approach (RA) as one of the means of verification of its energy sector GHG estimates in accordance with the UNFCCC decision 24/CP.19 paragraph 40. The Sectoral Approach is the detailed ‘bottom up’ sectoral methodology for estimating energy CO2 emissions described in Section 3.4, The Reference Approach is a ‘top down’ approach for estimating energy CO2 emissions using national fuel statistics that acts as a verification tool for the Sectoral Approach. The RA-SA comparison shows very close consistency between the two datasets (once the major known differences are accounted for) for the UK and provides verification of the reported SA emission estimates for 1A. The UK greenhouse gas inventory is compiled using a detailed Sectoral Approach methodology, to produce sector specific- inventories of the 7 pollutants in accordance with the IPCC reporting format. These UK GHGI emission estimates are based on bottom-up activity data, • national energy statistics (DUKES) that present annual consumption of primary and secondary fuels within different economic sectors in the UK; and • a wide range of o ther statistical datasets (e.g. : raw material extraction and use, production statistics for minerals, metals, glass, cement, specific chemicals, waste statistics, livestock and crop data, land use survey information) to generate estimates of non-combustion emissions from other known sources. As a verification of the detailed Sectoral Approach inventory estimates, the Inventory Agency also calculates alternative UK emission estimates for carbon dioxide from energy sources in the UK, using the IPCC Reference Approach.
This is a top -down inventory compilation method, which calculates emission estimates from National Statistics on production, imports, exports, stock changes and non -energy uses of fossil crude oil, natural gas and solid The Reference Approach inventory method utilises different sections of the UK national energy statistics, combining aggregated data on fuel inputs and outputs from the overall UK economy, using top -level data on oils, gas and solid fuels to assess the UK carbon bala nce for combustion sources. This more simplistic, non -source-specific methodology provides a very useful quality check against the more rigorous Sectoral Approach. Differences between the RA and SA arise primarily due to statistical differences between production-side and demand-side fuel estimates within national energy statistics and the more aggregated approach to applying emission factors to activity data across fuel types. More data on the RA, SA and RA -SA comparison can be found in CRF Table1 .A(b), 3.2.1.1 Discrepancies between the IPCC Reference and Sectoral Approach fossil fuels, and under the new 2006 GLs approach the Reference Approach (RA ) CO 2 estimates for the UK range between 0.8% lower and 1.3% higher than the comparable bottom-up emission totals of the Sectoral Approach (SA). There are a number of ‘known differences’ between the reference approach and sectoral approach which are discussed in the subsequent sections. UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 129 3.2.1.1.1 Statistical Differences in Energy Balance Data The SA is based on the demand side of the national energy statistics, which is some cases informs us to what quality of fuel may be used (e.g. petroleum coke used for anodes we expect to be calcined). The RA however, uses the supply side of the national energy statistics. The difference between the total of the supply and demand sides of energy statistics is the statistical difference, which is a cause of differences betwe en the RA and SA. Because of evolving methodologies and improved data collection the statistical difference is generally quite small in later years, but as some data are not available for earlier years the gap is much The system of energy statistics operated by DESNZ aims to keep UK statistical differences (without normalisation) at less than 0.5% of energy supply, for total supply and also for each fuel. Nevertheless, a proportion of the difference between the Reference Approa ch and the Sectoral Approach totals will be accounted for by statistical differences. 3.2.1.1.2 Application of Carbon Aggregated (RA) vs. Detailed (SA) In the RA the carbon balance is calculated based on the apparent consumption of fuels, for primary fuels (e.g. crude oil). This mean that the estimated carbon content of fuel that’s transformed into other fuels (e.g. petroleum products) is assumed to be accounted for by the commodity balance for the primary fuel from which they’re derived, which differs from the SA which estimates emissions at end use. Because the estimates of primary and derived fuel carbon contents are made independently, the estimated carbon content of the primary fuel to be transformed and the estimated carbon content of the resulting transformed secondary fuel can differ, particularly as primary fuels have a generally more variable carbon content. In general, we have greater confidence in the SA Carbon Emission Factors (CEFs) because they are fuel/process/site specific and the carbon cont ent of end use fuels are less variable than 3.2.1.1.3 Fuels Excluded from the UK RA Emissions from use of waste oils, fossil -containing wastes, scrap tyres and waste solvents that are reported within the SA but are not included in the estimates for the RA in the UK. The RA doesn’t include complete emissions from these fuels because there isn’t complete reporting of these fuels in UK energy statistics; the data for the SA is based on EU ETS and 3.2.1.1.4 Deviations from National Statistics The UK GHG SA method deviates from UK energy statistics for specific fuels (e.g. natural gas, OPG), in a handful of cases where industry data indicates higher usage than DUKES suggests. More details on deviations from DUKES can be found in Annex 4.2.1 . As the reference approach is based on DUKES fuel balances, deviations from DUKES will lead to discrepancies between the SA and RA. 3.2.1.1.5 Comparisons of UK Sectoral Approach vs. Reference Approach and between the IPCC Reference Approach and the UK GHGI (Sectoral Approach) IPCC sector 1A, for each year since 1990 and the resulting comparison when we have accounted for most

UK NIR 2023 (Issue 1) Ricardo Energy & Environment Page 130 Liquid Fuels 1.015 0.959 0.986 1.6% Solid Fuels 1.297 0.971 1.044 4.8% Gaseous Fuels 1.025 0.987 1.000 0.6% a Note that the average deviation is the average of the absolute values of (RA/SA-1) for each year, as the average ratio has the potential to mask the scale of deviations by cancelling out higher and lower deviations. average 1.4%48) than the sectoral approach; there are some years with larger deviations, the highest being a 4.1% deviation in 1997. For solid fuels, the RA is within 4% of the SA for 1990-2014, with a divergence of up to 30% for recent years . We are continuing to investigate this divergence but note that this is exaggerated by a rapid decline in coal used in power stations; the 30% deviation seen for 2021 is not outside the range of deviations seen for years where those deviations represent The RA for gaseous fuels, which is based on supply statistics, only deviates from the SA by more than 1% in four years after 1996, for earlier years the relationship is less consistent. While there are ‘other fossil fuels’ included in the overall SA -RA comparison, these are not minor. When expressed as a %, the differences between the RA and SA are much larger than the other fuel groups, although these are larger % of a much smaller total quantity.