In the case of beef cattle, for England, Wales and Scotland it is assumed 12% of slurry and 33% of FYM is spread to cropland and for Northern Ireland the values are 9.5% and 20% for slurry and FYM, For sheep, all (100% as FYM) of managed manure is assumed to be spread to improved grassland as a simplification of actual practice. Based on statistical analyses of a limited number of survey records from the BSFP (2007 to 2012) for England and Wales we estimated that 87% of all managed manure from all sheep in the UK is spread to improved grassland, and 13% to cropland (no survey records were available for Scotland and Northern Ireland, but the location of managed manure spreading is likely to be more similar to Wales than England, on the basis of the similarity of relative national crop and grass areas). These percentages are based on assumptions from regional data (BSFP 2007-2012), where 94.7% of managed sheep manure in Wales was spread to improved grass land and the remainder to cropland; and that 77.5% of managed sheep manure in England was spread to improved grassland and the remainder to cropland. No survey records were available for Scotland and Northern Ireland, but the location of managed manure spr eading is likely to be more similar to Wales than to England, on the basis of the similarity of relative national crop and grass areas (England 50% grass; Wales 92% grass; Scotland 70% grass; and Northern Ireland 93% grass). The model assumption of 100% applied to grassland has no actual impact on the emission estimate. In the case of pigs, for England, Wales and Scotland, 54% of slurry and 78% of FYM is spread to cropland. For Northern Ireland, 16% of slurry is spread to cropland and 78% of FYM is In the case of poultry, the percentage of layer manure and all other poultry manure spread to Defra, 2024c). The amount of manure sent for incineration is excluded from these data. The inventory model currently assumes that all (100%) of managed manure from minor livestock (horse, goat and deer) is spread to improved grassland. Country-specific direct N 2O EF values were derived from a large number of experiments distributed across the UK (Defra, 2016a, Defra, 2014b). Derived values for the direct N 2O EF are 0.75, 0.33 and 1.01% of applied N for slurry, farmyard manure and poultry manure, respectively (Topp et al., in prep.). 5.5.2.3 Application of other organic sources to land Emissions of N2O are calculated Where Q is the quantity of organic material applied (m 3), TN is the total N content of the material (kg m-3); EFN2O is the emission factor applied (as % of the TN applied). For sewage sludge and non-manure based digestates the default IPCC EF1 of 0.01 kg N2O-N per kg total N applied is used to estimate direct N2O emissions. For manure-based digestates the same EF as slurry is used (0.75% of N applied). Agriculture (CRT Sector 3) 5 UK NID 2025 (Issue 1) Ricardo Page 376 Emissions from sewage sludge application to land are calculated following the IPCC methodology (2006, equation 11.1). The calculation involves estimating the amount of N contained per DM unit of sludge that is applied to land. Activity data are provided by Ricardo from a combination of the UK regulatory agencies and water companies. The N content is assumed to be 3.6% of the DM content. According to CEH (2017), in the UK 95% of sewage sludge is assumed to be applied as sludge cake and 5% as a liquid (ADAS, personal communication, December 2006), with no change across the time series. The data are disaggregated at the most at England and DA level, with the proportions applied to arable and grassland being derived from the BSFP from 2005. Uniform application rates across land are assumed per England and DA. For the inventory model we use the average RB209 value for the total N content of biosolids (4 digested cake, thermally dried, lime -stabilised and composted), assuming equal proportions of each, giving 3.7% on a DM basis. For the purposes of expressing the NH 3 emission factor as a %TAN applied, the TAN content is assumed to be 10% of the TN content (RB209) for sludge cake and 50% (assumed similar to livestock slurry) for liquid sludge. The N2O EF from application of sewage sludge is presented No data have currently been collated regarding the proportional split in application to grassland and arable land, so a simplistic assumption is made that it is applied approximately in proportion to the ratio of improved grassland to arable land at DA lev el. Based on 2010 land area values (and used across the time series for simplicity) this gives a proportional application to improved grassland of 50%, 94%, 71% and 93% for England, Wales, Scotland and Northern Ireland, respectively, with the remainder to arable. Sewage sludge activity data has been updates between 1990-2022. Data for 2023 is assumed the same as 2022. 5.5.2.3.2 Manure-based digestate and other non-agricultural organic N additions Application to agricultural land in GB was addressed according to Hulin et al. (2015). These Digested liquid sewage sludge, composted green manure, digested sludge cake, thermally dried sludge cake, lime -stabilised sludge and biosolids. The N 2O EFs for these Four categories of digestate applied to land are included depending on livestock manure, energy crops, food -waste and other organic residues, and for the purpose of the emission calculations each is treated individually (i.e. excludes any potent ial interactions that may arise through co-digestion). Emissions from digestate arising from the anaerobic digestion of livestock manures are included in the relevant livestock sector calculations. Emissions from spreading of digestate arising from the ana erobic digestion of manures, food waste, energy crops and other organic residues are included in this sector. Material inputs to anaerobic digestion facilities are derived from the National Non-Food Crops Centre (most recently NNFCC, 2024), with estimated capacity and type of feedstock.
Total N content of digestates is based on literature review (Tomlinson et al., 2019) giving mean values of 5.00, 3.97 and 3.35 kg t -1 for food-waste, energy crop and other organic residue based digestates, respectively, and it is assumed there is no trend across the time series. The TAN content of all digestate types is assumed as 80% of the total N content (RB209). Although co- digestion of two or more feedstocks is commonly practiced, for the purpose of the emission calculations each is treated individually. As with sewage sludge, we currently have no data relating to the proportion of digestate applied to grassland or arable land, so t he same assumptions are applied (i.e. application in proportion to total land area as improved grassland or arable at England and DA level). Thus, the proportion applied to improved grassland is

Agriculture (CRT Sector 3) 5 UK NID 2025 (Issue 1) Ricardo Page 377 assumed as 50%, 94%, 71% and 93% for England, Wales, Scotland and Northern Ireland, respectively, with the remainder to arable, and constant across the time series. Composted materials subsequently applied to land include green wastes, other organic N additions (e.g. kitchen wastes) and mixed other materials (e.g. cardboard), with activity data for recent years sourced from government and local authority statistics and the Waste Data Interrogator returns system (Tomlinson et al., 2019). Emissions from the composting process are reported in the Waste sector. Emissions from the composting and subsequent land application of livestock manures are currently not estimated in the UK GHGI due to a lack of activity data; it is not a widespread practice and to date the UK farm survey data have not identified any activity data for use in the inventory. The EFs to estimate emissions of N 2O from dairy, sheep, pig, poultry and minor livestock manure spread to land (as a % of N applied) were derived from a large number of experiments distributed across the UK also under Defra project AC0116 (Topp et al., in prep.). The resulting values for slurry 0.7475%, and for FYM and poultry manure 0.3635%, for digestate is assumed to be the same as that for slurry. 5.5.2.4 Urine and dung deposited by grazing animals in the field Emissions are calculated with a slightly modified IPCC methodology (equation 11.1), as different EFs are applied for urine and dung in the case of cattle. Estimates of the times of the year when ruminant stock types are housed were made by Parsons and Will iams (2015) in a module of the Farm Business Survey (FBS) in England. It is assumed that all excretion from grazing livestock is deposited on grassland. N excretion by cattle is partitioned to urine and dung N as described in Section 5.3.2.2, and the separate UK-specific values for EF3 for urine experimental data specifically for sheep grazing, EF 3 for sheep excreta deposited to land is estimated by scaling down from cattle the ratio of EF 3 for excreta from sheep vs cattle as exactly 50% of the CS values for cattle urine and dung. For swine, poultry, goats, deer and horses where behaviour of outdoor animals is quite different to that of cattle and sheep, the default value in IPCC (2019) EF3 is used, as this EF is regarded as the most representative of UK circumstances in the expert opinion of the UK Inventory Agency. The UK applies a CS N 2O EF for cattle urine and dung, based on measurements, but there are insufficient CS data for N 2O emissions from sheep excreta during grazing. According to of the value for cattle excreta. This is supported, for sheep urine, by information in the 2019 0.39% for sheep compared with 0.77% fo r cattle), whil e the EF for sheep dung contained therein is less than 50% of the value for cattle (0.04% for sheep compared with 0.13% for cattle). On the basis of this information, the UK has derived an N 2O EF for sheep urine and dung by halving the CS values for cattle urine and dung. We note that the resulting values (0.315% and 0.097% for sheep urine and dung, respectively) are closely comparable the revised values for sheep given in the 2019 Refinement to the 2006 IPCC Guidelines, and hence the UK considers that their use is justified and representative of UK circumstances. 5.5.2.5 Crop Residues returned to soils Direct N2O emissions from crop residues are estimated following IPCC (2006, equation 11.2) using the default value for EF1. However, a country-specific approach is taken for deriving the quantity of N returned in crop residues, based on UK -specific data for the harvest index and, where available, UK-specific data for N content of crop residues (Annex Tables A 5.1.20 and A 5.1.21). More specifically, the IPCC calculation involves the ratio of crop yield (DM) to total

Agriculture (CRT Sector 3) 5 UK NID 2025 (Issue 1) Ricardo Page 378 above-ground dry weight (DM harvest index, HI DM). The harvest index can also be defined with respect to nitrogen (N) as nitrogen harvest index (NHI). The DM harvest index is the ratio of the primary crop DM yield of crop T over the sum of the primary crop DM yield (CropT) and the above ground biomass DM (eq. 4). The NHI is shown in eq. 5 and with data for the DM harvest index, AG DM(T) can be calculated by rearranging eq.5 to obtain the above ground residue per unit area (𝐴𝐺𝐷𝑀(𝑇)) (eq.6 and 7). HIDM = CropT / CropT + AGDM(T) (eq.4) HIN = (CropT ∗ CropN(T)) / (CropT ∗ CropN(T) + AGDM(T) ∗ NAG(T)) (eq.5) CropN(T) = fraction of N in the DM of cropT. AGDM(T) = CropT − (CropT ∗ HIDM )HIDM / HIDM (eq.6) AGDM(T) = (1 − HIDM ) ∗ CropT/ HIDM (eq.7) The IPCC default values for the ratio of above to below ground biomass were used, except for crops not defined by the IPCC.
These include oilseed rape, linseed and flax, vegetables, other horticultural crops, fruit and energy crops for which the value give n is 0.349 ( pers. comm. Adrian Williams). In the case of sugar beet, we updated the methodology in this submission by using primary yields and harvest index to calculate the total above and below ground residue, i.e. deriving a country-specific parameter for sugar beet residue emissions (Sylvester-Bradley et al., 2015). These were evaluated by Williams and Goglio (2017). Estimates of the N returned to soil under cover crops were made from the NDICEA crop simulation model (van der Burgt et al., 2006), which was calibrated and tested in UK conditions N2O emissions from mineralisation of soil organic matter on land converted to Cropland more than 20 years ago are included in the Agricultural inventory (emissions from more recent land use change are included in the LULUCF inventory). Details are included i n the LULUCF chapter (Section 6.3 Category 4B Cropland and in Annex 5.1). N2O emissions from mineralisation of soil organic matter as a result of Cropland Management activities are estimated from the change in soil carbon stocks due to Cropland Management using a Tier 1 approach with the mineralised N calculated mineral soil carbon stock losses * (1/C:N ratio), where C/N is the IPCC default value of 15 The N in mineral soils that is mineralised as a result of historical land use change to Cropland was 77 kt N/y in 2023, and the amount mineralised as a result of Cropland Management was 0.5 kt N/y. The methodology used to assess change in soil carbon stock s due to Cropland Management is described in Section 6.3 and Annex 5.1 and briefly consists of using a Tier 3 model described in section A 5.1.4.2 of the NID annex. 5.5.2.7 Cultivation of histosols (organic soils) Direct N2O emissions from the cultivation of histosols are estimated following IPCC (2006, equation 11.2) using UK-specific data for the area of cultivated histosols. Areas are based on an estimate from a BEIS (now DESNZ)-funded research project (Evans et al., 2017), specified as cropland or intensive grassland (367,2 kha combined areas in 2023). IPCC Tier 2 EFs from the Peatland Code report (Defra, UK - Science Search) are used for cropland and intensive grassland (see LULUCF chapter, Section 6.3 Category 4C Grassland). Annex section A 5.1.4.6 covers emissions from organic soils and EFs are listed in a supplementary Excel file (see Supplementary file EFs UK inventory agriculture_2025 submission.xlsx)

Agriculture (CRT Sector 3) 5 UK NID 2025 (Issue 1) Ricardo Page 379 Updates to the deforestation areas on organic soils feed through into changes to the total cropland and intensive grassland areas on organic soils over time. In this submission, minor changes to organic soil areas due to new rewetting data for NI and Scotl and, and minor changes to forest planting data were introduced. 5.5.2.8 Atmospheric deposition of NOX and NH3 Indirect emissions of N 2O from the atmospheric deposition of NH 3 and NO x are estimated according to IPCC (2006, equation 11.9) using a country-specific value for EF4 (Pers. Anthony, 2022). The derived overall emission factor is similar to the recently revised IPCC (2019) default N 2O EF 4 of 1.4±0.15%, for a ‘wet climate’ where annual rainfall exceeds potential evapotranspiration, based on an updated global database of measurements of emissions following applications of synthetic fertiliser N and organic manures (excluding urine has not led to the derivation of a UK -specific EF, we note that the UK evidence was used to derive a value consistent with the value presented in the 2019 Refinement, and hence in our expert judgement to use the 2019 Refinement EF is the most representative EF option available to reflect UK circumstances; we consider that applying that EF minimises the uncertainty in the UK Inventory for this source. Country -specific values were also applied for the fraction o f N that is volatilised as NH 3 and NO x from inorganic fertiliser and organic (livestock manure, sewage sludge, digestate, grazing returns) N applications to land (FracGASF and FracGASM, respectively) derived directly from the combined ammonia and greenhouse gas inventory model for UK agriculture, using an N-flow approach (Webb and Misselbrook, 2004). UK-specific NH3 EFs are used for inorganic fertiliser and organic manure applications to land, as detailed in the UK Informative Inventory Report. Frac GASF values range between 0.026 - 0.043 and Frac GASM values range between 0.080 -0.087; the NH 3 EFs are given in a supplementary excel file. NOx emissions from fertiliser, organic manure applications, grazing returns to grassland, and for crop residues are assumed to be a factor of 0.6 of the N 2O emissions estimated for each source, whereas those from applications to arable land are assumed to be a factor of 0.4 (see detail in the UK Informative Inventory Report). The method used corrects for the N content of manures used as fuel (poultry litter incineration) which are therefore not applied to land. Indirect emissions of N 2O from leaching and runoff are estimated according to IPCC (2006, equation 11.10) using the default value for EF 5. The sources of N considered are synthetic fertiliser application, animal manures, digestates and sewage sludge applied to soils, excretal grazing returns (dung and urine), crop residues and mineralisation. A country -specific value for the proportion of N applied that is leached (Frac LEACH) is used for both inorganic fertiliser and manure application to grassland and excretal returns from grazing livestock, based on the UPCYCLE model (Pers. Anthony, 2022). For fertiliser and manure application to arable land, crop residues and sewage sludge the default IPCC (2006) FracLEACH value is used as this was supported by Cardenas et al. (2013a) for UK conditions. For mineralisation, the default IPCC (2006) value is also used. The method used corrects for the N content of manures used as fuel (poultry litter incineration) which are no t applied to land.
For other organic source s applied to land, FracLEACH values of 10 and 30% of applied N are used for grassland and arable land, respectively, to estimate leached N based on Cardenas et al. (2013a). In the case of NOx, the emission multiplier was set to 0.60 and 0.40 of direct emission from N application to grassland and arable land, respectively. In the case of swine and goats, the value was set to 0.60 of direct N2O emissions for outdoor pigs. Agriculture (CRT Sector 3) 5 UK NID 2025 (Issue 1) Ricardo Page 380 5.5.3 Uncertainties and time-series consistency The uncertainty analysis in Annex 2 provides estimates of uncertainty according to IPCC The estimates of uncertainties in emissions were calculated using Approach 2 (Monte Carlo simulation) described by the IPCC. The uncertainties in the estimates of crop areas were provided by the devolved administrations, and the uncertainties in estimates of fertiliser application rates to crops were calculated from the BSFP. Together these give estimates of fertiliser use. Estimates of the uncertainty in the amount of sewage applied to the land were omitted but will be included in further developments of the model. The uncertainties in the new UK specific emission factors and model parameters were calculated from the data used to Emissions are calculated from a range of activity data and appropriate emission factors (see Annex 5.1). Emissions of N2O from the use of fertilisers are important in this source category. The annual consumption of synthetic fertiliser is estimated based on crop areas (crop area data reported annually by the Devolved Administrations) and fertiliser application rates (reported annually in the BSFP). These are both long running datasets and the compilers of the activity data strive to use consistent methods to produce the activity data. The time-series consistency of these activity data is very good due to the continuity in data provided. The UK has updated the indirect N2O EF4 (mean and uncertainty parameters) for poultry, deer and goats, EF5 (uncertainty bounds only) and the N2O EF3 (mean and uncertainty, lower mean value and narrower uncertainty bounds) for poultry, deer, horses, pigs and goats according to the IPCC 2019 refinement to the 2006 Guidelines, as they are regarded as more representative of UK circumstances based on the expert judgement of the UK Inventory Agency. 5.5.4 Source-specific QA/QC and verification This source category is covered by the general QA/QC procedures, which are discussed in 5.5.5 Implied emission factors The direct UK N 2O IEFs differ from the IPCC default value of 1% for inorganic and manure 0.67 and 0.61, respectively. Values for application of sewage sludge, crop residues and mineralisation agree with the default value. The UK value for pasture, range and paddock (0.33%) is lower than the IPCC default (2% for cattle), and the value for histosols with 11.9 kg N ha-1, is higher than the IPCC default values of 8 kg N ha-1, respectively. 5.5.6 Source-specific planned improvements There are a number of methodological improvements that the UK Inventory Agency will consider for future submissions, dependent on the availability of evidence from research and statistics agencies, • Review methods and assumptions in grassland and cropland; including the estimates of fertiliser application rates from the BSFP; calculate N 2O emissions from spreading

Agriculture (CRT Sector 3) 5 UK NID 2025 (Issue 1) Ricardo Page 381 • Seek UK activity data or identify a suitable IPCC good practice gap -filling option, in order to address the minor gap in the UK GHGI estimates from the spreading of • Improve estimates of the urea content of the ‘other nitrogen’ compound fertiliser types. • Emission factors and activity data will continue to be reviewed including the use of more detailed emission factors and activity data to improve emission estimates and allow estimation of the effect of future mitigation policies. • Introduce NH3 from Residue – potential underestimate 5.5.7 Source-specific recalculations Urea N applied as a late foliar spray, primarily to milling varieties of winter wheat in the BSFP, is included as a category to the total amount of urea from 2021. Updates in activity data were made as i) For Northern Ireland, 2022 N fertiliser data were replaced for surveyed fertiliser use data provided by DAERA; ii) for Northern Ireland and Scotland revisions to 2022 cereal and oilseed rape yields resulting in a net decrease of around 4% in total crop offtake; iii) average use of urease inhibitors of all surveyed years replaced by 3-year rolling average for urea ammonium nitrate due to larger sample size (BSFP, 2024); iv) the grass consumed by grazing anima ls was adjusted from field measurements of Jackson and Williams (1979) with an efficiency of 75% on all pastures for a system akin to paddock grazing, to an efficiency of 75% on the temporary grass area and 65% on the permanent grass area of efficient area for permanent grass; v) revised the rate of fleece growth for growing lambs from a yearly value to a function of live-weight applied daily, derived from measurements of clean fleece and animal weights for UK breeds presented in Saul et al.
(1993; n=27) resulting in a small decrease in nitrogen excretion; vi) previous estimates of the protein content of grazed grass consumed by grazing sheep, were derived from an area weighted average of model simulations for pastures that were both cut & grazed or grazed; they have been replaced with an average value for pastures that were exclusively grazed increasing the protein content of Changes in activity data and to emission factors due to these recalculations to are given in the

UK NID 2025 (Issue 1) Ricardo Page 382 2024 submission 2025 submission Units Comment/Justification 1990 2022 1990 2022 3.D.1.a Direct N2O Emissions from Managed Inorganic N fertilisers 20.14 8.71 20.14 8.58 kt Replacement of estimated Farm Business Survey fertiliser rate and type data for Northern Ireland (copied forward from 2021) with surveyed data for the year 2022 3.D.1.b.i Direct N2O Emissions from Managed Organic N Fertilisers – Animal 4.64 3.92 4.63 3.86 kt N entering spreading and therefore emissions affected by the upstream changes detailed for ‘Manure 3.D.1.b.ii Direct N2O Emissions from Managed Organic N Fertilisers – Sewage 0.30 0.90 0.35 0.92 kt Updated amounts of sewage sludge spread to land 3.D.1.b.iii Direct N2O Emissions from Managed Organic N Fertilisers - Other Organic Fertilisers Applied to Soils 0.00 1.09 0.00 1.30 kt Updated amounts of manure- and non-manure- based 3.D.1.c Direct N2O Emissions from Managed Urine and Dung Deposited by 2.95 2.37 2.98 2.41 kt Emissions from urine and dung affected by the changes detailed for ‘Manure Nitrous Oxide emissions’, i.e. changes in cattle N excretion associated with changes to milk yield and slaughter weights; For sheep, update to the method of calculating the crude protein content of grazed grass (an average based on exclusively grazed swards replaced an average of grazed and cut & grazed swards) resulted in a small increase in the protein intake surplus to requirements, with a consequential increase in nitrogen excretion - driving an increase in nitrous oxide emissions. 3.D.1.d Direct N2O Emissions from Managed 4.50 5.16 4.50 5.17 kt A small downward adjustment to grazed grass utilisation efficiency resulting in a greater quantity of residue nitrogen from which there are nitrous oxide emissions. UK NID 2025 (Issue 1) Ricardo Page 383 2024 submission 2025 submission Units Comment/Justification 1990 2022 1990 2022 Revisions to government reported cereal and oilseed rape yields for Scotland and Northern Ireland in the year 2022. Revision to potato yields in England in the year 3.D.1.e Mineralisation/Immobilization Associated with Loss/Gain of Soil Organic Matter 0.61 1.28 0.61 1.26 kt Minor changes to crop type areas for Cropland Management - corrected double counting of hops in England between 2002 and 2006. Minor changes to organic soil area impact Management CSC which is calculated from all soil cropland area minus organic soil cropland area 3.D.1.f Direct N2O Emissions from Managed Cultivation of Organic Soils 7.314 6.903 7.313 6.902 kt Minor changes to organic soil areas due to DESNZ-funded re-analysis of the organic soil base maps; Minor changes to 3.D.2.a Indirect N2O Emissions From Managed Soils – Atmospheric Deposition 3.017 2.568 3.026 2.613 kt As ‘Direct N2O Emissions from Managed Soils’- Changes in ammonia emission as a result of, e.g. amounts of N fertiliser applied and N excretion at grazing and revised manure spreading mitigation contribute to changes in indirect nitrous oxide from the re-deposition of ammonia nitrogen. 3.D.2.b Indirect N2O Emissions From Managed Soils - Nitrogen Leaching and Run-off 6.190 5.120 6.158 5.123 kt As ‘Direct N2O Emissions from Managed Soils’ - Changes in e.g. amounts of N fertiliser applied and N excretion at grazing result in changes in the quantity of nitrate leached and the indirect nitrous oxide emitted from leached nitrate. UK NID 2025 (Issue 1) Ricardo Page 384 2024 submission 2025 submission Units Comment/Justification 1990 2022 1990 2022 3.D.1.a Direct N2O Emissions from Managed Inorganic N fertilisers 0.00815 0.00670 0.00815 0.00667 kg N2O-N/kg N A small downward adjustment to grazed grass utilisation efficiency resulting in a greater quantity of residue nitrogen from which there are nitrous oxide emissions. Revisions to government reported cereal and oilseed rape yields for Scotland and Northern Ireland in the year 2022. Revision to potato yields 3.D.1.b.i Direct N2O Emissions from Managed Organic N Fertilisers – Animal 0.00610 0.00609 0.00610 0.00606 kg N2O-N/kg N Minor changes to crop type areas for Cropland Management - corrected double counting of hops in England between 2002 and 2006. Minor changes to organic soil area impact Management CSC which is calculated from all soil cropland area minus organic soil cropland area 3.D.1.b.iii Direct N2O Emissions from Managed Organic N Fertilisers - Other Organic Fertilisers Applied to Soils na 0.00928 na 0.00930 kg N2O-N/kg N Minor changes to organic soil areas due to DESNZ-funded re-analysis of the organic soil base maps; Minor changes to forest planting data 3.D.1.c Direct N2O Emissions from Managed Urine and Dung Deposited by 0.003293 0.003326 0.003285 kg N2O-N/kg N As ‘Direct N2O Emissions from Managed Soils’- Changes in ammonia emission as a result of, e.g. amounts of N fertiliser applied and N excretion at grazing and revised manure spreading mitigation contribute to changes in indirect nitrous oxide from the re-deposition of ammonia nitrogen. UK NID 2025 (Issue 1) Ricardo Page 385 2024 submission 2025 submission Units Comment/Justification 1990 2022 1990 2022 3.D.1.f Direct N2O Emissions from Managed Cultivation of Organic Soils 11.863 11.944 11.863 11.945 kg N2O-N/kg N As ‘Direct N2O Emissions from Managed Soils’ - Changes in e.g. amounts of N fertiliser applied and N excretion at grazing result in changes in the quantity of nitrate leached and the indirect nitrous oxide emitted from leached nitrate. UK NID 2025 (Issue 1) Ricardo Page 386 This source is not relevant in the UK. It does not occur. 5.7.1 Source category description Source included Method Emission Gases Reported CH4, N2O, NOx, CO, NMVOC, SOx Key Categories None identified Completeness No known omissions. A general assessment of completeness for the inventory is The National Atmospheric Emissions Inventory reports emissions from field burning under the category agricultural incineration.
The estimates are derived from methodology and emission factors according to IPCC (1996) and from EMEP/EEA (2016). The estimates of the masses of residue burnt of barley, oats, wheat and linseed are based on crop production data from DEFRA (England & Wales), The Scottish Government (Scotland) and DAERA (Northern Ireland), a UK -specific harvest index approach to derive residue amounts (Williams and Goglio, 2017) and data on the fraction of crop residues burnt (MAFF, 1995; ADAS, 1995). Field burning ceased in 1993 in England and Wales. Burning in Scotland and Northern Ireland is considered negligible, so no estimates are reported from 1993 onwards. The CO2 emissions are not estimated because these are part of the annual carbon

UK NID 2025 (Issue 1) Ricardo Page 387 5.7.3 Uncertainties and time-series consistency The uncertainty analysis in Annex 2 provides estimates of uncertainty according to IPCC Field burning ceased in 1993, and emissions are reported as NO after this date 5.7.4 Source-specific QA/QC and verification This source category is covered by the general QA/QC procedures, which are discussed in 5.7.5 Source-specific recalculations No recalculations were carried out in this sector 5.7.6 Source-specific planned improvements 5.8.1 Source category description Emissions sources Source included Method Emission Key Categories None identified Completeness A general assessment of completeness for the inventory is CO2 emissions from liming occur as carbonates in the form of limestone (Ca(CO3) and dolomite (CaMg(CO3)2) are applied to soils to increase their pH. Source category significance, trends and drivers Total UK CO2 emissions from liming in 2023 were 1188 kt CO2. Emissions in 2023 were 16% higher compared to 1990 and 1% higher in 2023 compared to 2022. UK NID 2025 (Issue 1) Ricardo Page 388 CO2 emissions due to the application of lime and related compounds are estimated using the Tier 1 IPCC (2006) methodology. For calcium carbonate (limestone, chalk and sugar beet lime - LimeX) an emission factor of 120 t C / kt applied is used, and for dolomite application, 130 t C / kt. These factors are based on the stoichiometry of the CO2 loss from the carbonates and assume pure limestone/chalk and dolomite. Liming activity data (% area limed and application rate to three land use ‘all tillage’, for 1990 and 1991 were assumed to be the same as for 1992. The % area limed and application rate of lime in Northern Ireland was assumed to be the same as that for Scotland by land use type. For each of the liming types in i) ground limestone, ii) ground chalk, iii) magnesian limestone, iv) sugar beet lime, iv) other), the application rate and % area limed were multiplied by the area of ‘all tillage’, ‘grass under 5 years old’ and ‘grass 5 years and over’ to derive the total limestone and dolomite applied for each Devolved Administration. The ‘other’ category in BSFP is made up of Ag slag, calcified pelleted limestone, Calcifert, granules, Humistar, lime slag, screed lime (Defra, pers. comm. ); the majority of these are CaCO3 based limes and thus were included in the activity data for limestone. Limex is assumed to have 46% CaCO3 content (British Sugar, Chemical Safety Data; Median of LimeX45 (45%) and LimeX70 (52%) CaCO3 content). 5.8.3 Uncertainties and time-series consistency Uncertainty in both the activity data and emission factor are judged to be low. The main source of uncertainty in the estimates is caused by non -publication of some activity data due to commercial restrictions although these are not judged to be very significant. There is good time series consistency as there has been continuity in the published data 5.8.4 Source-specific QA/QC and verification This source category is covered by the general QA/QC procedures, which are discussed in

UK NID 2025 (Issue 1) Ricardo Page 389 5.8.5 Source-specific recalculations 2024 submission 2025 submission Units Comment/Justification 1990 2022 1990 2022 3G CO2 from Limestone and 1021.10 1180.57 1021.10 1180.57 kt Negligible revisions to crop areas in 2016, 2018 and 2019 to

UK NID 2025 (Issue 1) Ricardo Page 390 5.8.6 Source-specific planned improvements Emission factors and activity data will continue to be reviewed when new data are available. 5.9.1 Source category description Emissions sources Source included Method Emission Key Categories None identified Completeness A general assessment of completeness for the inventory is The application of urea (CO(NH2)2) fertiliser generates CO2 emissions due to its conversion to Source category significance, trends and drivers Total UK CO2 emissions from urea application in 2023 were 401 kt CO 2. Emissions in 2023 were 37 % higher compared to 1990 and 54 % higher in 2023 compared to 2022. The annual amount of fertiliser as urea, alone or as part of urea ammonium nitrate (UAN), used in kt N was estimated from the BSFP (for England, Wales and Scotland) and the Northern Ireland Fertiliser Supply statistics. Both fertilisers are applied to grassland and cropland in the UK. It was assumed that 35% of UAN was urea. The EF used was the IPCC (2006) default value of 0.2 tonne of C per tonne of urea, and emission estimates were made using IPCC Tier 5.9.3 Uncertainties and time-series consistency The uncertainty analysis in Annex 2 provides estimates of uncertainty according to IPCC source category. The same data source is used for the entire time series to ensure 5.9.4 Source-specific QA/QC and verification This source category is covered by the general QA/QC procedures, which are discussed in

UK NID 2025 (Issue 1) Ricardo Page 391 5.9.5 Source-specific recalculations Details of and justifications for recalculations to activity data and to emission factors are given

UK NID 2025 (Issue 1) Ricardo Page 392 2024 submission 2025 submission Units Comment/Justification 1990 2022 1990 2022 3H CO2 from Urea Application 292.95 263.01 292.95 261.00 kt Revisions to urea-based fertiliser use as detailed in ‘Direct N2O Emissions from Managed Inorganic N fertilisers’

UK NID 2025 (Issue 1) Ricardo Page 393 5.9.6 Source-specific planned improvements Emission factors and activity data will continue to be reviewed when new data are available.
Emissions sources 3A: Enteric Fermentation 3F: Field Burning of Agricultural Residues In the CRT, all UK overseas territories and crown dependencies emissions data are reported in sector 3J. Emission Factors Default EFs (OTs), UK implied EFs (CDs) Key Categories None identified Completeness Emissions are not estimated for 3G Liming for Bermuda, Cayman Islands and the Falklands, for 3H Urea application for Bermuda and the Falklands, and for 3F Field Burning of Agricultural Residues for any OT. Livestock and crop production occur in all of the UK overseas territories (OTs) and crown dependencies (CDs), resulting in emissions from categories 3A, 3B and 3D for all OTs and CDs. Agricultural GHG emissions from OTs and CDs combined made up less than 1% of the total UK agricultural emissions in 2023. Note that no agricultural activities occur in Gibraltar, so emissions and activity data are zero for Gibraltar for all agriculture sector sources. 5.10.2.1 Emissions from livestock The CDs have similar farming systems to the mainland of the UK and are located nearby with a similar climate. Due to this similarity, emissions for CDs are calculated by applying implied EFs calculated from the UK GHGI to data on livestock numbers for CDs aggregated to a basic classification. The implied EFs are calculated for each year, so that the implied EF can vary across the time series. Tables of animal numbers used in calculations are presented in Annex For OTs, emissions from livestock are calculated using Tier 1 methodology from the IPCC 2006 Guidelines (2019 Refinement for deer enteric fermentation and wastes), by applying default EFs for the appropriate geographic region and climate type to the number of livestock

UK NID 2025 (Issue 1) Ricardo Page 394 For both CDs and OTs, data on livestock numbers were provided by local contacts (Bermuda Government, 2023; Cayman Islands Government, 2023; Falkland Islands Government 2023; Government of Jersey, 2023; Isle of Man Government, 2023; States of Guernsey Government, 5.10.2.2 Emissions from 3D Agricultural Soils For the CDs, estimates of emissions from agricultural soils for all sub -categories were made by applying UK GHGI implied EFs to animal numbers (for livestock manure -related activities) and areas of cropland and grassland (for non-manure fertilisers and emissions related to loss of soil carbon). For OTs, the Tier 1 methodology from the 2006 IPCC Guidelines was applied to calculate emissions from agricultural soils. Livestock numbers, mineral fertiliser application and crop production data were provided by each of the OTs or sourced from FAO; these data can be found in Annex 5.1.6. Emission factors taken from the 2006 IPCC guidelines were applied to all activity data from OTs. In the Falklands, according to local expert judgement, no synthetic fertilisers are applied, so emissions from this source are not estimated there. In the Falklands, despite there being a very large area of grassland histosols, N 2O emissions from managed histosols are only reported for cropland areas. The reason for this is that information from local experts indicates that grasslands are unmanaged (i.e. no fertilisation, liming, drainage or cultivation) and livestock density is low, so these soils are not likely to be a source of N2O emissions. The UK understands managed organic soils to be present only in the Falkland Islands and the Isle of Man, and absent from all other CDs and OTs. 5.10.2.3 Emissions from other agriculture categories For the CDs, emissions from 3F Field Burning of Agricultural Residues and 3H Urea Application are estimated in the same way as emissions from 3D Agricultural soils, by applying implied EFs from the UK GHGI to the area of cropland (for both field burning an d urea application) and grassland (for urea application only). Emissions from 3G Liming are calculated using the default 2006 IPCC EF of 0.12 kg C/kg limestone, and are applied to data on the quantity of limestone applied. For the OTs, no emissions were estimated for categories 3F Field Burning of Agricultural Residues due to a lack of available activity data. Emissions were not estimated for 3G Liming due to local experts indicating that relevant activities do not occur. Em issions from 3H Urea Application are estimated for the Cayman Islands only from 2014.
Total agricultural land area

UK NID 2025 (Issue 1) Ricardo Page 395 dependencies and all other overseas territories Territory Category 1990 1995 2000 2005 2010 2015 2020 2021 2022 2023 5,429 5,385 5,296 5,147 4,957 4,772 4,751 4,730 10,281 10,160 9,808 10,065 9,980 9,965 10,136 9,730 Isle of Man Cropland area (kha) 11.2 10.4 10.4 10.5 10.4 8.6 7.2 7.0 7.7 7.7 Grassland area (kha) 39.7 39.7 38.8 38.0 37.2 38.4 39.1 39.1 38.2 38.1 3F emissions (ktCO2e) 0.466 NO NO NO NO NO NO NO NO NO 3G emissions (ktCO2e) 0.592 0.565 0.571 0.574 0.570 0.531 0.531 0.531 0.531 0.531 3H emissions (ktCO2e) 0.178 0.112 0.086 0.119 0.158 0.175 0.103 0.100 0.110 0.110 0.566 0.566 0.566 0.566 0.793 0.793 0.793 0.793 0.793 0.793 1,215 1,215 1,215 1,215 1,215 1,215 1,215 1,215 3F emissions (ktCO2e) NE NE NE NE NE NE NE NE NE NE 3G emissions (ktCO2e) NO NO NO NO NO NO NO NO NO NO 3H emissions (ktCO2e) NE NE NE NE NE NE NE NE NE NE 6.86 7.03 6.61 5.89 6.34 5.82 5.84 5.84 5.84 5.84 Grassland area (kha) 4.83 4.66 4.85 5.17 4.52 5.11 5.04 5.03 5.03 4.98 3F emissions (ktC2e) 0.0174 NO NO NO NO NO NO NO NO NO 3G emissions (ktCO2e) 0.0691 0.0691 0.0691 0.0688 0.0685 0.0683 0.0683 0.0683 0.0683 0.0683 3H emissions (ktCO2e) 0.0066 0.0045 0.0038 0.0077 0.0137 0.0185 0.0129 0.0129 0.0129 0.0129 0.740 0.740 0.740 0.740 0.740 0.740 0.740 0.740 0.740 0.740 Grassland area (kha) NO NO NO NO NO NO NO NO NO NO 3F emissions (ktCO2e) NE NE NE NE NE NE NE NE NE NE 3G emissions (ktCO2e) NO NO NO NO NO NO NO NO NO NO 3H emissions (ktCO2e) NE NE NE NE NE 0.000356 0.000745 0.001245 0.001245 0.007467 NO = not occurring, NE = not estimated

UK NID 2025 (Issue 1) Ricardo Page 396 To provide an indication of the magnitude of emissions reported as “not estimated” (NE) for 3F Field Burning and 3H Urea Application, cropland areas for the OTs were calculated as a percentage of UK cropland area. Cropland area in the Falkland Islands does not exceed 0.02% of UK cropland area, as is the case for Bermuda and the Cayman Islands. The magnitude of emissions currently not estimated is therefore below the threshold of Whilst grassland area in the Falklands Islands is a sizeable proportion of UK grassland area at 12%, local contacts indicate that liming does not occur, and that synthetic fertiliser (including 5.10.3 Uncertainties and time-series consistency Activity data available for several sub -categories are incomplete, including for field burning activity, crop production, application of synthetic fertiliser, liming and urea application. • Livestock statistics are not collected every year for all livestock types in all the OTs and CDs, so in some cases extrapolation was necessary, such as for non -cattle livestock for Jersey and all livestock types for Bermuda. • For synthetic fertiliser application, in the Cayman Islands there are no data available before 2010, so this is extrapolated backwards based on an average. In Bermuda, only a single value is available for the whole time series, which has been assumed to remain • For emissions from crop residues, no data are available for the Falkland Islands so this source is not estimated. For Bermuda, crop production data are sourced from FAO up to the year 2016 but are not available for later years, so 2016 values have been • For the CDs, data on the application of limestone were compiled until 2015 but are not now available, so 2015 values have since been extrapolated. • Due to a lack of activity data for any year, emissions are not estimated for 3G Liming for Bermuda, for 3H Urea application for Bermuda and the Falklands, and for 3F Field Burning of Agricultural Residues for any OT. IPCC Tier 1 default factors from the 2006 Guidelines have been used to estimate emissions for the OTs, using the closest regional values matching the climate and production systems. However, this does introduce uncertainty, as local geography, livestock breeds and production practices may differ. A similar uncertainty in CD emissions arises from the use of UK GHGI implied emission factors because local production practices may differ significantly from the UK average. However, there is generally a lack of available data and resource to support using higher-tier methods or developing local-specific EFs. Due to the proportionally small contribution of OTs and CDs to the national inventory, the UK only periodically aligns the CD emission factors with UK emission factors (currently the values from the 2024 submission are used), and for simplicity the UK presents all OT and CD agriculture data in the CRT against 3J. The UK is considering changes to the institutional arrangements to make the process of updating the UK GHGI IEFs more robust in the future, to apply to activity data in the CDs. Improvements could be made to the method to update these IEFs regularly, inste ad of maintaining constant IEFs across the time series. It has been added to the improvement plan to discuss the changes to the institutional structure to make it more feasible to fully integrate emissions from the OTs and CDs and other data, into the appropriate CRT categories, rather than having emissions reported under 3J. UK NID 2025 (Issue 1) Ricardo Page 397 The Inventory Agency is consulting with stakeholders to seek more complete activity data for the OTs and CDs where these are currently lacking, including updated livestock, fertiliser and crop production data from OTs, and liming data from the CDs. Further, the Inventory Agency will review assumptions based on local expert judgement, e.g. that no synthetic fertiliser, limestone or urea is applied in the Falklands. Finally, there is a longer-term research project into organic soils and emissions in the Falkland Islands, the results of which will inform future inventory improvements once completed.
The UK Agriculture Inventory has a documented QA/QC plan covering the annual compilation of the inventory by the contracted consortium (led by ADAS) addressing governance, data management, quality control (procedures and checks) and quality assurance activ ities. The organisational roles and responsibilities of the delivery team and government stakeholders are described. The inventory compilation, reporting, review and improvement cycle for an annual submission to UNFCCC and UNECE is outlined with an overvie w of the key QC and QA activities at different stages in the cycle, including the timings for the annual compilation cycle and details of source -specific quality checks to be performed on the incoming data, the calculation models and the data validation ch ecks on model outputs. The QA/QC plan is The agriculture inventory data quality objectives are based on the inventory quality objectives of Transparency, Accuracy, Consistency, Comparability and Completeness (TACCC) as set out in the IPCC national inventory reporting guidelines and clear statemen ts are provided as to how these are to be met. Security, scope and timeliness of data supply are addressed, with Data Supply Agreements being developed with suppliers of key input data. Procedures are in place for the management of confidential data (e.g. farm holding level data) and for data storage, back-up and archiving. During the finalisation of the agriculture “master” dataset and the integration of these data into the wider UK inventory data for onwards submission to the UNFCCC and UNECE, there are iterative quality checks performed by the Inventory Agency (under contr act to DESNZ) to highlight any data anomalies, recalculations and inventory trends compared against previous inventory submissions. There is then a period of dialogue and clarification of the agriculture data and supporting information is provided to the Inventory Agency where applicable. Peer and bilateral reviews of the Agriculture inventory have been conducted, and the revised methodological approaches introduced in the 2018 submission through the Defra GHG improvement programme were reviewed by an international Research Expert Group (including several IPCC Inventory Review Experts) as part of the programme. An inventory method improvement has been considered to disaggregate the activity and emissions across the livestock manure management systems (MMS), aiming to develop a method that will more accurately represent the emissions and the fate of materials across different manure management in storage, in housing and at the point of spreading, for slurry and manure materials. UK sector experts prepared a draft paper for submission to international peer reviewers from Ireland, Denmark and France. Peer reviewer feedback on th e proposed method indicated that the rationale and objective of the proposed improvement is sound and should be explored further, noting that further work is needed to address data and evidence gaps before the UK can move to implementation. The inventory t eam will progress this item, subject to resource availability and identification of relevant evidence to populate the proposed

Land-Use, Land-Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 398 6 Land-Use, Land-Use Change and emissions of greenhouse gases and precursors (CO2, CH4, N2O, NOx and CO) from Land Use, Land-Use Change and Forestry (LULUCF) activities. Removals of carbon dioxide are conventionally presented as negative quantities. Total LULUCF - - 10.7 0.6 1.1 -0.1 -0.2 A. Forest Land 16 (CO2) 15% -13.7 -18.1 -17.5 -0.1 -0.4 B. Cropland 17 (CO2), 24% 15.4 13.4 13.3 0.1 0.1 C. Grassland 30 (CH4) 680% 2.3 0.4 0.1 0.0 0.3 D. Wetlands 31 (CH4) 27% 2.9 2.7 3.2 0.0 -0.1 E. Settlements 24 (CO2) 35% 5.9 4.3 4.3 0.1 0.0 2All values for uncertainty refer to those associated with the latest year CO2 emissions 3The values given are the difference in 1990 or 2022 emissions/removals from the data reported in the previous UK GHGI submission using AR5 GWP values (without feedbacks). The summary analysis of the trends in greenhouse gas emissions from the LULUCF sector is provided in Section 2. The methodological differences since the previous UK GHGI submission are explained in this chapter. This information is presented in the last cell of the tables at the start of each section providing an overview of each of the LULUCF categories (Major improvements since last submission). The LULUCF sector covers emissions and removals of direct greenhouse gases under seven categories, of which Forest Land (4A) and Harvested Wood Products (4G) are net sinks, and 6.1). The UK does not report any emissions or removals from the Other Land (4F) category. The LULUCF sector is the only sector within the national greenhouse gas inventory which reports both sources and sinks. The sinks are provided by CO 2 removals from carbon stock gains in above-ground and below-ground biomass, litter, deadwood, soils and harvested wood products. The sources of emissions are carbon stock losses from those same pools and GHG

Land-Use, Land-Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 399 6.1.1 The land use transition matrix The areas used for the three UK CRT submissions are based on the Standard Area Measurement to mean high water is used for the total area of the UK (24,438.5 kha) (Office for National Statistics 2017) and the land areas reported in national statistics for the OTs and

Land-Use, Land-Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 400 • Falkland 1,217.3 kha Only the UK, Jersey, Guernsey and the Isle of Man are included in the Paris Agreement submission. All areas are assigned to one of the LULUCF land use categories (Forest Land, Cropland, Grassland, Wetland, Settlements, Other). All land use is considered to be a small area of wetland (0.12 kha) in Jersey has been used for land reclamation from the sea since 2009, and was therefore previously unmanaged. Approach 2 (IPCC 2006) is used for the representation of land use areas in the inventory. UK land use change is estimated using a Bayesian data assimilation approach (Annex 5.1.4.3.1).
This constrains estimates of gross land -use change with national -scale census data, whilst retaining the detailed information available from other land -use data sources. The data sources are compiled at the individual country level (England, Scotland, Wales and Northern Ireland) and results are combined to give UK totals. CRT Reporter) and the CRT carbon stock reporting tables, it is assumed for the UK o The total areas of land use categories from recent reports (2015 or 2023) are the most o The areas of LUC used for carbon stock changes are the most consistent sources of land use matrix. The initial land use areas in 2015 are also the final land use areas in 2014. These are used with the transitions to and from each land use category in 2014 (see the individual land use c ategory Sections 6.2 to 6.6 for details) to calculate the initial land use areas in 2014 and area of each category that does not undergo any change. This approach is used to calculate the initial and final land use areas back in time to 1990, and forward in time from 2015. Forest Land is the exception- the area in the latest inventory year is considered to be the most reliable and the initial and final areas are calculated back in time from that point. Land cover surveys and agricultural land statistics are used to compile annual land -use change matrices for the OTs and CDs. Information on these data sources is given in Annex Source dataset Relevant components of Forest Land National Forest Inventory (NFI) (GB)1 and Northern Ireland Woodland Base Annual afforestation and deforestation Cropland UK Agricultural Census (Defra, DAERA, Scottish Government, Welsh

Land-Use, Land-Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 401 Source dataset Relevant components of Grassland ONS Standard Area Measurement land area – area of other categories3 Wetlands ONS Standard Area Measurement UK Directory of Mines and Quarries, Google Earth imagery and Growing Media Association data (peat extraction Peat condition maps (Evans et al. 2017), Growing Media Association and Peatland Action (peatland restoration Settlements Land Cover Map 2015 (UKCEH 2015) Urban land cover class Other Land Land Cover Map 2015 (UKCEH 2015) Inland rock, supra-littoral 1 Forestry Commission (2017) “Tree cover outside woodland in Great Britain report” year summed across all LULUCF categories may not equal the total land area in some years because of small rounding differences. Land-Use, Land-Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 402

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Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 407 Emissions sources 4A Forest carbon stock change 4(I).A Direct and indirect nitrous oxide (N2O) emissions from nitrogen (N) inputs to managed soils 4(II).A Emissions and removals from drainage and rewetting and other management of organic and mineral soils 4(III).A Direct and indirect nitrous oxide (N2O) emissions from nitrogen (N) mineralization/immobilization associated with loss/gain of soil organic matter resulting from change of land use or management of mineral soils Methods T3 for carbon stock changes, T2 for direct CO2 and CH4 and Emission Factors Country-specific for T3 methods Key Categories 4A: Forest land - CO2 (L1, L2, T1, T2), N2O (L2) Improvements to the CARBINE process modelling and minor This section describes LULUCF emissions and removals from Forest Land in the UK. A description of LULUCF emissions and removals from the OTs and CDs is given in Section Forest Land includes carbon stock gains and losses and GHG emissions from forest management and overall is the biggest net sink in the UK. All UK forests are temperate and about 74% of these have been planted since 1921 on land that had not been forested for many The UK reports carbon stock changes in all forests. Forest surveys have been intermittent in the UK and to date there has been no network of permanent sample plots suitable for constructing a GHG inventory. Consequently, estimates of carbon stock gains and losses for biomass and soils are modelled based on planting history, assessed tree age class area distributions and productivity (yield class) estimates, and assumptions over approaches to forest management. Forest carbon stock changes and fluxes are mode lled by CARBINE, the Forest Research forest carbon stock and carbon balance model (described in Annex 5.1.4.1). CARBINE takes account of the effects of forest management on carbon stocks and estimates the carbon stocks in the Harvested Wood Products pool. Carbon stock changes resulting from afforestation on Cropland, Grassland and Settlement on both mineral and organic soils are calculated. Conversion of Other Land or Wetland to Forest Land does not occur in the UK. The reported forest area and carbon stock changes take account of losses of forest land converted to other land use categories (deforestation) and the associated carbon stock changes and emissions and removals are then estimated and reported under the category concerned. Associated direct and indirect N2O emissions from N mineralization are reported under 4(III).A. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 408 In the UK inorganic nitrogen fertilisers are only applied to forest when absolutely necessary. This occurs during the first rotation on ‘poor’ soils, such as reclaimed slag heaps, impoverished brown field sites and upland organic soils, hence N fertilisati on is assumed for all areas of Settlements converted to Forest Land and Grassland converted to Forest Land on organic soils. Direct and indirect N 2O emissions from this fertilisation are reported under 4(I).A.2.
Nitrogen fertilisers are not generally applied to native woodlands, mature forests or re-planted forests in the UK, so emissions of N 2O from N fertilisation of forests for 4(I).A.1 are reported Drainage of forest land occurs in UK forests planted on certain soil types. It is assumed that all forests planted on organic soils are drained prior to planting. Forests planted on mineral or organo-mineral soils which have slow natural drainage and are prone to waterlogging are also assumed to be artificially drained. CO2 emissions from drainage are included with carbon stock of forests on organic soils results in a land use change and emissions are reported under 4D2.c.i Forest converted to other wetlands and 4(II).D.2.c.i Controlled burning of forest land (for example for habitat management) does not take place in the UK. Wildfires do occur but the activity data are not sufficient to split reporting between 4.A.1 and 4.A.2. Therefore, emissions of greenhouse gases from wild fires are all reported under 6.2.2 Information on approaches used for representing land areas and on land use databases used for the inventory preparation The agencies responsible for forests in the UK are the Forestry Commission (England), Scottish Forestry and Forestry and Land Scotland, Natural Resources Wales and the Northern Ireland Forest Service. Areas of forest planted annually are published in Forestry Statistics100 and a detailed breakdown (by forest type and management) is used as input to the CARBINE model, supplemented by information from the National Forest Inventory (NFI) field survey and the Northern Ireland Woodland Register. The allocation of land -use change from other land use categories is based on the proportional changes in the land-use change matrices from the data assimilation of multiple land-use data sources (see Section6.3 and Annex 5.1.4.3). More information on the stratification of the UK forest area can be found in the UK National Forestry The area of forests on organic soils in the UK was based on peatland extent and condition mapping outputs from the BEIS -funded project to implement the 2013 IPCC Wetlands Supplement (Evans et al. 2017) (see Annex 5.1.4.7). 6.2.3 Land-use definitions and the classification system used and their correspondence to the LULUCF categories The UK uses the following definition of forest for reporting UK forestry statistics as it relates to the UK’s greenhouse gas inventory submitted under the • Minimum area of 0.1 hectares; • Tree crown cover of at least 20 per cent, or the potential to achieve it; • Minimum height of 2 metres, or the potential to achieve it. 100 101

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 409 This definition includes felled areas awaiting restocking and integral open spaces (open areas up to 1 hectare). The annual Forestry Statistics publication uses a minimum area assumption of 0.5 ha, with the “Tree cover outside woodland” report providing th e additional area of woodlands between 0.1 -0.5 ha (Forestry Commission, 2017). The definitions are consistent with information provided by the UK to the Food and Agriculture Organization of the United Nations (FAO). If an international source uses a different minimum area definition, for example 0.5 ha in the Global Forest Resource Assessment 2010, the UK areas are adjusted to this different definition (FAO, 2010). All forest areas in the UK can be regarded as managed from the point of view of regulation against deforestation and protection against fire, storms and disease. In general, forest areas are actively managed for landscape, soil protection, habitat conserva tion, amenity and recreation, which may or may not include active management for wood production. In this inventory submission the carbon uptake by UK forests is calculated using a Tier 3 carbon accounting model, CARBINE. Overall carbon uptake is calculated as the net change in the pools of carbon in standing trees, dead organic matter, soil and produc ts from harvested material, for conifer and broadleaf forests. The model is able to represent all of the introduced and native plantation and naturally occurring species relevant to UK forestry, the different growth rates of forests and four broad classes of forest management (clear-fell with thinning, clear-fell without thinning, thinned but not clear -felled and no timber production). The forest carbon sub -model is further compartmentalised to represent fractions associated with tree stems, branches, foliage, and roots. The CARBINE model produces separate estimates of gains and losses for carbon stock change in above - and below-ground living biomass, rather than net change. Carbon stock changes in dead wood litter and soil are also reported. Further detail on the CARBINE model is given in Annex 5.1.4.1 and Matthews et al. (2014). There have been revisions to the activity data for afforestation for this these revisions and their impact are described in the recalculations (Section 6.2.7). Emissions from fluvial carbon from forest on organic soils are reported using the Tier 1 emission factors from the 2013 IPCC Wetlands Supplement for dissolved organic carbon and particulate organic carbon. Areas of forest planted on organic soils are estimated by overlaying a map of soils with the forest map from the National Forest Inventory in England, Scotland and Wales. For Northern Ireland a similar method was used to estimate areas based on the NI wood land basemap. Further details on this work are given in Annex 5.1.4.7. Other greenhouse gas emissions, including those arising from forest fertilisation and wildfires together with estimates of N2O emissions from forest drainage, are estimated using Tier 1 or Tier 2 approaches, and are described in Annex 5.1.4.2. 6.2.5 Uncertainties and Time-Series Consistency The uncertainty in 1990 and 2023 respectively are estimated at 20% and 15% for CO 2, 85% and 75% for CH4, and 80% and 90% for N2O. These uncertainties are based on an uncertainty analysis using the updated activity data and methodology for this submission.
Details are The planting statistics used as activity data mostly come from operational systems, for grants and for planting on the National Forest Estates of the four countries comprising the UK (supplemented by information from the NFI field survey). Complete geographical coverage of the UK in these statistics and accurate division of the UK into the four constituent countries is assumed and the associated statistical uncertainties are assumed to be negligible. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 410 Grants are paid once planting has occurred. The grant -aided planting is allocated by year of payment, so all the recorded planting should have taken place. There is ongoing work within Forest Research to assess the level of error attached to the data e.g., for failed planting. The area of forest in GB is based on the new NFI woodland map, together with small woods of between 0.1 and 0.5 ha. A field survey used to estimate the stocked area and composition (including age distribution) of the non-FC/NRW forest estate is based on a sub-sampling of the population and scaling to the mapped level. With regard to series • For forest carbon stock changes, N fertilization of forests and emissions from drainage, time series consistency is expected to be good as activity data are obtained consistently from the same national forestry sources; • For emissions from wildfires, data have been collated from several published sources. From 1990 – 2004 all data originate from the state forestry agencies so there is good time series consistency during this period. Data have been extrapolated for 2005-2009. A newer and more complete data source for England, Scotland and Wales is used from 2010 onwards, and gives wildfire burnt areas which are the same magnitude as the • Emissions from forests on organic it is assumed that all organic soils planted with forests are drained and there has been no recorded planting of new forests on organic soils since 2012. An area of 13.179kha has been rewetted to Wetland since 2000. A significance analysis has been undertaken for key categories in the LULUCF sector. In Forest Land carbon stock changes in soil, living biomass, dead wood and litter in the 4.A.1 Forest Land remaining Forest land and 4.A.2.b Grassland converted to Forest Land are the A.1. Forest Land remaining Forest A.2.d. Settlements converted to

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 411 4(I) Direct N2O Emissions from N Inputs to Managed Soils - forest 4(II) Emissions and removals from drainage and rewetting and other management of organic and mineral 4(II) Emissions and removals from drainage and rewetting and other management of organic and mineral 4(III) N from mineralization resulting 1 Percentages may not sum to 100% due to rounding 6.2.6 Category-Specific QA/QC and Verification This source category is covered by the general QA/QC procedures, which are discussed in Section 6.10. Information on the area affected by wildfires is consistent with that reported to As part of a separate research project, a comparison was made of the predictions made by the UKCEH C-Flow model and Forest Research CARBINE model. The results demonstrated that the models produce consistent predictions when given the same input data and as sumptions (e.g. about woodland management practices). Further work has been undertaken comparing the inventory as predicted by CARBINE to the inventory as predicted by C-Flow and detailing the changes in assumptions that drive the changes in the inventory (Matthews et al., 2014). Verification of carbon stock changes will be undertaken once the second cycle of the NFI is A review of inventory data and models has been undertaken (Levy and Rowland, 2011), during which data were collated and critically assessed on soil carbon stocks following afforestation. Generally, soil carbon stocks are assumed to increase after afforestation in the UK, following on as a result of the increased above -ground biomass and litter inputs, based on a small number of long term studies. In fact, in the UK studies which attempt to measure this, soil carbon stocks in forested plots were 15 to 60 % l ower than in adjacent unplanted, grassland or moorland (Reay et al., 2001; Chapman et al. 2003; Zerva and Mencuccini 2005; Mitchell et al. 2007; Bellamy and Rivas -Casado 2009; Levy and Clark 2009). These results are in agreement with global meta -analyses, which have reported mean changes in soil carbon stocks of around -10 %, -7 %, +3 % and -4 % associated with conversion of pasture to forest plantation (Guo and Gifford 2002; Laganiere, Angers et al. 2010; Poeplau, Don et al. 2011 respectively). The treatment of the litter layer in these studies is a significant uncertainty, as it is possible that some of the reported decreases in soil carbon following afforestation were compensated by increases in carbon stocks of the above -ground litter layer which is not The full specification and information on the validation of the soil and litter model that has been implemented in CARBINE will be published in a separate technical report. In broad terms, the comparisons done so far show that the model gives broad-scale soil carbon stock results that are consistent with collected data and reported estimates. Verification of the carbon stock changes in soils is made more difficult by the general lack of repeat measurement and we are attempting to identify potential sources of additional data. An analysis of existing data sources and literature helped to identify data gaps and prioritise additional data collection. Additional

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 412 measurements of soil carbon stocks in England and Scotland have been made in the last two years to help with this validation.
In 2018, a new automatic algorithm was introduced in CARBINE to adjust the assumptions about forest management to ensure a good match between modelled forest harvest, and thus HWP, and the wood production statistics. This has also improved the repeatability and QC of this part of the inventory. As part of this project, the timber volume production module of CARBINE was re -implemented to enable that automation. This semi -independent implementation of this part of the model was cross validated against the ver sion in the 6.2.7 Category-Specific Recalculations The reported overall net GHG sink in category 4.A has changed between -0.1 and -0.4 Mt CO2e (2%) across the time series compared to the previous inventory. The changes were mainly seen in the carbon stock changes in the carbon pools for Forest Remaining Forest and Land converted to Forest. The main cause of this change was updates to activity data and to the CARBINE model. The changes and their justification • Updated wildfire activity data. Wildfire activity data from Wales was not available for 2022 in the previous submission but is now included. • Updates to the CARBINE model. These include improved estimates of early tree growth, the incorporation of carbon from dead branches into the soil carbon pool, a change in the dead branch decay rate from 4% to 14% to match the model description, a correction to the anaerobic conditions soil water availability modifier in Scotia soil sub-model, and a correction to the Northern Ireland reconcile process to improve estimation of harvest intensity for private forests. • Updated forest land activity data from the 2024 preliminary Forestry Statistics and updated estimates of deforestation based on new peatland rewetting data for Scotland

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 413 Category Source Name Old 1990 value Old 2022 value New 1990 value Units Comment / Justification 4.A.1/4(IV) Biomass burning - wildfires 10.35 9.32 10.36 11.77 Gg C Updated wildfire data living biomass - gains -10587.17 -16387.75 -10649.82 -16566.17 Gg C living biomass - losses 7934.69 13814.74 7998.80 13929.70 Gg C 4.A.1 Net carbon stock change in dead wood -639.04 -1007.46 -635.51 -991.38 Gg C 4.A.1 Net carbon stock change in litter -147.66 -140.31 -150.44 -145.00 Gg C 4.A.1 Net carbon stock change in soils - mineral soils -510.53 -1208.33 -565.72 -1268.75 Gg C 4.A.1 Net carbon stock change in soils - organic soils 129.55 -16.45 126.33 -40.17 Gg C living biomass - gains -84.53 -28.06 -85.47 -28.39 Gg C 4.A.2.a Carbon stock change in living biomass - losses 17.55 5.48 17.70 5.59 Gg C 4.A.2.a Net carbon stock change in dead wood -2.73 -0.74 -2.77 -0.75 Gg C 4.A.2.a Net carbon stock change in litter -2.32 -0.67 -2.37 -0.69 Gg C 4.A.2.a Net carbon stock change in soils - mineral soils 50.07 22.88 54.28 25.01 Gg C soils - organic soils 16.72 1.30 16.76 1.32 Gg C

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 414 Category Source Name Old 1990 value Old 2022 value New 1990 value Units Comment / Justification living biomass - gains -1035.35 -210.32 -1046.58 -211.50 Gg C 4.A.2.b Carbon stock change in living biomass - losses 211.50 40.69 214.03 41.34 Gg C 4.A.2.b Net carbon stock change in dead wood -34.69 -5.82 -35.12 -5.88 Gg C 4.A.2.b Net carbon stock change in litter -30.99 -5.47 -31.67 -5.56 Gg C 4.A.2.b Net carbon stock change in soils - mineral soils 425.19 175.72 456.33 193.28 Gg C 4.A.2.b Net carbon stock change in soils - organic soils 420.47 15.31 422.03 15.00 Gg C living biomass - gains -17.68 -10.14 -18.89 -10.19 Gg C 4.A.2.d Carbon stock change in living biomass - losses 3.57 1.96 3.79 1.99 Gg C 4.A.2.d Net carbon stock change in dead wood -0.58 -0.28 -0.62 -0.28 Gg C 4.A.2.d Net carbon stock change in litter -0.50 -0.27 -0.53 -0.27 Gg C 4.A.2.d Net carbon stock change in soils - mineral soils 7.28 8.34 8.08 9.21 Gg C soils - organic soils 7.49 0.65 7.56 0.64 Gg C 4.A.1/4(IV) Biomass Burning - wildfires 0.14 0.13 0.14 0.17

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 415 Category Source Name Old 1990 value Old 2022 value New 1990 value Units Comment / Justification and mineral soils 3.39 3.64 3.39 3.65 4.A.1/4(IV) Biomass Burning - wildfires 0.008 0.007 0.008 0.009 from N mineralisation 0.064 0.029 0.070 0.032 from N mineralisation 0.546 0.226 0.586 0.248 from N mineralisation 0.009 0.011 0.010 0.012 Managed Soils 0.056 0.005 0.056 0.005 and mineral soils 1.097 1.188 1.098 1.193

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 416 6.2.8 Category-Specific Planned Improvements DESNZ have funded a program of work looking at improving estimates of GHG emissions/removals relating to forest land, including validation of the existing models, targeted improvements to the models and collection of additional forest soil carbon measurements. This work is intended to lead to improvements in both activity data and modelling of emissions/removals . Specific improvements intended for inclusion in the near term • the impacts on litter, deadwood and soil of a fallow period following felling; • the impact of species change when restocking to comply with guidance outlined in the • any improvements to the soil model as a result of the current validation work.
Emissions sources 4B carbon stock change 4(II).B Emissions and removals from drainage and rewetting and other management of organic and mineral soils 4(III).B Direct and indirect nitrous oxide (N2O) emissions from nitrogen (N) mineralization/immobilization associated with loss/gain of soil organic matter resulting from change of land use or management of mineral soils Methods T3 for carbon stock changes, T2 for organic soils, T1 for other Emission Factors Country-specific for T3 methods, T2 for direct CO2 and CH4 emissions from organic soils, T1 for other emissions Key Categories 4B: Cropland - CO2 (L1, T1, L2, T2) Completeness No known omissions. This section describes LULUCF emissions and removals from Cropland in the UK. A description of LULUCF emissions and removals from the OTs and CDs is given in Section Net emissions from the Cropland category include carbon stock gains and losses and GHG emissions due to land -use change (LUC), cropland management, drainage and biomass burning. Overall, the Cropland category is the largest net source in the LULUCF sector. Ongoing carbon stock changes in soils arising from LUC to Cropland are reported under both 4.B.2. (for LUC in the past 20 years) and 4.B.1 (for historic LUC >20 years before the inventory reporting year). These non-organic soil net carbon stock changes are the largest component of the category total emissions and are calculated using a Tier 3 dynamic soil carbon model. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 417 Carbon emissions from drainage of cropland on organic soils are the next largest component and are reported under 4.B.1 and 4.B.2. They are calculated using Tier 2 country -specific Other contributors to the Cropland net total emissions • CH4 emissions resulting from drainage of organic soils (4(II).B); • carbon stock changes in biomass and soils resulting from changes in cropland • biomass carbon stock changes due to LUC (4.B.2); • N2O emissions from soil disturbance associated with LUC (4(III).B); • biomass burning emissions of GHGs from controlled burning following forest land conversion to cropland (4(IV).B.2); and • biomass burning emissions of GHGs due to wildfires (4(IV).B.1). All forms of land -use change, including deforestation, are considered and both mineral and organic soils are included. In some categories, e.g. Forest Land converted to Cropland, the area of land undergoing transition falls to zero and is subsequently reported as Not Occurring for some carbon stock changes and emissions. Ongoing N2O emissions from soil as a result of land -use change > 20 years ago and from drainage of organic soils are reported in the Agricultural sector inventory as N 2O emissions from managed agricultural soils. UKCEH provide the appropriate areas and emission factors to Rothamsted Research. Nitrous oxide emissions from loss of soil organic matter as a result of Cropland Management are also reported in the Agricultural sector inventory as N 2O emissions from managed agricultural soils. Emissions of CO 2, CH4 and N2O from controlled biomass burning arising from Forest Land straw or stubble) are reported under category 3F Field Burning of Agricultural Residues. Full details of the method and activity data are given in Annex 5.1.4.5. 6.3.2 Information on approaches used for representing land areas and on land use databases used for the inventory preparation The UK uses Approach 2 (IPCC 2006) for the representation of land use areas in the inventory and compiles several different data sources into a non -spatially-explicit land use conversion matrix (see Annex 5.1.4.3.1 for details). Data sources that contain area information for reporting carbon stock changes and/or o The Countryside Survey (DAERA 2016, UKCEH 2020a) which gives repeated field surveys of stratified 1km sample squares. o Monitoring Landscape Change (MLC 1986) habitat survey based on aerial • Extent of cropland on organic soils and rewetting of cropland back to wetland (Evans et al. 2017 and further updates). o Areas of the main crop types are obtained from the June Agricultural Censuses o Agricultural holdings farm-level detail on agricultural land areas. o field-level register of agricultural subsidy claims under the EU Common

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 418 o crop classification of satellite imagery for England, with ground-truth data from agricultural subsidy inspectors o The areas of Cropland receiving inputs of manure, fertiliser and crop residues are obtained from the British Survey of Fertiliser Practice. • Land-cover from satellite imagery classification o Land Cover Map (UKCEH 2020b): thematic land-cover classification of satellite o Land Cover® Crops (UKCEH 2016): Based on the LCM parcel framework with additional crop information from satellite data o CORINE Land Cover (CORINE 2020): Survey of European land cover and land cover change from semi -automatic interpretation of high -resolution satellite • Data on wildfires on agricultural land from Fire and Rescue service and satellite data. o Areas of wildfire on Cropland for 2010 to the present come from Fire and o Between 2001 and 2009 the area of wildfire on Cropland is calculated by using satellite data on the total area of wildfires in the UK which are apportioned to land use using the same ratios as found in the Fire and Rescue service data o Cropland wildfire areas prior to 2001 are extrapolated (see Annex 5.1.4.6 for 6.3.3 Land-use definitions and the classification system used and their correspondence to the LULUCF categories Cropland is defined in accordance with the Agriculture, Forestry and Other Land Use Guidance (IPCC 2006). The crop types in the different data sources that contribute to the Cropland category are described in Annex 5.1.4.3.1. Activity data for land -use change are estimated using a land -use change (LUC) matrix approach. Detailed descriptions of the methods, emission factors and data flows used for Cropland activities are given in Annex 5.1.4.3. Land use change on organic soils is split out from the land-use change matrices to produce a non-organic soil set of LUC change matrices.
Emissions arising from land -use and land-use change on organic soils are calculated using methodologies consistent with chapters 2 and 3 of the 2013 IPCC Wetlands supplement described in Annex 5.1.4.7. A dynamic model of carbon stock change is used with the non -organic LUC matrices to estimate non-organic soil carbon stock changes due to LUC. Non -organic soil carbon stock changes are modelled as changing exponentially between initial and final land uses. The carbon stocks on non-organic soils for each land use category are calculated as averages for Scotland, England, Northern Ireland and Wales using a database of soil carbon density for the UK (Milne and Brown 1997; Cruickshank et al. 1998; Bradley et al. 2005) which has been constructed based on information on soil type, land cover and carbon content of soil cores to a depth of 1 m or to bedrock, whichever was the shallower, for mineral and organo -mineral soils. The rate of loss/gain of soil carbon is de pendent on the type of land use transition. A Monte Carlo approach is used to vary the rate of change, the area activity data and the values for soil carbon equilibrium, under initial and final land use. The mean soil carbon flux for each region is summed to give the UK total for the Inventory. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 419 Biomass carbon stock change is calculated using the LUC matrix and literature-derived Tier 2 stock change factors, with all stock gains or losses assumed to occur in a single year. Direct and indirect N2O emissions associated with non-organic soil disturbance from LUC are reported using the areas of Forest land and Grassland converted to Cropland from the LUC matrices and the IPCC Tier 1 emission factors (see Annex 5.1.4 for details). Carbon stock change (CSC) in mineral soils as a result of cropland management is estimated using agricultural survey activity data, country -specific soil carbon densities and Tier 1 CSC factors for most activities except for tillage reduction (Tier 2). Carbon stock changes in biomass due to cropland management activities are estimated using literature-derived Tier 2 stock change factors and activity data from agricultural surveys. Carbon stock changes in biomass can arise from changes in annual crops, orchards, bioenergy crops and shrubby perennial crops (see Annex 5.1.4.3.2 for details). Emissions of carbon and CH4 from Cropland on drained organic soils are reported using Tier 2 emission factors ( Annex 5.1.4.7 ). Emissions of N 2O from cropland on organic soils are calculated using the same activity data and are reported in category 3.D in the Agriculture 6.3.4.4 Biomass burning emissions Emissions from controlled burning on cropland are only reported for Forest Land conversion to Cropland and are estimated using Tier 1 emission factors and country-specific fuel densities. Emissions from wildfires on Cropland are reporting using Tier 1 emission factors and activity from a range of sources (see Section 6.3.2). 6.3.5 Uncertainties and Time-Series Consistency The uncertainty in 1990 and 2023 respectively are estimated at 15% for CO 2, 65% and 70% for CH4, and 40% for N2O. These uncertainties are based on an uncertainty analysis using the updated activity data and methodology for this submission. Details are provided in Annex 5.1.4.12. The areas undergoing land-use change are the biggest source of uncertainty in the With regard to time series • Drainage of organic it is assumed that all drainage of organic soils on Cropland occurred before 1971 as recent policy has favoured protection of organic soils. There have been no policy incentives to encourage new land drainage for agricultural use since 1990, and major drainage of large areas of Cropland on organic soils in areas such as the East Anglian fens is known to have occurred well before this. A small area has been rewetted to Wetland since 2000 ( 6.248 kha), almost all of which is in England. • Changes in biomass and soil carbon due to the land-use change data assimilation methodology draws on multiple data-sources and takes account of random uncertainty and false positive rates. The time series now show more inter-annual variation but more • Controlled biomass burning after conversion of Forest Land to there is good time series consistency as there has been continuity in the activity data source. • a consistent dataset is used from 2010 onwards. Burnt areas are extrapolated back to 2001 based on remote sensing data, but between 1990 and 2001 there are no

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 420 observed data on the extent of wildfires on Cropland, and the time series is filled by extrapolating the 2001 – 2011 average wildfire area. • Cropland The June Agricultural censuses are very long -standing datasets with good time series consistency. The British Survey of Fertiliser Practice has contained information on the proportion of Cropland receiving manure since 2008. For years prior to 2008, the 2008 – 2015 average value has been used. The British Survey of Fertiliser Practice has contained information on the proportion of Cropland receiving fertiliser since 1992. For years prior to 1992, the 1992 - 2001 average value A significance analysis has been undertaken for key categories in the LULUCF sector. In Cropland the 4.B.2.b Grassland converted to Cropland and the 4.B1 Cropland remaining in mineral and organic soils the biggest pool contributions. B.1. Cropland remaining Cropland 41% 62% cropland management (soils and Mineral Soils (due to land use B.2.a. Forest Land converted to B.2.d. Settlements converted to • 1 Percentages may not sum to 100% due to rounding 6.3.6 Category-Specific QA/QC and Verification This source category is covered by the general QA/QC procedures, which are discussed in A resampling of the 1980-based National Soil Inventory (NSI) in England and Wales in 1995- 2003 found large losses of soil carbon across all land use types (Bellamy et al. 2005).
It was hypothesized that this loss was due to climate change because all land uses showed losses and the size of the loss was related to initial carbon concentration, suggesting that the UK’s LUC modelling approach was incorrect. In contrast, a mo re recent study using Countryside Survey (CS) data (Reynolds et al. 2013) found no sign ificant change in soil carbon stocks under most Grassland habitat types between 1978 and 2007. The reason for the different results obtained by NSI and CS is not clear (Kirk et al . 2011), although there are

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 421 methodological differences between the two surveys. Subsequent modelling studies (e.g. Smith et al . 2007, Barraclough et al . 2015) have shown that climate changes could only account for a small part of the decrease in soil carbon reported in Bellamy et al. (2005). The importance of prior land use history in priming soil carbon dynamic models has also been 6.3.7 Category-Specific Recalculations The reported overall net GHG source in category 4B has decreased by < -0.01 Mt CO2e (0%) across the time series compared to the previous inventory. The changes were due to minor The changes and their justification • Updates to organic soil areas . New activity data on existing and rewetted organic soils have been included and consistency improvements have been implemented. • Updates to cropland management activity data . Newly available bioenergy crop activity data for England (2021 -) has been included and other minor inconsistencies

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 422 value Units Comment / Justification biomass 6.16 1.12 6.16 0.91 Gg C Updates to cropland management activity soils - mineral soils 497.20 1177.02 497.05 1177.08 Gg C soils - organic soils 1146.66 1076.15 1146.66 1076.13 Gg C Updates to organic soil areas

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 423 6.3.8 Category-Specific Planned Improvements DESNZ have funded the GHG Inventory Improvement Project “Assessment of robustness of LULUCF emission factors” to identify the robustness of the 182 factors (excluding those in the CARBINE model) in the LULUCF sector and identify priorities for improvement, for example, through empirical in-country measurements. This project will finish in March 2025. The second step in implementing the BEIS -funded Land-Use Tracking project is in progress (see Annex 5.1.4.3). This will revise the soil carbon dynamics model and LULUCF inventory reporting methods to use vectors of land-use change rather than independent annual land-use change matrices, which will improve the representation of rotational management of cropland and improved grassland. The DESNZ -funded GHG Inventory Improvement Project “Investigation of Pre-1950 land use data for LULUCF reporting” has identified and processed seven datasets for incorporation in the LUC data assimilation methodology. These have been used to extend the LUC time series back to 1900, which makes a systematic difference to the estimated soil carbon stock change and reduces uncertainty, mainly by constraining the time- series of urban expansion. The timing of the implementation of these improvements in the inventory will be considered with other improvements to LUC and soil carbon modelling. The 2021 UNFCCC expert review team of the 1990-2020 NGHGI recommended improving the reporting of SOC (soil organic C) stock changes and GHG emissions under different land use categories. DESNZ have funded the GHG Inventory Improvement Project “Potential Implementation of a Process-Based Soil Model in the UK GHG Inventory” to address these recommendations and assess whether a method based on biogeochemical process modelling would allow estimation of soil organic C changes and GHG emissions from land management and LUC (particularly for agricultural land) and the factoring out of indirect anthropogenic factors such as impacts of climate change. Recommendations from this project are being taken forward in a further project “Testing of process-based soil models for use in the UK GHG Inventory”. This is preparing two process-based models to run spatially for the UK and testing the accuracy of the models against soil carbon stock changes form repeat-sampled plots, compared with current inventory estimates. A BEIS/DESNZ-funded research project on GHG emissions from lowland wasted peat soils under intensive agriculture was delayed by the COVID -19 pandemic. Flux tower measurements from this study have been used to develop a specific Tier 2 CO 2 EF for (Evans et al. 2022b). At present, separate EFs for grassland on wasted peat cannot be derived due to lack of data, and measurements are ongoing for N2O. Analysis of the project results has The 2019 UNFCCC review team inquired about the estimation, and reporting of, inorganic carbon stock change in soil. A subsequent review team stated that this only needs to be considered when the necessary data, a monitoring system for routinely collecting such data, and appropriate (Tier 3) soil process -modelling capacity becomes available. Therefore, no further work on inorganic soil carbon stocks is currently planned. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 424 Emissions sources 4C carbon stock change 4(II).C Emissions and removals from drainage and rewetting and other management of organic and mineral soils 4(III).C Direct and indirect nitrous oxide (N2O) emissions from nitrogen (N) mineralization/immobilization associated with loss/gain of soil organic matter resulting from change of land use or management of mineral soils Methods T3 for carbon stock changes, T2 for organic soils, T1 for other Emission Factors Country-specific for T3 methods, T2 for direct CO2 and CH4 emissions from organic soils, T1 for other emissions Key Categories 4C: Grassland - CO2 (L1, L2, T1, T2), CH4 (L1, T1, L2, T2) Completeness No known omissions- areas are reported for land uses with no This section describes LULUCF emissions and removals from Grassland in the UK.
A description of LULUCF emissions and removals from the OTs and CDs is given in Section Net emissions from the Grassland category include carbon stock gains and losses and GHG emissions due to land-use change (LUC) and GHG emissions from grassland management, drainage and rewetting and biomass burning. Grassland is a small net source that red uces Ongoing carbon stock changes in soils arising from LUC to Grassland are reported under both 4.C.2 Land Converted to Grassland (for LUC in the past 20 years) and 4.C.1 Grassland Remaining Grassland (for historic LUC >20 years before the inventory reporting year). These soil carbon stock changes and CO 2 emissions from mineral and organic soils are the largest components of the category total emissions and removals. Carbon stock changes on mineral soils are calculated using a Tier 3 dynamic soil carbon model and CO2 emissions from organic soils are calculated using Tier 2 country-specific emission factors. The area of undisturbed grassland on mineral soils which has not been converted from other land uses in the past is reported in 4.C.1. “Undisturbed” grassland. This sub-category is used as a buffer category on the recommendation of UNFCCC reviewers, as Grassland is the most extensive land type in the UK. The undisturbed grassland area is calculated as the difference between the total land area (from the official national statistic of UK land area, Office for National Statistics) and the sum of all other land use areas (calculated from land use matrices, afforestation areas, organic soil areas etc.) for each year. No anthropogenic emissions or removals are associated with this undisturbed area. The Evans et al. (2017) report identified large areas of grassland on organic soils in the UK that are not intensively cultivated but nevertheless have been degraded by anthropogenic activities, for example by over -grazing or management for game species. Emissions of N 2O

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 425 from these unintensive grassland areas are reported under 4C Grassland, while N 2O emissions from intensive cultivated grassland on organic soils are reported under 3D in the Other contributors to the Grassland net total emissions • CH4 emissions resulting from drainage and rewetting of organic soils (4(II).C); • N2O emissions from drainage and rewetting of unintensive grassland on organic soils • carbon stock changes in biomass resulting from changes in grassland management • biomass carbon stock changes due to LUC (4.C.2); • N2O emissions from mineral soil disturbance associated with LUC (4(III).C); • biomass burning emissions of GHGs from controlled burning following forest land conversion to grassland (4(IV).C.2.a); and • biomass burning emissions of GHGs due to wildfires (4(IV).C.1.b). Full details of the methods and activity data are given in Annex 5.1.4 6.4.2 Information on approaches used for representing land areas and on land use databases used for the inventory preparation The UK uses Approach 2 (IPCC 2006) for the representation of land use areas in the inventory and compiles several different data sources into a non -spatially explicit land use conversion matrix (see Annex 5.1.4.3.1 for details). Data sources that contain area information for reporting carbon stock changes and/or • Habitat/landscape surveys (see Section 6.3.2). • Extent of grassland on organic soils and rewetting of grassland that stays within the grassland category (Evans et al. 2017 and further updates). • Agricultural survey data (see Section 6.3.2). • Land-cover from satellite imagery classification (see Section 6.3.2). • Data on deforestation areas from various o Post-2000 deforestation areas are assessed from the NFI and administrative records of the conversion of areas in the public forest estate as part of habitat restoration and windfarm development. o 1990-1999 deforestation areas are estimated from unconditional felling licence data (felling licences granted without a requirement to restock), national forest estate administrative information and land conversion ratios from Countryside Survey. Details are given in Annex 5.1.4.5. • Data on wildfires on agricultural land and moorland from Fire and Rescue service and satellite data (see Section 6.3.2 for further details). 6.4.3 Land-use definitions and the classification system used and their correspondence to the LULUCF categories Grassland that has undergone land -use change and direct management is defined in accordance with the Agriculture, Forestry and Other Land Uses guidance (volume 4, IPCC 2006). There are also large areas of extensively grazed semi -natural grassland on minera l soils, which are assigned to the 4.C.1 “Undisturbed grassland” sub-category and calculated as the area remaining after all other land use areas are subtracted from the total UK land area. This is the buffer land use category for the UK, so may contain small areas of other land uses that are not directly managed. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 426 Grazing is the main land use on semi-natural peatland habitats that would otherwise fall within in the Wetland category, so areas of peatland habitat not used for peat extraction or not explicitly identified as near-natural bog or fen, are included in the Grassland category. Areas of grassland that have undergone rewetting (or other activities that restore peatland habitats and reduce emissions) remain within the Grassland category. The grassland and semi -natural habitat types in the different data sources that contribute to the Grassland category are described in Annex 5.1.4.3.1. Activity data for land -use change are estimated using a land -use change (LUC) matrix approach. Detailed descriptions of the methods, emission factors and data flows used for the Grassland activities are given in Annex 5.1.4.3. Land use change on organic soils is split out from the land-use change matrices to produce a non-organic soil set of LUC change matrices. Emissions arising from land use and land -use change on organic soils are calculated using methodologies consistent with chapters 2 and 3 of the 2013 IPCC Wetlands Supplement described in Annex 5.1.4.7. The dynamic model of soil carbon stock change is described in Section 6.3.4.1.
Biomass carbon stock change is calculated using the LUC matrix and literature-derived Tier 2 stock change factors with all stock gains or losses assumed to occur in a single year. Direct and indirect N2O emissions associated with the non-organic soil disturbance from LUC are reported using the appropriate areas of Grassland remaining Grassland and Forest land converted to Grassland from the LUC matrices and the IPCC Tier 1 emission factors. Carbon stock changes in biomass due to grassland management activities are estimated using literature-derived Tier 2 stock change factors and activity data from agricultural surveys. All carbon stock changes associated with changes in the length and condit ion of hedgerows are Emissions of carbon and CH 4 from Grassland on drained and undrained organic soils, and N2O emissions from unintensive grassland, are reported using Tier 2 emission factors (Annex 5.1.4.7). Emissions of N2O from intensive grassland on organic soils are calculated using the same activity data and are reported in category 3.D in the Agriculture sector. 6.4.4.4 Biomass burning emissions Emissions from controlled burning on grassland are only reported for Forest Land conversion to Grassland and are estimated using Tier 1 emission factors and country -specific fuel densities. See Annex 5.1.4.6 for further discussion of controlled burning for game management on upland habitats. Emissions from wildfires on Grassland (agricultural grassland and semi-natural grassland) are reporting using Tier 1 emission factors and activity from a range of sources (see Section In 2023 the DESNZ-funded GHG Inventory Improvement Project “Earth Observation Detection of UK Wildfires for LULUCF Reporting” investigated whether the use of earth observation/satellite imagery could improve the wildfire activity data timeseries and potentially be implemented in calculations for emissions from wildfire burning of soil organic matter (on organic soils). A key finding was that satellite burnt area products could not be used as stand- alone datasets to reliably estimate wildfire burnt areas, as there was poor correspondence with

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 427 fire locations in the administrative records, producing high random uncertainty. The results of this project have not been implemented in the current inventory. 6.4.5 Uncertainties and Time-Series Consistency The uncertainty in 1990 and 202 3 respectively are estimated at 15% for CO 2, 35% for CH 4, and 40% for N2O. These uncertainties are based on an uncertainty analysis using the updated activity data and methodology for this submission. Details are provided in Annex 5.1.4.12. The areas undergoing land -use change are the biggest source of uncertainty in the LULUCF inventory (see Annex 5.1.4.12). With regard to time series • Drainage of organic it is assumed that all drainage of organic soils under Grassland occurred before 1990, as recent policy has favoured protection of organic soils. There have been no policy incentives to encourage new land drainage for agricultural use since before 1990, and major drainage of large areas of improved Grassland on organic soils in areas such as the Somerset Levels fens is known to have occurred well before this. An area of 109.62 kha of grassland has been rewetted since 1990, and an area of 1.139 kha has been converted to peat extraction since 1990. • Changes in biomass and soil carbon due to the land-use change data assimilation methodology draws on multiple data-sources and takes account of random uncertainty and false positive rates. The time series now show more inter-annual variation but more • Controlled biomass burning after conversion of Forest Land to there is good time series consistency as there has been continuity in the activity data source. • Grassland activity data come from Countryside Survey, which is also used to estimate change in carbon stocks due to land -use change and has good • a consistent dataset is used for 2010 onwards. Burnt areas are extrapolated back to 2001 based on remote sensing data, but between 1990 and 2001 there are no observed data on the extent of wildfires on Grassland, and the time series is filled by extrapolating the 2001 - 2011 average wildfire area. 6.8). The largest contributing sub -categories/pools for carbon dioxide are from Grassland remaining Grassland organic and mineral soils and Cropland converted to Grassland mineral soils. The largest contributory sub -category for methane is almost entirely emi ssions from drainage and rewetting of organic soils. C.1. Grassland remaining Grassland 61% 67% biomass due to land use change 0% 0%

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 428 C.2.a. Forest Land converted to C.2.b. Cropland converted to Grassland 35% C.2.d. Settlements converted to 4(II) Emissions and removals from drainage and rewetting and other management of organic and mineral 1 Percentages may not sum to 100% due to rounding 6.4.6 Category-Specific QA/QC and Verification This source category is covered by the general QA/QC procedures, which are discussed in As discussed in Section 6.3.6 resampling of the 1980-based National Soil Inventory (NSI) in England and Wales in 1995-2003 found large losses of soil carbon across all land use types (Bellamy et al. 2005) but, a more recent study using Countryside Survey (CS) data (Reynolds et al. 2013) found no significant change in soil carbon stocks under most Grassland habitat types between 1978 and 2007. The possible reasons for these differences are unclear, as 6.4.7 Category-Specific Recalculations The Category 4C net source has increased by between 0.0 to 0.3 Mt CO 2e across the time series compared to the previous inventory. The changes were mainly in carbon stock change as a result of newly available deforestation activity data. The changes and their justification • Updates to organic soil areas. New activity data on existing and rewetted organic soils have been included and consistency improvements have been implemented. The rewetted fen areas between grassland and wetland have been separated in the methodology to ensure that these areas end up in the right LULUCF categories after • Updates to deforestation areas .
Newly available activity data for deforestation to grassland in England has been included. • Updates to wildfire activity data. Wildfire activity data from Wales was not available for 2022 in the previous submission but is now included. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 429 value Units Comment / Justification in soils - organic soils 1590.16 1341.75 1589.65 1347.16 Gg C 4.C.2.a/4(IV) Biomass burning - controlled burning 5.77 46.10 5.76 71.48 Gg C Updates to deforestation areas 4.C.2.a Carbon stock change in living biomass - Losses 8.18 60.97 8.19 95.87 Gg C 4.C.2.a Net carbon stock change in dead organic matter 1.93 19.83 1.91 29.41 Gg C 4.C.2.a Net carbon stock change in soils - organic soils 0.10 22.69 0.10 22.76 Gg C 99.994 101.256 99.971 101.444 Gg CH4 wildfires 0.331 0.414 0.330 0.478 Gg CH4 Updates to wildfire activity data 4.C.2.a/4(IV) Biomass burning - controlled burning 0.063 0.506 0.063 0.785 Gg CH4 Updates to deforestation areas 0.417 0.363 0.417 0.368 Gg N2O wildfires 0.015 0.028 0.030 0.044 Gg N2O Updates to wildfire activity data 4.C.2.a/4(IV) Biomass burning - Controlled Burning 0.004 0.028 0.003 0.043 Gg N2O Updates to deforestation areas

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 430 6.4.8 Category-Specific Planned Improvements See Section 6.3.8 for planned improvements also affecting the Grassland and Settlement A BEIS -funded research project on GHG emissions from lowland wasted peat soils under intensive agriculture was delayed by the COVID-19 pandemic. Flux tower measurements from this study have been used to develop a specific Tier 2 CO2 EF for Cropland on Wasted Peats, present, separate EFs for grassland on wasted peat cannot be derived due to lack of data, and measurements are ongoing for N2O.Analysis of the results has not yet been finalised. Emissions sources 4D Carbon stock change 4(II).D Emissions and removals from drainage and rewetting and other management of organic and mineral soils Methods T2 for organic soils, T1 for water bodies Emission Factors T2 for direct CO2 and CH4 emissions from organic soils, T1 for Key Categories 4D Wetlands- CH4 (L1, T1, L2, T2) Completeness No known omissions- areas are reported for land uses with no since last submission No major improvements This section describes LULUCF emissions and removals from Wetland in the UK. A description of LULUCF emissions and removals from the OTs and CDs is given in Section 6.9. Net emissions from the Wetlands category includes emissions peatlands that are cleared and drained for peat production (for energy or horticultural purposes); areas of near -natural peatland; areas of former peat extraction, forest and cropland that are now rewetted; and areas converted to permanently flooded land (reservoirs). Emissions from on -site peat production and off -site emissions from horticultural peat are reported under 4.D.1.a and 4(II).D.1.a. Areas of former peat extraction that are now rewetted are reported under 4.D.1.c and 4(II).D.1.c. Areas of conversion to Wetla nd of grassland converted to Wetland for peat extraction are reported under 4.D.2.a and 2(II).D.2.a; grassland converted to flooded land are reported under 4.D.2.b and 4(II).D.2.b; and rewetted former forest and cropland are reported under 4 D.2.c and 4(II).D.2.c. The associated emissions and living biomass carbon stock changes estimated using the appropriate Tier 1 or 2 The area of UK natural inland water is reported in the category Other Wetlands remaining Other Wetlands (4.D.1.c) and the area of reservoirs created before 1990 is reported in Flooded Land remaining Flooded Land (4.D.1.b). Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 431 6.5.2 Information on approaches used for representing land areas and on land use databases used for the inventory preparation The approach used for representing Wetlands differs from that used for other land use categories because peat extraction sites and reservoirs are not explicitly identified in the habitat and landscape surveys used for the land use matrix. The area of wetlands on organic soils in the UK was revised based on peatland extent and condition mapping outputs from the BEIS-funded project to implement the IPCC Wetland Supplement (Evans et al . 2017) and subsequent updates. This included areas of near-natural wetlands and rewetted organic soils as well as areas of inactive peat extraction(see Annex 5.1.4.7 for details). This information is supplemented by the areas of active peat extraction obtained from the Directory of Mines and Quarries, Google Earth, the Minerals Extraction in Great Britain report (and its predecessor the Minerals Raised Inquiry, Office for National S tatistics), and site operations data provided by Growing Media Association . These sources and papers on peat extraction in Northern Ireland were used in combination to produce an activity dataset for active peat extraction areas in the UK (see Annex 5.1.4.8 for further details). Activity data for post -1990 constructed reservoirs were compiled from the Public Register of Large Raised Reservoirs (supplied by the Environment Agency for England and Wales) and the SEPA Water Body Classification database (see Annex 5.1.4.9 for further details). The remaining area of inland water (natural water bodies and reservoirs established before 1990) is known from the area of inland water reported as part of the Standard Area Measurement. There are no emissions or removals associated with this area. 6.5.3 Land-use definitions and the classification system used and their correspondence to the LULUCF categories Areas of active peat extraction are defined as areas that are currently undergoing, or have recently undergone, peat extraction activities (locations are known from administrative see Section 6.5.2). It is assumed that extraction areas continue to produce emissions while there is visible evidence of exposed peat soil from Google Earth satellite imagery, and do not convert back to functioning peatlands without restoration intervention.
An extraction site is considered to have ceased emissions when there is visible evidence of the re -establishment of wetland vegetation cover on the satellite imagery and evidence of rewetting (ditch blocking) from online documentation of the restoration works and communication with site managers. “Near-natural” peatlands are areas that were identified in Evans et al (2017) as having no anthropogenic degradation but which can still be considered as managed e.g. for biodiversity purposes. They are a carbon sink but also a source of CH4 emissions. Rewetted peatlands are those that have undergone restoration activities to restore normal peatland biogeochemical functioning. These have been identified from a database of peatland restoration projects (see Annex 5.1.4.7) and more recent government-funded restoration. The area of inland water is taken from the “UK Standard Area Measurements” (Office for National Statistics). It defines inland water as ‘bounded’ permanent water bodies, e.g. lakes, lochs and reservoirs, exceeding 1 km2 (100 hectares) in area. ‘Open’ tracts of water, e.g. rivers, canals and streams are excluded from this definition. Reservoirs (flooded land) were identified either by their inclusion in the Public Register of Large Raised Reservoirs or by their classification as “Heavily modified” in the SEPA Water Body Classification database. Areas of water below the size threshold are included in the 4F Other Land category. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 432 Emissions from peat extraction are estimated using Tier 1 and Tier 2 methodology, which does not distinguish between peat extraction production phases, i.e. it includes conversion and vegetation clearing. On -site emissions associated with peat extraction a re reported under 4.D.1.a. For on-site emissions due to extraction activities and drainage, a Tier 2 CO2 emission factor is employed for Industrial (horticulture) Extraction, and a Tier 1 CO 2 emission factor (IPCC, 2014) is used for Domestic (fuel) Extract ion. A Tier 2 CH 4 emission factor and Tier 1 N2O emission factor is applied to emission estimates for both Industrial and Domestic Peat Extraction (see Annex 5.1.4.7). Off-site carbon emissions from horticultural peat that has been extracted are assumed to be emitted during the extraction year. Mapping outputs from Evans et al. (2017) and administrative records categorise sites as producing horticultural or energy source (fuel) peat. Further information is given in Annex 5.1.4.8. Google Earth imagery is used to track the area change of individual extraction sites over time. Google Earth imagery is checked annually and extraction site areas are updated as new The site records show that the area under active horticultural peat extraction between 1990 and 2023 diminished for England, and decreased slightly overall for Scotland, but is more variable for Northern Ireland. No peat extraction is reported in Wales. The time series of active fuel peat extraction has decreased across the UK. Sites that have no active record of extraction, and show no change in area on the Google Earth imagery, are assumed to be abandoned extraction sites that are still producing emission s (reported under 4D1). Sites where extraction is no longer visible on the Google Earth imagery are identified as potentially being restored to rewetted Wetland and investigated further. As these sites are often part of peatland restoration schemes managed by UK nature reserves, information on site history and success of the restoration (rewetting) works are gathered online and from reserve managers to support reporting a condition change. Changes in organic soil carbon from this condition change are estimated using a Tier 2 approach based on the IPCC 2013 Guidelines. A small area of land conversion to Wetlands (all from Grassland) occurs across the time series. This area and the associated on-site emissions are reported under 4.D.2.a Land converted to Wetlands. Rewetted former peat extraction sites remain as Wetland an d are reported under 6.5.4.2 Land converted to Flooded Land A Tier 1 methodology was applied for emissions from Flooded Lands (4.D.2.b). This estimated carbon stock changes in living biomass stock in the year of flooding (for reservoirs established since 1990) but not carbon stock changes in soils. The locations of the reservoirs were established on maps, and due to their location in upland areas, all were assumed to be Grassland prior to flooding. A living biomass density of 2 t dry matter/ha was used to estimate 6.5.4.3 Land converted to other wetlands Forest and cropland on organic soils that undergo rewetting are converted to Wetlands (4.D.2.c.i and 4.D.2.c.ii, respectively) as they do not retain their original land use. A Tier 2 methodology using areas and EFs from Evans et al (2017) is applied. Emiss ions from controlled burning following deforestation and carbon stock changes in biomass and dead organic matter are also calculated for conversion of forest land to wetland. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 433 6.5.5 Uncertainties and Time-Series Consistency The uncertainty in 1990 and 2023 respectively are estimated at 40% and 35% for CO 2, 55% and 50% for CH4, and 125% and 50% for N2O. These uncertainties are based on an uncertainty analysis using the updated activity data and methodology for this submission. Details are Time-series consistency for activity data for peat extraction sites is affected by uncertainty in survey dates but has been improved by the incorporation of additional site data from the Growing Media Association. Time -series consistency for flooded lands was good due to the complete nature of the data set. Methane emissions from category 4.D are a key category and are 100% and 99% due to respectively. In 2023 1% of CH 4 emissions are due to controlled burning (deforestation on organic soils for habitat restoration). 6.5.6 Category-Specific QA/QC and Verification Operational site areas are provided by the Growing Media Association (GMA). The UKCEH peat extraction database matched the GMA data closely for Scotland, Wales, and Northern Ireland, but were adjusted accordingly where more robust data were available.
For England, the inventory areas were revised downwards based on improved on-site information primarily The peat extraction site activity dataset has also been partially verified by comparing the measured areas with reported areas of planning permission, which were available for some extraction sites in England and Scotland. The measured areas either matched or were smaller than the planning permission areas, which is to be expected as it is known that not all areas with planning permission are undergoing active extraction. The locations and previous land -use of new reservoirs were verified using the geographic information portal. 6.5.7 Category-Specific Recalculations The Category 4D net source has reduced by between 0.0 and 0.1 Mt CO2e (-4.7%) across the time series compared to the previous inventory. This is mainly due to updates in the activity The changes and their justification • Updates to organic soil areas. New activity data on existing and rewetted organic soils have been included and consistency improvements have been implemented. The rewetted fen areas between grassland and wetland have been separated in the methodology to ensure that these areas end up in the right LULUCF categories after 20 • Updates to forest rewetting activity data. Newly available activity data for deforestation to wetland in Scotland(from 2013) and Northern Ireland (from 2020) has now been included. This is the first year that Forest to Wetland data for NI has been available. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 434 value Units Comment / Justification 4.D1.a Net carbon stock change in soils 652.00 527.07 651.97 527.55 Gg C 4.D.1.c Net carbon stock change in soils -495.98 -494.99 -495.98 -495.09 Gg C 4.D.2.a/4(IV) Biomass burning - controlled burning 0.00 29.08 0.00 17.60 Gg C Updates to forest rewetting activity data 4.D.2.c.i Carbon stock change in living biomass - losses 0.00 37.84 0.00 23.39 Gg C 4.D.2.c.i Net carbon stock change in dead organic matter 0.00 13.12 0.00 7.46 Gg C 4.D.2.c.i Net carbon stock change in soils 0.00 1.05 0.00 0.86 Gg C 82.47 85.52 82.47 85.06 Gg CH4 Updates to organic soil areas 4.D.2.a/4(IV) Biomass burning - controlled burning 0.00 0.32 0.00 0.19 Gg CH4 Updates to forest rewetting activity data 4.D.2.a/4(IV) Biomass burning - controlled burning 0.000 0.018 0.000 0.011 Gg

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 435 6.5.8 Category-specific planned improvements There are ongoing discussions with policy experts and peatland managers to improve the register of peat restoration activities across all nations of the UK and update the rewetting activity data as appropriate. A Defra -funded project to assess the status o f former domestic peat extraction for fuel in England is due to be completed in March 2025. This project will assess whether the current assigned peat condition category and associated EFs, which are similar to that of industrial peat extraction (for horticultural use) are appropriate for these areas. BEIS (now DESNZ) commissioned a review of current knowledge and gaps of GHG emissions and removals from UK coastal wetlands, which provided recommendations for moving towards inclusion of saltmarshes in the UK GHGI (Burden and Clilverd, 2022). Evidence gaps identified in this report were addressed in a Defra -funded project to provide a roadmap for inclusion of saltmarsh in the UK GHGI by defining terminology, and mapping implications of different terminologies on saltmarsh areal extent (Burden at al. 2024). Subsequent government-funded projects are underway - 1) compile a database of carbon stocks and GHG fluxes, 2) develop Tier 2 emission factors for saltmarsh, and 3) develop a baseline map of UK saltmarsh extent. Emissions sources 4.E Carbon stock change 4(II).E Emissions and removals from drainage and rewetting and other management of organic and mineral soils 4(III).E Direct and indirect nitrous oxide (N2O) emissions from nitrogen (N) mineralization/immobilization associated with loss/gain of soil organic matter resulting from change of land use or management of mineral soils Methods T3 for carbon stock changes, T2 for organic soils, T1 for other Emission Factors Country-specific for T3 methods, T2 for direct CO2 and CH4 emissions from organic soils, T1 for other emissions Key Categories 4E: Settlements – CO2 (L1, T1, L2, T2) Completeness No known omissions- areas are reported for land uses with no This section describes LULUCF emissions and removals from Settlement in the UK. A description of LULUCF emissions and removals from the OTs and CDs is given in Section Net emissions from the Settlements category include carbon stock gains and losses due to land-use change (LUC) and associated GHG emissions. It is the second largest net source in

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 436 Ongoing carbon stock changes in soils arising from LUC to Settlements are reported under both 4.E.1 Settlements remaining Settlements (for historic LUC >20 years before the inventory reporting year) and 4.E.2 Land converted to Settlements (for LUC in the past 20 years). Direct and indirect N2O emissions from N mineralization from these land use changes are reported in 4(III).E. These non-organic soil net carbon stock changes are the largest component of the category total emissions and are calculated using a Tier 3 dynamic soil carbon model. Other contributors to the Settlements net total emissions • Carbon, CH4 and N 2O emissions resulting from drainage of organic soils (4.E and • biomass carbon stock changes due to LUC (4.E.2); • N2O emissions from soil disturbance associated with LUC (4(III).E); and • biomass burning emissions of GHGs from controlled burning following forest land conversion to Settlements (4(IV).E.2.a). Full details of the methods and activity data are given in Annex 5.1.4. 6.6.2 Information on approaches used for representing land areas and on land use databases used for the inventory preparation The UK uses Approach 2 (IPCC 2006) for the representation of land use areas in the inventory and compiles several different data sources into a non -spatially-explicit land use conversion matrix (Annex 5.1.4.3.1 for details).
Data sources that contain area information for reporting carbon stock changes and/or emissions from Settlements • Habitat/landscape surveys (see Section 6.3.2). • Extent of settlement on organic soils (Evans et al. 2017 and further updates). • Land-cover from satellite imagery classification (see Section 6.3.2). • Data on deforestation areas from various sources; o Post-2000 deforestation areas are assessed from the NFI and administrative records of the conversion of areas in the public forest estate as part of habitat restoration and windfarm development. o Pre-2000 deforestation areas are estimated from unconditional felling licence data (felling licences granted without a requirement to restock), national forest estate administrative information and land conversion ratios from Countryside Survey. Details are given in Annex 5.1.4.5. 6.6.3 Land-use definitions and the classification system used and their correspondence to the LULUCF categories Settlement is defined in accordance with the Agriculture, Forestry and Other Land Use The settlement land-cover types in the different data sources that contribute to the Settlement category are described in Annex 5.1.4.3.1. Activity data for land -use change are estimated using a land -use change (LUC) matrix approach. Detailed descriptions of the methods, emission factors and data flows used for the Settlement activities are given in Annex 5.1.4.3.1. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 437 Land use change on organic soils is split out from the land-use change matrices to produce a non-organic soil set of LUC change matrices. Emissions arising from land use and land -use change on organic soils are calculated using methodologies consistent with chapters 2 and 3 of the 2013 IPCC Wetlands Supplement described in Annex 5.1.4.7. The dynamic model of soil carbon stock change is described in Section 6.3.4. Biomass carbon stock change is calculated using the LUC matrix and literature-derived Tier 2 stock change factors with all stock gains or losses assumed to occur in a single year. Detailed descriptions of the methods, emission factors and data flows used for the Settlement category are given in Annex 5.1.4.7. Direct and indirect N2O emissions associated with the non-organic soil disturbance from LUC are reported using the areas from the LUC matrices and the IPCC Tier 1 emission factors. Emissions of carbon, CH 4 and N2O from Settlements on drained organic soils are reported using Tier 2 and Tier 1 emission factors (Annex 5.1.4.7). 6.6.4.3 Biomass burning emissions Emissions from controlled burning on settlement land are only reported for Forest Land conversion to Settlements and are estimated using Tier 1 emission factors and country-specific 6.6.5 Uncertainties and Time-Series Consistency The uncertainty in 1990 and 2023 respectively are estimated at 45% for CO 2, 75% and 70% for CH4, and 115 and 110% for N2O. These uncertainties are based on an uncertainty analysis using the updated activity data and methodology for this submission. Details are provided in Annex 5.1.4.12. The areas undergoing land-use change are the biggest source of uncertainty in the LULUCF inventory (see Annex 5.1.4.12). With regard to time series • Drainage of organic It is assumed that all existing Settlement areas on organic soils are drained. The only land use change from Settlement on organic soils is to and from Forest land and the areas involved are small (1.639 kha to Forest Land since 1990, and 3.957 kha from Forest Land since 1990) and all assumed to be drained. • Changes in biomass and soil carbon due to the land -use change data assimilation methodology draws on multiple data -sources and takes account of random uncertainty and false positive rates. Estimated rates of change are lower and more gradual than in p revious submissions, although the uncertainty bounds are • Controlled biomass burning after conversion of Forest Land to there is good time series consistency as there has been continuity in the activity data source. A significance analysis has been undertaken for key categories in the LULUCF sector. Carbon stock changes in mineral soils in 4E1 Settlements remaining Settlements and 4.E2.3 E.1. Settlements remaining Settlements 27% 37%

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 438 E.2.a. Forest Land converted to 1 Percentages may not sum to 100% due to rounding 6.6.6 Category-Specific QA/QC and Verification This source category is covered by the general QA/QC procedures, which are discussed in 6.6.7 Category-Specific Recalculations The reported overall net GHG source in category 4.E has decreased by 0 - 0.01 Mt CO 2e across the time series compared to the previous inventory. The changes were mainly due to updates in deforestation activity data. The changes and their justification • Updates to organic soil areas. Updated activity data for settlement to forest on organic soil has affected the total area of settlement on organic soil • Updates to deforestation activity data.
Newly available activity data for deforestation to grassland in England has been included and affected the area of deforestation to

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 439 4.E.1 Net carbon stock change in soils - organic soils 3.15 2.95 3.14 2.96 Gg C Updates to organic soil areas 4.E.2.a/4(IV) Biomass burning - controlled burning 13.57 46.54 13.53 45.12 Gg C Updates to deforestation activity data 4.E.2.a Carbon stock change in living biomass - losses 19.26 61.53 19.28 59.70 Gg C 4.E.2.a Net carbon stock change in dead organic matter 4.53 20.05 4.44 19.39 Gg C 4.E.2.a Net carbon stock change in soils - organic soils 0.01 0.66 0.01 0.67 Gg C drainage and rewetting and other 0.53 0.61 0.53 0.61 Gg CH4 Updates to organic soil areas 4.E.2.a/4(IV) Biomass burning - controlled burning 0.15 0.51 0.15 0.50 Gg CH4 Updates to deforestation activity data 4.E.2.a/4(IV) Biomass burning - controlled burning 0.008 0.028 0.008 0.027 Gg N2O Updates to deforestation activity data

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 440 6.6.8 Category-Specific Planned Improvements See Section 6.3.8 for planned improvements also affecting the Grassland and Settlement Key Categories None identified Completeness No known omissions- areas are reported for land uses with no No emissions or removals are reported in this category in the UK. It is assumed that there are very few areas of land of other types that become bare rock or water bodies, which make up 6.7.2 Information on approaches used for representing land areas and on land use databases used for the inventory preparation The approaches used for representing land use areas in the inventory are described in 6.7.3 Land-use definitions and the classification system used and their correspondence to the LULUCF categories Other Land is defined as areas that do not fall into the other land use categories. The land - cover types in the different data sources that contribute to the Other Land category are described in Annex 5.1.4.3.1. As described in Section 6.4, areas of inland water exceeding 1km2 are included in 4D Wetlands, but water bodies below this threshold would still be included 6.7.4 Category-specific recalculations There are no emissions associated with Other Land and no recalculations. 6.7.5 Category-specific planned improvements

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 441 Emissions sources 4G Harvested Wood Products Emission Factors Country-specific Key Categories 4G Harvested Wood Products – CO2 (L1, T1) Completeness No known omissions HWP stocks result from normal forest management processes (thinning and harvesting) in the Forest Land category and from conversion of Forest Land to Cropland, Grassland or Settlements (deforestation). Carbon stock gains and losses from HWP in use from the The UK has elected to use the production approach B2 as set out in the IPCC 2006 Guidelines for estimating HWP. The carbon accounting model (CARBINE) is used to calculate the net changes in carbon stocks of harvested wood products (at the product type level), in the same way as it is used to estimate carbon stock changes in 4.A Forest Land. Changes in carbon stocks from HWP arising from deforestation (conversion of Forest Land to Grassland, Cropland or Settlement) are also estimated using CARBINE. The estim ated carbon in harvested wood is split in to harvested wood product classes based on information on wood use from Forestry Commission statistics and the FAO, producing a time series from 1961 to the latest inventory year. A description of the method is out lined in Annex 5.1.4.10. Data from the Forestry Statistics on consumption of wood products in the UK are then used to disaggregate the HWP into either consumed domestically or exported. This dataset exists from 2002 onwards and the 2002-2011 average values are used for 1990-2001. 6.8.3 Uncertainties and Time-Series Consistency 4G Harvested Wood Products is estimated to have a combined uncertainty of 15-20% for CO2. These uncertainties are based on an uncertainty analysis using the updated activity data and methodology for this submission. Details are provided in Annex 5.1.4.12. Activity data for areas planted and consequently harvested are obtained consistently from the same national forestry sources, which helps ensure time series consistency of estimated removals. Data on the total quantity of softwood and hardwood production a re available from 1976 using Forestry Commission reported statistics and from 1961 -1975 using FAO timber production data. Data on the relative proportions of wood from UK sources used for different harvested wood products is available from 1994 onwards, th e proportions prior to 1994 are estimated from FAO data. Data on the export of products is also obtained from national forestry sources, however it is only available from 2002 onwards. The 1990-2001 values are based on the ten-year average of the 2002-2011 values. Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 442 A significance analysis has been undertaken for key categories in the LULUCF sector. In Harvested Wood Products HWP Produced and Consumed Domestically is the most significant HWP Produced and Exported 15% 2% 6.8.4 Category-Specific QA/QC and Verification This source category is covered by the general QA/QC procedures, which are discussed in Section 6.10. The timber production predicted has been compared to the national timber production statistics produced by Forest Research based on timber sales data from the public forest estate, a private sector softwood removals survey, a survey of sawmills, a survey of round fencing manufacturers and a survey of pellet and briquette production. 6.8.5 Category-Specific Recalculations The reported overall net GHG sink in category 4G has increased by between 0.0 and 0.4 Mt CO2e (0 to 2%) across the time series compared to the previous inventory. • The changes resulted from updated activity data for afforestation, deforestation and wood production, as described in Section 6.2.7.
Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 443 value Units Comment / Justification consumed domestically -489.38 -588.48 -489.88 -577.70 Gg C 4.G HWP produced and exported -84.10 -13.65 -84.14 -12.37 Gg C

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 444 Emissions sources Carbon stock 4.A Forest Land, 4.B Cropland, 4.C Grassland, 4.D Wetlands, 4.E Settlements 4(II) Emissions and removals from drainage and rewetting and other management of organic and mineral soils (4.A Forest Land, 4.B Cropland, 4.C Grassland) 4(III) Direct and indirect N2O emissions from N mineralization (4.B Cropland, 4.C Grassland, 4.E Settlements) 4(IV) Biomass Burning (4.A Forest Land, 4.C Grassland) Methods Tier 1, T2 for organic soils Emission Factors T1 and T2 for direct CO2, CH4 and N2O emissions from organic soils, T1 for other emissions Key Categories None identified Completeness No known omissions GHG emissions and removals from the UK Crown Dependencies (CD) and Overseas Territories (OT) are reported under the relevant categories for the LULUCF sector in the CRT Guernsey and the Isle of Man and the OTs of the Falkland Islands, Cayman Islands and Bermuda. Gibraltar has only one land-use category of Settlement remaining Settlement, with no associated GHG emissions. Annex 5.1.4.11 provides detailed descriptions of the methods Crown Dependency/ Overseas Territory 1990, Mt CO2e 2023, Mt CO2e

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 445 The Forest Land and Grassland categories are net sinks in the OTs and CDs while other land use categories are net sources. The LULUCF sector in the OTs and CDs is a net source in all years. The individual territory trends • Isle of increasing net sink, with net sources in cropland and settlement counterbalanced by net sinks in forest and grassland • small net sink, with net sources in cropland and settlement counterbalanced by net sinks in forest and grassland • moves between being a small net source to a small net sink across the time series, with net sources from cropland, settlements and wetlands and a net sink in • Falkland stable net source 1990-2005, then variable slowly decreasing source due to reduced emissions from cropland • Cayman stable net source 1990 -2006, then a variable net source primarily due to conversion of mangrove (organic) soils to settlement and forest conversion to • small stable net source 1990 -2011 due to forest conversion to settlement, becoming a very small net sink from 2012 due to a net sink in settlement. Land cover surveys and agricultural land statistics have been used to compile annual land- use change matrices for the OTs and CDs, which are converted into the UNFCCC land -use change matrices using the 20 -year transitions (reported in CRT tables 4.A -4.E in the GBR submission). The total land area of the OTs and CDs is mainta ined at a constant area by including a small area of unmanaged wetland to account for land reclamation from the sea in The definition of each land category is in accordance with the Agriculture, Forestry and Other Land Use Guidance (IPCC 2006). The Grassland category is used as the ‘buffer’ category to ensure consistency in total land area. Similar climate and land management parameters are assumed as for the UK for Guernsey, Jersey and the Isle of Man. Appropriate parameters for the other OTs have been taken from the IPCC 2006 and 2013 guidance (Annex 5.1.4.11). There is incomplete information on land areas for all territories, so land areas have been interpolated between, or extrapolated from, land area surveys as required. A Tier 1 method has been used to estimate forest carbon stock changes for all territories, using the appropriate emission factors for the climatic region and forest type. The IPCC Tier 1 default factors from the 2006 Agriculture, Forestry, and Land Use (AFOLU) Guidelines and the Tier 1 EFs for mangroves from the 2013 Wetland Supplement have been used to estimate all other emissions and removals. The net LULUCF emissions from the OTs and CDs changed compared to the previous 2022. The main recalculation arose from updates to the area of Other Land in the Cayman

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 446 Islands, and a correction to the implementation of the carbon fraction used for biomass losses in Land converted to Settlement in the Cayman Islands. Total LULUCF 0.038 0.041 0.015 0.030 A. Forest Land -0.041 -0.041 -0.083 -0.085 B. Cropland 0.013 0.013 0.025 0.043 C. Grassland -0.010 -0.010 -0.029 -0.029 D. Wetlands 0.000 0.000 0.001 0.001 E. Settlements 0.076 0.079 0.101 0.101 The UK Government is funding longer -term research into organic soils and emissions in the Falkland Islands. There a new peatland map of the Isle of Man uplands102 that could potentially be included in the next inventory. Peat extent and depths have been mapped by the Darwin Plus project DPLUS083, and there are ongoing projects to map undisturbed reference habitats, estimate above -ground biomass stocks and measure C O2 and CH 4 fluxes. The Falkland Islands have different peat-forming species to the Northern Hemisphere, and UK Tier 2 emission factors are an imperfect analogue for Falkland conditions, hence the need for UKCEH has adopted the quality assurance principles set out in the Joint Code of Practice for Research issued by the Biotechnology and Biological Sciences Research Council, the Department for Environment, Food and Rural Affairs, the Food Standards Agency an d the Natural Environment Research Council. UKCEH is accredited to ISO9001, the internationally recognised standard for the quality management of businesses. Forest Research are dedicated to delivering world-class scientific research which fully meets our customers’ requirements for quality, timeliness and cost. The quality of science is supported by a Quality Management System (QMS) which ensures that appropriately-trained and qualified personnel use correctly maintained and calibrated equipment and appropriate techniques to produce reliable outputs.
Our system of records management enables us to fully demonstrate the quality of our science. Forest Research applies the standards required by the Defra Joint Code of Practice for Research as described above for UKCEH. The Expert Committee on Forest Science provides guidance for the Forestry Commission on the quality and direction of their research. 102

Land-Use, Land Use Change and Forestry (CRT Sector 4) 6 UK NID 2025 (Issue 1) Ricardo Page 447 In 2015 a review of the QA framework and procedures for the full UK inventory was carried out (Hartley McMaster Ltd, 2015). In 2016 all the LULUCF models based in Excel spread spreadsheets were reviewed by Hartley McMaster using a bespoke quality auditing tool developed in Excel. The outputs from this auditing tool resulted in improvements to model documentation and the correction of a few minor errors. In addition to internal quality assurance procedures the submitted inventory data is also checked by Ricardo (the national inventory compilers) and the European Environment Agency, as part of the European Union Monitoring Mechanism. A programme of upgrade to the LULUCF models ran from 2016 to 2020. This included verification of model calculations, improvement of documentation, addition of built in QA checks and storage in a version control repository. A Microsoft Access database is us ed to compile all the LULUCF inventory numbers and associated data. This database is used to produce consistent outputs for the CRT and other national and international reporting requirements, and for archiving purposes. In collaboration with Ricardo, UKCE H has developed a QA/QC plan to standardise and structure the way checks are carried out within the LULUCF inventory. The plan is implemented and revised as required in each inventory cycle. The QA/QC Plan is embedded into all planning, preparation and management activities of the Inventory. The plan sets out five key Data Quality Objectives (DQOs), covering Transparency, Consistency, Completeness, Comparability and Accuracy, which ensure consistency to the IPCC core QA/QC criteria during inventory preparation and checking. UK NID 2025 (Issue 1) Ricardo Page 448 5A: Solid Waste Disposal on Land 5B: Biological Treatment of Solid Waste Gases Reported CO2, CH4, N2O, NOx, CO, NMVOC, SO2 5A: Solid waste disposal – CH4 (L1, T1, L2, T2) 5B: Biological treatment of waste – CH4 (T1, L2, T2) 5B: Biological treatment of waste – N2O (L2, T2) 5C: Waste incineration – CO2 (L2, T2) 5D: Wastewater handling – CH4 (L1, L2) 5D: Wastewater handling – N2O (L2, T2) Emissions from all sectors are included within UK CRT tables. Completeness No known omissions. A general assessment of completeness for the inventory is Revised estimates for 5A, solid waste disposal 5D2, based upon an average delay of 6 months before the decay reaction commences; for 5D municipal wastewater treatment, based upon a new tier 1 approach for release of sewage sludge Emissions from the waste sector contributed 5.2% to greenhouse gas emissions in 2023. Emissions consist of CO2, N2O and CH4 from waste incineration, CH4 from solid waste disposal on land, and both CH 4 and N2O from wastewater handling and biological treatment of solid waste. Overall emissions from the waste sector have decreased by 72% since 1990. This is mostly due to the implementation of methane recovery systems at UK landfill sites and reductions in the amount of waste disposed of at landfill sites from Monte Carlo analysis. Emission trends are presented for 1990 -2023 and 2022-2023. A description of the trends and the main drivers behind these can be found in Chapter 2. UK NID 2025 (Issue 1) Ricardo Page 449 Total waste 20.07 -72% -1% 6% -3% 103 The categories in the Waste sector are explained in the IPCC categories section. UK NID 2025 (Issue 1) Ricardo Page 450 7.1.1 Waste Related Activities Reported in Other Sectors The waste sector as defined in the 2006 IPCC guidelines relates to emissions from processes associated with the treatment and disposal of waste. However, if waste or waste -derived products are utilised for another process, emissions associated with this are reported according to the process, and therefore excluded from waste sector reporting. This section discusses such sources, where those sources are reported in the inventory, and how waste management, waste disposal and waste utilisation interact in the waste, energy and agriculture sectors, and where these are reported in the inventory. UK NID 2025 (Issue 1) Ricardo Page 451

UK NID 2025 (Issue 1) Ricardo Page 452 of increasing redirecting of waste away from landfill and into either biological treatment of waste or energy from waste; this is further illustrated in the decline in diges tible and in quantities of non -degradable waste recycling (such as plastics, glass, and metals) or exported from the UK, as within this context these do not directly generate emissions, and therefore are not explicitly referred to in the inventory. It is expected that at least some of the decline in total waste presented will be due to increase in non-degradable recycling rates. of its combustibility and digestibility. Data are presented only for 2008 onwards as detailed breakdown of waste composition by European Waste Catalogue classification is available for these years only.
Note that a large proportion of waste is classified as unspecified mixtures of waste, meaning that there is significant uncertainty as to the classification presented; the 104 Recycling or waste exported are not included, as these do not result in direct emissions occurring in the UK, and therefore it has not been a priority for Inventory Agency to collect estimates of the quantities of waste disposed by these routes Solid waste disposed (Mt wet weight) Energy from Waste (1A1a) Other use of waste as a fuel (1A2/1A4) Anaerobic Digestion (5B) MSW Incineration (5C) Other waste incineration (5C) Small-scale waste burning (5C)

UK NID 2025 (Issue 1) Ricardo Page 453 7.1.1.1 Utilisation of Waste-Derived Biogas A large proportion of methane generated in the anaerobic digestion of biodegradable material, occurring in sewage treatment plants, landfills and sites conducting biological treatment of solid wastes is captured and utilised as a fuel. Fuel use is typically on -site with the energy used for other activities on the site, or exported as electricity, but also increasingly, some methane is injected into the national natural gas distribution network for use as a fuel by any user of natural gas. Using methane as a fuel oxidises it, preventing it being released into the atmosphere as methane, instead releasing carbon dioxide and very small quantities of methane and nitrous oxide. The emissions as a result of combustion of biogases for energy is reported in sector 1A, including biogases that are injected into the national natural gas distribution network. The UK includes emissions from the utilisation of biogases for energy as • Sewage gas and landfill gas used to generate electricity or heat are reported in sector • Other biogases used for energy are reported in sector 1A2gviii, described in MS 3; • Any biogases that are injected into the natural gas network are reported in energy statistics as a transfer from the renewables balance to the natural gas balance and are therefore included in the inventory as part of natural gas in all downstream uses of natural gas, mostly in various sub-sectors in 1A, described in various sub -sections in Section 3. Data on the quantity of biogases transferred to natural gas are used to determine the proportion of CO2 emissions from natural gas combustion which are of Note that for all sources of biogas, in the 2022 update of DUKES data reported for 2019 onwards has been reduced significantly compared to what DUKES reporting in 2021. In most cases this creates a divergence in the agreement between DUKES (and therefor th e NAEI 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 Solid waste disposed to landfill (Mt wet weight) Digestible, Non-combustible Digestible, Combustible Non-digestible, Non-combustible Non-digestible, Combustible Not clearly combustible or digestible

UK NID 2025 (Issue 1) Ricardo Page 454 energy sector estimates) and the NAEI waste sector estimates for recent years, and we are engaging with the UK energy stats team to understand how to interpret this. wastewater company reported estimates of sewage gas utilisation and UK energy statistics on sewage gas when noting that methane flaring is not a fuel use application, so is excluded from energy statistics. Data are only presented for 2013 onwards, as company reported data in this format is only available for these years; estimates of methane recovered for earlier years are extrapolated based on UK energy statistics. When capture is compared to emission rates, we see implied capture rates of 95 -98% in these years, which is within the range suggested in the 2006 IPCC guidelines to expect. utilisation and UK energy statistics on landfill gas when noting that methane flaring is not a fuel use application, so is excluded from energy statistics. Both UK energy statistics and landfill gas capture estimates for landfill gas utilisation are based on data on electricity generated from engines consuming landfill gas, however, for landfill gas capture estimates we estimate that these engines improve in efficiency in more recent years, reducing the landfill gas required to generate the electricity observed. The UK Inventory Agency and energy statistics team are aware of this difference and are considering whether these can be aligned. 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 Company reported sewage gas flared Company reported sewage gas injected into the grid Company reported sewage gas utilised (excl. injection) UK Energy statistics sewage gas utilised (incl. injection)

UK NID 2025 (Issue 1) Ricardo Page 455 manure solid waste anaerobic digestion emissions estimates and UK energy statistics on other biogas use. Data are only presented for 2008 onwards, as all datasets present extremely low values in the early part of the time -series. It is not currently feasible to make more direct comparisons between the waste and energy sector due to the energy sector biogas including biogas derived from animal manures and the non -animal manures solid w astes estimates If comparing non-animal manure solid waste anaerobic digestion emissions estimated to total biogas utilisation, the implied capture rate strictly increases from 95% in 2009 to over 99% since 2016. We suspect that the very high implied capture rate in recen t years reflects an increasing contribution from manure anaerobic digestion biogas capture and utilisation, which will be included in the methane utilisation data, but not in the non-manure anaerobic digestion Inventory estimate of landfill gas utilised Inventory estimate of landfill gas flared Landfill use estimated for the energy sector

UK NID 2025 (Issue 1) Ricardo Page 456 Information about the methods and data relating to waste incineration is reported under Section 7.4 and emissions are reported under sector 5C. However, if useful energy is extracted from waste incineration, then for inventory reporting purposes, the activity is considered an energy sector process and emissions are reported under 1A.
Due to a ban on the incineration of MSW without energy recovery in 1996, the quantity of emissions that are The UK includes emissions from the combustion of waste for energy as • Energy from Waste plants are reported in sector 1A1a, described in MS 1; • A range of industries’ use of waste are reported in sector 1A2, described in MS 2 and, • Commercial and public sector use of waste is reported in sector 1A4, described in MS 7.1.1.3 Biological Treatment of Waste The reporting of biological treatment (composting or anaerobic digestion) of waste depends on the nature of the waste treated. • For animal manure emissions are reported against 3B, described in Section 5.3; • For sewage, industrial liquid wastes, or sludge derived from these wastes that are treated at a wastewater treatment plant emissions are reported against 5D, described • For other solid wastes emissions are reported against 5B, described in Section 7.3. 7.1.1.4 Utilisation of Digestates and Sewage Sludge If digestates or sewage sludge are utilised as a fertiliser, then any emissions from the spreading of these products are reported as an agricultural soils emission, 105 i.e., not sewage gas or landfill gas 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 Emissions estimates (kt methane) Other biogas use estimated for the energy sector UK Energy statistics energy biogas injected into the grid Inventory estimate of emissions (solid waste other than animal manure anaerobic digestion)

UK NID 2025 (Issue 1) Ricardo Page 457 • For digestates spread on agricultural land emissions are reported against 3D12c, described in Section 5.5.2.3.2; and, • For sewage sludge spread on agricultural land emissions are reported against 3D12b, described in Section 5.5.2.3.1. spread on agricultural land and waste digested or waste sector estimates of sewage sludge disposed to agricultural land. For agricultural waste spreading, a nitrogen balance approa ch is used to estimate N2O emissions, and hence activity data for those sources are in terms of Nitrogen content instead of total mass. for Digestates and Sewage Sludge 7.1.1.5 Disposal Routes of Sewage Sludge (Other than Utilisation) The reporting of disposal emissions of biologically treated waste depends on the nature of the 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 Spread on agricultural land (kt N) Non-manure digestate spread Non-manure digestion 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 Sludge disposed to agriculture (kt) Spread on agricultural land (kt N) Agriculture estimate of sewage sludge spread Water sector estimate of waste sent to farmland

UK NID 2025 (Issue 1) Ricardo Page 458 • For sewage sludge disposed to landfill emissions are reported against 5A, described • For sewage sludge incinerated without energy recovery emissions are reported against 5C, described in Section 7.4. sludge disposal to landfill or incineration and the estimates of sewage sludge received at landfills and incineration plants. Note that data for sewage sludge received at landfills are the total weight of matter received, which means it includes a large proportion of water which would not be included in the wastewater data presented in kt tds. Sector Estimates for Sewage Sludge disposal Water sector estimate of sewage incineration Incineration sector estimate of sewage sludge incineration (5C) 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 Water sector estimate of sewage to landfill Landfill sector estimate of sewage sludge to landfill (5A)

UK NID 2025 (Issue 1) Ricardo Page 459 7.2.1 Source category description Emissions sources Sources included Method Emission Key Categories 5A: Solid waste disposal - CH4 (L1, T1, L2, T2) OT & CD emissions for 5A are included as a separate Completeness No known omissions. A general assessment of completeness for the inventory is The NAEI category “Landfill” maps directly on to IPCC category 5A (Solid Waste Disposal) for methane emissions. Emissions are reported from Solid Waste Disposal Sites (SWDS – also known as landfills) that started receiving waste in 1980, when legislative changes took effect to improve management of landfill sites, and old unmanaged waste disposal sites that closed prior to 1980. Emissions from the use of landfill gas to generate power are reported in IPCC Estimated emissions from this sector in 2023 were 13.5 Mt CO2e. Emissions have been on a downward trend in almost every year since 1996. In addition to CH 4, anaerobic decomposition also produces an approximately equivalent amount of CO2, and CO2 is produced by other processes. However, as the decaying organic matter originates from biomass sources derived from contemporary crops and forests, we do not need to consider the greenhouse impacts of this carbon dioxide. For this reason, emissions of CO2 from landfills are not estimated as they are considered to be entirely biogenic in origin and therefore not counted towards the national total as this would introduce a double count with net carbon losses reported in the LULUCF sector (this is also discussed in Section 1.7.4.3). Landfilled Solid Waste also contains fossil-derived organic matter, predominantly in the form of plastics, but it assumed that these are essentially non-biodegradable under landfill conditions, and so emissions of fossil-derived CO2 from SWDS are not considered further. Non-methane volatile organic compounds (NMVOCs) are also released by SWDS. These are estimated using an emission factor relating the NMVOC to the amount of CH 4 emitted. The IPCC Guidelines do not provide emission factors for NMVOCs, therefore emission factors from the EMEP/EEA Air Pollutant Emission Inventory Guidebook are used. An emission factor of 0.0036 kg NMVOC/tonne landfill gas was used.
This value quoted in the Guidebook is a UK a country -specific factor taken from the UK Informative Inventory Report (IIR) and is based The IPPC 2006 Guidelines confirm that nitrous oxide emissions from SWDS are not

UK NID 2025 (Issue 1) Ricardo Page 460 The amount of methane emitted from landfills depends primarily on the amount of carbon in biodegradable waste landfilled and how the sites are operated to reduce the escape of the methane produced from such wastes. Policy measures to reduce methane emissio ns from landfills have focused on both these aspects. Diverting biodegradable waste away from landfill avoids the future formation of methane, but landfills continue to produce CH4 for many years from biodegradable waste that has already been deposited. Im proving the efficiency of gas capture from landfills results in an immediate reduction in emissions, but is by nature an “end of pipe” solution, which does not itself prevent the formation of methane. In practice, a combination of measures based on both re ducing the amount of biodegradable waste landfilled and improving the management of sites have, in the UK, provided the foundations for reducing emissions from this source. These two broad approaches are outlined below. The most important legislative and regulatory measures which have reduced the emissions of methane from UK landfills derive from the 1999 Landfill Directive (1999/31/EC). The requirements of the Directive were transposed into national legislation through t he Landfill (England and Wales) Regulations 2002, subsequently amended in 2004 and 2005 to transpose the requirements of Council Decision 2003/33/EC on Waste Acceptance Criteria. The provisions were re -transposed most recently as part of the Environmental Permitting (England and Wales) Regulations 2016, and their ongoing applicability confirmed through the Environmental Permitting (England and Wales) (Amendment) (EU Exit) Regulations 2018. In Scotland, the Landfill Directive is implemented through the Landf ill (Scotland) Regulations 2003, as amended, and in Northern Ireland, through the Landfill Regulations (Northern Ireland) 2003. The provisions of the Landfill Directive require reduction of the amount of biodegradable waste landfilled to specific targets a nd improved landfill design, operation and management in order to reduce release of methane. The EU Waste Framework Directive 2008/98/EC and Landfill Directive 1999/31/EC provides the legislative framework for collection, transport, recovery and disposal of waste. The Waste Framework Directive mandates management of waste according to the waste hierarchy – with the first and preferred method being prevention, followed by reuse, recycling, recovery, and lastly disposal. Defra’s Resources and Waste Strategy published in December 2018 set out how the Government intends to minimise waste, promote resou rce efficiency and move towards a circular economy in England. Similar approaches are being adopted in the Devolved The UK approach to calculating emissions of methane from landfills uses a “Tier 2/Tier3” methodology based on national data on waste quantities, composition, properties and disposal practices over several decades and on some country-specific key parameters. The equations for calculating methane generation use a first-order decay (FOD) methodology (IPCC (2006) p3.6 – 3.12). The IPCC FOD methodology is based on the premise that Dissimilable Degradable Organic Carbon compounds (DDOC; those that can be converted to methane and carbon dioxide)106 decay under the anaerobic conditions in landfills to form methane, carbon dioxide and a variety of stable decomposition products that remain in the landfill, and represent long-term storage of carbon. First order means that the rate of reaction is proportional to the amount of reactant (i.e. DDOC) present at any given time. This means that as the reactant is used up, the rate of reaction slows down. In the UK model, the various waste types are allocated to three pools (p) of DDOC that decompose according to their characteristic first order rate constant, k p. This parameter defines the proportion of material decomposing per year in each year following disposal. The 106 DDOC is the amount of degradable organic carbon (DOC) that is converted (i.e. dissimilated) to methane and carbon dioxide under landfill conditions. DDOC = DOC x DOCF where DOCF is the fraction of DOC that

UK NID 2025 (Issue 1) Ricardo Page 461 three pools are described as Rapidly, Moderately, and Slowly Decomposing Organics (RDO, MDO and SDO, respectively). Allocation of DDOC in waste materials to these pools was described in a report produced by Eunomia Consulting and Research (2011) and updated for the 2013 and 2014 inventories. Fats, sugars and proteins are assigned to the rapidly degrading pool (RDO), lignin to the slowly degrading pool (SDO) and cellulose, hemicelluloses and remaining compounds are allocated to the moderately degrading pool (MDO). Methane generation is calculated using the methodology set out in the IPCC 2006 Equations 3.1 to 3.6. The equations set out below are copied directly from the IPCC 2006 Guideline. • Equation 3.1 represents the overall approach of calculating methane formation for each year, subtracting the quantity of methane collected, and allowing for the quantity of methane oxidised in the Solid Waste Disposal Site (SWDS) cover layer. This equation is used explicitly in the UK inventory as set out in IPCC (2006). The IPCC 2006 Guideline default value of 0.1 is used for OX T, the proportion of methane oxidised on passing through the landfill surface. • Equation 3.2 enables the mass of DDOC deposited to be calculated from the mass of waste deposited, the fraction of Degradable Organic Carbon (DOC) in the waste, and the methane correction factor. This equation is applied to individual waste streams in the UK inventory based on their lignin and non -lignin carbon contents (rather than Research, 2011). Separate Methane Correction Factors are applied to waste deposited in unma naged sites prior to 1980, and waste deposited in managed sites from 1980 onwards (see below). These are taken from the IPCC 2006 Guidelines.
The following values are used for DOC (derived from Eunomia Consulting and Research, 2011) (there is some overlap between categories because of historical definitions used to characterise residual waste landfilled): Paper 8% 3% 21% 0% 0% 0% 0% 0% 0% 0% Card 8% 3% 20% 0% 0% 0% 0% 0% 0% 0% Nappies 0% 0% 7% 0% 0% 0% 0% 0% 0% 0% Textiles and footwear 0% 5% 5% 0% 0% 0% 0% 0% 0% 0% Miscellaneous combustible 0% 9% 8% 0% 0% 0% 0% 0% 0% 0% Wood 14% 4% 14% 0% 0% 0% 0% 0% 0% 0%

UK NID 2025 (Issue 1) Ricardo Page 462 Food 1% 1% 3% 2% 1% 3% 2% 2% 0% 0% Garden 6% 3% 4% 0% 0% 1% 0% 0% 5% 0% Soil and other organic 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% Furniture 1% 4% 4% 0% 0% 0% 0% 0% 0% 0% Mattresses 0% 5% 5% 0% 0% 0% 0% 0% 0% 0% Non-inert Fines 0% 7% 6% 0% 0% 0% 0% 0% 0% 0% Inert 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% Commercial 1 0% 2% 19% 0% 0% 0% 0% 0% 0% 0% Paper and Card 8% 3% 21% 0% 0% 0% 0% 0% 0% 0% General industrial waste 1 0% 2% 19% 0% 0% 0% 0% 0% 0% 0% Food and Abattoir 1% 1% 1% 5% 1% 1% 2% 0% 0% 0% Food effluent 0% 9% 1% 0% 0% 0% 0% 0% 0% 0% Construction and Demolition 0% 3% 2% 0% 0% 0% 0% 0% 0% 0% Miscellaneous processes 1 0% 4% 3% 0% 0% 0% 0% 0% 0% 0% Other waste 1 0% 9% 8% 0% 0% 0% 0% 0% 0% 0% Sewage sludge 0% 2% 2% 0% 0% 0% 0% 0% 0% 0% Textiles / Carpet and Underlay 0% 5% 5% 0% 0% 0% 0% 0% 0% 0% Sanitary 0% 0% 7% 0% 0% 0% 0% 0% 0% 0% Other 1 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% Note 1: This category no longer used in waste descriptions These values are calculated by multiplying the dry matter content of each waste component o Hemicellulose 44.6% dry matter o Readily soluble 45.0% dry matter The following values are used for moisture content and DOC f (Eunomia Consulting and

UK NID 2025 (Issue 1) Ricardo Page 463 Textiles and footwear 20% 5.0% 65.0% Miscellaneous combustible 20% 5.0% 65.0% Soil and other organic 30% 5.0% 65.0% Non-inert Fines 40% 0.0% 50.0% General industrial waste 1 37% 5.0% 65.0% Food and Abattoir 70% 15.0% 70.0% Construction and demolition 30% 5.0% 65.0% Miscellaneous processes 1 20% 5.0% 65.0% Textiles / Carpet and Underlay 20% 5.0% 65.0% Note 1: This category no longer used in waste descriptions Guidelines. However, the IPCC Tier 1 model contains default DOC values for some waste 7.4. However, the sensitivity test set out in Section 7.2.5 indicates that the UK values are more representative of wastes landfilled in the UK Disposable nappies 0.07 0.24 29% The values used for the MCF are in accordance with the IPPC 2006 default values for managed and unmanaged sites (see below). Equation 3.3 is a calculation of methane generation potential from the mass of DDOC deposited, and the fraction of methane in landfill gas. This equation is used in the UK inventory

UK NID 2025 (Issue 1) Ricardo Page 464 as set out in IPCC (2006). Following a review of data on the composition of landfill gas, the fraction of methane in landfill gas as formed in UK landfill sites is assumed to be 50%, the default value given in the 2006 IPCC Guidelines. Equation 3.4 describes the accumulation of DDOC in the landfill site, accounting for new material deposited, and material which decomposes in each year. This equation is used in the UK inventory as described in IPCC (2006) Section 3A1.4, by carrying out a calculation of the mass of rapidly, medium and slowly -decaying carbon present in the landfill in each year, o The mass of DDOC remaining from the preceding year o Plus the mass of DDOC landfilled in that year o Minus the mass of DDOC removed due to decomposition in that year The calculation has been amended to account for the commencement of decomposition during the year of deposition, as described in IPCC (2006) Equation 3A1.12. Equation 3.5 describes the rate at which DDOC is removed from landfill sites in each year by decomposition and formation of methane and carbon dioxide in landfill gas. The calculation has been amended to account for the commencement of decomposition during the year of deposition, as described in IPCC (2006) Equation 3A1.13. The decomposition rate constants used for rapidly, medium and slowly decaying wastes are for a wet boreal climate. The average of two default values for slowly decay ing waste was used. These are allocated to the organic components of waste as o Rapidly decaying Starch, Sugar, Fat, Proteins, Fibre, Readily soluble o Medium decaying Hemicellulose, Cellulose o Slowly decaying Lignin Equation 3.6 is a calculation of methane generated from the mass of DDOC which decomposes during any given year, and the fraction of methane in landfill gas. This equation is used in the UK inventory as set out in IPCC (2006). As described for Equation 3.3 , the fraction of methane in landfill gas as formed in UK landfill sites is assumed to be 50%. UK NID 2025 (Issue 1) Ricardo Page 465 The values used for DOC and DOC f for different material types, and the composition of The total methane generated in each inventory year is determined by summing the quantity of methane emitted over all waste types, all three decomposition pools, all landfill types, and all years in which the waste is landfilled.
A Methane Correction Factor (MCF) is used as a multiplier on methane formation to reflect the fact that shallow or unmanaged disposal sites do not develop extensive anaerobic conditions typical of modern landfills and hence a proportion of waste decays aerobically and does not produce methane. For modern landfills, the MCF term is given the value of 1 (IPCC All solid waste disposal sites in the UK that have received biodegradable wastes since 1980 have been required to adhere to a number of regulations are classed as landfills and assigned a MCF value of 1. MCF has been assigned a value of 0.6 for old, closed landfills that operated A spreadsheet model system known as MELMod was used to carry out these calculations from 2008 (Brown et al., 2008). Separate calculations are carried out for England, Scotland, Wales and Northern Ireland. In 2010, the UK government commissioned further wor k to update the activity data and emission factors for landfill methane (Eunomia Consulting and Research, 2011), which was peer reviewed by independent experts from academia, industry, regulators and consultants in 2010. The principal changes to the input data at that time were summarised in the 2011 NIR submission for the 1990-2009 inventory. Further details on data sources and rationale are given in Eunomia’s report. In the 2017 submission, the UK implemented for the first time a revised set of input data for the inventory model calculations, whilst not altering the methodology itself. This followed research to access and use more data from within individual Devolved Administrations (Scotland, Wales and Northern Ireland) and England, in order to better-reflect differences in waste management around the UK, as it is an Records of individual waste consignments treated and disposed, together with European Waste Category (EWC) codes are compiled by the regulatory authorities in the Devolved • Data on waste consignments landfilled in England for the period 2006 to 202 3 are published by the Environment Agency. • Data on waste consignments landfilled in Scotland for the period 2005 to 202 3 are published by the Scottish Environmental Protection Agency. • Data on waste consignments landfilled in Wales for the period 2006 to 202 3 are published by Natural Resources Wales. • Data on waste consignments landfilled in Northern Ireland for the period 2008 to 2023 were provided by the Northern Ireland Environment Agency. This information is considered to be of good quality. The composition of waste landfilled was evaluated by allocating EWC codes to the categories used in the UK model, as set out in For years prior to 2005-2008, the quantities of waste landfilled and its composition were taken from a report compiled and peer-reviewed on behalf of the UK Government (Eunomia, 2011). 7.2.3.1 Methane recovery from modern landfills Landfill operators are required under their permit conditions to control the release of landfill gas. For large landfills containing biodegradable wastes, this requires the use of impermeable

UK NID 2025 (Issue 1) Ricardo Page 466 liners and cover material, and gas extraction systems. These typically consist of a system of gas wells (perforated pipes sunk into the waste) connected to a network of gas collection pipes. Suction is applied to the gas wells, resulting in a slight negati ve pressure sufficient to draw out the landfill gas but not enough to draw excessive air into the waste. Air ingress is avoided, as it can result in aerobic decomposition of the waste, which produces considerable heat, and may lead to the waste catching fire, as well as shutting off methane formation. The landfill gas collected is normally used to generate electricity on a commercial basis. Where this is not practicable, gas collected can be burnt in flares. In either case, the net effect of the combustion process is to convert the methane to carbon dioxide. The carbon dioxide so produced is not taken into further consideration for inventory purposes as it is considered to be entirely biogenic in origin. Small quantities of other GHGs (methane and nitrous oxide) are emitted from landfill gas use for power generation, and are included in Section 1.A.1.a. The key factors in determining methane emissions are estimates of the quantity of methane generated, and information on the amount of methane collected, either for utilisation or flaring. Data on utilisation is available and of good quality (see Section 7.2.3.2), but recent analysis indicates that data on flaring prior to 2009 is either unavailable or only accessible at disproportionate cost. The current inventory uses operator-provided data on the quantities of gas collected and burnt in landfill gas flares (se e Section 7.2.3.3). No gas collection is assumed to be carried out at old pre-1980 closed sites. At sites and inventory years for which robust data on landfill gas flaring are not available, it is conservatively assumed that no landfill A high standard of gas collection and combustion efficiency is achieved by compliance with the Landfill Directive requirements for gas collection, and by implementing national guidance on landfill gas collection. This is enforced via the landfill permitting and regulatory processes. Large-scale passive venting of landfill gas is no longer accepted under permitting conditions and impermeable barriers are required as best practice to prevent the migration of landfill gas Power generation is currently the dominant use for landfill gas in the UK and good data are available on this from official sources. The method for calculating methane combusted in landfill gas engines is as reported in the 2013 UK NIR. In summary, the qua ntity of methane combusted was calculated as Mass of methane combusted (kT) = Electricity generated (GWh) / Net calorific value of methane (50,000 GJ/kT) The assumed efficiency of landfill gas engines in these calculations was calculated in accordance with research carried out for the UK Government (Golder Associates, 2014). Engine efficiency was assumed to be 30% up to 1996, and 36% from 2012 onwards.
Between 1996 and 2012, engine efficiency was assumed to increase linearly from 30% to 36% Current data on the amount of methane used for power generation in England, Scotland, Wales and Northern Ireland, calculated from the electricity generated from landfill gas as 2022, 3,301 GWh renewable electricity was generated from combustion of landfill gas. Carbon dioxide emitted from the combustion of landfill gas is biogenic in origin and is therefore not

UK NID 2025 (Issue 1) Ricardo Page 467 Since 2009, operators of landfills in England and Wales permitted under the Integrated Pollution Prevention and Control (IPPC) Directive and subsequently the Industrial Emissions Directive (IED), have been required to report the annual quantity of methane flared at the regulated sites under the terms of their operating permits. As it has been obtained under the terms of IPPC operating permits, this data has documentation and quality control built in via the permitting procedures and operator obligations at an individual site level. The use of this dataset is therefore a robust and appropriate basis on which to evaluate the quantities of methane flared by operators. Based on guidance from the Expert Review of the 2013 GHG Inventory (para 98 of the 2013 Annual Review Report), this dataset was used to estimate the quantity of methane flared at landfill sites in England and Wales in 2008. Similarly, landfill site operators in Scotland have been required to compile a similar annual report on the quantity of landfill gas flared since 2013. This dataset was used to evaluate the quantity of methane flared by operators at landfill sites in Scotland from 2013 onwards. Further work was commissioned by DESNZ (then DECC) to identify all reasonably available data on the quantities of methane flared at landfill sites in England, Scotland and Wales for other years (DECC, 2015). This project identified some additional site-specific data which was also taken into account in compiling the inventory. Additionally, landfill operators voluntarily provided further site-specific data on the quantities of methane flared at older sites without a reporting requirement set in permit conditions since 2010. The amount of flared methane from these sites may not be complete, as operators are not required to report flare data, leading to potential underreporting of flaring quantities. The landfill methane flaring data provided represents information for approximately 370 individual sites in 2023. Data checking/validation therefore relies on the regulatory authorities and processes, rather than comprising additional checks on individual operators. The information on landfill gas flaring is provided via under the Environmental Permitting (England/Wales) and Pollution Prevention and Control (Scotland/Northern Ireland) regulatory processes. This information is consequently subject to quality obligations under these regulations, as with any other information reported to the regulatory authorities by regulated process operators under the terms of their operating permits. The data is then forwarded to the compilation agency by each regulatory authority. At all other sites and inventory years, robust data on landfill gas flaring was not available, and it was conservatively assumed that no landfill gas was flared. generation added to the estimated quantity of methane flared. The minor proportion of landfill gas used for non -electricity generation purposes such as direct use and as a vehicle fuel is neglected in th ese calculations due to a lack of data, and assumed to be emitted to the atmosphere as a conservative assumption. 7.2.3.4 Overseas Territories and Crown Dependencies The IPCC landfill model is used for all landfill estimates. Where available, country -specific waste generation and composition data have been applied and appropriate defaults have been chosen e.g. taking into account climatic variation. There are no landfi ll emissions for Gibraltar as waste is exported. Parameters used in these calculations are shown in Annex 7.2.4 Uncertainties and time-series consistency The uncertainty analysis in Annex 2 provides estimates of uncertainty according to IPCC source category and fuel type. There are many uncertainties in estimating methane emissions from landfill sites. The model is sensitive to the values assumed for the degradable organic

UK NID 2025 (Issue 1) Ricardo Page 468 carbon (DOC) present in different fractions of waste, and the amount of this that is dissimilable (i.e. is converted to methane and carbon dioxide), as well as to the quantity of methane combusted in engines and flares, and the oxidation factor. The uncertainty estimates in Annex 2 are intended to reflect the current uncertainties in data and model parameters. The estimates for all years have been calculated from the MELMod model and thus the methodology is consistent throughout the time series. Estimates of waste composition and quantities have been taken from different sources as described in Section 7.2.3. The new sources of data on waste receipts from 2005 – 2008 onwards are considered to be more robust and consistent than the previous combination of data sources. The approach to calculating DDOC, the main driver behind methane formation, was reviewed and u pdated in 2011, and was endorsed by peer reviewers. Uncertainty in the quantity of methane collected is also an important contributory factor to uncertainty in the calculation of overall landfill methane emissions. Uncertainties in the key components of this calculation are as follows. • Current and historical combustion of methane in landfill gas Reliable data on methane collected for power generation are available, based on national statistics for energy generated from landfill gas engines ( DESNZ, 2023). The methane to carbon dioxide ratio of gas burnt in landfill gas engines is assumed to be 50:50, following the IPCC default approach. Gas engine efficiency is assumed to be 30% up to 1996, increasing linearly to 36% in 2012 and thereafter, following pee r review (Golder Associates, 2014). This is considered to be a reasonably reliable calculation of the quantity of methane combusted in landfill gas engines; and • Combustion of methane in flares. These data are based on site-specific records where available and are considered to be accurate for the sites where data exist.
However, records of the quantity of landfill gas are incomplete, particularly for the years pri or to 2008. In cases where records of landfill gas flaring are not available, the quantity of methane flared was assumed to be zero. This means that the landfill methane inventory is subject to greater uncertainty for the years prior to 2008, although because of the conservative approach adopted in respect of landfill gas flaring, it is considered that the inventory represents an over-estimate of methane emissions from landfill sites in the UK, particularly for the years prior to 2008. Landfill permit conditions are designed to deliver a high standard of gas collection and combustion efficiency. Requirements to design and operate landfills in order to minimise gas escape have strengthened considerably since the 1990s. In this context, th e calculated collection efficiencies of 44% to 536% for the period 2009 to 2023 107 derived in this analysis appear reasonable. Lower collection efficiencies in the years between 1990 and 2008 are likely to be more conservative. Oxidation of methane in the surface layers of landfills is a further source of uncertainty in overall emissions. In the absence of better data, the IPCC oxidation default factor of 10% is applied to the estimated quantity of gas released as a fugitive emission. A pilot survey carried out on behalf of the UK Government and Environment Agency included measurements of surface methane oxidation. This study did not support a move away from the IPCC default position. A particular challenge in deciding oxidation r ates for use in a national landfill model is the high level of variability in field measurements, reflecting a wide range of factors such as nature and porosity of the surface layers, moisture content and temperature, along with methane production rates in the underlying waste. UK NID 2025 (Issue 1) Ricardo Page 469 7.2.5 Source-specific QA/QC and verification This chapter provides the information described in IPCC (2006) Section 3.8 “QA/QC, Methodological data are described in Section 7.2.2 above, with quantitative data in Annex 5.1.5.1. Activity data are described in Section 7.2.3 above, with quantitative data on annual waste amounts and the quantities of landfill gas collected in Annex 5.1.5.1. A breakdown of waste composition for each year is available but as noted in IPCC (2006) Section 3.8, it is not practical to provide all documentation in the National Inventory Report. In relation to specific recommendations of IPCC (2006) Section 3.8: • “Countries using other methods or models should provide similar data (description of the method, key assumptions and parameters)” – this is provided in Section 7.2.2. • “If country -specific data are used for any part of the time series, it should be documented.” – country-specific data on DOC, DOCf and MCF are used, as • “The distribution of waste to managed and unmanaged sites for the purpose of MCF estimation should also be documented with supporting information. ” This is • “If CH 4 recovery is reported, an inventory of known recovery facilities is desirable. Flaring and energy recovery should be documented separately from each other.” Data on methane recovery for electricity generation is based on national statistics on electricity generation from landfill methane combustion, rather than reports of recovery at individual facilities. Data on methane recovery and flaring in 2019 is base d on records from a total of 186 individual facilities in England, 40 in Scotland, 17 in Wales, and 3 in Northern however, it is not practical to provide documentation for all these facilities in the National Inventory Report. Methane recovery for flaring and energy recovery are separately documented in Section 7.2.3 and Annex 5.1.5.1. • “Changes in parameters from year to year should be clearly explained and referenced.” There was no change in parameters between 2017 and 2019. The landfill methane model has been subject to peer review in 2011 and 2014 (see Eunomia Consulting and Research, 2011; Golder Associates 2014). The landfill methane model is subject to normal quality assurance procedures, as described in Annex 4. IPCC (2006) guidelines, section 3.8 suggests that calculated emissions can be compared with those of similar countries. Relatively few countries have a similar history of landfill use to the UK, but in 2017 emissions for the period 1990-2015 were compared to data taken from NIRs recently produced by Ireland and Italy where landfill use has been extensive in the past, and 1990 93.3 1.9 25.2 2709 53 726 1% 0% 15% 1995 104.5 2.0 28.5 2939 64 677 5% 0% 21% 2000 84.9 2.1 27.4 3028 74 776 17% 32% 28% 2005 72.6 2.3 21.2 2870 90 787 32% 55% 40%

UK NID 2025 (Issue 1) Ricardo Page 470 2010 51.4 1.6 19.1 2278 98 701 53% 89% 60% 2011 52.5 1.4 16.7 2159 96 678 55% 84% 65% 2012 49.6 1.2 14.4 2041 93 680 55% 87% 61% 2013 48.4 1.0 13.8 1929 89 612 60% 79% 76% 2014 48.2 0.8 12.6 1820 84 600 63% 69% 74% 2015 51.0 0.6 11.4 1716 80 565 62% 63% 81% There is no more than a very approximate connection between the amount of waste landfilled in any year, and the amount of methane generated. The connection is stronger in cases where the quantities and composition are constant over a longer period of time. Nevertheless, for the majority of years, the reported quantity of methane generated in all three countries was in the range 24 to 50 kT methane per Mt waste landfilled. The UK was in the range 28 to 44 kt methane per Mt waste landfilled throughout the time series, with both higher and lower values exhibited by Italy and Ireland. This indicates that there are no causes for concern regarding any obvious inconsistency in the overall results for methane generation with the values reported by these other countr ies. Since 2013, the UK has reported an estimated methane collection efficiency of between 59% and 63%. This is comparable with, and, if anything, lower than the collection efficiencies reported by Ireland and Italy.
This indicates that there are no causes for concern regarding any obvious inconsistency in the estimated methane collection efficiency with the values reported by these other countries. This onetime comparison was specifically performed to compare the methane collection efficiencies between the countries but was not carried out for the purposes of verification of For the 2019 submission, an ad -hoc verification of the MELMod model was also carried out by comparing the estimation of emissions for 1990-2017 from the UK (Tier 2) model with the IPCC Tier 1 model. The IPCC model was set up in two firstly, to reflec t the UK Tier 1 model inputs so far as possible, and secondly, to reflect IPCC default inputs. The key methodological differences between MELMod and the IPCC-waste model with IPCC defaults • The MELMod model contains a more detailed breakdown of waste types with different categories to those used in the IPCC model. Hence it was not possible to accurately represent the MELMod inputs in the IPCC default model. • The UK model allows for different waste types to have a range of rapidly, moderately and slowly decaying wastes, compared to the single value for each waste type used • Additionally, the IPCC model includes a category of “Industrial waste” whereas the UK model is based on the EWC codes for every waste consignment, and so does not have an equivalent to the “industrial waste” category. This category was therefore not used in the IPCC model, further restricting the range of inputs available. The model results are compared with each other, and with results derived from analysis of

UK NID 2025 (Issue 1) Ricardo Page 471 results and estimates derived from environmental measurements The following conclusions were drawn from this a) In view of the similarity between the UK model and the IPCC Model Configuration 1, the UK model does not appear to have significant errors in how it is set up. b) The results obtained using the UK Tier 2 model and IPCC Tier 1 Model set up to reflect UK waste and landfill management practices are more reliable than the results obtained using the IPCC Tier 1 Model default inputs. c) The UK landfill methane model provides a reliable calculation of landfill methane emissions for the period 2010 to 2016. d) The UK landfill methane model diverges from the estimated quantities calculated from environmental measurements for the period 1990 to 2005. This is currently under review via a separate initiative. e) The IPCC Tier 1 model using default inputs does not provide a robust estimate of UK landfill methane emissions. The MELMod outputs have been compared to the outputs that would result from applying the IPCC Tier 1 methodology to the available data on UK waste receipts. This process indicated that the UK model does not have significant errors in how it is set up, and the use of UK - specific inputs to the UK Tier 2 model or the IPCC Tier 1 model gives more reliable results than the use of the IPCC Tier 1 model with IPCC default inputs. In conclusion, this analysis provides confidence in the UK greenhouse gas inventory for Sector 5.A. The verification of MELMod has been described in the 2008 NIR. The update undertaken by Eunomia (Eunomia, 2011) in 2010 resulted in the updating of input data to the model only,

UK NID 2025 (Issue 1) Ricardo Page 472 with no changes implemented as to calculation methodology other than where indicated. The changes to the model input data recommended by Eunomia were peer reviewed by independent experts from academia, industry, regulators and consultants in late 2010, before their incorporation into the UK inventory. The implementation of the recommended changes within the model has now also been reviewed, and the changes arising from this review were MELMod was subject to a further peer review process in 2014 (Golder Associates, 2014). In the light of this peer review, changes were made to the assumed efficiency of landfill gas As described in Annex 5.2, the UK GHGI is verified against data measured from the InTEM network of measurement masts. These measurements indicate good agreement with the UK inventory for the period 2010 onwards, during which time there has been no strong trend in the landfill meth ane inventory, the total UK methane inventory, or the estimated inventory derived from the InTEM measurements. However, over the period 1990 – 2010, the InTEM measurements indicate a reduction of about 30% to 40% in the total UK methane emissions, whereas the GHGI for sector 5A indicates a more significant reduction of up to 60%. The trend in the UK GHGI is driven mainly by reductions in landfill methane emissions. The reasons for this discrepancy are currently under review, as discussed in Section 7.2.7. 7.2.6 Source-specific recalculations Changes to the UK landfill methane inventory for 2023, as • Revision to delay time for the decay reaction assumed in the calculation of emissions from SWDS to be in line with 2006 IPCC GLs. The default delay time of 6 months has now been applied to calculate emissions using MELMod. This change has a significant impact on methane emissions from SWDS. • Updates to the material sent to landfill in 2020 for Scotland, using waste data interrogator statistics that were not available at the time of reporting last year were incorporated into the inventory. • Revision of methane flaring data for England for 2022. • Minor adjustments in landfill gas data in 2021 regional statistics for Scotland As a result, slight changes to the landfill methane inventory for England, Scotland, Wales and Northern Ireland were calculated. The UK inventory of methane emissions from this combusted in engines and flares, oxidised by the landfill surface and emitted to the 7.2.7 Source-specific planned improvements The Inventory Agency is working on improvements to the spatial distribution of landfill methane emissions data.