3.1.1 Agriculture - Summary of historical emissions

• Overall contribution of agricultural emissions to the UK total in 2020 was 11%.
• Emissions from the agriculture sector have decreased by 16% since 1990, driven by a fall in animal numbers over the period, together with a decrease in synthetic fertiliser use.
• Methane is the dominant GHG emitted, accounting for 55% of emissions from this sector in 2020.
• The most significant sources here are emissions of methane due to enteric fermentation (digestion processes) from livestock, particularly cattle; and nitrous oxide emissions related to the use of fertilisers on agricultural soils.

3.1.3 Agriculture - Sources of emissions and data sets

• Combustion includes all emissions from the direct combustion of fuel for heating or other uses including mobile machinery (e.g. tractors, combines). The main data sets used are the Digest of UK Energy Statistics (DUKES) and mobile machinery fleet and utilisation data from the UK’s Non-Road Mobile Machinery (NRMM) model.
• Emissions from enteric fermentation relate to methane emissions associated with the digestion of food. The main data set for this is the June Survey of Agriculture and Horticulture, published by the Department for Environment, Food & Rural Affairs (Defra).
• Animal wastes and manure management give rise to emissions of methane and nitrous oxide (N₂O) due to anaerobic decay and denitrification. Estimates are also based on the Defra June Survey.
• A small amount of CO₂ is released from the breakdown of urea used as a fertilizer, and from the application of lime to agricultural soils.
• Agricultural soil emissions arise from: the use of fertilisers (synthetic and animal manures); biological fixation of nitrogen by crops; ploughing in of crop residues; cultivation of organic soils; indirect emissions from atmospheric deposition of NO_x and NH₃; and leaching and runoff of nitrate. Key data sources include the British Survey of Fertiliser Practice (Defra), and the June Survey.

3.1.4 Agriculture - Methodology

• The inventory for the agriculture sector is compiled by a consortium led by Rothamsted Research and including: RSK ADAS, Cranfield University, the UK Centre for Ecology and Hydrology, Scotland’s Rural College, and Ricardo.
• Stationary fuel combustion emissions are estimated by multiplying the fuel use estimates in DUKES by an emission factor. Emission factors are either UK specific or are taken from published inventory guidelines (Intergovernmental Panel on Climate Change (IPCC) and the European Monitoring and Evaluation Programme-European Environment Agency (EMEP-EEA)).
• Emissions from mobile machinery are modelled based on the population of the various machinery types, the age profile, the lifetime of the equipment, and average annual usage.
• For emissions from livestock and soils, a combination of methods is used, dependent on the importance of the source. For small sources, a simple method (Tier 1, as defined in the IPCC Guidelines) can be used. For larger sources, such as emissions from livestock, more complex (Tier 2 or 3) methods are used to ensure accurate calculation of emissions.
• Emissions from enteric fermentation for the main types of relevant livestock (cattle and sheep) are calculated using UK-specific energy balance equations. For other animals, a simpler approach using default emission factors is used.
• Methane emissions from animal wastes are estimated using a combination of country specific and default parameters and emission factors.
• Nitrous oxide emissions from manure management are calculated using both country specific and default parameters and emission factors, and utilising the UK’s Nitrogen-flow model.
• Direct emissions of nitrous oxide from agricultural soils are estimated using country specific emission factors and parameters where available including spatially disaggregated emission factors for fertiliser application, which accounts for rainfall and soil type. Indirect nitrous oxide from soils is calculated using a combination of methods from the IPCC Guidelines, and country specific methods.
• Carbon dioxide emissions due to application of urea and related compounds, and from liming, are estimated using a simple methodology from the IPCC 2006 guidelines, using default emission factors.

3.1.5 Agriculture - Uncertainties

• The GHG Inventory quantifies uncertainties on emission factors and activity data, which in turn allow for the production of uncertainty estimates on the emissions; overall uncertainty by gas; and estimates of sector level uncertainties.
• The uncertainty estimate for this sector indicates that the true value of agriculture emissions has a 95% probability of being within the range 42-49 Mt CO₂e in 2020.
• The uncertainties for methane emissions in 2020 range from +/- 11% for Enteric Fermentation to +/- 13% for Manure Management, as a 95% confidence interval.

3.1.6 Agriculture - Improvements

• The 1990-2020 inventory includes several method improvements for enteric fermentation methane emissions including updates to diet and feed rates for dairy cattle, updates to dairy cattle ages for conception, calving and death, plus updates to dairy cattle allocation across different management regimes in N Ireland. Emission factors have been improved for sheep and goats.
• Manure management method improvements comprise the dairy cattle changes as above, plus revised emission factors for goats and horses, updated Volatile Solids (VS) excretion rates for broilers, revised nitrogen excretion values for poultry, deer and goats, and updated indirect N₂O EF₄ (the IPCC default emission factor for volatilisation/deposition of N₂O) to use values from the 2019 Refinement to the 2006 IPCC Guidelines.
• Agricultural soils method improvements included use of a UK-specific N₂O emission factor for fertiliser applied to grassland, updated analysis of fertiliser application to cropland, a revision to the country specific emission factor for application of farm yard manure and poultry manure to soils and updates to EF₃ for goats, deer, horses, pigs and poultry (the IPCC default emission factor for the amount of N₂O emitted from urine and dung nitrogen deposited by grazing animals on pasture, range and paddock) and to the indirect N₂O EF₄ (the IPCC default EF for volatilisation/deposition of N₂O) to apply the values from the 2019 Refinement to the 2006 IPCC Guidelines.

3.2.1 Business - Summary of historical emissions

• The business sector contributed 18% of total UK GHG emissions in 2020.
• Carbon dioxide from fuel combustion is the dominant GHG emission source.
• Emissions from the business sector have decreased by 35% since 1990. Most of this decrease came between 2001 and 2009, with a significant drop in 2009 likely driven by economic factors. There has been a gradual decline in emissions in recent years. The main driver of the decrease in emissions since 1990 is a reduction in emissions from industrial combustion (including iron and steel) which has led to a 45% reduction in carbon dioxide emissions since 1990.
• Emissions from F gases have increased significantly, mainly due to an increase in emissions from refrigeration and air-conditioning as HFCs replaced ozone depleting substances which were previously used as refrigerants. This increasing trend has reversed in recent years following the introduction of the HFC phase down as part of the European Union (EU)’s 2014 F-Gas Regulation, and F gas emissions have fallen by 11% since their peak in 2016.
• Industrial combustion is the largest source of business sector emissions in the UK.

3.2.3 Business - Sources of emissions and data sets

• Stationary combustion in the Business sector includes commercial combustion; industrial combustion; iron and steel; non-ferrous metals; chemicals; pulp, paper and print; food, drink and tobacco; and other industrial sectors. This comprises all emissions from the direct combustion of fuel, either to provide the energy required for certain industrial processes or for heating. The main data set used is the Digest of UK Energy Statistics (DUKES).
• Industrial off-road machinery includes emissions from equipment such as portable generators and forklift trucks.
• Emissions of hydrofluorocarbons (HFCs) from refrigeration, air conditioning and heat pumps are modelled based on bottom-up statistics for the various types of refrigeration units in use in the UK.
• Other emissions in this sector include emissions from foam blowing, fire extinguishers, solvents, and energy recovery in the chemicals industry. Data are taken from a range of industry experts, literature, and the Environment Agency’s Pollution Inventory.

3.2.4 Business - Methodology

• Stationary fuel combustion emissions are estimated by multiplying the fuel use estimates in DUKES by an emission factor. Emission factors are either UK specific or are taken from published inventory guidelines (Intergovernmental Panel on Climate Change (IPCC) and the European Monitoring and Evaluation Programme-European Environment Agency (EMEP-EEA)). For some sources, independent estimates of fuel use are provided by industry, and therefore the sector allocations in DUKES are modified. The total fuel consumption estimates remain consistent with DUKES (aside from some exceptions where the scope of DUKES differs from the inventory or where strong bottom-up data justifies a deviation from DUKES).
• Fuel use from industrial off-road machinery are not reported separately in DUKES; emissions from this source are therefore modelled. A detailed study was undertaken in 2004 to estimate the total UK population of this equipment. Annual estimates are based on population growth drivers or sales data for the various machinery types, the age profile, the lifetime of the equipment, and average annual usage.
• Emissions of fluorinated gases (F-gases) arising from their use in products can occur in a range of phases: when the product is manufactured and filled; during the lifetime of the product as it operates; and when the product is decommissioned or disposed of. Emissions of F-gases during each phase of the product’s lifetime are estimated using a model. The model takes into account parameters such as leakage rates at each phase, and product lifetime.
• Estimates of CO₂ emissions from energy recovery in the chemicals industry (the use of waste solvents as a fuel) are based on an estimate of the amount of solvent recovered (as reported to the Environment Agency’s Pollution Inventory), and the carbon content of solvents (supplied by the Mineral Products Association (MPA)).

3.2.5 Business - Uncertainties

• Total emissions within this category are dominated by fuel combustion. CO₂ emissions from fuel combustion are relatively certain, since the carbon content of fuel is well known, and the energy statistics are of good quality.
• Methane and nitrous oxide emissions from fuel combustion are dependent on more factors than just the fuel quality, and are therefore more uncertain.
• F-gas emissions reported within this sector are also uncertain, since they are largely based on modelled data. Uncertainties for these sources in 2020 range from +/-5 to +/-50%, as a 95% confidence interval.
• The overall uncertainty for the business sector is estimated to be +/- 3%, as a 95% confidence interval in 2020.

3.2.6 Business - Improvements

• Estimates of emissions from Airborne Warning And Control Systems for military aircraft have been improved by gathering new information from the Ministry of Defence, replacing the previous estimates and IPCC default approach.
• A project has recently completed to improve estimates for off-road machinery, to obtain more up to date data on equipment population and use. The outputs from this will feed into next year’s inventory.

3.3.1 Energy Supply - Summary of historical emissions

• Energy supply was the biggest single contributor to the UK’s total net GHG emissions across most of the time series (1990-2015). In 2016, the Transport sector became the largest single contributor to the UK’s total net GHG emissions.
• The energy supply sector contributed 21% to total UK GHG emissions in 2020.
• Emissions have decreased by 70% since 1990, mainly from changes in the mix of fuels being used for electricity generation, moving away from less efficient technology and more carbon intensive fuels such as coal to greater use of natural gas, nuclear and the growth of renewables.
• Carbon dioxide is the dominant GHG emitted by the Energy Supply sector.
• Emissions from power stations are the biggest contributor accounting for 60% of energy supply emissions in 2020.

3.3.3 Energy Supply - Sources of emissions and data sets

• Power generation is the largest source in this sector.
• Other significant sources are fuel combustion emissions from the manufacture of solid fuels (notably coke ovens), from oil refineries and from upstream oil and gas exploration and production activities.
• Key data sources include the Digest of UK Energy Statistics (DUKES), the EU Emissions Trading System (EU ETS), upstream oil and gas emissions data from the Department for Business, Energy & Industrial Strategy Offshore Petroleum Regulator for Environment & Decommissioning (BEIS OPRED), emissions data for onshore sites from the pollution inventories of UK environmental regulators and from coke oven operators, and activity data from the Oil and Gas Authority (OGA), the British Geological Survey (BGS) and the Iron & Steel Statistics Bureau (ISSB).

3.3.4 Energy Supply - Methodology

• Emissions associated with fuel combustion are estimated by using fuel consumption data and appropriate emission factors.
• For most sectors the fuel consumption data are taken from DUKES; for upstream oil and gas, the predominant data source for fuel use is the EU ETS.
• Emission factors are taken from a variety of sources including the EU ETS, data provided by industry operators and trade associations, or from literature sources.
• For most energy industry sources, comprehensive site-specific emissions data are available from the EU ETS and the regulator pollution inventories.
• Fugitive methane emissions from coal mining activities are based on DUKES annual coal production data (for deep mines and open-cast mines separately), combined with a UK industry emission factor for open-cast mines and operator data for deep mines. Fugitive methane from closed coal mines are based on a UK industry model.
• Fugitive emissions from upstream oil and gas installations are derived from the Environmental Emissions Monitoring System (EEMS) managed by BEIS OPRED for all offshore installations and from the pollution inventories of onshore regulators for oil and gas terminals.
• Fugitive methane emissions from gas transmission and distribution networks are provided annually by National Grid and the Distribution Network Gas Transporters respectively, using a UK industry gas shrinkage model developed by British Gas.

3.3.5 Energy Supply - Uncertainties

• The energy supply sector is dominated by emissions from fuel combustion in power stations, refineries and upstream oil and gas installations. Activity data and the carbon content of the fuels is reported via EU ETS to a high level of accuracy and is Third Party verified, as required for all high-emitting EU ETS participants. Hence the CO₂ emissions from this source are associated with low uncertainty. The emissions of N₂O and CH₄ are more uncertain due to the number of factors that affect emissions of these gases, but their overall contribution to sector GHG totals is low.
• Similar to fuel combustion sources, emissions from gas flaring, including at upstream oil and gas installations, are reported under EU ETS and are associated with low uncertainty.
• Fugitive emissions from the energy supply sector may arise from many sources per installation, not only from point sources such as vents or stacks, but also from valves, connectors, compressors, flanges and other leaks from infrastructure. Estimating the fugitive emissions from such a large number of small release points is inherently difficult to do, with few measurements and a range of different monitoring and reporting techniques deployed by energy sector operators across refineries, oil and gas plant and other sites in reporting to regulators. These fugitive emission estimates are therefore much more uncertain than emission estimates from fuel combustion.
• The overall uncertainty for this sector is estimated to be +/- 3% in 2020, as a 95% confidence interval.

3.3.6 Energy Supply - Improvements

• A BEIS-funded inventory improvement project to access new OGA data resources and to model GHG estimates from across the upstream oil and gas sector has been finalised and used in the 1990-2020 inventory for the first time. Whilst the recalculations in recent years are relatively small, estimates for the 1990s have been revised to use the best available industry data from the trade association, then the UK Offshore Operators Association (UKOOA) now Offshore Energies UK.

3.4.1 Industrial Processes - Summary of historical emissions

• The industrial processes sector contributed 2% to total UK GHG emissions in 2020.
• Emissions from the industrial processes sector have decreased by 84% since 1990. This was most notably due to a large reduction in emissions from adipic acid production and halocarbon production between 1998 and 1999 following the fitting of abatement equipment at production facilities. Combined emissions from these facilities were almost zero in 2020.

3.4.3 Industrial Processes - Sources of emissions and data sets

• Since 1999, carbon dioxide has been the dominant GHG emitted by the industrial processes sector. It accounted for 96% of emissions in 2020.
• Emissions of nitrous oxide across the time series occur mainly from the production of nitric and adipic acid. These emissions have decreased significantly since 1990 due to the installation of abatement equipment, and plant closures (the UK’s only adipic acid production site closed in 2009).
• The two largest remaining sources of emissions are carbon dioxide emissions from process sources in cement production and from the iron and steel sector.
• Data are supplied by a wide range of sources. Key data sets include the Digest of UK Energy Statistics (DUKES), the Environment Agency’s Pollution Inventory, the Scottish Environment Protection Agency’s Scottish Pollutant Release Inventory, UK Minerals Yearbook (British Geological Survey) and data from the Iron & Steel Statistics Bureau, Mineral Products Association, Tata Steel, British Steel, and British Glass.

3.4.4 Industrial Processes - Methodology

• Emission factors and activity data are used to calculate the following sources: use of limestone, dolomite, soda ash and sodium bicarbonate in the glass industry and other sectors; oxygen steelmaking; cement production; lime production; nitric acid/adipic acid (for earlier years); ceramics other than bricks; non-energy use of fossil fuels such as lubricants and waxes.
• The use of emissions data reported by process operators is used for the following sources: nitric acid/adipic acid (for more recent years); other chemical processes (including petrochemicals, soda ash & titanium dioxide production); fletton and non-fletton brickworks; electric arc furnaces.
• Fluorinated gas (F-gas) emissions arising from halocarbon production, aluminium production and their use as magnesium cover gas are estimated based on operator reported data to the Regulators’ Inventories (e.g. Pollution Inventory), or data supplied directly from operators.

3.4.5 Industrial Processes - Uncertainties

• Cement production and the iron and steel sector are the two largest sources of emissions in recent years, but other sectors such as lime and ammonia production make significant contributions as well. The uncertainties for almost all of these sources are low as the processes involved are well understood and data are complete. EU ETS data are used for many sectors including cement, lime, glass, bricks and various types of chemical process, and these data should be reliable.
• Other (generally small) sources within the sector have higher uncertainties associated with them. This can be the case where estimates are based on operator reported emissions in the Regulators’ Inventories, where sometimes emissions are below reporting thresholds and therefore gaps need to be filled, or where it is not possible to obtain a complete data set directly from operators.
• The overall uncertainty for this sector is estimated to be +/- 2% in 2020, as a 95% confidence interval.

3.4.6 Industrial Processes - Improvements

• A new source has been added to the inventory - emissions from production of ceramics other than bricks. Brickmaking and manufacture of roofing tiles have been included in the UK inventory for many years but other ceramics such as sanitaryware were not included due to a lack of data (these ceramics processes are largely outside the scope of EU ETS). A new method has been developed which calculates the clay used to manufacture these other types of ceramics and then assumes that carbon emission factors used by brick manufacturers when reporting their emissions to EU ETS are applicable for these ceramic processes as well.
• The methodology for electric arc steelmaking has also been revised. Previously we used emission factors suggested by industry, but we now use emissions data reported in the EU ETS data set. The EU ETS data only covers the larger sites, and only provides data back to 2005 so we have used estimates of production each year at each site to extrapolate from reporting to non-reporting sites.

3.5.1 LULUCF - Summary of historical emissions

• The LULUCF sector contains both sources (of GHG emissions to the atmosphere) and sinks or removals of CO₂ from the atmosphere.
• LULUCF contributed 3.7 Mt CO₂e (net) to total UK GHG emissions in 2020.
• Net emissions from the LULUCF sector have changed from 13.1 Mt CO₂e in 1990 to 3.7 Mt CO₂e in 2020. This long-term fall has been driven by a reduction in emissions from grassland, cropland and settlements, and an increase in the sink provided by forest land, with an increasing uptake of carbon dioxide by trees as they reach maturity, in line with the historical planting pattern. There has also been some reduction in emissions since 1990 due to changes in agricultural practices.
• Methane is the dominant GHG emitted by the LULUCF sector in 2020.
• Cropland remaining cropland and land converted to cropland are the dominant sources of GHG emissions, and forest land remaining forest land is the dominant sink in 2020.

3.5.3 LULUCF - Sources of emissions and data sets

• The main data sets which provide areas of land use and land use change are the Countryside Surveys for the UK constituent countries and statistics published by the Forestry Commission.
• Emissions and removals of CO₂ associated with changes in carbon stocks in vegetation and soils of forests are estimated on the base of a forestry model, CARBINE, calibrated among other with information on the growth rate and management of the Forestry Commission and Natural Resources Wales.
• The estimates for forest carbon emissions and removals are based largely on data from the Forestry Commission, which has carried out inventories of woodlands in Great Britain at 15-20 year intervals since 1924.

3.5.4 LULUCF - Methodology

• Estimates of land use change emissions rely on separate land use change matrices for each country in the UK. These matrices are derived from surveys on land use conducted in 1947, 1980, 1984, 1990, 1998 and 2007. The matrices show the pattern of land use change between different categories of land which have been grouped into the broad land types of Grassland, Cropland, Forest Land, Settlements and Other Land. The change of carbon stocks in cropland is included as part of the LULUCF sector rather than agriculture based on the Intergovernmental Panel on Climate Change (IPCC) nomenclature.
• The inventory compilers for the LULUCF sector are the UK Centre for Ecology and Hydrology (UKCEH) and Forest Research (FR).
• Annual planting data and management information are used to update the estimates of the size and age structure of the national forest estate between the periodic inventories. This information, together with data derived from the growth characteristics of UK forests (so-called ‘yield classes’) is used in a dynamic carbon accounting model (CARBINE) to estimate annual uptake and storage of atmospheric carbon in forestland.
• Areas of land use change to forest (afforestation) in Great Britain since 1920 come from planting data provided by the Forestry Commission and areas pre-1920 come from modelling the age class structure of existing forests given by the National Inventory of Woodlands and Trees.
• Changes in soil carbon density for types of land undergoing transition are estimated from soil survey data and used in a dynamic model to estimate annual gains and losses of soil carbon associated with land use transitions in the matrix.

3.5.5 LULUCF - Uncertainties

• Uncertainties arise both from natural variability in vegetation and soils, and incomplete knowledge about the extent of activities and the underlying processes affecting sinks and sources.
• Typically, uncertainties in the estimates associated with the soil carbon pool are much greater than those in above ground standing biomass in trees.
• The land use change data and the parameterisation of the forest model and its parameters are the largest contributor to overall uncertainty in this sector.
• Relative uncertainty is particularly high for the LULUCF sector as these uncertainties are for net emissions, which can be much higher in percentage terms than the separate uncertainties for the sources and sinks that contribute to net emissions.
• The overall uncertainty for this sector is estimated to be +/- 121% in 2020, as a 95% confidence interval.

3.5.6 LULUCF - Improvements

• There has been a methodological update to the land-use change activity data used in the LULUCF soils and non-forest biomass models. The new approach assimilates a wider range of land use and land-use change data sources to produce an annual time series, rather than the previous approach that used decadal rates of change based on the Countryside Survey. This has had a range of impacts to emissions across the different land types, including:
  • Emissions from carbon stock change in the year of change show more annual variability and are lower than previously estimated.
  • Estimates of land-use change from grassland to cropland before 2000, particularly in England, are lower than in the previous activity data set, resulting in lower carbon stock change emissions in mineral soils.
  • The use of an annual time series results in a more gradual change in modelled carbon stock changes due to land-use change in mineral soil.
  • Overall estimates of land-use change to grassland are lower than in the previous activity data set, resulting in smaller carbon stock change removals in mineral soils, but the direction of change varies between countries and land use transitions.
  • Overall estimates of land-use change to settlement are lower than in the previous activity data set, resulting in smaller carbon stock change emissions in mineral soils.
  • There are lower direct and indirect nitrous oxide emissions from mineralisation corresponding to the lower emissions from land-use change transitions resulting in mineral soil carbon stock losses.
• Small changes were made to the activity data for forest planting and wood production which included new data from the 2021 Forestry Statistics Publication. An improvement was made to the adjustment for open space within forests and estimation of forest planting data for Northern Ireland was updated to the same method as used for the rest of the UK. These changes resulted in minor changes to the forest carbon stock change and Harvested Wood Products modelled in CARBINE. A minor change was also made in the CARBINE model to improve drainage assumptions.
  • The deforestation activity data time series was also updated to improve consistency in assumptions for land use change following deforestation.

3.6.1 Public - Summary of historical emissions

• This sector covers public sector stationary combustion and is dominated by emissions from natural gas combustion.
• Overall contribution of the public sector to UK GHG emissions in 2020 was 2%.
• Emissions in recent years fluctuate in line with temperature variations - warmer winters reduce demand for gas for heating and vice versa.
• Emissions from the public sector have decreased by 44% since 1990, driven by a change in the fuel mix, with less use of coal and oil, and more use of natural gas).
• Carbon dioxide is the dominant GHG emitted.

3.6.3 Public - Sources of emissions and data sets

• Emissions of GHGs from this sector occur from the combustion of fuel in public sector buildings.
• Activity data (fuel use) is taken from the Digest of UK Energy Statistics (DUKES).
• The DUKES category “Public Administration” includes:
  • Public Administration and Defence; Compulsory Social Security
  • Education
  • Health and Social work
• Emission factors for carbon dioxide are UK-specific. Annual natural gas composition data are supplied by the network operators and other fuels data are mostly based on the Carbon Factors Review conducted in 2004.
• Emission factors for methane and nitrous oxide are based on the Intergovernmental Panel on Climate Change (IPCC 2006) default values.

3.6.4 Public - Methodology

• The UK inventory estimate for fuel combustion is based on a top-down method, using the total fuel use data for the sector reported in DUKES multiplied by an emission factor. It is not possible to further break this down into different sub-sectors across the public sector.
• The emissions reported for the public sector are from fuel use in buildings, to raise heat and to fire boilers. Emissions from public sector transport sources (including ambulances, for example) are not reported explicitly nor under the public sector; they are included within the inventory estimates for the transport sector.

3.6.5 Public - Uncertainties

• The uncertainty associated with the emission factors for CO₂ is low, since the carbon content of the fuels used is well known. For non-CO₂ gases, the emission factors are dependent on a range of contributing factors, such as boiler size and efficiency. Therefore the uncertainty on the non-CO₂ emission factors used in this sector is high, although the contribution to total emissions is much lower, so this uncertainty is not particularly significant to the sector as a whole.
• The overall uncertainty for the public sector in 2020 is +/- 5%, as a 95% confidence interval.

3.6.6 Public - Improvements

• No notable improvements

3.7.1 Residential - Summary of historical emissions

• The residential sector contributed 16% to total UK GHG emissions in 2020.
• Carbon dioxide is the dominant GHG emitted (97%).
• Emissions from the residential sector are 17% lower in 2020 than in 1990. Emissions in recent years fluctuate in line with temperature variations - warmer winters reduce demand for gas for heating and vice versa. Emissions in 2014 were 16% lower than in 2013, largely for this reason. 2020 was an exception to this due to the COVID-19 pandemic, as despite being a warmer year than 2019 residential emissions increased by 1% as more people stayed at home during the pandemic.
• Emissions from stationary combustion dominate residential sector emissions (97%) and have decreased by 19% since 1990.

3.7.3 Residential - Sources of emissions and data sets

• Domestic combustion includes all emissions from the direct combustion of fuel for heating or cooking. The main data set used is the Digest of UK Energy Statistics (DUKES).
• Emissions from aerosols and metered dose inhalers (MDI) relate to hydrofluorocarbons (HFCs) used as a propellant. The main data sources for these emissions are the British Aerosol Manufacturers’ Association (BAMA) and prescription data from the National Health Service (NHS).
• Emissions from the breakdown of household products arise from the decomposition of products such as soaps and detergents.
• Other emission sources include household and garden machinery, accidental vehicle and house fires, home composting, and recreational use of N₂O.

3.7.4 Residential - Methodology

• Domestic fuel combustion emissions are estimated by multiplying the fuel use estimates in DUKES by an emission factor. Emission factors are either UK specific or are taken from published inventory guidelines (Intergovernmental Panel on Climate Change (IPCC)).
• Emissions from MDIs are estimated from the UK NHS prescription data. HFC emissions have been calculated with estimates of the species and volumes of HFCs used as MDI propellants.
• Aerosol HFC emission estimates have been derived on the basis of fluid consumption data provided by BAMA.
• For the breakdown of consumer products, estimates of the carbon content of these products are combined with an estimate of how much carbon is stored, and how much is released. These estimates are based on a study conducted by Atlantic Consulting, supplemented by sales data from the Cosmetics, Toiletries & Perfumery Association, and data from the United States Environmental Protection Agency (US EPA).
• Estimates for recreational use of nitrous oxide are based on the Home Office Drug Misuse Tables.
• Inputs to household composting are calculated by using population statistics and district level analysis for home composting in the UK.

3.7.5 Residential - Uncertainties

• The uncertainty associated with the emission factors for carbon dioxide is low, since the carbon content of the fuels used is well known. For non-CO₂ gases, the emission factors are dependent on a range of contributing factors, such as boiler size and efficiency. Therefore, the uncertainty on the non-CO₂ emission factors used in this sector is high, although the contribution to total emissions is much lower so this uncertainty is not particularly significant to the sector as a whole.
• The overall uncertainty for the residential sector is +/- 4%, as a 95% confidence interval in 2020.

3.7.6 Residential - Improvements

• For the 2022 inventory, emissions from residential wood combustion have been revised in line with updated statistics within DUKES, based on Defra’s Burning in UK Homes and Gardens report.

3.8.1 Transport - Summary of historical emissions

• The transport sector was the largest contributor to UK GHG emissions in 2020 with an overall contribution of 24%.
• Emissions from the transport sector have decreased by 23% since 1990, although most of this fall was in 2020 as people travelled less during the pandemic.
• Emissions from road transport followed an increasing trend until 2007; increasing by 10% from 1990. Emissions decreased from 2007 to 2013, increased from 2013 to 2017, and decreased from 2017 to 2020. This pattern from 1990 to 2020 is largely a reflection of the balance between increasing traffic volumes (which tends to lead to higher emissions) and fuel efficiency improving over time (which tends to lead to lower emissions). The significant decrease in 2020, relative to 2019, is due to the impacts of COVID-19.

3.8.3 Transport - Sources of emissions and data sets

• Emissions of GHGs from this sector occur mainly from road transport, which accounts for 91% of emissions in 2020.
• Other sources include aviation, railways, navigation (including inland waterways), aircraft support vehicles, and stationary combustion from railways.
• CO₂ is the dominant GHG emitted by the transport sector making up 98.9% of transport emissions in 2020.
• Key data sources include the Digest of UK Energy Statistics (DUKES), UK Department for Transport publication “Transport Statistics Great Britain”, Office of Rail Regulation (ORR) National Rail Trends Yearbook and ORR data portal, fuel consumption data from the Ministry of Defence, and Civil Aviation Authority aircraft movement data.

3.8.4 Transport - Methodology

• Aviation: Emission estimates are based on the number of aircraft movements broken down by aircraft type at each UK airport.
• Railways: Both mobile and stationary emissions are reported. Stationary emission sources are based on fuel consumption data from DUKES. Emissions are calculated by multiplying emission factors by either fuel consumption or train kilometres.
• Road Transport: Emissions are calculated either from a combination of total fuel consumption data and fuel properties or from a combination of speed related emission factors and road traffic data. CO₂ is calculated using fuel consumed and the carbon content of the fuel. CH₄ and N₂O emissions are modelled taking into account of a number of factors including vehicle type, age, fuel type, speed and distance travelled. The modelled results will then be normalised based on the amount of fuel reported in DUKES to be consistent with the CO₂ calculation.
• Coastal shipping: A bottom-up method is used, based on high resolution terrestrial Automatic Identification System (AIS) vessel movement data supplied by the UK Maritime and Coastguard Agency.
• Inland waterways: Emissions from inland waterways are also included in domestic shipping. These are estimated using population, engine size and hours of use of different types of craft, combined with emissions factors from the European Monitoring and Evaluation Programme/European Environment Agency (EMEP/EEA) Guidebook.
• Military aircraft and naval shipping: Data from the Ministry of Defence is used to calculate emissions from naval and air force activities. Fuel consumption data provided by the Ministry of Defence is used in conjunction with default emission factors
• Aviation ground operations: Emissions from aircraft support vehicles are modelled, using estimates of the total amount of different types of equipment in use, together with assumptions about the annual hours of usage and age profile.

3.8.5 Transport - Uncertainties

• The uncertainty associated with the emission factors for CO₂ is low, since the carbon content of the fuels used is well known. For non-CO₂ gases, the emission factors are dependent on a range of contributing factors, such as engine size and efficiency. Therefore the uncertainty on the non-CO₂ emission factors used in this sector is high, although the contribution to total emissions is much lower so this uncertainty is not significant to the sector as a whole.
• The overall uncertainty for the transport sector is estimated to be +/- 2%, as a 95% confidence interval in 2020.

3.8.6 Transport - Improvements

• Time series revisions in road transport emissions are a result of extensive improvement work carried out this year which included the implementation of new basemap speeds, the revision of the fleet turnover model and the adoption of COPERT 5.4 emission factors.
• Natural gas use in transport has been identified separately in the DUKES estimates for the first time, enabling it to be distinguished from other uses of natural gas. Therefore, a new category has been introduced in the emissions estimates for emissions from the use of natural gas in transport engines. Note that this is a reallocation - total gas use in DUKES would have included this small component in earlier years and so CO₂ overall is likely to be unchanged. Emissions of N₂O and CH₄ will be different but as it is not possible to identify which category the gas has been reallocated from it is not possible to quantify this difference.

3.9.1 Waste management - Summary of historical emissions

• Overall contribution of waste sector to UK GHG emissions in 2020 was 4%.
• Emissions from the waste sector have decreased by 73% since 1990. This was due to a combination of factors, including improvements in the standards of landfilling, changes to the types of waste going to landfill (such as reducing the amount of biodegradable waste), and an increase in the amount of landfill gas being used for energy.
• Methane is the dominant GHG emitted.
• Emissions from landfill dominate waste sector emissions in the UK.

3.9.3 Waste management - Sources of emissions and data sets

• Emissions of GHGs from this sector occur from the disposal and treatment of waste.
• Managed waste disposal on land covers emissions of CH₄ arising from waste disposed to landfill. CH₄ is produced as organic wastes decay in the oxygen deficient lower layers of the landfills.
• Wastewater handling leads to emissions of CH₄ and N₂O.
• Waste incineration includes combustion of chemical and clinical waste, Municipal Solid Waste (MSW), and sewage sludge.
• Emissions from waste incineration with energy recovery are reported under the energy supply sector.
• The use of anaerobic digestion (often to generate biogas) or composting to treat biological waste can lead to fugitive CH₄ or N₂O emissions.
• Key data sources include the Environment Agency’s Pollution Inventory, the Expenditure and Food Survey (Defra), UK population statistics (Office for National Statistics), data on waste consignments landfilled compiled by the regulatory authorities in the Devolved Administrations, and raw data from water companies.

3.9.4 Waste management - Methodology

• Landfill activity data is taken from records of individual waste consignments treated and disposed, which are compiled by the regulatory authorities in the UK Devolved Administrations. This is used to calculate the amount of methane generated, after which the amount of methane removed in engines, flares, and the landfill surface layers is calculated from a combination of national statistics, site-specific data, and IPCC default factors, and subtracted off to give the remaining quantity of methane emitted.
• Estimates of CH₄ emitted from domestic wastewater handling are based on activity and emissions data from the water industry annual reporting system. From these, implied emission factors for specific emission sub-sources can be derived.
• Estimates of N₂O from domestic wastewater handling are based on protein consumption data and emission factors from the Intergovernmental Panel on Climate Change (IPCC) Guidelines.
• For industrial wastewater handling, CH₄ emissions have been estimated using default parameters from the 2006 IPCC Guidelines and industrial output for the chemicals industry, and data from a specific study for the food and drink industry.
• Emissions from waste incineration are estimated from a combination of data reported to the Environment Agency’s Pollution Inventory, supplemented with the use of literature based emission factors.
• Emissions from composting are estimated using activity data from annual organics recycling reports and IPCC 2006 default emission factors.
• Emissions of GHGs from anaerobic digestion are calculated from industry compilations of anaerobic digestion facility capacity and throughput. IPCC default emission factors are used to calculate CH₄ and N₂O emissions from this sector.

3.9.5 Waste management - Uncertainties

• There are many uncertainties associated with estimating CH₄ emissions from the waste sector. For example, the landfill model is particularly sensitive to certain input values such as the amount of degradable organic carbon (DOC) present in the waste and the amount of this that is converted to CH₄ and CO₂, as well as the oxidation factor.
• The estimated uncertainty for landfill in 2020 was +/- 53%, as a 95% confidence interval. Emissions from waste incineration are more uncertain, where the estimated uncertainty in 2020 was +/- 95%, as a 95% confidence interval. For biological treatment of solid waste, the uncertainty in 2020 has been estimated at +/- 48%, as a 95% confidence interval.
• The estimated uncertainty for the whole waste sector is estimated to be +/- 41%, as a 95% confidence interval in 2020.

3.9.6 Waste management - Improvements

• A project has been commissioned by BEIS to improve estimates for biological treatment of waste, to obtain more up-to-date data on the data sets available for anaerobic digestion, composting, aerobic/anaerobic treatment in mechanical biological treatments (MBTs), and biogas production.
• For waste incineration, the site-specific activity data has been reviewed and revised to ensure completeness and correct allocation. Since 2021 the reported emissions are handled by the Regulators’ Inventory Database (RIDB) to standardise gap filling and extrapolation, ensuring all available data are included.
• For industrial wastewater, activity data gap-filling has been improved and the method to derive the fraction of chemical oxygen demand treated in industrial Waste Water Treatment Works has been reviewed and revised.
• Activity data for anaerobic digestion has been reviewed and revised.
• Waste landfilled and flaring data have been reviewed and revised.
• For domestic wastewater, a nitrogen balance approach is now used to account for nitrogen in sewage sludge recovery instead of the previous less accurate approach to avoiding N₂O emissions double-counts.

4.1.1 Carbon dioxide - Summary of historical emissions

• Carbon dioxide emissions have decreased by 47% from 1990 to 2020 and are currently 321 Mt CO₂ (megatonnes of carbon dioxide) (79% of UK total GHGs).
• The main sources of CO₂ emissions in 2020 are the Transport, Energy Supply, Residential, and Business sectors, which together account for 94% of total net CO₂ emissions, and are dominated by fuel combustion.
• Carbon dioxide emissions from electricity production decreased by 76% from 1990 to 2020 and contributed 54% of the total net change in CO₂ during this period.
• All sectors have shown a decrease in CO₂ emissions between 1990 and 2020. Some individual emission sources have increased, including Upstream Gas Production, House and garden machinery, and Natural gas.

4.1.2 Carbon dioxide - Plot: Emissions by Source, 1990-2020

This chart is interactive; hover over the chart to see the data values.

Note: LULUCF can be a sink, and so for clarity, is shown at the bottom of this chart.

4.1.3 Carbon dioxide - Sources of emissions and data sets

• The predominant source of emissions is fuel combustion, with the main uses being electricity generation, and use in the transport sector, manufacturing industries, and residential sector.
• The Digest of UK Energy Statistics (DUKES) and the EU Emissions Trading System (EU ETS) are key data sets for stationary combustion sources, together with information direct from operators and trade associations, such as Tata Steel and the Mineral Products Association.
• For transport, key data sources include DUKES, the UK Department for Transport (DfT) publication “Transport Statistics Great Britain”, the Rail Emissions Model, fuel consumption data from the Ministry of Defence, Civil Aviation Authority movement data, and the DfT’s Maritime Statistics.
• Most emission factors for carbon dioxide are UK-specific, based on data supplied by organisations such as the UK Petroleum Industries Association.

4.1.4 Carbon dioxide - Methodology

• For large combustion sources, emissions are estimated by combining activity data (from DUKES) with emission factors that are taken from a variety of sources including from the EU ETS, data provided by industry groups, and literature sources. For some emission sources, site specific data are available.
• Carbon dioxide emissions from transport are estimated from fuel consumed and the carbon content of fuels, with movement and journey characteristics taken into account where applicable, e.g. to provide a breakdown by vehicle type for road transport, or the domestic/international split for aviation.
• Residential fuel combustion emissions are estimated by multiplying the fuel use estimates in DUKES by an emission factor. Emission factors are either UK specific or are taken from published inventory guidelines (Intergovernmental Panel on Climate Change (IPCC) and the European Monitoring and Evaluation Programme-European Environment Agency (EMEP-EEA)).
• Emissions and removals from LULUCF are modelled according to IPCC Guidelines.

4.1.5 Carbon dioxide - Uncertainties

• Uncertainty in UK net carbon dioxide emissions in 2020 is 2%. Total emissions of carbon dioxide are dominated by fuel combustion. Carbon dioxide emissions from fuel combustion are relatively certain, since the carbon content of fuel is well known, and the energy statistics are of good quality.
• The central estimate of total carbon dioxide emissions in 2020 was estimated as 324 Mt CO₂. The Monte Carlo uncertainty analysis suggested that there was a 95% probability that the real value was between 318-330 Mt CO₂.
• Uncertainty in the trend: The Monte Carlo analysis indicates that there is a 95% probability that carbon dioxide emissions in 2020 differed from those in 1990 by -48% to -46%.

4.1.6 Carbon dioxide - Improvements

• Methodological updates to activity data in the LULUCF sector.
• The inclusion of emissions from production of ceramics other than bricks and a revision to the methodology for electric arc steelmaking in the industrial processes sector.

4.2.1 Methane - Summary of historical emissions

• Methane emissions have decreased by 62% from 1990 to 2020 and are currently 51 Mt CO₂e (13% of UK total GHGs).
• The main source sectors for methane emissions in 2020 were agriculture (48%), waste management (30%) and energy supply (10%).
• Landfilled waste methane emissions reduced by 79% from 1990 to 2020 and contributed to 57% of the total methane reduction for this period.
• Agricultural methane emissions from enteric fermentation and manure management reduced by 15% and 8%, respectively, and combined are responsible for 5% of the reduction of total methane emissions since 1990.
• Within the energy supply sector, methane emissions from open and closed coal mines decreased by 98%, which equated to 26% of the total reduction of methane emissions over the period.

4.2.2 Methane - Plot: Emissions by Source, 1990-2020

This chart is interactive; hover over the chart to see the data values.

4.2.3 Methane - Sources of emissions and data sets

• The main sources of methane emissions are waste management (mostly landfill), agriculture, and fugitive emissions from fuels (within the Energy Supply sector).
• Key data for waste management includes the pollution inventories of onshore environmental regulators, the Expenditure and Food Survey (Department for Environment, Food & Rural Affairs), UK population statistics (Office for National Statistics), water company returns to the Water Services Regulation Authority (Ofwat), and data supplied directly by the water companies. Waste arisings data are taken from waste consignments landfilled compiled by the regulatory authorities in the Devolved Administrations.
• For agriculture, the main data set used in estimation is the June Survey of Agriculture and Horticulture, published by Defra.
• Key data for fugitive methane emissions from fuels are from the Coal Authority, the Oil and Gas Authority, gas transporters, National Grid, from the pollution inventories of onshore environmental regulators and from the Environmental Emissions Monitoring System (EEMS) managed by BEIS OPRED.

4.2.4 Methane - Methodology

• Methane emissions from landfill are modelled, based on the amount and type of waste sent to landfill, the characteristics of the waste, and information about landfill management such as the amount of gas captured and used in flares and engines.
• Estimates of methane emitted from domestic wastewater handling are based on activity and emissions data from the water industry annual reporting system. From these, implied emission factors for specific emission sub-sources can be derived. Emissions from industrial waste-water treatment are estimated using the Intergovernmental Panel on Climate Change (IPCC) defaults together with UK statistics and studies.
• Emissions from enteric fermentation for the main types of relevant livestock (cattle and sheep) follow the IPCC 2006 Guidelines Tier 3 approach, using UK-specific energy balance equations. An IPCC Tier 1 approach is used for other livestock types.
• Emissions from operating coal mines are estimated by combining coal production data with an emission factor. Emissions from closed coal mines are modelled, based on estimates of the methane reserves, on mine closure dates and flooding rates.
• Emissions from upstream oil and gas production are estimated by offshore operators and reported to BEIS OPRED via EEMS, and by terminal operators that report to the onshore environmental regulatory agencies.
• Natural gas leakage from gas transmission and distribution network is estimated by the National Grid and UK gas transporters using a UK industry gas shrinkage model, combined with the methane content of natural gas based on compositional analysis.

4.2.5 Methane - Uncertainties

• Uncertainty in UK methane emissions in 2020 is 15%.
• The central estimate of total methane emissions in 2020 was estimated as 52 Mt CO₂e. The Monte Carlo uncertainty analysis suggested that there was a 95% chance of the actual value being between 45-60 Mt CO₂e.
• Uncertainty in the trend: The Monte Carlo analysis indicated that there is a 95% probability that methane emissions in 2020 differed from those in 1990 by -71% to -50%.

4.2.6 Methane - Improvements

• Methodological updates to activity data in the LULUCF sector.
• Method improvements for enteric fermentation methane emissions including updates to diet and feed rates for dairy cattle, updates to dairy cattle ages for conception, calving and death, plus updates to dairy cattle allocation across different management regimes in N Ireland.
• For waste incineration, the site-specific activity data has been reviewed and revised to ensure completeness and correct allocation.

4.3.1 Nitrous oxide - Summary of historical emissions

• Nitrous oxide emissions have decreased by 58% from 1990 to 2020 and are currently 21 Mt CO₂e (5.2% of UK total GHGs).
• The main sources of nitrous oxide emissions in 2020 were Agricultural Soils (56%), Manure Management - Ruminant (10%), and Road transport (4%). The chemical industry was a significant source in the 1990s.
• Emissions from agricultural soils decreased by 20% over the time series and contributed 10% to the total decrease in nitrous oxide emissions.
• Emissions from chemical industry processes, such as nitric and adipic acid production, decreased by over 99% from 1990 to 2020, as a result of the installation of abatement equipment and plant closures. The decrease in these emissions equates to 83% of the total decrease in nitrous oxide emissions from 1990 to 2020.

4.3.2 Nitrous oxide - Plot: Emissions by Source, 1990-2020

This chart is interactive; hover over the chart to see the data values.

4.3.3 Nitrous oxide - Sources of emissions and data sets

• Agriculture is the dominant source of nitrous oxide emissions and accounted for 69% of total nitrous oxide emissions in 2020. Chemical processes are no longer a significant source, but have had a large impact on the trend.
• The main data sets used for agriculture emissions are the June Survey of Agriculture and Horticulture and the British Survey of Fertiliser Practice published by the Department for Environment, Food & Rural Affairs (Defra).
• For fuel combustion, the key data sets are the Digest of UK Energy Statistics (DUKES) and emission factors from the Intergovernmental Panel on Climate Change (IPCC) and the European Monitoring and Evaluation Programme-European Environment Agency (EMEP-EEA) guidance.
• For industrial processes, the key data set is the Environment Agency Pollution Inventory and site specific information directly from plant operators.

4.3.4 Nitrous oxide - Methodology

• Nitrous oxide emissions from manure management are estimated by combining livestock numbers with livestock specific and animal waste system specific emission factors. The emission factors used are from UK-specific research.
• Emissions from agricultural soils are modelled using various statistical inputs, such as crop areas and fertiliser use to estimate the nitrogen cycle processes such as biological fixation and leaching.
• Emissions from fuel combustion are estimated by combining activity data (from DUKES) with emission factors that are taken from a variety of sources, mostly literature sources.
• Emissions from nitric acid production are estimated based on information supplied directly from the plant operators for the later time series. For the early part of the time series, emissions were based on total nitric acid produced and an appropriate emission factor.

4.3.5 Nitrous oxide - Uncertainties

• Uncertainty in UK nitrous oxide emissions in 2020 is 17%.
• The central estimate of total nitrous oxide emissions in 2020 was estimated as 21 Mt CO₂e. The Monte Carlo uncertainty analysis showed that there is a 95% chance that the actual value was between 18-26 Mt CO₂e.
• Uncertainty in the trend: The Monte Carlo analysis indicates that there is a 95% probability that nitrous oxide emissions in 2020 differed from those in 1990 by -70% to -42%.

4.3.6 Nitrous oxide - Improvements

• Use of a UK-specific N₂O emission factor for fertiliser applied to grassland for agricultural soils.
• For domestic wastewater, a nitrogen balance approach is now used to account for nitrogen in sewage sludge recovery instead of the previous less accurate approach to avoiding N₂O emissions double-counts.

4.4.1 Fluorinated gases - Summary of historical emissions

• Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF₆) and nitrogen trifluoride (NF₃) together comprise the fluorinated gases (F-gases). Their Global Warming Potentials (GWPs), given relative to the same mass of CO₂ range from 12 to 22,800.
• Emissions of the F-gases have decreased by 29% from 1990 to 2020 and are currently 12.245 Mt CO₂e (3% of UK total GHGs).
• Emissions of PFCs have decreased by 90% from 1990 to 2020. Emissions of SF₆ have decreased by 66% from 1990 to 2020. Emissions of NF₃ have increased by 207% from 1990 to 2020. Emissions of HFCs have decreased by 19% from 1990 to 2020.
• The majority of 2020 F-gas emissions, 95.4% (11.7 Mt CO₂e), are HFCs, with the remainder comprised of 0.41 Mt CO₂e SF₆, 0.16 Mt CO₂e PFCs, and 0.0004 Mt CO₂e NF₃.
• HFCs from halocarbon manufacture (fugitive emissions from HFC production, and HFCs from HCFC production) have decreased to 0.1 Mt CO₂e by 2020, due to the installation of abatement equipment and plant closures. Emissions from end use sources (such as refrigeration and air conditioning) therefore made up 99% of all HFC emissions in 2020.

4.4.3 Fluorinated gases - Sources of emissions and data sets

• Emissions of F-gases can occur:
  • As a by-product or fugitive emission from the production of fluorinated gases
  • As a by-product from certain industrial processes
  • Through the use of F-gases, either in products or for specific industrial applications
• The main source of HFC emissions in 2020 is refrigeration and air conditioning (9.7 Mt CO₂e). 50% of 2020 PFC emissions arise from electrical equipment and sporting goods and 48% from the manufacture of halocarbons. Electrical insulation accounted for 81% of total SF₆ emissions in 2020.
• Emissions of HFCs from refrigeration are modelled, based on bottom-up statistics for the various types of refrigeration units in use in the UK.
• Emissions of HFCs from aerosols have been derived on the basis of fluid consumption data provided by the British Aerosol Manufacturers’ Association (BAMA).
• Key data sets for other sources include the Environment Agency’s Pollution Inventory, data supplied directly by plant operators, literature sources, and international guidance.

4.4.4 Fluorinated gases - Methodology

• Emissions of F-gases from fluorinated gas manufacture and aluminium production are based on data supplied either directly from the operators to the inventory compilers, or via the regulators’ inventories (e.g. the Pollution Inventory).
• When F-gases are filled into products, emissions can occur during manufacture or filling of the product, through leakage during the product’s lifetime, and at disposal. Examples of this type of source include refrigeration and air conditioning equipment, foams and aerosols, and electrical equipment.
• Emissions from products filled with F-gases are modelled. This requires information about the amount of products in use, their typical lifetime, the amount of gas which leaks at manufacture or filling, annually during the lifetime of the product, and at the end of life.

4.4.5 Fluorinated gases - Uncertainties

• Uncertainties in UK F-gas emissions in 2020 are 10% for HFCs, 24% for PFCs, 46% for NF₃, and 5% for SF₆.
• Uncertainty on the trend: The Monte Carlo analysis indicates that there is a 95% probability that emissions in 2020 differed from those in 1990 by -29% to +2% for HFCs, -93% to -87% for PFCs, +61% to +513% for NF₃, and -70% to -62% for SF₆.

4.4.6 Fluorinated gases - Improvements

• Estimates of emissions from Airborne Warning And Control Systems for military aircraft have been improved by gathering new information from the Ministry of Defence, replacing the previous estimates and IPCC default approach.
• Estimated emissions from semiconductor manufacture have been revised to account for the outcomes of stakeholder consultation with relevant bodies to refine assumptions for growth within the sector.