Additional information on the greenhouse gas inventory

Transcription

1 Additional information on the greenhouse gas inventory During the Environment, Climate Change and Land Reform Committee session on 8 May 2018, Scottish Government officials committed to provide more detailed, written explanation of how the emissions from all the different sectors are measured in the greenhouse gas inventory. For the convenience of the Committee, this information now includes the results of the latest Scottish Greenhouse Gas Statistics release, published on 12 June The summary note on pages 23 provides information in two areas; A summary of the methodologies and data used to compile the Scottish and UK inventories. A summary of the revisions that have occurred within the Scottish inventory to date. Annexes A and B (page 4 onwards) cover these same areas but in more detail, including descriptions of methodologies used in each emissions sector; and summaries of the causes and effects of revisions to each annual publication. Office of the Chief Economic Advisor Scottish Government June 2018

2 Additional information on the greenhouse gas inventory The greenhouse gas inventory covers a wide variety of anthropogenic sources of greenhouse gas emissions; each requiring different approaches to their estimation. There are a large number of data sources used; obtained from Government statistics, regulatory agencies, trade associations, individual companies, surveys and censuses. The methods used to compile the greenhouse gas inventory are consistent with international guidance on national inventory reporting from the Intergovernmental Panel on Climate Change (IPCC). Large emitters of greenhouse gases (e.g. power stations) generally participate in the European Union Emissions Trading System (EUETS) and are required to submit sitespecific verified emissions for their activities each year. These verified emissions are used directly when compiling the inventory. Emissions from smaller emitters in the industrial and business sectors are generally estimated using information on the range of fuels and mineral inputs used in their production process, multiplied by emissionsfactors which are specific to the UK. The main emissions estimates for the residential and transport sectors follow a similar methodology, The most challenging estimates in the inventory relate to emissions involving complex biological processes and can be found in four main sectors: Forestry, landuse, agriculture and waste management. Emissions estimation in these areas generally involves complex models built upon the results of a considerable programme of academic research in each field. Irrespective of the particular methodology deployed, these methods are subject to continuous review by United Nations assessors and multilateral teams composed of members of third countries to ensure that the methodologies used in the UK (and Scottish) inventory adhere to international guidance and bestpractice. Revisions to the inventory In each release of the Scottish Greenhouse Gas Statistics publication, there have been revisions to previously published data; a feature common to all similar publications internationally. These revisions reflect improvements to the data and methodologies used to construct the UK and Scottish greenhouse gas inventories. Whilst these can pose challenges when these data are used to track emissionsreduction performance; from a dataquality perspective, revisions are desirable. This sentiment was recently echoed by the CCC in a recent report on the UK GHG inventory 1 : In summary, the UK has a robust and accurate inventory when compared internationally. Uncertainty has consistently fallen as new methodologies are incorporated. This accuracy is in part due to a comprehensive internal and international review process to ensure that the methodologies employed in producing the UK GHGI incorporate the latest scientific research, international processes and good practice guidance. 1

3 The Scottish inventory is disaggregated from the UK s National Inventory, which is prepared in line with UN guidelines and regularly reviewed for compliance with these guidelines. The UK inventory and all aspects of its development is overseen by a National Inventory Steering Committee (NISC), which makes recommendations on improvements; their prioritisation, and the timing of revisions. The Scottish Government is represented on this group although final decisions on the UK inventory are made by the UK Government. Revisions to the Scottish inventory have occurred for four main reasons; Changes to international scientific guidelines. The methods used to compile the UK inventory are consistent with international guidance from the UN. This guidance is periodically reviewed and updated. Improvements to UKlevel methodologies. The UK inventory is submitted for regular peer review by the UN and in some cases bi/multilateral reviews, which make recommendations for its improvement. Continuous improvement is also conducted locally and is encouraged by the UN. Revisions to UKwide data sources. Occasionally, revisions to statistical publications (e.g. fuel consumption statistics) can lead to revisions in the UK inventory, although these tend to be minor. However, in some cases the scope of data available is enhanced which can lead to more substantial revisions. Improvements to the methods used to disaggregate the UK inventory. Occasionally, improvements in Scotlandspecific data can allow for improvements in how the UK inventory is disaggregated. Chart 1 below shows the level of emissions in the baseline period (1990 for most gases) in each publication since the time of the current Climate Change (Scotland) Act. It shows that prior to the 2014 publication, revisions consistently acted to increase the baseline; with revisions due to revised IPCC methodologies in the 2013 publication being particularly notable. Comparison of baseline levels has been used as these impact upon the achievability of the legislated targets increases to the baseline make targets more challenging and reductions to the baseline make them relatively easier to achieve

4 Total emissions (MtCO 2 e) Chart 1 Total GHG emissions for Scotland in the 1990/1995 baseline period in successive publications Publication The net effect of the revisions to date has been to increase the baseline by around 7.8 per cent, thereby making targets harder to achieve.

5 Annex A Sectoral methodologies used to compile the Scottish and UK GHG inventories The methods used to compile the greenhouse gas inventory are consistent with international guidance on national inventory reporting from the Intergovernmental Panel on Climate Change (IPCC). The emissions estimates for specific emissions sources and sinks are calculated using either an IPCC Tier 1, Tier 2 or Tier 3 approach depending on the detailed level of data available. The tiers are summarised below: Tier 1 Simple methods with default data. Tier 2 Country specific emission factors and other data. Tier 3 Complex approaches including modelling. The direct and indirect GHGs reported in the UK and Scottish GHG inventories are estimated using methodologies which mostly correspond to the detailed sectoral Tier 2 and 3 methods in the IPCC Guidelines. Emissions are generally estimated using the following equation: Emission estimate=emission Factor Activity Data Where: Emission Factor = the amount of GHG emitted per unit of activity, e.g. CO2 per km travelled; Activity data = the total amount of activity for that sector, e.g. km driven by petrol fuelled cars. Energy supply These emissions are derived from fuel combustion for electricity and other energy production sources, and fugitive emissions from fuels (such as from mining or onshore oil and gas extraction activities). These UK emission estimates are based on bottomup activity data, including the Digest of UK Energy Statistics (DUKES) that present annual consumption of primary and secondary fuels within different economic sectors in the UK. Offshore emissions are not allocated to Scotland. Business and industrial process Emissions for this sector are derived from combustion in industrial/commercial sectors, industrial offroad machinery, process sources from decarbonisation of raw materials (such as from limestone use in cement plants) and refrigeration and air conditioning. These UK emission estimates come from various data sources including the annual UK production of clinker data and emission factors are provided by the Mineral Products Association (MPA). Some sources also include EU ETS data, the Pollution Inventory (PI) and the British Geological Survey (BGS). Transport (including International Aviation and Shipping) Transport emissions are derived from domestic aviation, road transport, railways, domestic navigation, fishing and aircraft support vehicles. It also includes

6 international aviation and shipping emissions attributed to Scotland. International Aviation and Shipping use Tier 3 methodology. A Tier 3 methodology is used for calculating exhaust emissions from passenger cars, light goods vehicles, heavy goods vehicles, buses and coaches and motorcycles. Petrol and diesel vehicle fuel consumption (and emissions) are estimated for individual vehicle types from a bottom up approach using an array of traffic statistics and exhaust emission and fuel consumption factors representing realworld performance of vehicles. These estimates are reconciled to national energy consumption statistics from DUKES. Activity data and emissions factors are used to calculate rail emissions. A new shipping emissions model has been developed as part of the UK s Greenhouse Gas Inventory Improvement Programme using 2014 high resolution terrestrial Automatic Identification System (AIS) vessel movement data supplied by the UK Maritime and Coastguard Agency. The new methodology meets and exceeds the requirements of a Tier 3 methodology set out in the EMEP EEA Emissions Inventory Guidebook 2016 and the requirements for reporting national greenhouse gas emissions to the UNFCCC under the 2006 IPCC Guidelines. The new methodology carries out an emission calculation specific to each vessel and for each point of the vessel s voyage around the UK coast that is tracked with AIS receivers on the UK shore. Public Sector Buildings These emissions are derived from the combustion of fuel in public sector buildings. Emissions for this category are calculated based on multiplying activity data on fuel consumption by an emission factor. Residential emissions Residential emissions are derived from fuel combustion for heating/cooling and garden machinery and fluorinated gases released from aerosols/metered dose inhalers. Emissions for this category are calculated based on multiplying activity data on fuel consumption by an emission factor. Agriculture and Related Land Use Agriculture emissions are derived from cropland, grassland along with emissions from land converted to cropland and grassland. It also covers emissions from livestock, agricultural soils, stationary combustion sources and offroad machinery. For livestock, all cattle and sheep, a Tier 3 approach has been implemented whereby enteric methane emissions are estimated from dry matter intake, and feed dry matter intake is estimated using UKspecific metabolisable energy balance equations together with animal production and feed characteristics. Enteric methane emissions from other cattle, including dairy sector replacements and calves, and all beef sector cattle, are estimated using the same approach as for dairy cows but with different relationships between enteric emission and dry matter intake for lactating and nonlactating cattle. Emissions from manures during storage are calculated for different animal waste management systems as defined by the IPCC.

7 Direct emissions of nitrous oxide from agricultural soils are estimated using IPCC (2006) Tier 2 methodology. CO2 emissions due to the application of urea and related compounds are estimated using the Tier 1 methodology from the IPCC 2006 Guidelines. Emissions are estimated for 77 different types of portable or mobile equipment powered by diesel or petrol driven engines. These range from machinery used in agriculture such as tractors and combine harvesters; industry such as portable generators, forklift trucks and air compressors; construction such as cranes, bulldozers and excavators; domestic lawn mowers; aircraft support equipment. Development emissions These are derived from settlements and from land converted to settlements. Activity data includes Land Cover Map 2015, urban and suburban land cover. This is multiplied by relevant emissions factors. Forestry emissions Forestry emissions and sequestration activities are derived from changes in net emissions relating mainly to stock changes, resulting from afforestation, deforestation and harvested wood products. The UK reports carbon stock changes in all forests. Estimates of carbon stock gains and losses for biomass and soils are modelled based on planting history, productivity (yield class) data and assumptions over approaches to forest management. Forest carbon stock changes and fluxes are modelled by CARBINE, the Forest Research forest carbon stock model. CARBINE takes account of the effects of forest management on carbon stocks, and also calculates the carbon stocks in the Harvested Wood Products pool. Carbon stock changes resulting from afforestation on Cropland, Grassland and Settlement areas are calculated. 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. Waste management Emissions from water are derived from waste disposed of to landfill sites, waste incineration, and the treatment of waste water. The UK approach to calculating emissions of methane from landfills uses a Tier 2 methodology based on national data on waste quantities reported to the Scottish Environmental Protection agency; composition, properties and disposal practices over several decades. The equations for calculating methane generation use a first order decay (FOD) methodology.

8 Baseline Period Total emissions (MtCO 2 e) Annex B: Historical revisions to the Scottish GHG Inventory Chart 1 below shows the level of emissions in the baseline period (1990 for most gases) in each publication since the time of the current Climate Change (Scotland) Act. It shows that prior to the 2014 publication, revisions consistently acted to increase the baseline. Comparison of baseline levels has been used throughout this section as these impact upon the achievability of the legislated targets increases to the baseline make targets more challenging and reductions to the baseline make them relatively easier to achieve Chart 1 Total GHG emissions for Scotland in the 1990/1995 baseline period in successive publications Publication The net effect of the revisions to date has been to increase the baseline by around 7.8 per cent, thereby making targets harder to achieve. Whilst comparison of baseline levels is used as the main metric in this section, the chart below also illustrates the net effect of revisions between the and (most recent) inventories across the timeseries. Chart 2 Cumulative impact of all revisions to total GHG emissions between the 2008 (used for original target levels) and 2016 (latest) publications

9 Revisions to the Scottish inventory have occurred for four main reasons; Changes to international scientific guidelines. The methods used to compile the UK inventory are consistent with international guidance from the UN. This guidance is periodically reviewed and updated. Improvements to UKlevel methodologies. The UK inventory is submitted for regular peer review by the UN and in some cases bi/multilateral reviews, which make recommendations for its improvement. Continuous improvement is also conducted locally and is encouraged by the UN. Revisions to UKwide data sources. Occasionally, revisions to statistical publications (e.g. fuel consumption statistics) can lead to revisions in the UK inventory, although these tend to be minor. However, in some cases the scope of data available is enhanced which can lead to more substantial revisions. Improvements to the methods used to disaggregate the UK inventory. Occasionally, improvements in Scotlandspecific data can allow for improvements in how the UK inventory is disaggregated. The UK participates in a number of bilateral exchanges and regular reviews with other countries. This allows for sharing of good practice as well as to provide independent expertise to review estimates. The UKs programme of peer review is managed by the NISC as part of the improvement programme. A summary of recent international reviews is listed in the table below. Summary of recent UN and multilateral reviews of the UK GHG Inventory. Year Review 2017 Report on the individual review of the annual submission of the United Kingdom of Great Britain and Northern Ireland submitted in 2017 (report received march 2018) 2015 Bilateral review with Denmark on the Energy and Industrial Process Sectors 2015 Multilateral review on Quality Assurance and Quality Control UK, Denmark, France and the Netherlands Annual UNFCCC review 2014 Independent Review of the UK Kyoto Protocol LULUCF Inventory Estimates 2014 Bilateral review with Germany on the energy and waste sectors 2012 Peer review of all Sectors except Sector 5 conducted by EC Technical Experts 2011 Bilateral review of Fgases (2E, 2F) between Austrian, German and UK inventory The following section documents the reasons for the main revisions to the Scottish inventory in each year since the 2008 release. A more detailed account of these revisions has been published for each successive publication in the annual official statistics release

10 Key baseline revisions in the 2009 inventory (MtCO 2 e) Agriculture and Related Land Use Forestry Business and Industrial Process Waste International Management Aviation and Shipping (IA&S) 0.76 Residential Public Energy Supply Development Transport (excluding IA&S) Waste Management. The model which was used to estimate methane emissions from waste from landfill sites was altered to incorporate a range of data specific to the devolved administrations. Agriculture and Related Land Use. New data became available from the Countryside Survey (2007) which led to revisions to estimates of landcover. Data on emissions from sewage sludge used as fertiliser in agricultural soils were included in the inventory for the first time. Energy Supply. Data scope changed, making it possible to calculate emissions from a larger number of point sources than previous inventories. Aviation and Shipping. There was a reallocation of emissions from national to international shipping. The revised method reestimated domestic navigation using better quality data on national ship movements and assigned the remaining emissions to international shipping. Transport (other). Revised DVLA data indicated that there were more newer cars than previously estimated for Scotland and that there were more smallerengined cars registered in Scotland than the GB average. Residential. Revised estimates in the source data for fuel consumption by households specifically larger estimates of nongas fuel use (such as solid fuels). These revisions led to a 1.6 Mt increase in baseline emissions compared to the previous publication.

11 Key baseline revisions in the 2010 inventory (MtCO 2 e) Agriculture and Related Land Use Forestry Business and Industrial Process Waste International Management Aviation and Shipping (IA&S) Residential Public Energy Supply Development Transport (excluding IA&S) Business and Industrial Process Revision to the allocation of other petroleum gas use in Scotland. Change to the sectoral classification of number of installations in response to a UNFCCC review. Revision to the UKwide model for hydrofluorocarbon emissions. Agriculture and Related Land Use Incorporation of Scotlandlevel data on crop areas and crop production. routine updates to data on animal numbers. Public Sector. Routine revisions to source data. Energy Supply. Incorporation of revised data on petroleum fuels in refining and for the allocation of gas and oil to the upstream oil and gas sector. Waste Management. Consultation with waste sector experts led to the collation of new information from new waste survey and compositional studies, such as a municipal solid waste composition study for Scotland. These revisions led to a 0.5 Mt increase in baseline emissions compared to the previous publication. Summary of the impact of revisions to this, and the previous, inventory against targets. Annual targets (MtCO2e) Original emissions reduction required Emissions reduction now required (2010 publication) Baseli ne

12 Key baseline revisions in the 2011 inventory (MtCO 2 e) Agriculture and Related Land Use Forestry Business and Industrial Process Waste Management 6 International Aviation and Shipping (IA&S) Business and Industrial Process Incorporation of new estimates in the UK inventory for the use of petroleum fuels in industrial boilers, particularly offgases from petrochemical production processes being used in boilers on specific industrial sites. Incorporation of new UKwide estimates for emissions from biomass use as a fuel, impacting upon both the Scottish Inventory and the Digest of UK Energy Statistics (DUKES) activity data for gasfired autogeneration. Waste Management Inclusion of emissions from industrial wastewater treatment had been included in the UK and devolved administration inventories for the first time. A revision was made to the methane emissions factors for waste water treatment, sludge treatment and disposal of sewage sludge to land. These revisions led to a 0.7 Mt increase in baseline emissions compared to the previous publication. Summary of the impact of revisions to this inventory against targets Residential Public Energy Supply Development Transport (excluding IA&S) Annual targets (MtCO2e) Original emissions reduction required Emissions reduction now required (2011 publication) Baselin e

13 Key baseline revisions in the 2012 inventory (MtCO 2 e) Agriculture and Related Land Use Forestry 4 2 Business and Industrial Process 8 Waste International Management Aviation and Shipping (IA&S) Residential Public Energy Supply Development Transport (excluding IA&S) Agriculture and Related Land Use. Estimates of methane (CH4) emissions increased due to improved estimates of the treatment of animal wastes. Waste Management. Revisions to latter part of the timeseries due to incorporation of data on methane from landfill gas collected and burnt in landfill gas engines and flares. Forestry. Change in the methodology in models of forest land area, particularly the representation of forest areas which have been in existence prior to Improved data of tree species, growth rates, forest management practices; and a better estimation of the capture and storage of carbon within forest soils. Public Sector. Reallocation of the economic classification of some buildings which consume natural gas in the underlying energy statistics. Also incorporation of new datasets such as Display Energy Certificates. These revisions led to a 2.6 Mt increase in baseline emissions compared to the previous publication. Summary of the impact of revisions to this inventory against targets. Annual targets (MtCO2e) Original emissions reduction required Emissions reduction now required (2012 publication) Baselin e

14 Key baseline revisions in the 2013 Inventory (MtCO 2 e) Waste Management Agriculture and Related Land Use Business and Industrial Process Energy Supply Transport (including International Aviation and Shipping) Development Public Sector Buildings Forestry Residential Implementation of IPCC (2006) Guidelines The UK and the Scottish greenhouse gas inventory are required to comply with reporting guidelines as prescribed by the IPCC. This publication included a number of substantial changes resulting from incorporation the revised guidance contained in the IPCC s 4th Assessment Report. The main revisions included: 1. Revised Global Warming Potentials (GWP) of greenhouse gases. In this release: the GWP of methane was raised from 21 to 25 which led to substantial increased emissions from waste management and agriculture in particular; The GWP of Nitrous Oxide was lowered slightly from 310 to 298, affecting landuse; and A number of revisions were made to the range of Fgases included in the inventory, mainly affecting business and industry. 2. Incorporation of new data sources and methodologies. New sources included the use of nitrous oxide in anaesthesia and emissions from composting. Some existing sources where updated with new IPCC methodologies, one example related to emissions of F gases in the Business and Industrial Process sector. 3. New greenhouse gas. Nitrogen trifluoride (NF3) was included in the inventory for the first time. Overall, these revisions resulted in a 5.2 Mt increase in baseline emissions compared to the previous publication. Summary of the impact of revisions to this inventory against targets. Annual targets (MtCO2e) Original emissions reduction Baselin e

15 required Emissions reduction now required (2013 publication) Key baseline revisions in the 2014 Inventory (MtCO 2 e) Agriculture and Related Land Use Forestry Residential Waste Management Business and Industrial Process Public Sector Buildings Development Energy Supply Transport (including International Aviation and Shipping) Forestry. A UKwide correction was made to the model used to estimate net emissions from forestry and harvested wood products Agriculture and Related Land Use. A revision was made to the emission factor for grassland drainage; and Research to derive more representative, UKspecific emission factors to Nitrous Oxide emissions in the Agriculture and Related Land Use sector was completed and incorporated into the land use models. These methodological changes resulted in a reduction of 3.5 MtCO2e in baseline emissions compared to the previous publication Summary of the impact of revisions to this inventory against targets. Baselin e Annual targets (MtCO2e) Original emissions reduction required Emissions

16 reduction now required (2014 publication) Key baseline revisions in the 2015 inventory (MtCO 2 e) Agriculture and Related Land Use Forestry. 4.2 Forestry Residential Waste Management Business and Industrial Process Public Sector Buildings Development Energy Supply Transport (including International Aviation and Shipping) Methodological changes affecting the soil carbon stocks following afforestation, particularly when planted upon the types of carbonrich soils found in Scotland. This particularly affected the biomass carbon stock change in "Forest Remaining Forest" category, e.g. harvesting and thinning of trees. Waste Management Methodological changes to the waste model for Scotland resulted in larger revisions earlier in the series due to previous overestimation of Scotland's share of UK waste activity. This was due to revisions to the assumptions around decay rates of waste materials; how much methane is generated over time and then when it is generated, and how much of it is oxidised within the landfill boundary layer or captured and used in flares and engines. These methodological changes resulted in a net reduction in the baseline of 0.2 MtCO2e compared to the previous publication Summary of the impact of revisions to this inventory against targets. Annual targets (MtCO2e) Original emissions reduction required Emissions reduction now Baselin e

17 required (2015 publication)

18 Key baseline revisions in the 2016 inventory (MtCO 2 e) Agriculture and Related Land Use Forestry Residential Waste Management Business and Industrial Process Public Sector Buildings Development Energy Supply Transport (including International Aviation and Shipping) Forestry Methodological changes related to the inclusion of the effect of accumulation of leaflitter in lowering emissions was incorporated more accurately into forestry models. This acted to increase the carbon sink associated with forestry activities in Scotland. The area reported as forest remaining forest was also revised upwards. There were also changes in the CARBINE model for calculating forest carbon stock. This resulted in an increase in the magnitude of the sink from forest land across the time series, increasing the sink in the latter part of the timeseries in particular. Shipping Improvements to the methodology for estimating shipping emissions has resulted in an increase in the estimates for gas oil and fuel oil used in Scotland. This has caused recalculations for emissions from domestic navigation and fishing vessels. Agriculture and Related Land Use Lower estimated nitrous oxide emissions from agricultural soils and the use of a new emission factor model for enteric fermentation incorporating UKspecific parameters are the largest contributors to recalculations from the agriculture sector in Scotland These methodological changes resulted in a net reduction in the baseline of 1.4 MtCO2e compared to the previous publication Summary of the impact of revisions to this inventory against targets. Annual targets (MtCO2e) Original emissions reduction required Emissions reduction now Baselin e

19 required (2016 publication)