Aircraft Emissions
<P>Aircraft Emissions</P><P>**** Hidden Message *****</P> Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories<BR>Aircraft Emissions 93<BR>AIRCRAFT EMISSIONS<BR>ACKNOWLEDGEMENTS<BR>This paper was written by Kristin Rypdal (Statistics Norway). It was reviewed by Niels Kilde, Steve Seide and<BR>Karen Treanton.<BR>ABSTRACT<BR>The current tiered methodologies in the Greenhouse Gas Inventory Reference Manual provide a good framework<BR>for good practice for estimating and reporting the emissions from aviation. The main difficulty and uncertainty<BR>lies in the distribution of fuel between domestic and international use. Only domestic use is to be included in the<BR>national total when reporting to the United Nations Framework Convention on Climate Change (UNFCCC).<BR>Consequently, good practice methodologies are particularly needed in order to collect relevant and accurate data<BR>on domestic fuel used for aviation. Emissions of nitrous oxide (N2O) and methane (CH4) from aviation are highly<BR>uncertain, but do not contribute much to national totals.<BR>Background Paper<BR>94 Energy Sector<BR>1 INTRODUCTION<BR>The total contribution of aircraft emissions to total anthropogenic carbon dioxide (CO2) emissions was considered to<BR>be about 2 percent in 1990 (IPCC, 1990). However, air traffic in the world is growing, and will likely continue to<BR>grow. Though there is an improvement in fuel efficiency of new aircraft, the long lifetime of aircraft and the<BR>expected growth in air traffic imply that this emission source in the future will increase in importance.<BR>The UNFCCC Secretariat has concluded that the method to estimate bunker (ships and aircraft) emissions is<BR>incomplete and not consistent between Parties, and that most parties have not specified the methodology used.<BR>Reported data also indicate that, for shipping and aircraft bunkers, CO2 accounts for 98 percent of the CO2<BR>equivalent emissions.<BR>The effect of emissions from aircraft at high altitudes (especially nitrogen oxides (NOx) and water vapour) is of<BR>particular concern. In the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC<BR>Guidelines), emissions from aircraft are to be reported in an equal manner to emissions from other sources, not<BR>specifying the altitude of the emissions and applying the same Global Warming Potential (GWP) values.<BR>Nitrogen oxides and water vapour are not included in the Kyoto Protocol.<BR>1 . 1 Nature, magnitude, and distribution of<BR>sources<BR>Emissions from aircraft originate from fuel burned in aircraft engines. Greenhouse gas emissions are the<BR>combustion products and by-products. CO2 and NOx are most important, but also methane, nitrous oxide and<BR>other by-product gases are emitted. The fuel use and emissions will be dependent on the fuel type, aircraft type,<BR>engine type, engine load and flying altitude.<BR>Two types of fuels are used. Gasoline is used in small piston engined aircraft only. Most aircraft run on kerosene,<BR>and the bulk of fuel used for aviation is kerosene.<BR>In general, there exist two types of engines; reciprocating piston engines, and gas turbines (Olivier (1991) and<BR>EEA (2000)). In piston engines, energy is extracted from a combustion chamber by means of a piston and crank<BR>mechanism that drives the propellers to give the aircraft momentum. In gas turbines compressed air is heated by<BR>combustion in a combustion chamber and the major part of this is used for propulsion of the aircraft. A part of<BR>the energy contained in the hot air flow is used to drive the turbine that in turn drives the compressor. Turbojet<BR>engines use only energy from the expanding exhaust stream for propulsion, whereas turbofan and turboprop<BR>engines use energy from the turbine to drive a fan or propeller for propulsion.<BR>The air traffic is often divided into four categories (EEA 2000):<BR>• Civil IFR (Instrumental Flight Rules) flights;<BR>• Civil VFR (Visual Flight Rules) flights, also called general aviation;<BR>• Civil Helicopters, and<BR>• Operational Military flights.<BR>Most emissions originate from the first category, which covers the scheduled flights of “ordinary” aircraft.<BR>Operations of aircraft are usually divided into two main parts (Figure 1) (EEA 2000):<BR>• The Landing/Take-off (LTO) cycle which includes all activities near the airport that take place below the<BR>altitude of 3000 feet (1000 m). This therefore includes taxi-in and out, take-off, climb-out, and approachlanding.<BR>The LTO is defined in ICAO (1993), and<BR>• Cruise which here is defined as all activities that take place at altitudes above 3000 feet (1000 m). No upper<BR>limit of altitude is given. Cruise, in the inventory methodology, includes climb to cruise altitude, cruise, and<BR>descent from cruise altitudes.<BR>Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories<BR>Aircraft Emissions 95<BR>F i g u r e 1 S t a n d a r d f l y i n g c y c l e<BR>3000 feet<BR>(ca. 1000 m)<BR>Landing<BR>Taxi / idle<BR>Take-off<BR>Taxi / idle<BR>Descent<BR>Climb<BR>LTO-cycle<BR>Cruise<BR>1 . 2 The current state of inventory methodologies<BR>The current methodology proposes two Tiers. The most simple methodology (Tier 1) is based on knowledge of<BR>fuel use only, while the Tier 2 is also based on information of the number of LTOs. In both Tiers emissions from<BR>domestic and international air traffic are to be estimated separately. The fuel used for international air traffic is<BR>defined as all fuel sold for aviation in the reporting country not used for domestic aviation.<BR>1.2.1 Tier 1<BR>The simplest methodology is based on an aggregate figure of fuel consumption for aviation to be multiplied with<BR>average emission factors. The emission factors have been averaged over all flying phases based on an assumption<BR>that 10 percent of the fuel is used in the LTO phase of the flight.<BR>The following are the default emission factors:<BR>CO2 : 19.5 tonne C/PJ;<BR>CH4 : 0.5 kg/PJ, and<BR>N2O : 2 kg/PJ<BR>Aggregate emission factors are also given for NOx, carbon monoxide (CO), sulphur dioxide (SO2) and nonmethane<BR>volatile organic compounds (NMVOCs).<BR>1.2.2 Tier 2<BR>In the Tier 2 methodology, a distinction is made between emissions below and above 1000 m (3000 feet). The<BR>emissions in these two flying phases are estimated separately.<BR>LTO emissions<BR>Emissions and fuel used in the LTO phase are estimated from statistics on the number of LTOs (aggregate or per<BR>aircraft type) and default emission factors or fuel use factors per LTO (average or per aircraft type).<BR>For the aircraft type based approach (Table 1), the table covers aircraft types frequently used for domestic and<BR>international aviation. The methodology also gives aggregate emission factors per LTO (Table 2). The<BR>aggregated emission factors are proposed for national and international aircraft separately, and for old and<BR>average fleet.<BR>Background Paper<BR>96 Energy Sector<BR>TABLE 1<BR>DEFAULT FUEL USE AND EMISSION FACTORS FOR SOME AIRCRAFT TYPES FOR LTO CYCLE. KG/LTO<BR>Aircraft<BR>typea)<BR>CO2 CH4<BR>b) N2Oc) NOx CO NMVOCs SO2<BR>d) Fuel<BR>A300 5470 1.0 0.2 27.21 34.4 9.3 1.7 1730<BR>A310 4900 0.4 0.2 22.7 19.6 3.4 1.5 1550<BR>A320 2560 0.04 0.1 11.0 5.3 0.4 0.8 810<BR>BAC1-11 2150 6.8 0.1 4.9 67.8 61.6 0.7 680<BR>BAe 146 1800 0.16 0.1 4.2 11.2 1.2 0.6 570<BR>B707* 5880 9.8 0.2 10.8 92.4 87.8 1.9 1860<BR>B727 4455 0.3 0.1 12.6 9.1 3.0 1.4 1410<BR>B727* 3980 0.7 0.1 9.2 24.5 6.3 1.3 1260<BR>B737-300 2905 0.2 0.1 8.0 6.2 2.0 0.9 920<BR>B737* 2750 0.5 0.1 6.7 16.0 4.0 0.9 870<BR>B737-400 2625 0.08 0.1 8.2 12.2 0.6 0.8 830<BR>B747-200 10680 3.6 0.3 53.2 91.0 32.0 3.4 3380<BR>B747* 10145 4.8 0.3 49.2 115 43.6 3.2 3210<BR>B747-400 10710 1.2 0.3 56.5 45.0 10.8 3.4 3390<BR>B757 4110 0.1 0.1 21.6 10.6 0.8 1.3 1300<BR>B767 5405 0.4 0.2 26.7 20.3 3.2 1.7 1710<BR>Caravelle* 2655 0.5 0.1 3.2 16.3 4.1 0.8 840<BR>DC8 5890 5.8 0.2 14.8 65.2 52.2 1.9 1860<BR>DC9 2780 0.8 0.1 7.2 7.3 7.4 0.9 880<BR>DC10 7460 2.1 0.2 41.0 59.3 19.2 2.4 2360<BR>F28 2115 5.5 0.1 5.3 54.8 49.3 0.7 670<BR>F100 2340 0.2 0.1 5.7 13.0 1.2 0.7 740<BR>L1011* 8025 7.3 0.3 29.7 112 65.4 2.5 2540<BR>SAAB 340 945 1.4(E) 0.03(E) 0.3(E) 22.1(E) 12.7(E) 0.3(E) 300 (E)<BR>Tupolev<BR>154<BR>6920 8.3 0.2 14.0 116.81 75.9 2.2 2190<BR>Concorde 20290 10.7 0.6 35.2 385 96 6.4 6420<BR>GAjet 2150 0.1 0.1 5.6 8.5 1.2 0.7 680<BR>Source: IPCC Guidelines on National Greenhouse Gas Inventories. Reference Manual, page 1.96.<BR>*The emission factors for domestic aviation have been derived from an average of a number of typical aircraft. For domestic aircraft, the<BR>average fleet is represented by Airbus A320, Boeing 727, Boeing 737-400, Mc Donell Douglas DC9 and MD 80 aircraft. The old fleet is<BR>represented by Boeing B737 and Mc Donell Douglas DC9. For international traffic the average fleet is represented by Airbus A300,<BR>Boeing 767, B747 and Mc Donell Douglas DC10, whilst the old fleet is represented by the Boeing B707, Boeing 747 and Mc Donell<BR>Douglas DC8. Sulphur content of the fuel is assumed to be 0.05% S for both LTO and cruise activities<BR>Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories<BR>Aircraft Emissions 97<BR>TABLE 2<BR>DEFAULT FUEL USE AND EMISSION FACTORS FOR AVERAGE AIRCRAFT FOR LTO CYCLE AND CRUISE<BR>Domestic Fuel SO2 CO CO2 NOx NMVOCs CH4 N2O<BR>LTO (kg/LTO) - Average fleet 850 0.8 8.1 2680 10.2 2.6 0.3 0.1<BR>LTO (kg/LTO) - Old fleet 1000 1.0 17 3150 9.0 3.7 0.4 0.1<BR>Cruise (kg/ton) 1.0 7 3150 11 0.7 0 0.1<BR>International Fuel SO2 CO CO2 NOx NMVOCs CH4 N2O<BR>LTO (kg/LTO) - Average fleet 2500 2.5 50 7900 41 15 1.5 0.2<BR>LTO (kg/LTO) - Old fleet 2400 2.4 101 7560 23.6 66 7 0.2<BR>Cruise (kg/ton) 1.0 5 3150 17 2.7 0 0.1<BR>Source: IPCC Guidelines on National Greenhouse Gas Inventories. Reference Manual, page 1.98.<BR>Cruise emissions<BR>The cruise emissions will be dependent on the length of the flight (among other variables). In the Tier 2<BR>methodology, the fuel used in the cruise phase is estimated as total fuel use minus fuel used in the LTO phase of<BR>the flight (Figure 2). This is performed for domestic and international aviation separately.<BR>The estimated fuel use is to be multiplied with aggregate emission factors (Table 2) in order to estimate the<BR>emissions. According to the default emission factors, methane is not emitted in the cruise phase of the flight.<BR>2 METHODOLOGICAL ISSUES<BR>We will here highlight some issues of particular concern related to the proposed methodologies. Some of these<BR>issues are common to both Tiers, while some are specific.<BR>The main difficulty in applying the methodology is to get the correct data on fuel use. The energy statistics in<BR>most countries only give data on total sales or supply of fuel for aviation, without distinguishing between<BR>domestic and international as required for reporting of emissions of greenhouse gases. The IPCC Guidelines do<BR>not give any advice on how to obtain these data as required.<BR>Kerosene is also used for heating purposes. Kerosene used for aviation and kerosene used for heating is usually<BR>distinguished in the energy statistics (different qualities), but there may be countries where these data are aggregated.<BR>The emission factors of CO2 per fuel basis are well determined as aviation fuel has a well-defined quality. This<BR>means that country-specific values of CO2 emission factors (on a per fuel basis) should never deviate much from<BR>default values. The emission factors of N2O and CH4 must be considered to be highly uncertain. However, as the<BR>latter pollutants do not contribute much to total emissions in the overall inventory, this is not of a great concern.<BR>Countries should be encouraged to determine better emission factors for CH4 and N2O to improve the default<BR>values in the future.<BR>2 .1 Tier 1<BR>The Tier 1 methodology is very simple, but is usually appropriate for estimating CO2, CH4 and N2O emissions<BR>with the current knowledge of emission factors.<BR>The main reasons for encouraging the use of higher tiers are as follows:<BR>• Increased transparency with respect to reporting of other pollutants in other inventories (e.g. CORINAIR);<BR>• Gives the possibility to obtain time series reflecting changes in technology;<BR>• Gives the possibility to verify the estimates;<BR>• Allows (possible future) reporting of emissions from cruise and LTO separately, and<BR>• Gives more accurate NOx estimates.<BR>Background Paper<BR>98 Energy Sector<BR>F i g u r e 2 T i e r 2 m e t h o d o l o g y f o r e s t ima t i n g e m i s s i o n s f r o m<BR>a i r c r a f t<BR>2 .2 Tier 2<BR>Data to be used in the Tier 2 methodology (the aggregated number of LTOs) are likely to be available in most<BR>countries. However, the LTO per aircraft type is not always available. In both cases, the methodology will require<BR>that the number of LTOs be available for domestic and international aviation separately, which may not always<BR>be the case.<BR>There are some weaknesses in the Tier 2 methodology:<BR>• The aggregate emission factors and fuel use factors are based on fuel use of average aircraft. If the average<BR>aircraft is different in a particular country the estimated fuel use may be wrong. This may be the case in<BR>countries with a higher proportion of small or large aircraft than assumed in Table 2. The default aircraft are,<BR>in fact, quite large and will overestimate LTO emissions in most countries;<BR>• If the estimation is based on Table 1, some common aircraft will not be found in the table. These may be new<BR>aircraft with presumably lower fuel consumption than average (e.g. MD80, MD90 and new generation 737s)<BR>and perhaps also some special type of aircraft that may be in use outside USA and Western Europe, and<BR>x EF x EF<BR>x EF x EF<BR>Emissions for<BR>Domestic<BR>LTO<BR>Emissions for<BR>International<BR>LTO<BR>Domestic Cruise<BR>Fuel Use<BR>Emissions for<BR>Domestic<BR>Cruise<BR>Emissions for<BR>International<BR>Cruise<BR>International Cruise<BR>Fuel Use<BR>Fuel Sold for<BR>International<BR>Use<BR>Fuel Sold for<BR>Domestic<BR>Use<BR>Number of<BR>LTO’s for<BR>Domestic<BR>Flights<BR>Domestic LTO<BR>Fuel Use<BR>International LTO<BR>Fuel Use<BR>Fuel Consumption<BR>per Domestic<BR>LTO<BR>Fuel Consumption<BR>per International<BR>LTO<BR>Number of<BR>LTO’s for<BR>International<BR>Flights<BR>Total National Number<BR>of LTO’s<BR>Total National Fuel Sold for<BR>Aircraft<BR>Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories<BR>Aircraft Emissions 99<BR>• LTO data are available for scheduled flights only (category 1). Flights with e.g. helicopters, taxi flight,<BR>pleasure flights etc. will not be covered by the methodology. In most countries these emissions are<BR>insignificant, but in some countries they will have to be taken into account.<BR>The emission factors given in the Tier 2 methodology reflect the state-of-the-art knowledge (ICAO (1995) and<BR>ANCAT/EC (1998)). The knowledge on emissions during the LTO part of the flight is, however, far better than<BR>the knowledge on emissions during cruise. The emission factors for methane and nitrous oxide are generally<BR>highly uncertain. The methane data are taken from Olivier (1991), but the source of the nitrous oxide data in the<BR>IPCC Guidelines is not quite clear. The default value is, however, consistent with AERONOX (1995). Nitrous<BR>oxide emission per TJ oil is presented to be 3.5 times higher for aviation than for other forms of oil combustion.<BR>As almost all types of aircraft are widely used all over the world, the default fuel use factors and emission factors<BR>for individual aircraft should in principle be applicable to all countries. The national average may vary from<BR>country to country depending on the average aircraft fleet and average distance flown.<BR>However, as the current methodology is based on total fuel use for aviation, most of the weaknesses presented<BR>above will not influence the accuracy of the reported direct greenhouse gas emission figures to a large extent.<BR>2 . 3 Other aircraft methodologies<BR>More detailed methodologies have been developed to better estimate fuel use and NOx emissions from aircraft<BR>based on more exact data on flying conditions (e.g. ANCAT/EC2). As mentioned, this level of sophistication is<BR>not really necessary for the current reporting requirements.<BR>A “high tier” methodology has been developed for the UNECE Emission Inventory Guidebook that enables<BR>emission estimates to be made from flight movement data only. This will be a simplification of the ANCAT/EC2<BR>methodology. This methodology requires data on cruise flight distances and gives fuel use factors for individual<BR>aircraft per mile cruised in addition to LTO. This methodology may help countries to estimate their fuel use for<BR>domestic and international air traffic directly, if other sources of data not are available. The methodology may<BR>also be used for verification of other data.<BR>The UNECE Emission Inventory Guidebook also provides a methodology for estimating emissions from military<BR>aircraft, helicopters and propelled aircraft. Emissions of water vapour, may, if required, be estimated from the<BR>CO2 emissions, assuming a stoichiometric equation.<BR>2 .4 Selection of good practice methods<BR>The current guidelines form the background for selecting good practice methodologies based on the available<BR>data in the reporting country. Use of Tier 2 rather than Tier 1 will increase flexibility, transparency and<BR>comparability more than the accuracy. However, good practice may also be used to estimate the emissions from<BR>more advanced approaches not mentioned in the current guidelines. Such methodologies may involve modelling<BR>the emissions for specific aircraft from various flight modes, depending on altitudes, cruise distances etc.<BR>However, it should be emphasised that such advanced methodologies will, in particular, improve the estimates of<BR>nitrogen oxides emissions, but will not have any effect on the carbon dioxide estimates and only small effect on<BR>methane and nitrous oxide estimates.<BR>2.4.1 Activity Data<BR>The options for determining good practice activity data will depend on the available data and options for data<BR>collection in the reporting country. The most important activity data are the consumption of kerosene (and<BR>aviation gasoline) used for domestic and international aviation, respectively. When using Tier 2, data on the<BR>number of LTOs are also needed. It is assumed that total fuel used for aviation is available from the fuel statistics<BR>in all countries.<BR>Good practice methodologies for determining the domestic fuel used include:<BR>• Determining the domestic fuel use from surveys: In most countries there will be just a few airline companies<BR>involved in domestic air transport. Consequently, it will be easy to request annual data from these companies.<BR>This will be difficult if there are very many airline companies in the country, too few (due to confidentiality)<BR>or the airline companies themselves may find it difficult to distinguish their domestic fuel usage from the<BR>international one, and<BR>Background Paper<BR>100 Energy Sector<BR>• Determining the domestic fuel use from sales statistics: In a lot of countries, sales statistics may give a split<BR>between domestic use and international use since they may be taxed at different rates. This is easier, but less<BR>transparent, than option 1.<BR>If options 1 and 2 not are possible, the domestic fuel use has to be estimated from aircraft movement data and<BR>fuel use factors. This may be time consuming and not always very accurate.<BR>2.4.2 Emission factors<BR>The choice of emission factors for aircraft will depend on the national aircraft fleet:<BR>• Are data on national type of aircraft in use available? If not the default data have to be used;<BR>• Are the emission factors for national aircraft fleet close to the default values in Table 2? If this is so the<BR>default values are appropriate, if not, the use of aircraft specific default values are encouraged;<BR>• Are the aircraft types used in the country included in Table 1? If yes, the table is directly useful. If not, data for<BR>missing aircraft have to be supplemented or use of data for similar aircraft type in the table is necessary, and<BR>• Is there a high proportion of flights with helicopters and small aircraft in the country? If yes, the emissions<BR>from these will have to be estimated separately.<BR>As aircraft have a fixed technology, it is usually not appropriate to use country-specific emission factors unless<BR>documented very thoroughly and are found to be better than the default values. Reasons for such deviations may be<BR>different technologies/aircraft types, different flying conditions and/or high level investigations of national emissions.<BR>2.5 Uncertainty assessment<BR>There is uncertainty connected to both activity data and emission factors:<BR>Activity data The uncertainty will depend on the data collection methodology. The uncertainty will be lowest for<BR>option 1 above and higher for all other options. With option 1, covering all airline companies, the uncertainty<BR>will most likely be less than ± 5 percent The uncertainty may be very high if appropriate data on domestic and<BR>international fuel consumption are not obtained.<BR>Emission Factors (uncertainty ranges will be subject to discussion)<BR>• The CO2 emission factor is well determined (within ± 5 percent);<BR>• The uncertainty of the methane emission factor may be as high as a factor of 2, and<BR>• The uncertainty of the nitrous oxide emission factor may be orders of magnitude.<BR>2 .6 Compl e teness<BR>Only the emissions from domestic aviation are to be reported as a part of national totals. Emissions from bunkers<BR>(international aviation) are to be reported as a memo-item.<BR>As the methodology is based on a fuel balance, also emissions from aircraft types not included in the<BR>methodology (small aircraft, new aircraft, and helicopters) will be indirectly included. Emissions from military<BR>aircraft are reported separately (see reporting issues). However, movement of military aircraft may be partially<BR>included in standard LTO-figures. This implies that if one of the default methodologies is followed, all CO2 is<BR>accounted for. Emissions of NOx at high altitudes are of particular concern. Methodologies for estimating aircraft<BR>NOx emissions are given in the IPCC Guidelines.<BR>Emissions from water vapour are not included in the reporting guidelines (and are not to be reported). It is,<BR>however, straightforward to estimate them using the current methodology (stoichiometric considerations).<BR>2 . 7 Other important issues<BR>2.7.1 Baseline determination<BR>Emissions of CO2 will be proportional to the fuel use. Preferably, fuel use should be determined by the same<BR>methodology for all years. If this is not possible, data collection should overlap at least one year in order to check<BR>for consistency.<BR>Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories<BR>Aircraft Emissions 101<BR>Emissions of CH4 and NOx (and N2O) will depend on technology. Different aircraft type will have different<BR>technologies. In order to estimate a correct time series to account for change of national aircraft fleet, countries<BR>should use the Tier 2 methodology based on individual aircraft types for 1990 and other years. If this is not<BR>necessary or possible (see options for good practice methodologies) the same set of emission factors should be<BR>used for all years.<BR>2.7.2 Detection of mitigation measures<BR>Mitigation measures may be directed towards changes in specific fuel use or specific emissions of aircraft. As the<BR>recommended methodologies are based on a fuel balance, measures directed towards reductions in specific fuel<BR>use will be seen as reductions in total fuel consumption. In order to keep track of changes in specific emissions,<BR>the Tier 2 methodology, based on individual aircraft, will have to be used.<BR>3 REPORTING AND DOCUMENTATION<BR>It is likely that all countries have emissions from aircraft. Consequently, reporting of “NO” (Not Occurring) is<BR>never appropriate. The current methodology has options for easy estimation so it should not be necessary to<BR>apply “NE” (Not Estimated).<BR>The UNFCCC Secretariat has intimated that bunker emissions are reported separately from national totals for<BR>only 27 Parties. Some countries are not reporting because data are missing or because emissions most likely are<BR>insignificant. Many countries report emissions from marine and aviation bunkers together.<BR>3.1 Current reporting IPCC Guidelines<BR>In the current reporting IPCC Guidelines emissions from aircraft are reported as one separate item. No<BR>distinction is made between altitudes. Reporting shall include emissions from fuel used by all civil domestic<BR>passenger and freight traffic inside a country. This includes emissions from all stages of the flights (take-off,<BR>climb, cruise, descent and landing). Emissions from ground operations and stationary combustion are reported<BR>elsewhere. Reporting would become more transparent if a distinction was made between emissions in various<BR>altitudes (1000 meters).<BR>Emissions from aircraft bunkers are reported as a separate item (memo item). This includes emissions from fuel<BR>sold to aircraft to be used for all international aviation in the reporting country. These emissions are not to be<BR>reported as part of national totals.<BR>Emissions from military aircraft used domestically are to be reported in an “other” category (IA5). This category<BR>is not transparent in the current reporting guidelines. These emissions are, however, to be reported if data are<BR>available. Emissions from military aircraft used internationally shall, in principle, be included in the separate<BR>aircraft bunker item discussed above.<BR>3 .2 Documentation<BR>It is particularly important to document the origin of the fuel use data and explain how the split between national<BR>and international aviation has been made.<BR>The number of LTOs (preferably separately for domestic and international) is useful for documentation of<BR>verification of reported data. Use of other emission factors than default should be explained.<BR>3 .3 Confidential business informati o n<BR>Confidentiality may be a problem for reporting if there are less than three airline companies operating domestic<BR>traffic in the country or if one airline company is dominating the market. This may be the case in some countries.<BR>Background Paper<BR>102 Energy Sector<BR>4 INVENTORY QUALITY<BR>4 .1 Internal inventory QA/QC systems<BR>There are some options for internal checking of data, viz:<BR>• As the guidelines provide a Tiered methodology, more Tiers may be used for cross-checking the output;<BR>• The country must ensure that the fuel reported for domestic aviation and bunkers sums up to the total fuel<BR>sold for aviation in the country, and<BR>• The number of passenger kilometres travelled is known in most countries. The ratio between fuel used for<BR>domestic aviation and the passenger kilometres travelled shows the fuel used per passenger kilometres<BR>travelled. This figure may be compared with similar ratios for other countries. Emission estimates may also<BR>be compared in the same manner.<BR>4 .2 External inventory QA/QC systems<BR>Some of the options suggested for internal QA (quality assurance)/QC (quality control) are also suitable for<BR>external QA/QC.<BR>Additional options are:<BR>• Checking reported emission data against output from large scale aircraft inventories (e.g. ANCAT/EC,<BR>AERONOX, NASA), and<BR>• Checking total fuel data against data from IEA (International Energy Agency) energy statistics.<BR>5 CONCLUSIONS<BR>The current tiered methodologies in the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories<BR>Reference Manual provide a good framework for good practice for estimating and reporting the emissions from<BR>aviation. The main difficulty and uncertainty, lies in the distribution of fuel between domestic and international<BR>use. Relevant activity statistics is often not directly available. This makes CO2 emission estimates from domestic<BR>aviation quite uncertain in many countries. Emissions of nitrous oxide and methane from aviation are highly<BR>uncertain due to little knowledge of magnitude of emission factors, but do not contribute much to national totals.<BR>REFERENCES<BR>AERONOX (1995): Ed. U Schumann. The impact of NOx emissions from aircraft upon the atmosphere at flight<BR>altitudes 8-15 km. Final report to the Commission of European Communities. ISBN 92 826 8281 1.<BR>ANCAT/EC2 (1998): Global Aircraft Emission Inventories for 1991/1992 and 2015. Report by the<BR>ECAC/ANCAT and EC working group. Ed. R Gardener. ISBN 92-828-2914-6, 1998.<BR>FCCC/SBSTA/1998/7 Methodological issues. Methodological issues identified while processing second national<BR>communications: Summary of issues and related options. Note by the secretariat.<BR>ICAO (1993): International Standards and Recommended Practices, Environmental Protection Annex 16,<BR>Volume II Aircraft Engine Emissions (second ed.) ICAO, 1993.<BR>ICAO (1995): Engine exhaust emissions databank. First edition. Doc 9646-AN/943.<BR>IPPC (1990): IPCC First Assessment Report. Volume III: WG III Formulation of Response Option Strategies.<BR>NASA (1996): Baughcun S. et al. Scheduled Aircraft Emission Inventories for 1992. Database development and<BR>analysis, NASA contract report no 4700, NASA Langley Research Centre.<BR>Olivier, J.G.J. (1991): Inventory of Aircraft Emissions: A Review of Recent Literature. National Institute of<BR>Public Health and Environmental Protection, Report no. 736 301 008, Bilthoven, the Netherlands.<BR>EEA (2000): UNECE/EMEP/EEA The emission inventory Guidebook. Snap codes 080501-04 Air traffic.
回复 1# 航空 的帖子
谢谢!!!!!!!!!!!!!!!!!!!!!!
页:
[1]