1.A.3.a Civil Aviation

Last updated on 04 Dec 2014 08:38 (cf. Authors)

Short description

Air transports differ significantly from land and water transports with respect to emissions production. In air transports, fuels are burned under atmospheric conditions that a) differ markedly from those prevailing at ground level and b) can vary widely. The main factors that influence the combustion process in this sector include atmospheric pressure, environmental temperature and humidity – all of which are factors that vary considerably with altitude.

In category 1.A.3.a - Civil Aviation the emissions from both national (domestic) and international civil aviation are reported with separate acquisition of flight phases LTO (Landing/Take-off: 0-3,000 feet) and Cruise (above 3,000 feet) where only emissions from LTO from both national and international flights have to be included in the national totals.

Emissions from military aircraft are not included in this category but are reported under 1.A.5.b - Other Mobile Sources: Military.

Country specifics:
The use of aviation gasoline is assumed to take place within the LTO-range of domestic flights only (below 3,000 feet). This assumption is a compromise due to a lack of further information and data.

Aircraft.PNG
NFR-Code Name of Category Method AD EF Key Source for (by1)
1.A.3.a Civil Aviation T12, T33 NS CS, D
consisting of / including source categories
1.A.3.a i (i) International Civil Aviation - LTO 4 T1, T3 NS CS, D no key source
1.A.3.a i (ii) International Civil Aviation - Cruise 5 T1, T3 NS CS, D no key source
1.A.3.a ii (i) Domestic Civil Aviation - LTO 4 T1, T3 NS CS, D no key source
1.A.3.a ii (ii) Domestic Civil Aviation - Cruise 5 T1, T3 NS CS, D no key source

1 T = key source by Trend / L = key source by Level
2 kerosene: all emissions depending on fuel quality only + avgas: all reported emissions
3 kerosene: for all emissions depending on altitude, type of engine, etc. and flight stage
4 LTO: included in national totals
5 Cruise: not included in national totals

Method

Estimation of aircraft emissions has been carried out using a tier 3a approach, i.e. under consideration of the annual distances flown by different types of aircraft, deviated into domestic and international flights, also considering the different flight stages LTO cycle (Landing/Take-off cycle, i.e. aircraft movements below 3,000 feet or about 915 meters of altitude) and cruise.

Essential for emissions reporting is the separation of domestic and international air traffic. This happens using a so-called split factor representing the ratio of fuel consumption for national flights and the over-all consumption.

For determination of the ratio used for 1990 to 2002 results of a research project have been used, based on the great circle distances flown by the different types of aircraft (Ifeu & Öko-Institut, 2010) [1]. Here, the ratio was calculated on the basis of statistics on numbers of national and international flights departing from German airports provided by the Federal Statistical Office (Statistisches Bundesamt). - For all years as of 2003, the breakdown is made in keeping with the national/international ratio for fuel consumption as given by Eurocontrol's ANCAT 3 model.

For further dividing kerosene consumption onto flight stages LTO and cruise, again results calculated within the TREMOD AV data base based on data provided by the Federal Statistical Office have been used.

Emissions are being estimated by multiplying the kerosene consumption of the flight stage with specific emission factors (EF). Here, emissions of SO2 and H2O are independent from the method used, depending only on the quantity and qualities of the fuel used. In contrast, emissions of NOx, NMVOC, and CO strongly depend on the types of engines, flight elevations, flight stage, etc. and can be estimated more precisely with higher tiers. The emission factors for NOx, CO, and NMVOC are therefore computed within TREMOD AV (TRansport Emissions MODel AViation).

The aviation gasoline (avgas) used is not added to the annual kerosene consumptions but reported separately. As proposed in IPCC 2006a, emissions caused by the incineration of avgas are calculated using adapted EF and calorific values following a tier 1 approach. Here, a split into national and international shares is not necessary as avgas is supposed to only being used in smaller aircraft operating on domestic routes and within the LTO range. - This conservative assumption leads to a slight overestimation of national emissions.

For further information on AD (entire time series), EF, key sources, and recalculations see sub-category chapters 1.A.3.a i and 1.A.3.a ii.

Activity Data

Kerosene

Emissions estimation is mainly based on consumption data for jet kerosene and aviation gasoline as provided in the national Energy Balances (AGEB, 2012) [2]. For very recent years with no AGEB data available (Normally the last year of the period reported.) data provided by the Federal Office of Economics and Export Control (BAFA) is being used.

Table 1: Sources for 1.A.3.a activity data

through 1994 AGEB - National Energy Balance, line 76: 'Luftverkehr'
from 1995 AGEB - National Energy Balance, line 63: 'Luftverkehr'
recent years / comparison BAFA - Official oil data, table 7j: 'An die Luftfahrt' + 'An Sonstige' 1

1 to achieve consistency with AGEB data, amounts given for deliveries 'to Aviation' ('An die Luftfahrt') and 'to Others' ('An Sonstige') have to be added
(see FAQs for more information)

Table 2: 1.A.3.a over-all jet kerosene consumption in German civil aviation 1990-2012 1

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
193,329 189,610 204,386 216,548 225,148 233,437 244,610 253,849 261,185 280,244
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
297,258 289,768 287,394 291,827 316,211 343,827 361,233 374,428 378,346 367,234
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
361,751 346,115 370,558

1 data source: Working Group on Energy Balances (AGEB): National Energy Balances (AGEB, 2013) [2]
italic: recalculated against submission 2013

For the present purposes, kerosene-consumption figures from the Energy Balance and from BAFA statistics have to be broken down by national and international flights using two approaches: For the years from 1990 to 2002, this breakdown has been carried out using the results of the study carried ot by ifeu and Öko-Institut Berlin (Ifeu & Öko-Institut, 2010) [1]. Here, the split has been calculated on the basis of statistics on numbers of national and international flights departing from German airports provided by the Federal Statistical Office (Statistisches Bundesamt). For all years as of 2003, the breakdown is made in keeping with the national/international ratio for fuel consumption as given by Eurocontrol's ANCAT 3 model.

Using the data from AGEB and BAFA, a distribution of the over all kerosene consumption onto national (= domestic) and international flights is necessary. Until submission 2007, this was done with a constant national share of 20% resulting from a study carried out by TÜV in 1989 (UBA, 2001a) [4]. Since 2007, revised assumptions following Öko-Institut (2009) [5] were used, taking into account data provided by Eurocontrol available from 2003 onwards.

Results of another study now allow a new and broad revision of this ratio: The calculations carried out within the newly compiled TREMOD AV (TREMOD Aviation) take into account the numbers of flights divided by any type of aircraft, and the great circle distances of national and international air routes. This happens with respect to the the number of commercial flights from selected airports collected and provided by the Federal Statistical Office. All other kinds of flights (from other airfields, non-commercial) are not being differentiated by destination by the Federal Statistical Office, but by weight and aircraft classes only. Here, commercial flights from other airfields consist mostly of flights with smaller avgas driven aircraft.
Within the non-commercial flights the share of this type of aircraft is even higher: Here, also balloons and gliders are included. The allocation of the entirety of flights onto the (totally domestic) avgas consumption proves to be appropriate within the comparative calculations carried out by Ifeu & Öko-Institut (2010).

Based on the effective starts registered by the Federal Statistical Office (separated by type of aircraft and great circle distances) and using consumption factors specific for types of aircraft and the two flight stages as well as a detour factor, the calculations show a domestic share much smaller than reported in past submissions for the entire time series.
Here, due to international comparability, from 2003 onwards the data provided by Eurocontrol are still being used. For the years from 1990 to 2002, a slight correction factor has been applied bringing together the data calculated within TREMOD AV and the Eurocontrol data.

Table 3: Annual split factors used for calculating shares of jet kerosene used in 1.A.3.a ii - Domestic and 1.A.3.a i - International Civil Aviation [%]

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
1.A.3.a i 84.9 85.9 87.5 88.7 89.0 89.2 89.2 88.9 89.2 89.6
1.A.3.a ii 15.1 14.1 12.5 11.3 11.0 10.8 10.8 11.1 10.8 10.4
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
1.A.3.a i 89.7 90.0 90.2 90.5 91.4 91.7 91.6 91.6 91.7 91.9
1.A.3.a ii 10.3 10.0 9.8 9.5 8.6 8.3 8.4 8.4 8.3 8.1
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
1.A.3.a i 92.4 92.9 93.2
1.A.3.a ii 7.6 7.1 6.8

data source: 1990-2002: research project [8]; from 2003: Eurocontrol
italic: recalculated within Eurocontrol models

Table 4: Resulting annual shares of jet kerosene used in 1.A.3.a ii - Domestic and 1.A.3.a i - International Civil Aviation ([TJ], rounded values)

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
1.A.3.a i 164,110 162,930 178,747 192,020 200,496 208,244 218,308 225,626 232,976 251,238
1.A.3.a ii 29,219 26,680 25,639 24,528 24,652 25,193 26,302 28,223 28,209 29,006
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
1.A.3.a i 266,574 260,744 259,372 264,233 288,973 315,158 330,823 343,101 347,026 337,524
1.A.3.a ii 30,684 29,024 28,022 27,594 27,238 28,670 30,410 31,327 31,319 29,710
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
1.A.3.a i 334,201 321,621 345,383
1.A.3.a ii 27,550 24,494 25,175

italic: recalculated against submission 2013

The deviation of the kerosene consumed onto the two flight stages LTO and cruise again has been carried based on TREMOD AV estimations allowing the export of kerosene consumption during LTO for both domestic and international flights (see: Ifeu & Öko-Institut 2010). Consumption during cruise phase is then calculated as the difference between total consumption as provided in the Energy Balances minus consumption during LTO.

Table 5: Annual shares of LTO phase in national and international civil aviation [%]

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
1.A.3.a i (i) 8.06 8.34 8.69 8.41 8.35 8.64 8.64 8.59 8.44 8.22
1.A.3.a ii (i) 31.35 32.51 34.79 34.41 33.97 35.37 33.66 32.90 31.80 31.13
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
1.A.3.a i (i) 8.14 8.23 7.94 8.15 8.34 8.23 8.24 8.30 8.43 8.26
1.A.3.a ii (i) 31.09 31.56 31.68 31.99 32.86 32.59 31.97 31.88 32.45 32.07
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
1.A.3.a i (ii) 8.67 9.52 8.83
1.A.3.a ii (i) 34.53 39.57 36.28

data source: number of domestic and international flights as provided by the Federal Statistical Office (Destatis, 2013)
italic: recalculated against submission 2013

Aviation Gasoline - AvGas

Consumption data have been taken from the national Energy Balance and (for 2013) by the Federal Office of Economics and Export Control (Working Group on Energy Balances (AGEB) [2], 2013; BAFA, 2013[3]). Here, it is assumed conservatively that the total consumption takes place within 1.A.3.a ii (i) - Domestic Aviation (LTO).

Emission factors

Kerosene

Emissions have been calculated for each flight phase, based on the respective emission factors. Therefore, the EF used have been taken from a wide range of different sources.
In contrast to earlier submissions, the emissions of NOx, CO und HC are based on aircraft-specific EF deposited within TREMOD AV. With this very detailed estimations average EF are being formed which are than used for emissions reporting.

The EF provided with the current submission represent annual average EF for the entire fleet, calculated as implied EF from the emissions computed within TREMOD AV and therefore differ from the values used in the past.

Sulphur dioxide (SO2) emissions depend directly on the kerosene's sulphur content which varies regionally as well as seasonally. The EF used by Eurocontrol of 0.84 kg SO2/t kerosene lies between the values used for German inventory for 1990 to 1994 (1.08 to 1.03 kg SO2/t) and from 1995 (0.4 kg SO2/t). In IPCC 2006b [6] with 1kg SO2/t kerosene value comes very close to the old inventory values provided, based on a sulfur content of 0.05 % of weight. Following current information of the expert committee for the standardization of mineral oil and fuels (Fachausschuss für Mineralöl-und Brennstoffnormung, FAM), the common value for sulphur content of kerosene in Germany is about 0.01% of weight, i.e. one fifth of the IPCC data. In IIR 2009, a sulfur content of 0.021 weight% have been used, based on measurements from 1998 (Döpelheuer 2002) [7]. As a EF decreasing due to improved production procedures and stricter critical levels seems plausible, for this report a constant decline between the annual values of 1.08 g SO2/kg for 1990, 0.4 g for 1998 and 0.2 g for 2009 has been assumed. Thereby, an exhaustive conversion of the sulfur into suflur dioxide is expected. - Due to the EF depending directly on the S content of the kerosene, one annual EF is used for both flight stages.

Nitrogen oxide (NOx), carbon monoxide (CO) and hydrocarbons (HC) emissions were estimated using IEF calculated within TREMOD AV, based upon more specific (depending on type of aircraft, flight stage) EF mostly taken from the EMEP-EEA data base. For 2009, 40 % of over-all starts (about 70 % of total kilometres flown) had to be linked with adapted EF as it was not possible to directly or even indirectly (via similar types of aircraft) allocate the aircraft used here. Therefore, regression analysis had to be carried out, estimating EF via emission functions that calculate an EF for the respective type of engine depending on the particular take-off weight. As a basis for these functions the EF of types of aircraft with given EF have been used (see: Ifeu and Öko-Institut 2010) [1]. From the trend of the emissions calculated within TREMOD AV, annual average EF for the entire fleet have been formed, which have then been used for reporting. Hence, the EF differ widely from those used in earlier submissions.

Ammonia (NH3) emissions were estimated using an EF of 0.173 g/kg kerosene for both flight stages (UBA, 2009).

The EFs for non-methane volatile organic compounds (NMVOC) were calculated as the difference between the EF for over-all hydrocarbons (HC) and the EF for methane (CH4).

Particulate Matter
Within the IPCC EF data base, there are no default data provided for emissions of particulate matter (TSP, PM10, and PM2.5). Therefore, the EF for dust (Total Suspended Particulate Matter – TSP) are taken over from Corinair (2006), giving specific values for an average fleet and for the two flight stages in table 8.2: For national flights 0.7 kg TSP/LTO and 0.2 kg TSP/t kerosene and 0.15 kg TSP/LTO and 0.2 kg TSP/t kerosene for international flights. Following this table, a kerosene consumption per LTO cycle of 825 kg for national and 1,617 kg for international flights have been assumed and the EF for the LTO stage have been estimated.

The EF for water vapor (H2O) provided by Eurocontrol (2004) is about 1,230g H2O / kg kerosene, whereas in Corinair (2006) [8] 1,237g H2O/kg is assumed. Based on the stoichiometric assumptions mentioned above a EF(CO2) of 1.24 kg H2O/kg can be derived. To reduce the number of sources for EF, here, the Corinair value has been used for both flight stages and for both national and international flights.

The conversion of EF representing emissions per kilo fuel combusted [kg pollutant/kg kerosene] into energy related EF [kg pollutant/TJ energy] has been carried out using a net calorific value of 43,000 kJ/kg.

Aviation gasoline

For aviation gasoline (avgas) a deviation onto LTO and cruise is assumed to be unnecessary. Therefore, there are no such specific EF used here. As for kerosene, the EF for NOx, CO and HC have been taken from the calculations carried out within TREMOD AV. Here, for calculating aircraft specific NOx, CO, and HC emissions corresponding EF from the EMEP-EEA data base have been used that have than been divided by the annual avgas consumption to form annual average EF for emission reporting.

With respect to fuel characteristics, there are no big differences between avgas and gasoline used in passenger cars (PC). Therefore, specific sulphur dioxide (SO2) emissions from PC gasoline can be carried forward to avgas. - Following the expert committee for the standardization of mineral oil and fuels (FAM), the critical value of sulfur content for gasoline sold at gas stations is 10 mg/kg, i.e. 0,001 % of weight - or one tenth of the kerosene value. Therefore, the EF(SO2) used for avgas equals the EF used for kerosene reduced by 90 %.

There are different sorts of avgas sold with different lead (Pb) contents. As an exact annual ration of the sorts sold is not available, the most common type of avgas (AvGas 100 LL (Low Lead)) with a lead content of 0.56 g/l is set as an approximation. This value lies slightly below the value of 0.6 g/l as proposed in the EMEP Guidebook 2009. – For estimating lead emissions here the value provided for AvGas 100 LL has been converted into an EF of about 0.75 g lead/kg avgas using a density of 0.75 kg/l.

The EF(TSP) were calculated from the lead content of AvGas 100 LL by multiplication with a factor 1.6 as used for leaded gasoline in road transport in the TREMOD system.

For NMVOC, an EF from the Revised IPCC Guidelines 1996 (pages I 42 and 40) [9], [10], have been used.

All other EF are not available specifically for small aircraft and therefore have been equalized with the EF used for kerosene, national, cruise.

Table 6: EF (2012) used for emission estimation from avgas use in aircraft, [g/kg]

Pollutant EF Source or estimation info
NOx 12.33 estimated within TREMOD AV
NMVOC 13.06 from Revised IPCC Guidelines 1996, page I.42
SO2 0.02 equals 1/10 of the EF used for kerosene, cruise/domestic/2008
CO 647 estimated within TREMOD AV
TSP 1.18 estimated from lead content AvGas 100 LL
Pb 0.75 estimated from lead content of AvGas 100 L

The conversion of the EF from [kg emission/kg avgas consumed] into [kg emission/TJ energy converted] has been carried out using a net calorific value of 44,300 kJ/kg.

Recalculations

With the over-all 1.A.3.a kerosene consumption remaining unchanged against submission 2013, recalculations only occur due to revised emission factors within 1.A.3.a i and 1.A.3.a ii.

For more information on the revisions and recalculations carried out for specific activity data, see sub-chapters on 1.A.3.a i and 1.A.3.a ii.
For information on the impacts on 1990 and 2011 emission estimates, please see the pollutant specific recalculation tables following chapter 11.1 - Recalculations.

Uncertainties

Information on uncertainties is provided here with most data representing expert judgement from the research project mentioned above.

For estimating uncertainties, the partial uncertainties (U1 to Un) of the components incorporated in emission calculations have to be quantified.
By additive linking of the squared partial uncertainties the overall uncertainty (Utotal) can then be estimated (IPCC, 2000) [11].

The uncertainties given here have been evaluated for all time series and flight stages as average values.
Estimating the overall uncertainty has been carried out as shown in the table below. In the very left column the components of the uncertainty estimations are listed with their partial uncertainties given in the next column. The next columns show the data linked to estimate the different overall uncertainties which themselves represent partial uncertainties for higher aggregated data and so on.

As an example, the uncertainty of the kerosene consumptions for domestic flights divided by flight stages (LTO and cruise) has been calculated from the partial uncertainty of the over-all kerosene consumption for domestic flights and the partial uncertainty of the LTO-cruise-split. Here, the split is based on the number of flights provided by the Federal Statistical Office and assumptions on the composition of the fleet. The overall uncertainties of both fuel consumption during LTO and cruise itself then represent a partial uncertainty within the estimation of the uncertainties of emissions.

Several partial uncertainties are based on assumptions. For example, the uncertainty given for the entire time series of the split factor domestic:international flights is an average value:
For the years 1990 to 2002 data is based upon estimations carried out within TREMOD AV which themselves are based on data from the Federal Statistical Office and EF from the EMEP-EEA data base. For 2003 to 2011 data from Eurocontrol are being used, that are calculated within ANCAT. Comparing results from the ANCAT model with actual consumption data show aberrations of ±12 %. Here, data calculated with AEM 3 model would have an uncertainty of only 3 to 5 % (EUROCONTROL 2006) [12].

The image below shows the partial uncertainties and correlations used for uncertainty estimations carried out during the research project. Mouseclick to enlarge!

As no uncertainty estimates were carried out for NH3 and particulate matter within the above-mentioned project, values from the PAREST research project mentioned for most over mobile sources were used. Here, the final report has not yet been published.

FAQs

Whereby does the party justify the adding-up of the two amounts given in BAFA table 7j as deliveries 'An die Luftfahrt' and 'An Sonstige' ?

For mineral oils, German National Energy Balances (NEBs) - amongst other sources - are based on BAFA data on the amounts delivered to different sectors. A comparison with consumption data from AGEB and BAFA shows that data from NEB line 76 /63: 'Luftverkehr' equates to the amount added from both columns in BAFA table 7j.

Why is there no aviation gasoline reported under 1.A.3.a i - International Civil Aviation?

Due to the lack of further information, the party assumes that aviation gasoline is only being used for domestic civil aviation. - Furthermore, the party also assumes that the use of aviation gasoline in domestic civil aviation takes place below 3,000 feet only - and therewith only within the LTO-range (1.A.3.a ii (i)).


Bibliography
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