Aviation emission accounting is the key to establishing
market measures to control aviation pollutant emissions. Based on the fuel
percentage method (FPM), this paper applies the improved BFFM2-FOA-FPM (Boeing Fuel Flow Method 2–First Order Approximation FPM) to calculate the emissions of six pollutants (CO
Air transportation between China and foreign countries has developed
dramatically in recent years. The turnover of China's foreign routes
totaled
To solve the problem of aviation pollutant emission, in
October 2016, the 39th General Assembly of the International Civil Aviation Organization (ICAO) adopted two critical
documents: the ICAO comprehensive statement on sustainable policies and
practices of environmental protection “climate change and ICAO complete
statement on sustainable policies and procedures of environmental protection
– global-market-based measure mechanism”. It aims to achieve the zero-carbon
emission growth goal of the international aviation industry from 2020
through the phased implementation of the “Carbon Neutral Growth 2020”
strategy (CNG2020 strategy), from 2021 to 2035. The CNG2020 strategy was implemented in 2021. The period from 2021 to 2023 is the pilot phase,
and the period from 2024 to 2026 is the first phase. All countries can
voluntarily participate in the plan in the pilot phase and the first phase.
The second phase is from 2027 to 2035. In the second phase, most countries
must participate in the plan, and the least developed countries and island and
landlocked developing countries can participate voluntarily. ICAO has
predicted the impacts of the CNG2020 strategy on the whole airline industry.
The estimated quantity to be offset to achieve carbon-neutral growth from
2020 would be of the order of 142–
Aiming at the accounting method of gaseous pollutant emission of aero-engine during a standard landing and take-off cycle, ICAO has successively developed simple methods, advanced methods, and complex methods according to different calculation methods and data requirements since the 1970s (Kesgin, 2006; Altuntas, 2014; Winther et al., 2015; Cokorilo, 2016; Xu et al., 2020). The direct use of the model reference value in ICAO's simple methods will bring uncertainty into the accounting results. On the other hand, the advanced and complex methods that have been further improved obtained highly accurate results. However, they have the limitations of high data requirements, complex implementation, and high research cost and are unsuitable for mass calculation. Therefore, the development of relevant research is relatively slow. Based on the ICAO calculation system, the U.S. Environmental Protection Agency (EPA) puts forward the EPA (Environmental Protection Agency) method combined with the actual situation (U.S. Environmental Protection Agency, 1999; Unal et al., 2005; Zhou et al., 2019; Baxter et al., 2020). Although the EPA method considers meteorological conditions and establishes the relationship between meteorological conditions and aero-engine emissions, it is helpful to understand the relationship between meteorological conditions and emissions. However, the calculation of emission inventory during the aircraft LTO cycle by the EPA method is the same as that of the ICAO simple B method. Therefore, there may be no significant difference between the two calculation results for a single aircraft. As a result, and because the ICAO-recommended method is applied by many organizations and projects, the ICAO-recommended method is the most effective method for LTO cycle pollutant emission evaluation (Kurniawan and Khardi, 2011). Meanwhile, the European Environment Agency (EEA) has established the EMEP (European Monitoring and Evaluation Program) cooperative action framework (Civil and Military Aviation, 2014; Park and O'Kelly, 2014; Pereira et al., 2014). This method is an accounting method of pollutant emission of aircraft during the whole flight based on fuel statistical data. Still, it focuses on analyzing the emission characteristics of aero-engines from the fuel perspective and ignores the differences between engine types. Furthermore, ICAO has further improved the calculation method and proposed the ICAO carbon emission calculator, which can estimate the aviation emission per unit passenger based on the data of various aircraft types (Wasiuk et al., 2016; Liu et al., 2019; ICAO, 2021).
However, there are some drawbacks to the approach provided by ICAO. First,
the distance difference is not enough. For example, according to
VariFlight (VariFlight, 2022), A320-214 flew between 360 and 3649 km on
domestic routes in China in 2018, exceeding the range of the methodology provided by the
ICAO. Second, there is no distinction between specific aircraft. ICAO's
calculation method only considers large sequences and does not consider
differences between subsequence. For example, the A320 family has many
families, such as the A320-100 and A320-200, with different engine types,
which may lead to a significant difference in the carbon emissions of the
two aircraft (Cui et al., 2022a). Third, various pollutants cannot be
calculated at the same time. Aiming at these problems, based on the fuel percentage method (FPM), Cui et al. built
the improved BFFM2-FOA-FPM (Boeing Fuel Flow Method 2–First Order Approximation) and the ICAO method to calculate the emissions
of CO
However, there is little study to analyze the emission difference before and
after the construction of CNG2020 strategy. This study can make up for this
deficiency. Generally, the entire flight process consists of seven steps:
engine starting, taxiing, taking off, climbing, cruising, descending, and
landing (Cui, 2019). It is usually divided into the landing and take-off
(LTO) cycle and the climbing, cruising, and descending (CCD) stage. This paper
will calculate the CCD emissions and LTO emissions of six pollutants
(CO
The original data were collected from
Statistical characteristics of the routes during 2014–2019.
Statistical characteristics of aircraft configuration during 2014–2019.
Carbon emission intensity of the aircraft (t km
As shown in Fig. 3a, under the A320 series, 320-214 and 320-232 have similar carbon emission intensity in a 0–500 km distance segment. However, in other distance segments, the carbon emission intensity of 320-214 is higher than that of 320-232. Therefore, 320-232 has a better performance in carbon emissions per kilometer, providing more references for airlines in arranging aircraft types. Under the B737 series, 737-700 and 737-800 have similar carbon emission intensity in a distance segment of 0–1000 km distance segment. In addition, the carbon emission intensity of 737-700 is higher than that of 737-800 at 3500–4000 km, but 737-800 has a more significant intensity than 737-700 at other distances. Therefore, the 737-700 is better than that of the 737-800 at 0–4000 km. Figure 3b shows that 330-343E has a lower carbon emission intensity than 330-243E in the 4000–9500 km distance segment. These two aircraft have similar intensity at 4500–5000 km, but the intensities of 330-243E are larger than 330-343E in other distance segments. In the distance segment 9500–13000 km, 787-8's carbon emission intensities are smaller than 777-300ER, so 787-8 has a better overall performance than 777-300ER in this distance segment.
The difference between the A320 series and the A330 series has little relationship with the engines, as the engines of the subseries are the same. The engines of 320-214 and 320-232 are CFM56-5/V2500, and those of 330-343E and 330-243E are PW4000/Trent 700/CF6-80E1. Therefore, their difference in carbon emission intensity may be related to airline route arrangement and actual flight operation. However, the engines of the other two pairs of aircraft are different. The engines of 737-700 are CFM56-7B20/CFM56-7B24, while those of 737-800 are CFM56-7B24/CFM56-7B27. The engines of 777-300ER are PW4090/Trent 895/GE90-94B, and those of 787-8 are Trent 1000/GEnx-1B. The engines of 737-800 and 777-300ER consume more fuel per kilometer, so the engine difference may lead to the emission intensity of these aircraft.
And we can also find that CO
Annual overall emissions of six pollutants before the CNG2020 strategy was proposed
(tonnes).
Annual overall emissions of six pollutants after the CNG2020 strategy was proposed
(tonnes).
In addition, we compared the changes in unit turnover emissions of six
pollutants before and after CNG2020. According to the relevant report data
of the Civil Aviation Administration of China, the total transportation
turnover in 2014–2019 was
Changes in average unit turnover emissions of six pollutants before and after the CNG2020 strategy was proposed (tonnes).
Annual average emissions of six pollutants from routes before
the CNG2020 strategy was proposed (tonnes).
Annual average emissions of six pollutants from routes after
the CNG2020 strategy was proposed (tonnes).
Meanwhile, the average unit turnover emissions of each route before and
after CNG2020 are shown in Fig. 9 (1 represents 2014–2016, and 2 represents
2017–2019). The average emissions per tonne-kilometer of CO
Average unit turnover emissions of each route before and after CNG2020.
Therefore, we further compare the average carbon emissions per unit turnover of the two groups of data hotspot routes, select the routes before and after the strategy, and study the impact of the CNG2020 strategy on them. Through analysis, 291 routes are available and can be defined as popular routes. As shown in Fig. 10a, we summarize the five routes with the largest increase in average unit turnover carbon emissions and the five routes with the largest reduction before and after the strategy was proposed. The red is the route with the largest increase, and the green is the route with the largest reduction. The former can indicate that the carbon emission per unit turnover increased rapidly after the CNG2020 strategy was proposed. The latter can indicate that the carbon emission per unit turnover decreased rapidly after the CNG2020 strategy was proposed. Among the top five routes with the largest emission reduction, four are associated with Guangzhou, China. It shows that Guangzhou, as one of China's air transport center cities, has achieved good results in carbon emission reduction. Figure 10b shows the five routes with the smallest change in average carbon emissions per unit turnover before and after the proposal of the CNG2020 strategy. Three of them are routes between China and South Korea. In addition, two of the five routes are from Shanghai and Beijing. Compared with Guangzhou, Shanghai, and Beijing, as important aviation hubs in China, they are not sensitive to the CNG2020 strategy. It is worth noting that only 14 of the 291 routes have increased their average carbon emissions per unit turnover after the proposal of the CNG2020 strategy, and the emissions of the remaining 277 routes have decreased after the proposal of the CNG2020 strategy. Moreover, among the 14 routes with increased emissions, 10 routes are shorter than 5000 km, indicating that under the CNG2020 strategy, airlines do not control the carbon emissions of short-haul routes enough.
The impacts of CNG2020 on some popular routes.
Changes in average emissions of six pollutant airlines before
the CNG2020 strategy was proposed (tonnes).
Changes in average emissions of six pollutant airlines after
the CNG2020 strategy was proposed (tonnes).
In addition, the average unit turnover emissions of airlines before and
after CNG2020 are shown in Fig. 13 (1 represents 2014–2016, and 2
represents 2017–2019). Airlines' average emissions per tonne-kilometer of
CO
Average unit turnover emissions of each airline before and after CNG2020.
Therefore, we further compare airlines' average carbon emissions per unit turnover in the two data hotspots. Through analysis, 63 airlines are available, which can be defined as popular airlines. We summarize the three airlines with the most significant increase in average unit turnover carbon emissions and the three airlines with the most significant decrease in carbon emissions of popular airlines before and after the strategy was proposed, as shown in Fig. 14. The red ones are the airlines with the most significant increase, and the green ones are the airlines with the most significant decrease. It is worth noting that among the 63 airlines, only four airlines have increased their carbon emissions per unit turnover after the CNG2020 strategy was proposed, namely, Asian Air, Lucky Air, Eastar Jet, and Pakistan International Air. The rest have decreased, indicating that most airlines have better controlled their carbon emissions after the CNG2020 strategy was proposed.
The impacts of CNG2020 on some popular airlines.
In this study, we discuss the impacts of the proposal of the CNG2020
strategy on the aircraft emissions of China–foreign routes during 2014–2019.
The emissions from 2014 to 2016 constitute the data before the CNG2020
strategy was put forward, and those from 2017 to 2019 are the data after the
CNG2020 strategy was put forward. We collect the flight information
(including aircraft types, flight frequency, airline, flight distance, and
flight time) of all the international routes between China and foreign
countries. Then we calculate the overall emissions for each route and
airline containing CO
We get some important results. First, after the proposal of the CNG2020
strategy, the overall emission of six pollutants is still increasing, but
the increase rate is no more than 27 %. The growth rate of the overall
emissions of pollutants in 2017–2019 is generally less than that in
2014–2016. And CO
The standard LTO method is adopted in the calculation of LTO phase emissions in this paper, without considering delays and flight turnover caused by weather. And this paper does not consider the emissions of freight transport. Future research could focus on emissions from delays, flight turnover, and freight.
The CCD and LTO emissions of each route and airline for the six pollutants from 2014 to 2019 can be found in Cui (2022)
(
The original data are collected from the
In this paper, the emissions in the CCD stage are calculated through the modified BFFM2-FOA-FPM. The LTO emissions are calculated based on the ICAO standard method.
In the modified BFFM2-FOA-FPM, the CCD emissions
As we only consider the CCD section in this study, we define the
The actual flight time of each flight is applied to check the results of
For CO and HC,
For NO
For PM
This paper uses the standard LTO cycle definition specified by ICAO to
calculate the fuel consumption, including all activities at an altitude
below 3000 ft (915 m) near the airport. The calculation formula of the five
non-CO
The fuel consumption rate is calculated as
The supplement related to this article is available online at:
QC designed the study. QC, YL, and BC compiled the original data and participated in writing and revising the manuscript.
The contact author has declared that none of the authors has any competing interests.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
This research has been supported by the National (grant no. 71701088) and the Fundamental Research Funds for the Central Universities (grant no. 2242022S20021).
This paper was edited by Bo Zheng and reviewed by two anonymous referees.