Accounting for the aircraft emissions of China’s domestic

This paper has not considered 2020 and 2021 because the pandemic began to spread globally in 2020. In addition, the outbreak of COVID-19 in December 2019 has had a significant impact on China’s aviation industry. As a result, China’s domestic routes completed a total transportation turnover of 58.767 billion ton-kilometers in 2020. Compared with 2019, China’s total domestic transportation turnover in 2020 decreased by 29.2%. Consequently, 2020 and 2021 are not selected in this paper. Therefore, the year from 2017 to 2019 was established after the 13th Five-Year Plan. Furthermore, 2014 to 2016 was chosen before the 13th Five-Year Plan for comparison. Finally, the total period is 2014–2019.

Statistical characteristics of China’s domestic routes

This paper gleans information on China’s domestic routes from 2014 to 2019, and the detailed statistical features are shown in Fig. 1. As shown in Fig. 2(a), the number of domestic flights in China has increased from 1,947,211 in 2014 to 3,116,880 in 2019, which shows the rapid growth of China’s domestic air transport demand. The number of routes has increased from 311 in 2014 to 492 in 2019, and the number of airlines has increased from 30 in 2014 to 40 in 2019. As shown in Fig. 2(b), from 2014 to 2019, the farthest flight route in China was always Guangzhou- Urumqi, and the distance was 3,836 km. However, the nearest routes within China had been in flux. The closest route in 2014 was Chengdu-Jiuzhai, with 350 km. From 2015 to 2017, Dali-Kunming became the nearest route with 275 km. In 2018, Changsha-Sanya (163 km) became the nearest route in China. In 2019, Xingyi-Guiyang became the nearest route in China, 305 km. Therefore, many airlines are constantly adjusting their routes to meet changing demands.

Fig. 2
figure 2

Statistical characters of the routes during 2014–2019. (a) Number of routes, number of airlines and number of domestic flights in China. (b) The farthest and nearest distance.

The impacts of the 13th Five-Year Plan on aircraft configuration

This article makes detailed statistics on the configuration of aircraft types involved in China’s domestic routes from 2014 to 2019. First, the top five aircraft types for each year are shown in Fig. 3. After further study, we can find that the top three aircraft types have not changed from 2014 to 2019 which are 737–800, 320–214, and 320–232. In addition, the total frequency of 737–800 aircraft types has increased from 993 in 2014 to 1,669 in 2019; the entire frequency of 320–214 aircraft types has risen from 469 in 2014 to 660 in 2019; the total frequency of 320–232 aircraft types has increased from 332 in 2014 to 379 in 2019. However, the fourth and fifth-ranked aircraft types have changed with the 13th Five-Year Plan for Civil Aviation Energy Conservation Proposal and Emission Reduction Plan. Specifically, 737–700 and 321–231 ranked fourth and fifth respectively in 2014–2016, but 321–211 in 2017 and 231–213 in 2019 replaced the 737–700 and ranked fifth.

Fig. 3
figure 3

Statistical characteristics of aircraft configuration during 2014–2019.

The emission intensity of the aircraft in the CCD stage

As mentioned earlier, different from the method of ICAO, we segment each route according to a section of 500 kilometers. Therefore, all routes are divided into 8 distance sections: 0–500 km, 501–1000 km, 1001–1500 km, 1501–2000km, 2001–2500km, 2501–3000 km, 3501–3500 km and 3501–4000 km. In addition, we also consider the differences between sub-series, such as 737–700 and 737–800. Then, we get the aircraft’s emission intensity of the six pollutions from 2014 to 2019 based on the Modified Fuel Percentage Method (MFPM). In the 0–4000 km section, 320–214, 320–232, 737–700 and 737–800 cover almost all distances sections. The 320–214 and 320–232 are sub-series of the A320 series, while the 737–700 and 737–800 are sub-series of the B737 series. Therefore, this comparison highlights the difference between this study and the ICAO method.

We summarize the average carbon emission intensity and show the detailed results in Fig. 4. As shown in Fig. 4(a), under the A320 series, carbon emission intensities of 320–214 and 320-232 are similar in the 0–4000 km distance segment. In the 3500–4000 km distance segment, the carbon emission intensity of 320-214 is lower than that of 320-232. However, at other distances, the carbon emission intensity of 320-232 is always less than 320-214. Therefore, 320-232 performs better in carbon emissions per kilometer, providing more references for airlines to arrange aircraft types. Under the B737 series, the carbon emission intensity of 737-700 and 737–800 is similar in 0–4000 km distance, and the 737–700 has always been less carbon-intensive than the 737–800. In addition, with the increase in aviation mileage, the emission intensity is gradually decreasing. This shows that the average emission of long-distance flights is less than that of short-range flights. Therefore, the 737-700 is superior to the 737–800 in the 0–4000 km distance segment. As shown in Fig. 4(b), compared to the A320 series, the B737 series has a lower carbon intensity. Hence, the overall performance of the B737 series at 0–4000 km is better than that of the A320 series.

Fig. 4
figure 4

Carbon emission intensity of the aircrafts (ton/km). (a) Comparison of 320-214 and 320-232, and 737-700 and 737-800. (b) Comparison of A320 series and B737 series.

The impacts of the 13th Five-Year Plan on the overall emissions

First, we check the accuracy of the calculation results in this paper. Then, we obtain each airline’s available tonnage and normal load rate from the “Civil Aviation from Statistics” released by CAAC (Civil Aviation Administration of China). The turnover in Table 1 is the total turnover of China’s domestic routes, and the fuel consumption per ton kilometer is the common data of China’s domestic routes and China’s foreign routes. The turnover of each route is the product of available tonnage, normal load rate, and distance. Then we can add up the turnover of all routes. In 2015, the fuel consumption of turnover was about 0.294 kg/ ton. Because of the error, the fuel consumption of turnover can be adjusted by 5%, and the result after adjustment is 0.3076 kg/ t-km. Based on this standard multiplied by the carbon emission coefficient of fuel consumption (3.157 kg/tons), it can be concluded that the carbon dioxide emission of major domestic routes in 2015 was 37,513,993.70 tons. Therefore, the carbon dioxide emissions calculated in this paper are 39,905,708.71 tons, with an error rate of 6.37%. Based on the above calculation method, the calculation errors from 2016 to 2019 are 0.75%, 0.9%, 15.05%, and 9.2%. Considering the statistical data of various airlines may also have errors, the calculation results of the method used in this paper are very accurate.

Table 1 The aviation emissions released by the CAAC from 2014 to 2019.

As mentioned earlier, the main emissions include CO2, CO, HC, NOx, PM2.5, and SO2, among which CO2 emissions are much higher than other emissions. For example, in 2019, CO2 emissions is 56,059,114.91 tons, accounting for 98.42% of the total emissions(56,960,300.60 tons); Emissions of CO, HC, NOx, PM2.5 and SO2 are 400,395.30 tons, 37,998.9572 tons, 388,677.70 tons, 5,393.817,46 tons and 68,719.9160 tons, which account for 0.7%, 0.07%, 0.68%, 0.01% and 0.12% of total emissions (see details in supplementary files). Since the 13th Five-Year Plan was put forward in February 2017, the data are divided into two groups. One is 2014–2019 (before the 13th Five-Year Plan), and the other is 2017–2019 (After the 13th Five-Year Plan). Fig. 5 is a comparison of the average emissions from 2014 to 2019. As shown in Fig. 5, after the 13th Five-Year Plan, the six emissions increased, but the growth rate was less than 35%. Further research finds that the growth rate of NOx is the highest, reaching 34.5%. HC has the lowest growth rate at 23.7%. In terms of the annual growth rates of the six emissions, the growth rates of 2015 and 2016 are higher than those of 2018 and 2019, which may be due to the 13th Five-Year Plan that urges airlines to take some measures to reduce the growth rate of aviation emissions.

Fig. 5
figure 5

Changes in total emissions of six pollutants from 2014–2019. (a) Annual change in carbon dioxide emissions from 2014 to 2019. (b) Annual changes in CO, HC, NOx, PM2.5 and SO2 emissions from 2014 to 2019.

In addition, we compared the change in unit turnover emissions of 6 pollutants before and after the 13th Five-Year Plan. According to the calculation of relevant report data from the CAAC, the total annual transport turnover from 2014 to 2019 was 34.88 billion ton-kilometers, 38.62 billion ton-kilometers, and 43.36 billion ton-kilometers, 48.16 billion ton-kilometers, 46.58 billion ton-kilometers, and 54.34 billion ton-kilometers. And then, unit turnover emissions of six gases from 2014 to 2019 can be calculated. The average results of the first three years and the last three years are shown in Fig. 6. The unit turnover emissions of HC decreased, while the unit turnover emissions of the other five gases all increased. Therefore, the 13th Five-Year Plan produces a miniature effect, and China’s domestic airline emission reduction work still needs improvement.

Fig. 6
figure 6

Unit turnover emissions in 2014–2016 and 2017–2019.

The impacts of the 13th Five-Year Plan on the emissions of the routes

We firstly analyze the effect of the 13th Five-Year Plan on the average emissions of airlines. Compared with 2014–2016, the average CO2, NOx, PM2.5, and SO2 in 2017–2019 increased by 2.58%, 4.67%, 1.61%, and 3.45%. In addition, the average emissions of CO and HC decreased by 0.03% and 3.57%. As a result, the average CO2, NOx, PM2.5, and SO2 increased by less than 5%, while the average emissions of CO and HC decreased. As a result, the average emissions growth rate of the six air routes in 2018 and 2019 was negative. Therefore, the 13th Five-Year Plan has slowed down the increase rate of airline emissions.

To investigate the influence of the 13th Five-Year Plan on air routes, we select 251 airlines from 2014 to 2019. However, we split the route data into two groups: 2014–2016 and 2017–2019. Besides, the paper calculates the average unit turnover carbon emissions of two data groups for 251 airlines. The calculation result shows that the average unit turnover carbon emissions of 126 airlines are reduced.

We summarize the impact of the 13th Five-Year Plan on unit turnover emissions of some popular air routes and show the detailed result in Fig. 7. As shown in Fig. 7, this paper picks out the five airlines with the most significant increase and the five airlines with the largest decrease in unit turnover emissions under the influence of the 13th Five-Year Plan. Specifically speaking, the five routes with the most significant increase in unit turnover carbon emissions are Korla-Urumqi, Dalian-Qingdao, Kunming-Lijiang, Shanghai-Wenzhou, and Xishuangbanna-Lijiang. As a result, the average unit turnover carbon emissions of these five airlines increased by 2.86E-02 tons, 2.66E-02 tons, 2.32E-02 tons, 2.04E-02 tons, and1.02E-02 tons. Moreover, the five airlines with the most considerable reduction in unit turnover carbon emissions are Guangzhou-Harbin, Guangzhou-Changchun, Guangzhou-Urumqi, Chongqing-Hefei, and Kunming-Tengchong. As a result, the average unit turnover carbon emissions of these five airlines decreased by 1.10E-03 tons, 1.31E-03 tons, 1.33E-03 tons, 1.71E-03 tons, and 2.06E-03 tons. On the other hand, the five routes least affected by the 13th Five-Year Plan are Guangzhou-Nanjing, Guangzhou-Shanghai, Shanghai-Xi’an, Shanghai-Shenzhen, and Guangzhou-Chengdu. More concretely, the average unit turnover carbon emissions of Guangzhou-Nanjing, Guangzhou- Shanghai, and Shanghai-Xi’an increased by 5.83E-08 tons, 2.92E-07 tons, and 1.06E-06 tons. On the other hand, the average unit turnover carbon emissions of Shanghai-Shenzhen and Guangzhou-Chengdu decreased by 3.37E-06 tons and 3.61E-06 tons.

Fig. 7
figure 7

Influence of the 13th Five-Year Plan on some popular routes.

The impacts of the 13th Five-Year Plan on the average emissions of airlines

Compared with 2014–2016, the average emissions of CO2, CO, HC, NOx, PM2.5 and SO2 in 2017–2019 increased by 12.03%, 8.95%, 5.05%, 14.36%, 10.81% and 12.98%. The average emission growth rate of CO2, CO, HC, NOx, PM2.5, and SO2 is 5%-15%. The average emissions of all six air routes showed a higher growth rate in 2017, which may be because there was no increase in the number of airlines in 2017 (38 in both 2016 and 2017), and the emissions of the six air routes in 2017 were higher than those in 2016.

To analyze the impacts of the 13th Five-Year Plan on airlines, this paper selected 27 standard airlines from 2014 to 2019. In addition, airline data is divided into two groups, one is 2014–2016, and the other is 2017–2019. And then, the paper calculates the average unit turnover carbon emissions of two data sets from 251 airlines. The calculation result shows that the carbon emissions per unit turnover of 16 airlines have been reduced. Finally, we summarize the change in carbon emissions per unit turnover of popular airlines before and after the 13th Five-Year Plan in Fig. 8. As shown in Fig. 8, the five airlines with the most significant increase in carbon emissions unit turnover were Grand China Airlines, Donghai Airlines, Qingdao Airlines, Okay Airways, and Air China. As a result, the five airlines’ average unit turnover carbon emissions increased by 4.91E-06tons, 2.25E-06tons, 2.05E-06tons, 1.85E-06tons, and 1.84E-06tons. The five airlines with the most significant drop in unit turnover carbon emissions are Ruili Airlines, Juneyao Airlines, Sichuan Airlines, Tibet Airlines, and China Express Airlines, respectively, which decreased by 3.45E-06 tons, 4.20E-06 tons, 5.56E-06 tons, 5.72E-06 tons, and 5.89E-06 tons. The five airlines least affected by the 13th Five-Year Plan of Civil Aviation Energy conservation and emission reduction are Shandong Airlines, Xiamen Airlines, Shenzhen Airlines, China Southern Airlines, and Hainan Airlines. Among these airlines, the unit turnover carbon emissions of Shandong Airlines, Xiamen Airlines, Shenzhen Airlines, and Hainan Airlines increased by 8.81E-08 tons, 1.39E-07 tons, 4.26E-07 tons, and 6.84E-07 tons. In contrast, China Southern Airlines’ unit turnover carbon emissions decreased by 6.14E-07 tons.

Fig. 8
figure 8

Influence of the 13th Five-Year Plan on some popular airlines.

About the Author: AKDSEO

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