Forests 2022 , 13 , 1856
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caliber of China Statistical Yearbook, the energy consumed in the pulp and paper stage includes coal, coke, crude oil, gasoline, kerosene, diesel, fuel oil, natural gas, and electricity. f j is theCO 2 emission coefficient of each energy source (tCO 2 /t, tCO 2 /m 3 , tCO 2 /kW-h). 2.2.3. Accounting for CO 2 Emissions in the Waste Paper Disposal Stage The accounting method on transportation CO 2 emissions mainly refers to the idea of the STIRPAT factor decomposition model [31,32], Which is based on constructing an accounting model of energy consumption in the transportation process of paper products, and then combining it with the carbon emission factor method. To account for CO 2 consumption during the transportation of paper products, the formula is as follows. C T = ∑ F × K F × E i K × µ i = ∑ F × K F × E i × µ i K = F × D × C K = ∑ F × D × ϕ j (6) In Equation (6), C T is the total CO 2 emission during the transportation of paper products (10 6 t), F is the freight volume of paper products (10 6 t); K is the turnover of paper products (10 6 t.km), and K F is the transportation distance of paper products (km), expressed as D; E i is the consumption of the i-th energy source during the transportation of paper products (10 6 t), and E i K is the consumption of various energy sources per 10 6 t of paper products in 1km-transportation (t/10 6 t.km), µ i is theCO 2 emission coefficient of each energy source, C K is theCO 2 emission per 10 6 t of paper product in 1km-transportation (tCO 2 /10 6 t.km), i.e., the CO 2 emission coefficient of transportation mode, expressed as ϕ j , j is the jth transportation mode. For the convenience of calculation, ϕ j is set constant for each transportation mode. (1) CO 2 emission accounting method for the transportation process of imported paper raw materials In international trade, the distance of cargo transportation is mostly measured by the shortest spherical distance between the capitals of the two trading countries [33,34], but this is generally applicable to air transportation methods, and if used as a distance measure for waterway transportation, it will greatly underestimate the actual distance of cargo transportation [35]. Due to the low cost and high volume of waterway transportation, Chi- nese paper raw material imports are mainly transported by waterway. To make up for the shortcomings of this international transport distance measure, the traditional international trade transport distance is split into the international and domestic distance measures [35], and in this paper, the transport distance of paper raw material import is divided into two parts with the main Chinese port as the transit point, the first part is the international distance transported from the paper raw material exporting country to the main Chinese port, and the second part is the domestic distance transported from the main Chinese port to the paper and paperboard main production provinces in China. The two paper raw materials (pulp and waste paper) source countries are not exactly the same and they are from numerous source countries, hence, for ease of accounting, we only set China’s largest port of international trade—Shanghai—for the international distance in the destination, the largest port of paper raw materials exporting countries as the starting place. The actual water transport distance between these two places is the international distance of paper raw materials imports. As for the domestic distance, according to reality, we set Qingdao port, Tianjin port, Shanghai port, Xiamen port, and Shenzhen port as the main ports of paper raw material imports [36]. The main provinces of paper and paperboard production follow the nearest and only principle, i.e., it will be from the nearest port and only from this port to import pulp and waste paper. Therefore, the actual distance between the main ports and the provincial capitals of the main paper and paperboard-producing provinces is the domestic distance. In summary, the formula for accounting for CO 2 emissions during the transportation of imported paper raw materials is as follows. C I = ∑ α α = 1 F p × D α × ϕ 1 + ∑ β β = 1 F w × D β × ϕ 1 + F p + F w × D N × ϕ 2 (7)
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