Feng FENG，Heliang HUANG，Pei ZHANG，Siying CHEN

School of Economics，F(xiàn)ujian Agriculture and Forestry University，F(xiàn)uzhou 350002，China

1 Introduction

In recent years，with the continuous development of China's paper making industry，there have been more and more studies on the paper making industry．At present，paper and paper products have become the main wood forest products for export in China，second only to furniture．The international trade of paper products has bidirectional effect on the carbon emission in China．On the one h and，voluminous imported wood pulp，waste paper and other raw materials have reduced the demand for domestic timber，thereby reducing the amount of harvesting of domestic forests，increasing forest carbon sinks and indirectly reducing emissions of carbon dioxide；on the other h and，paper，paperboard，paper products other manufactured goods will release large amounts of carbon dioxide during the production and processing， and the increasing export volume will increase domestic emissions of carbon dioxide．Domestic studies on the trade and carbon emission are mostly the overall analyses at the level of country［1－2］， and there are also some researches on the trade and carbon emission concerning the specific industry，such as theuse of panel data of China's industrial sector to analyze the carbon emission effect of export trade［3］， and the use of input-output analysis to assess the hidden carbon emission in the import and export of China's agricultural products［4］．However，there are few studies on the carbon emission of trade of paper products．Therefore，using the relevant data on China's paper making industry in 2012，this paper first converts the net imports of pulp into wood consumption and thus forest stock volume， and employs the volume-derived biomass equations and net primary productivity（NPP）method to calculate the decrement of carbon emission．Then based on the energy consumption of China's paper making industry，this paper uses IPCC inventory guidelines to calculate the increased carbon emissions arising from the Chinese net exports of paper and paper products．Finally，according to the calculation results，this paper gets the specific value of influence of trade of paper products on China's carbon emissions，in order to verify whether the trade of paper products has carbon reduction effect．

2 China's trade of paper products and its influence on China's carbon emissions

2．1 China's trade of paper productsChina is a major producer of paper in the world， and both the production and consumption of paper products rank first in the world．In 2012，the total production of paper pulp was 78．67 million t in China， and the total consumption of paper pulp was93．48million t．The production and consumption of paper products significantly increased．The production was 48．04 million t，an increase of 6．43%over 2011， and the consumption was 45．73 million t，an increase of 6．65%over 2011．The trade of paper products in China can be divided into two categories：trade of paper making raw materials and paper product trade［5］．In terms of paper making raw materials，the import volume of paper pulp and waste paper was 16．47 million t and 30．07million t in 2012，respectively，with a significant increase，while the export volume of paper pulp and waste paper was79900 t and 2400 t，respectively，with a significant decrease．Compared with the import and export trade of paper making raw materials，the paper product trade shows different characteristics．In 2012，the import volume of paper and paperboard was only 3．11 million t， and the export volume of paper products was 0．14million t，showing significant negative growth，while the export volume of paper and paperboard， and paper products was5．13 million t and 2．45 million t，respectively，with an increase over 2011．The import and export volume of paper pulp，waste paper，paper and paperboard is shown in Fig．1．The total import and export volume of paper making raw materials in China was 46．6223million t，while the total import and export volume of paper and paper products was only10．83million t，less than a quarter of the former．The net import of paper making raw materials has carbon reduction effect and the net export of paper and paper products has carbon emission effect，so it can be roughly inferred that the trade of paper products in China may have the carbon reduction effect．

2．2 The path of influence of paper product trade on China's carbon emissionThe flow process of import and export trade of paper products in China is shown in Fig．2， and since this process contains the carbon emission，it can be used for analyzing the path of carbon emission．Path I：The paper making raw materials produced at homepaper and paper products consumed at home．The paper products are not only manufactured and processed，but also consumed at home，so there is no increase or decrease in domestic carbon emission due to trade．Path II：The paper making raw materials produced athome—→to be directly exported．The paper making raw materials produced at home are exported directly， and the felling of timber for paper making is at home，so this path reduces the number of domestic forest，thereby reducing the forest carbon sequestration and increasing the domestic carbon emissions．Path III：The paper making raw materials produced at homepaper and paper products for export．The paper making raw materials are from domestic production and the processed paper and paper products are exported to meet foreign consumption，so this path increases the domestic carbon emissions．Path IV：The imported paper making raw materialspaper and paper products for export．Only the processing of paper making raw materials is carried out at home，so this path also increases the domestic carbon emissions，but the increased carbon emissions are from the processing and manufacturing process at home．Path V：The imported paper making raw materialspaper and paper products consumed at home．The paper making raw materials are from imported from abroad， and the processed paper and paper products are used to meet domestic consumption，so this path reduces the domestic carbon emissions and the reduced carbon emissions are from the saved timber for paper making at home．Path VI：The paper and paper products directly imported—→meet domestic consumption．The felling of paper making timber as well as processing and manufacturing of paper and paper products is conducted abroad，so this path reduces the domestic carbon emissions．Through the analysis，it can be found that compared with the closed conditions，Path Idoes not affect the total domestic carbon emissions；Path II，III and IV will increase the domestic carbon emissions；Path V and VI are conducive to the reduction of domestic carbon emissions．The combined effects of paper product trade on domestic carbon emissions depend on the import and export of paper making raw materials and paper products．Therefore，there is a need to perform checking and calculation from the two perspectives in order to study the carbon reduction effect of paper product trade in China．

3 Analysis of carbon reduction effect of trade of paper making raw materials in China

3．1 Data selection and research methodsChina is a net importer of paper making raw materials，so the import and export of paper making raw materials make China save a certain amount of wood for pulping，which indirectly increases China's forest stock volume and forest carbon sinks，with carbon reduction effect．Starting from this idea，we select the relevant data from Chinese Paper Industry Annual Report（2012），to examine the carbon reduction effect of trade of paper making raw materials in China in 2012．

3．1．1The paper pulp supply saved at home．Assuming there is no import and export trade of paper products in China（namely the whole industry needs to achieve self-sufficiency in accordance with the present consumption），it is calculated based on this Standard：The paper pulp supply saved in China＝paper pulp imports－paper pulp exports－pulp consumption for exported paper and paper products＋converted amount of pulp for the imported paper and paper products＝net imports of paper pulp－net pulp consumption for exported paper and paper products．The trade of paper making raw materials has saved China's paper pulp supply at about 36．11418 million t．They are mainly from the imported pulp and waste paper．Given that the imported pulp in 2012 is all wood pulp and the imported waste paper has been converted，so the domestic paper pulp saved can be approximately replaced by wood pulp．

3．1．2The corresponding amount of wood for the paper pulp saved．Different pulping methods will lead to different yields， and there are also differences in the raw timber materials consumed．The pulp yield rate of chemical pulping，semi-chemical pulping，chemical mechanical pulping and mechanical pulping methods is 40%－50%，65%－84%，85%－94% and 94%－98%，respectively， and chemical pulping method has the highest pulp yield rate［6］．The main component of paper pulp is cellulose and usually the wood cellulose content is about50%（mass ratio）［7］，so the pulp yield rate is selected as 50%．Based on the known pulp yield rate，we can calculate the wood consumption that corresponds to paper pulp amount as follows：The corresponding wood consumption＝paper pulp amount÷0．5＝72．22836 million t．According to the relevant data selected from wood density tables recommended by IPCC，the average density of common tree varieties for China's paper making is calculated at about0．5 t／m3．Thus the mass of wood consumed can be converted into volume，namely the timber volume＝timber mass÷0．5＝144．45672 millionm3．Based on the conversion relationship between timber volume and stock volume（timber volume＝stock volume×percentage of out-turn（generally 60%to 80%），the percentage of out-turn is taken at 0．8 and the corresponding total volume of timber is 180．5709 millionm3．

Table 1 The import and export of paper pulp，waste paper，paper and paper products in China in 2012 Unit：104 t

3．1．3The indirectly increased forest carbon sink．NPP（Net Primary Productivity）is used to calculate the annual average carbon sequestration of trees．NPP can explain the net fixed amount of CO2absorbed by vegetation from the atmosphere，so indirectly increased forest carbon sink is obtained using NPPmultiplied by factor of0．5［8］．There is a certain function relationship between NPP and biomass， and biomass can be obtained by volume-derived biomass equations，so this paper uses this function relationship to estimate the NPP．Because of different tree species，the specific calculation formula is also different，so this paper chooses four kinds of timber most commonly used for paper making in China（redpine，larch，eucalyptus and poplar）to calculate the indirectly increased forest carbon sinks for different tree species，respectively．The estimation equations of biomass and NPP of common tree species for paper making in China are shown in Table 2．

Table 2 Equations used to calculate biomass and NPP of China's common tree species for paper making

3．2 The carbon reduction effect of trade of paper making raw materials in ChinaThe total stock volume is 180．5709 millionm3， and there are differences in the estimated average annual amount of carbon sequestration based on different tree species．The average annual amount of carbon sequestration for larch is smallest，while the average annual amount of carbon sequestration for eucalyptus is largest；the average annual amount of carbon sequestration for redpine is equivalent to that for poplar（Table 3）．The four tree species represent the main types of timber for paper making in different regions of China，so the mean value（19021100 t／a）of the average annual amount of carbon fixed is regarded as the estimated value of carbon reduction effect of trade of paper making raw materials in China in 2012．The trade of paper making raw materials in China in 2012 saved 36．11418million tof domestic paper pulp supply，equivalent to 144．45672 million m3of wood．The increase in forest stock volume directly leads to increase in forest carbon sinks．In accordance with the tree species commonly used for China's paper making，the average annual carbon sequestration is calculated at about 17．7341，9．1637，31．1600 and 18．0266 million t／a，with the average of 19．0211 million t／a，which is equivalent to the reduction of 19．0211 million t of China's total carbon emissions．Therefore，the carbon re-duction effect of China's trade of paper making raw materials in 2012 was19．0211million t．

Table 3 Biomass，NPP and annual carbon sequestration of different tree specieswith the same stock volume

4 Carbon emission effect of paper and paper product trade in China

4．1 Data selection and research methodsThe carbon emissions of China's net exported paper and paper products are calculated based on IPCC inventory guidelines，that is，the carbon emissions are estimated by the product of energy consumption and emission factors．The energy consumption data of paper making industry are fromChina Energy Statistical Yearbook．It is calculated as follows：

whereEnxis the carbon emission of net exported of paper and paper products（t），which is calculated by the amount of carbon dioxide emissions；Fiis the total consumption of energyi（t），which is calculated by the Standard coal consumption；EFiis the efficient carbon emission factor of energyi；Pnxis the proportion between net exports and production of paper and paper products．

The fossil energy for paper making industry mainly includes coal，coking products，all kinds of oil，natural gas，electricity and so on．The carbon emission factors of various types of energy are from the IPCC carbon emission calculation guidelines．The effective carbon emission factors are obtained based on carbon emission factors and coal conversion coefficient（10000 t of coal equal to 2．93×1014J）［11］．Thermal coefficient is based on the heating carbon emission factors in 2012．The electricity emission coefficient is based on the Chinese regional grid baseline emission factor in 2013．Various types of energy carbon emission factors are shown in Table 4， and various kinds of energy consumption is shown in Table 5．

Table 4 The carbon em ission factors for various types of energy

Table 5 The consumption of main types of energy for China's paper making industry in 2012 Unit：104 t

4．2 The carbon emission effect of trade of paper and paper products in ChinaIn 2012，the net exports of paper and paper products in China reached 4．33 million t，accounting for 2．88%of total production of whole industry；the annual energy consumption for paper making industry was26．5809million t， and the total carbon emissions reached 17．83185 million t．Thus the carbon emissions of net exported paper and paper products in China in 2012 were calculated atabout 0．5136 t．This value can be used to represent the size of carbon emission effect of trade of paper and paper products in China in 2012．Compared with the carbon reduction effect of trade of paper making raw materials in China，the carbon emission effect of trade of paper and paper products in China is much smaller．Overall，the trade of paper products in China in 2012 reduced 18．5075 million t of domestic carbon emissions，with significant carbon reduction effect．

5 Conclusions and discussions

5．1 Carbon reduction effect of trade of Chinese paper making raw materials is significantThe results show that the carbon reduction effect of trade of Chinese paper making raw materials was 19．0211 million t in 2012，equivalent to the average annual carbon sequestration of 180．5709 million m3forest， and the carbon reduction effect is obvious．From the actual situation，the contradiction between lack of Chinese forest resources and rapid growth of demand for wood products is very prominent，coupled with logging ban and timber production limitation，leading to growing imports．Import has become an important source to meet domestic demand for paper making raw materials， and the exports are almost negligible relative to imports．This one-way import trade pattern makes China save a lot of paper making timber resources，which is bound to bring a huge offsetting effect of carbon emission，namely carbon reduction effect．From this perspective，the trade structure of the Chinese paper making raw materials is conducive to achieving national carbon reduction goal．

5．2 Carbon emission effect of Chinese trade of paper and paper products is not significantBased on IPCC inventory guidelines，it is calculated that the consumption of energy（coal）for China's paper making industry was 26．5809 million t in 2012， and the total carbon emission was 17．83185 million t． and the carbon emission effect of Chinese trade of paper and paper products was 0．5136million t in 2012．This result is equivalent to only 2．7%of carbon reduction effect of Chinese trade of paper making raw materials， and the carbon emission effect is not significant．This is mainly because China is not only a major importer of paper making raw materials，but also a major producer and consumer of paper products；the production of paper and paper products is mainly to meet domestic consumption， and the net exports of paper and paper products are too trivial or insignificant to mention．In 2012，the national production of paper and paperboard was 102．5 million t， and the production of paper products was 48．04 million t，a total of150．54million t．At the same time，the net exports of paper and paper products were only 4．33 million t，accounting for less than 3%of total production．It can be seen that the＂pollution haven＂hypothesis does not hold in the paper industry．

5．3 Overall，the Chinese trade of paper products has significant carbon reduction effectIn 2012，the carbon reduction effect of the Chinese trade of paper making raw materials was 190．211million t， and the carbon emission effect of trade of paper and paper products was0．5136 million t．Overall，the Chinese trade of paper products has significant carbon reduction effect， and the specific value is 18．5075 million t．This result fully proves that the China's trade structure of paper products is conducive to the reduction of domestic carbon emissions， and the offsetting effect is obvious．In summary，the conclusion can provide an important scientific basis for the structural adjustment of China's trade of paper products．

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