انتشار گاز متان توسط اقتصاد چین: تجزیه و تحلیل موجودی

Concrete inventories for methane emissions and associated embodied emissions in production, consumption, and international trade are presented in this paper for the mainland Chinese economy in 2007 with most recent availability of relevant environmental resources statistics and the input–output table. The total CH4 emission by Chinese economy 2007 estimated as 39,592.70 Gg is equivalent to three quarters of China's CO2 emission from fuel combustion by the global thermodynamic potentials, and even by the commonly referred lower IPCC global warming potentials is equivalent to one sixth of China's CO2 emission from fuel combustion and greater than the CO2 emissions from fuel combustion of many economically developed countries such as UK, Canada, and Germany. Agricultural activities and coal mining are the dominant direct emission sources, and the sector of Construction holds the top embodied emissions in both production and consumption. The emission embodied in gross capital formation is more than those in other components of final demand characterized by extensive investment and limited consumption. China is a net exporter of embodied CH4 emissions with the emission embodied in exports of 14,021.80 Gg, in magnitude up to 35.42% of the total direct emission. China's exports of textile products, industrial raw materials, and primary machinery and equipment products have a significant impact on its net embodied emissions of international trade balance. Corresponding policy measures such as agricultural carbon-reduction strategies, coalbed methane recovery, export-oriented and low value added industry adjustment, and low carbon energy polices to methane emission mitigation are addressed.

As the largest developing country in the world, China has been reckoned as the world's largest emitter of carbon dioxide (CO2) since 2007 (IEA, 2009), and the issue with greenhouse gas (GHG) emissions in China has become a focus for policy makers, researchers, and other groups around the world (Zhang, 2010). Methane (CH4) is considered as the second most important GHG after CO2 and contributed about 14.3% of the total anthropogenic GHG in 2004 over the world (IPCC, 2007). As to China, the GHG emission inventory for China 1994, according to the Initial National Communication on Climate Change of China (INCCCC, 2004), gave an estimate of CH4 emissions that totaled 34,287 Gg, accounting for 23.43% of the total GHG emission by the CO2-eq value. Direct anthropogenic CH4 emissions in China have been widely explored. China is the largest producer of rice grain with the world's second-largest area of rice paddies and has a flourishing livestock production with a rapid increase in livestock numbers and the largest meat and egg yields in the world. Over the years, the dominating role of agricultural activities on CH4 emissions has instigated a large number of studies on CH4 emissions from Chinese rice paddies (e.g., Cao et al., 1995, Cai, 1999, Wang, 2001, Li et al., 2002, Yan et al., 2003, Huang et al., 2006, Khalil and Shearer, 2006, Wang et al., 2008 and Zhang et al., 2009), CH4 emissions from Chinese livestock in specific years (e.g., Liu et al., 2000, Yamaji et al., 2003 and Zeng et al., 2009), or as long time series (e.g., Khalil et al., 1993 and Zhou et al., 2007), and total CH4 emissions from the Chinese agriculture as a whole (e.g., Song et al., 1996, Verburg and Denier, 2001 and Guo and Zhou, 2007). Meanwhile, China is the largest coal producer in the world, but effective exploitation of coalbed methane resources in China has been remaining in the assessing and testing stage for a long time (Yu et al., 2007). Many concrete efforts have been made to account the methane emissions from coal mines (e.g., Bibler et al., 1998, Zheng, 2002, Yuan et al., 2006 and Yang, 2009) and other sources such as municipal solid waste (MSW; e.g., Xu, 1997 and Gao et al., 2006) and fuel combustion of social-economic sectors (e.g., Ji and Chen, 2009). In particular, CH4 emission inventories of China in some early years such as 1980s, 1990, 1994 (e.g., Khalil et al., 1993, Wang et al., 1993, Zhang et al., 1999 and INCCCC, 2004) and some recent years such as 2005 and 2006 (e.g., EPA, 2006, Cai, 2009 and Zhang and Chen, 2010) have been provided. The embodied (direct plus hidden) methane emissions in economies have been extensively accounted in the multi-scale ecological input–output analyses of environmental emissions and resources use by Chen and his fellows: in his doctoral dissertation Zhou (2008) presented two sets of databases for embodiment intensity of CH4 emissions, one for Chinese economy 1992 under the Material Product System (MPS) for planning economies of the socialist Soviet style and another for Chinese economy 2002 under the System of National Accounts (SNA) for marketing economies; Chen et al. (2010) accounted the emission embodiment in Chinese economy 2005; Chen et al. (2009) simulated the emission embodiment in the global economy 2000; Zhou et al. (2009) provided the embodiment intensity in the regional urban economy of Beijing 2002. More detailed methane embodiment analysis via IOA remains to be made for the Chinese economy on updated inventory of CH4 emissions. The target of the present work is to present a detailed CH4 emission inventory 2007 covering main sources, including energy production, agricultural activities, waste treatment, etc., and to systematically reveal the CH4 emission embodiment in production, consumption, and international trade of Chinese economy, with the most recently available input–output table and relevant environmental resources statistics. The rest of the paper is composed as follows. In Section 2, the estimate method, related data sources, an aggregated input–output table, and the algorithms for input–output analysis and basic embodied emissions are introduced. The CH4 emission inventory by source and by sector is created and analyzed in Section 3. Section 4 presents embodied emission intensities and illustrates the embodied emissions in production, consumption, and international trade. Corresponding policy implications are addressed in Section 5, and main conclusions are drawn in the ending section.

A concrete CH4 emission inventory for Chinese economy 2007 is presented, covering emissions from agricultural activities, coal mining, oil and natural gas leakage, fossil fuel burning, industrial wastewater, domestic sewage, and municipal solid waste treatment. Using the input–output analysis method, emission structures of CH4 embodied in the final demand and international trade of China are analyzed with the integration of recent environmental resources statistics and the 2007 input–output table, the most recently available table. The data presented in CH4 emission embodiments show direct as well as induced emissions in industrial sectors, final demand, and international trade of China. The major conclusions are as follows: 1. The total CH4 emission by Chinese economy amounts to 39,592.70 Gg in 2007, which based on the global thermodynamic potentials in magnitude corresponds to 75.33% of the CO2 emission from fuel combustion. Even by the lower referred IPCC global warming potentials, the total methane emission corresponds to 989.82 Mt CO2-eq, in magnitude about one sixth of China's CO2 emission from fuel combustion and greater than the CO2 emissions from fuel combustion of many economically developed countries such as UK, Canada, and Germany. 2. Coal mining and agriculture are the dominant emission sources, responsible for 49.68% and 46.58% of the total emission and associated with the highest embodied emission intensities of 23.25 and 5.04 g/Yuan, respectively. Indirect emission intensity dominates the emission intensity for all sectors except for Coal mining and dressing and Agriculture. The embodied emission intensities in most manufacturing and service sectors are highly related to the direct CH4 emission from coal mining. 3. Embodied emissions from domestic production exceed those from domestic consumption by 7.98%. Construction holds the top CH4 emissions embodied in both domestic production and consumption. Agriculture and Food processing, food production, beverage production, and tobacco processing also contribute massive embodied CH4 emissions. The CH4 emission embodied in gross capital formation is more than those in other components of final demand characterized by extensive investment and limited household consumption. Rural and urban consumptions are CH4 intensive. 4. China is a net exporter of embodied CH4 emissions, with heavy emissions induced by the international trade. The amount of CH4 emissions embodied in China's exports is equal to 35.42% of the total direct emission. The leading CH4-export sectors are Electronic and telecommunications equipment and Textile with 15.08% and 12.39% of the total emission embodied in exports, respectively. China's textile products, industrial raw materials, and primary machinery and equipment products exports have significant impact on net embodied CH4 emissions in international trade balance. To reduce CH4 emissions, we have to pay equal attention to the direct emission of production on site in the sectors of Coal mining and dressing and Agriculture, and to the embodied emission induced by the final demand in terms of construction activities, urban consumption, capital investment, and export trade. The corresponding policy implications are addressed in depth.