Chinaʹs CH4 and CO2 emissions: Bottom-up estimation and comparative analysis

For the greenhouse gas (GHG) emissions in China, little attention has been given to CH4 emissions and related emission mitigation. This paper presents a detailed bottom-up estimation and comparison analysis of Chinaʹs CH4 and CO2 emissions for the first time. Chinaʹs CH4 emissions are shown with comparable importance to the CO2 emissions at the national and regional levels. The national total CH4 emission in 2008 amounts to 39 Tg, equivalent to about 1/8, 1/3 and 3/5 of the total CO2 emission by the 100-year global warming potential (GWP) factor, the 20-year GWP factor and the global thermodynamic potential factor, respectively. Increasing CH4 emissions could compromise Chinaʹs efforts to mitigate its GHG emissions. In contrast to energy-dominated emission pattern for CO2, the major sources of Chinaʹs CH4 emissions are coal mining, enteric fermentation, rice cultivation and waste management. Meanwhile, there exists a large gap between the eastern coastal regions and the western and central inland regions in the emission magnitude and emission intensity for CH4 and CO2, with different mitigation flexibilities. Reducing CH4 emissions should be integrated into the national and regional policies for GHG emission mitigation. In some central and western regions such as Shanxi, Henan, Sichuan, Guizhou, Qinghai and Tibet, the inclusion of CH4 emission intensity reduction can be more cost-effective than only setting a target for CO2 emission intensity to reduce the regional GHG emission intensity.