Evaluation of comprehensive monthly-gridded methane emissions from natural and anthropogenic sources in China

The observed atmospheric methane (CH4) concentration in China has grown rapidly in recent years, showing marked spatial-temporal variation. However, existing inventories, most of which are yearly, provincial, and incomplete, have failed to reflect the spatial variation and seasonal trends of CH4 emissions. This study aims to develop a high-resolution (0.05 degrees x 0.05 degrees) monthly inventory of CH4 emissions across China in 2015 from eight major natural and anthropogenic sources. The inventory evaluation of CH4 emissions was based on the gridded activity data and high spatial-temporal resolution emission factors, which were estimated by their relationship with environmental factors in most source sectors. The results showed that the annual CH4 emissions across China were 61.65 Tg, of which 85% was associated with anthropogenic emissions. Energy activities, livestock, and paddy fields were the largest contributors, accounting for 31% (19.06 Tg), 24% (15.01 Tg) and 19% (11.45 Tg) of the total emissions respectively, followed by vegetation (7%, 4.52 Tg), wetlands (7%, 4.20 Tg), wastewater (6%, 3.43 Tg), municipal solidwaste, (4%, 2.59 Tg) and biomass burning (2%, 1.40 Tg). However, these proportions varied by month; paddy fields, vegetation, and wetlands emitted the most CH4 in July and August with approximately 29%, 14%, and 8% of total emissions, respectively, and least in January and December with 0%, 2%, and 2%, respectively, leading to a CH4 emissions peak in summer and a valley inwinter. Moreover, the major contributing provinces of CH4 emissions in China were Inner Mongolia, Shanxi, Sichuan, Guizhou, and Hunan, accounting for 33% of China's total emissions. The dominant emission sources were energy activities in Mongolia, Shanxi, and Guizhou; livestock in Sichuan; and paddy fields in Hunan. This improved inventory of CH4 emissions can help understanding the spatial-temporal variation of CH4 concentration in the atmosphere and formulating regional-seasonal-specific emission reduction policies. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The atmospheric methane concentration in China has increased rapidly in recent years, with significant spatial-temporal variation. A high-resolution monthly inventory of CH4 emissions in China in 2015 was developed in this study, showing that energy activities, livestock, and paddy fields were the largest contributors to CH4 emissions. The major emitting provinces in China were Inner Mongolia, Shanxi, Sichuan, Guizhou, and Hunan.