What drives long-term variations in biomass burning emissions in China?

Emissions from biomass burning have decreased significantly in recent years, but the drivers remain unclear. This study developed a long-term emission inventory (2008-2023) for domestic and open biomass burning in China and applied the Kaya identity and the Logarithmic Mean Divisia Index (LMDI) decomposition model to quantify contributions of factors to PM_2.5 emission changes. The results showed that emissions of SO₂, NO_x, NMVOC, NH₃, PM_2.5, PM₁₀, CH₄, CO, EC and OC from biomass burning were 278, 872, 3.15 × 10³, 466, 3.22 × 10³, 3.73 × 10³, 2.29 × 10³, 3.53 × 10⁴, 501 and 1.41 × 10³ kt, respectively, in 2008 and have decreased by 50 %-65 % by 2023. During 2014-2023, PM_2.5 emissions from domestic biomass burning decreased primarily due to the economic impact on burned biomass (F) and urbanization (U), contributing 183.4 % and 54.7 %, respectively. Open crop straw burning emissions decreased primarily due to the straw-burning activity intensity (S), contributing -115 %. The negative impact of F decreased from 563.2 to 363.8 kt, while the positive impact of rural resident per capita income (R) decreased from 392.9 to 271 kt. The net contribution of economic factors (R + F) reduced emissions by 170.3, 26.0, and 92.8 kt in the control stages (2013-2017, 2017-2020, and after 2020) in China. S was the strongest negative factor for open crop straw burning, contributing -98.7 kt during 2014-2017, with diminished effectiveness afterward. F remained negative for all provinces, while S almost contributed negatively. This study highlights policies and economic development greatly reduce biomass burning emissions, providing important data for China's energy and policy decisions.