Decomposition analysis of the decoupling and driving factors of municipal solid waste: Taking China as an example

Greenhouse gas emissions and mitigation strategies in China's municipal solid waste sector under the impact of the COVID-19 pandemic

With the continuous increase in municipal solid waste (MSW) generation, greenhouse gas (GHG) emissions caused by MSW treatment have gradually become an important environmental concern. This study developed a comprehensive ten-factor analysis framework using the generalized Divisia index method (GDIM) to decompose the driving factors of GHG emissions from MSW sectors in China and its 31 provinces from 2010 to 2022, including population, economy, consumption, and waste generation. The heterogeneity of factor contributions was discussed from both temporal and spatial perspectives to propose mitigation strategies for provincial MSW sectors. The results indicated the following: (1) GHG emissions from the MSW sector increased from 2010 to 2019, followed by a 20.7% decrease from 2019 to 2022 due to the COVID-19 pandemic. Regionally, emissions were greater in the eastern provinces than in the central and western provinces. (2) The main positive contributors to the increase in GHG emissions were the consumption expenditure of urban households (HCE, 27.61 MtCO2e) and GDP (25.71 MtCO2e). GHG emissions per HCE (-27.31 MtCO2e) and GHG emissions per GDP (-25.45 MtCO2e) were the main factors for emission reduction. (3) The contributions of ten driving factors to each province varied significantly across different periods, with the negative effect of emission reduction factors increasing under the impact of the pandemic. The findings of this study can support policymakers in developing differentiated mitigation strategies at the provincial level to promote the sustainable transformation of waste management in China.

The temporal and spatial characteristics and influencing factors of CO2 emissions from municipal solid waste in China

Understanding the temporal and spatial characteristics of carbon dioxide (CO₂) emissions from municipal solid waste (MSW) and a quantitative evaluation of the contribution rate of the factors influencing the changes in CO₂ emissions are important for pollution and emission reduction and the realization of the "double carbon" goal. This study analyzed the spatial and temporal evolution of waste generation and treatment based on panel data from 31 Chinese provinces over the past 15 years and then applied the logarithmic mean Divisia index (LMDI) model to study the driving factors of CO₂ emissions from MSW. China's MSW production and CO₂ emissions displayed a rising trend, and the overall CO₂ emissions showed a geographical pattern of being high in the east and low in the west. Carbon emission intensity, economic output, urbanization level, and population size were positive factors that increased CO₂ emissions. The most important factors driving CO₂ emissions were carbon emission intensity and economic output, with cumulative contribution rates of 55.29% and 47.91%, respectively. Solid waste emission intensity was a negative factor in reducing CO₂ emissions, with a cumulative contribution rate of -24.52%. These results have important implications for the design of policies to reduce CO₂ emissions from MSW.

(Co-)gasification characteristics and synergistic effect of hydrothermal carbonized solid/liquid products derived from fresh kitchen waste

Kitchen waste has high moisture and rich organics, which can be transformed into hydrochar by hydrothermal carbonization (HTC) and then used for gasification efficiently. But process water (liquid product from HTC, containing organic compounds) has not been well utilized in the way of thermochemistry. In this study, a scheme of co-gasification of solid and liquid products of kitchen waste HTC process was proposed, and the separate gasification and co-gasification were studied. The results showed that after HTC process, the obtained hydrochar size became smaller and uniform, and the high heating value increased from 19.90 MJ/kg to 28.03 MJ/kg. The carbon skeleton of hydrochar was mainly composed of aromatic and alkyl C, which was easily converted into coke during gasification. Process water mainly contained pyrazine organics, and its C and N content were 18.94 g/L and 3.25 g/L, respectively. The co-gasification syngas yield of solid and liquid products was significantly higher than the calculated total yield of separate gasification. There was obvious synergistic effect in the coke co-gasification stage, and the H2 production was 1.24 times of the calculated value. Synergistic effect was mainly caused by the introduction of process water, which contained 785.82 mg/L of K and would catalyze the coke co-gasification. HTC coupled with co-gasification is an efficient disposal for kitchen waste with high moisture.