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Carbon sequestration in deep, unmineable coal seams is a viable strategy for carbon reduction. However, the impact of CO2 on coal mechanical performance poses safety concerns for a reservoir. This study proposes an integrated learning methodology that leverages experimental data involving CO2 immersion in various phases to evaluate the mechanical performance of coal seams during carbon sequestration. The approach integrates support vector regression (SVR) through the bagging method and employs a novel algorithm to optimize SVR. The model systematically assesses seven key factors, including coal rank, sample size, saturation medium, saturation time, saturation pressure, saturation temperature, and loading rate, to understand their influence on mechanical performance. The study identified saturation temperature, coal rank, and the saturated medium as pivotal elements affecting coal seam weakening. Evaluation metrics such as squared correlation coefficient (R2), mean absolute error, and root mean square error were employed for performance comparison between the polynomial model and the integrated model. The results demonstrate the superior performance of the integrated model, with R2 of 0.98, emphasizing its effectiveness in predicting coal seam strength weakening during carbon sequestration. These insights contribute to safety assessment of coalbed carbon sequestration practices. [ABSTRACT FROM AUTHOR]

The carbon budgets in terrestrial ecosystems in China are strongly coupled with climate changes. Over the past decade, China has experienced dramatic climate changes characterized by enhanced summer monsoon and decelerated warming. However, the changes in the trends of terrestrial net ecosystem production (NEP) in China under climate changes are not well documented. Here, we used three ecosystem models to simulate the spatiotemporal variations in China's NEP during 1982–2010 and quantify the contribution of the strengthened summer monsoon and warming hiatus to the NEP variations in four distinct climatic regions of the country. Our results revealed a decadal-scale shift in NEP from a downtrend of –5.95 Tg C/yr2 (reduced sink) during 1982–2000 to an uptrend of 14.22 Tg C/yr2 (enhanced sink) during 2000–10. This shift was essentially induced by the strengthened summer monsoon, which stimulated carbon uptake, and the warming hiatus, which lessened the decrease in the NEP trend. Compared to the contribution of 56.3% by the climate effect, atmospheric CO2 concentration and nitrogen deposition had relatively small contributions (8.6 and 11.3%, respectively) to the shift. In conclusion, within the context of the global-warming hiatus, the strengthening of the summer monsoon is a critical climate factor that enhances carbon uptake in China due to the asymmetric response of photosynthesis and respiration. Our study not only revealed the shift in ecosystem carbon sequestration in China in recent decades, but also provides some insight for understanding ecosystem carbon dynamics in other monsoonal areas. [ABSTRACT FROM AUTHOR]

The Belt and Road Initiative proposed by China is a common aspiration of all countries along their routes to achieve sustainable development of the environment, economy, society, and people's livelihood. Recently, prominently raised CO 2 concentration in the Belt and Road region is perceived to give rise to these serious greenhouse effects on severe and sustained global warming. It could lead to related climate instability, adverse natural disasters, glacier melting, and extreme weather patterns. CO 2 -enhanced oil recovery (CO 2 -EOR) is one of the essential CCU technologies. Due to lacking sustainable quantitative evaluation of CCU technology widely used in promising industries, it is imperative to conduct process simulation and optimization evaluation of CCU technology. Considering the lack of sustainable quantitative evaluation of CO 2 -EOR, we proposed a multi-objective optimization and sustainable quantitative assessment to provide insights and enhance the separation of produced gas and CO 2 capture for CO 2 -EOR. Their industrial applications before and after optimization were systematically simulated, discussed, and compared. With unremitting efforts, the optimized CO 2 capture process can stably separate oil field-produced gas into pure CO 2 and oilfield light hydrocarbons, with a mass content of CO 2 over 99.7 wt%. The optimized process demonstrated outstanding technical, economic, social, livelihood, and environmental properties. This study will undoubtedly benefit researchers in related fields of CCU process simulation, promote significant breakthroughs in basic research, superstructure, and commercial applications, and provide a perspective for the Belt and Road Initiative to establish better and optimize CCU devices and realize regional and global cooperation, future scientific and industrial progress. [Display omitted] • The first proposed simulation enhances the separation of produced gas and CO 2 capture for oil recovery. • Detailed process models, original simulation files, and detailed modeling steps are performed. • Life cycle optimization strategies using BAB methods are carried out from multi-dimension. • The optimized process has superior techno-economic-society-livelihood-environment property. [ABSTRACT FROM AUTHOR]