Polyethylene terephthalate (PET) is widely used as a primary plastic packaging material in the global socio-economic system. However, research on the metabolic characteristics of the PET industry across different countries, particularly regarding the entire life cycle supply chain of PET, remains insufficient, significantly hindering progress in addressing plastic pollution worldwide. This study employs the Life Cycle Assessment-Material Flow Analysis (LCA-MFA) method to comprehensively analyze the environmental impacts of PET plastics, with a focus on the processes from production to disposal in 12 regions (covering 41 countries) in 2020. By constructing 13 scenarios and analyzing the development trajectory of PET plastics from 2020 to 2030, this study provides scientific evidence and specific strategies for waste reduction and emission reduction measures in the PET industry. Overall, in 2020, the 12 regions (41 countries) consumed 7297.7 kilotons (kt) of virgin PET resin and 1189.4 kt of recycled PET resin; 23% of plastic waste was manufactured into recycled PET materials, 42% went to landfills, and 35% was incinerated. In 2020, the entire PET plastic supply chain emitted approximately 534.6 million tons (Mt) of carbon dioxide equivalent per year, with production emissions accounting for 46.1%, manufacturing stage emissions accounting for 44.7%, and waste treatment stage emissions accounting for 9.2%. Research indicates that under a scenario of controlled demand, resource efficiency improvement and emission reduction are the most effective, potentially reducing carbon emissions by up to 40%.

The carbon footprint factor of a power system is a crucial basis for calculating carbon emissions from electricity consumption. However, the current carbon footprint factor of China’s power system faces several issues, such as a limited spatial range, outdated updates, an incomplete accounting scope, and unclear accounting methods. To make the power system’s carbon footprint accounting method and its temporal and spatial scope more comprehensive, this study reconstructs the accounting method based on the emission factor method, adding factors such as transmission losses, power transmission across spatial ranges, and Sulfur hexafluoride (SF₆) gas leakage. This study’s analysis reveals that these three accounting factors have a significant impact on the power system’s carbon footprint factor. In terms of the time dimension, the carbon footprint factor has decreased by more than 20% over the past 18 years, and when the time interval is refined to a monthly scale, the carbon footprint factor exhibits significant seasonal fluctuations. In the spatial dimension, the coefficient of variation (CV) for regional and provincial power system carbon footprint factors reached 27.38% and 29.98%, respectively, in 2022. For the same geographic location, the difference in carbon footprint factors between provincial and regional levels ranged from −73.98% to 119.95%. This study shows that the current carbon footprint factor of the power system has limitations, and there is an urgent need to improve the accounting factors, establish multi-level spatial division standards for provincial and regional scales, and shorten the update intervals while ensuring data timeliness. This will enhance the temporal and spatial accuracy of the carbon footprint factor, providing scientific support for precise carbon emission management.

The transition to a low-carbon building sector will be greatly aided by hydrogen fuel cells. This paper examines their carbon emission reduction and economic advantages via Life Cycle Assessment (LCA) and Levelized Cost of Hydrogen (LCOH), alongside multiple carbon pricing scenarios. When using coal-produced hydrogen as a hydrogen source, hydrogen fuel cell applications have no carbon reduction effect. When hydrogen production from natural gas steam reforming is employed, the carbon reduction per unit of hydrogen in the HFC-CHP system ranges from 2.34 to 4.07 kgCO₂e, with a hydrogen cost per unit between 24.32 and 37.78 RMB/kg. When using blue hydrogen, the carbon reduction increases to 4.70–9.08 kgCO₂e, with costs ranging from 22.86 to 39.97 RMB/kg. Green hydrogen achieves the highest carbon reduction of up to 10.99 kgCO₂e, but costs rise to 47.51 RMB/kg under this pathway. The results revealed that pipeline transport outperforms trailer transport in carbon reduction and economic efficiency at the same distance. Simultaneously, solely incorporating the carbon market as a hydrogen subsidy measure is insufficient to close the cost disparity between hydrogen fuel cell energy supply and traditional energy supply methods. More types of subsidy measures are needed to enhance the competitiveness of hydrogen energy.