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Due to large number of doors used housing and construction products, the greenhouse gas (GHG) footprint related to door manufacturing is an interesting topic. Timber and bamboo products can reduce GHG emission due to their biogenic carbon storage via photosynthesis. The scientific evidence on the climate impact using wood-based door (WBD) and bamboo-based door (BBD) to replace steel-based door (SBD) is limited. In this study, life cycle assessments for WBD, BBD, SBD were conducted to evaluate the carbon impacts of raw materials, production, transport, and end-of-life stages. The GHG footprint of WBD, BBD, and SBD ranged from 270.42 to 363.24, 285.31–398.31, and 983.8–986.76 kg CO 2 e/m3, respectively, indicating that the bio-based doors exhibited lower energy consumption and GHG emissions. The raw material stage (484.78–569.34 kg CO 2 e/m3) was identified as a major source of GHG emissions throughout the product life cycle, while hot-pressing and coating processes were identified as emission hotspots in the production stage. Regarding biogenic carbon storage, the use of bio-based materials instead of steel-based materials for fire door manufacturing significantly reduced emissions. Considering disposal methods, recycling and incineration should be prioritized over landfills. Future research should focus on field survey in raw material stage, along with conducting a technical and economic analysis. The results provide valuable guidance for selecting doors in China in term of biogenic carbon storage and resource protection. [Display omitted] • GHG footprint of WBD and BBD ranged from 270.42 to 398.31 kg CO 2 e/m3. • Risk-relevance in GHG emissions of fire doors can be assessed using risk fraction. • Bio-based solution is preferrable over steel-based materials for fire doors. • Recycling and incineration should be favored over landfills. • The most influential mitigation method and future research directions are proposed. [ABSTRACT FROM AUTHOR]

With the rapid development of highway and railway transportation in China, many tunnels are constructed at the same time within the same region. It has become a challenge how to control dynamically such a large number of tunnel structures in long-term operation and ensure their safety. In this work, we focus on the construction of common characteristics of these tunnels built during the same period in the same region. In particular, we propose a concept and a systematic component of long-term health monitoring and develop a representative system of tunnel structure for such regional tunnels. Aiming at the engineering background, we consider the soft-rock tunnels in the Guang-Gan Expressway (GGE), which are located at the core of the Wenchuan earthquake zone, taking the Dujiashan Tunnel as a representative project. Based on the loading data of the secondary lining from long-term monitoring, the fuzzy model is employed to evaluate the structure conditions for its safety. On the basis of such theoretical analysis, we therefore establish the relationships between the representative project and other soft-rock tunnels, and then the structural safety status of the nonrepresentative project is deduced and achieved. The present study shows that the vast majority of segments of the soft-rock tunnels on the GGE are safe. At the same time, the network transmission hardware platform and security evaluation with the alerting software system are installed successfully for those tunnels. Using the long-term health monitoring and representative system of tunnel structure for soft-rock tunnels at the core of the Wenchuan earthquake zone, real-time monitoring and management of the safe status of all the soft-rock tunnels on the GGE across the entire life cycle can be realized. [ABSTRACT FROM AUTHOR]

Owing to its key role in high-tech industry and clean energy technology, cobalt has been regarded as a critical material in many countries. In this paper, material flow analysis was used to quantitatively track cobalt material flows in China throughout the entire life cycle from 2000 to 2021. Based on data pertaining to cobalt commodity trade, cobalt loss during raw material processing, and recovered cobalt, we analysed the actual cobalt consumption in China. During the study period from 2000 to 2021, the main findings were as follows: (1) China's cobalt raw material imports accounted for 84.7% of the total raw materials acquired, while the export of cobalt-containing end products amounted to 32.6% of the total production. (2) China's cumulative net import of all cobalt commodities reached 561 kt, and battery products accounted for 73.3% of the total cobalt consumption. (3) China recovered 77 kt of cobalt from end-of-life products, while 327 kt of cobalt was not recovered. (4) The cumulative cobalt loss during raw material processing reached 288 kt, with the highest loss occurring in refining (51.0%), followed by manufacturing and fabrication (26.5%), beneficiation (12.3%), and ore mining (10.2%). The overall utilization efficiency of cobalt was 73.8% throughout the entire life cycle. (5) China's actual cobalt consumption reached 497 kt, accounting for 51.9% of the apparent cobalt consumption. Moreover, 61.1% of the cobalt products produced in China was consumed domestically, while 38.9% was exported. The massive export of cobalt commodities resulted in China bearing a disproportionate responsibility for carbon emission reduction. The research results can provide a scientific reference for the reasonable adjustment of the trade structure of cobalt commodities and realization of the economic and efficient utilization of cobalt resources in China. • The utilization efficiency of cobalt was 73.8% throughout the entire life cycle. • Cobalt raw material imports accounted for 84.7% of the total raw materials acquired. • Cumulative cobalt loss reached 288 kt, 51.0% of which occurred in the refining stage. • China's actual cobalt consumption was about 51.9% of the apparent cobalt consumption. • 61.1% of China's cobalt products was consumed domestically, while 38.9% was exported. [ABSTRACT FROM AUTHOR]