A systematic review of the life cycle environmental performance of cotton textile products

The production of cotton textiles involves cotton cultivation, ginning, spinning, weaving, knitting, dyeing, finishing, cutting and sewing. It consumes large quantities of freshwater, energy and chemicals, causing serious environmental impacts. The environmental impacts of cotton textiles have been studied extensively through various methods. However, little literature comprehensively summarizes current status of researches on environmental impact of cotton clothing comprehensively and identifies common problems to further study. To fill this gap, this study collates published results on the environmental performance of cotton clothing based on different environmental impact assessment methods, i.e., life cycle assessment, carbon footprint, and water footprint. Apart from the environmental impact results, this study also discusses the key issues when assessing the environmental impact of cotton textiles, such as data collection, carbon storage, allocation methods, and the environment benefits brought by recycling. In the production process of cotton textile products, there will be other co-products with economic value so that the environmental impact should be allocated. The economic allocation method is the most widely used method in the existing researches. In the future, considerable efforts are required to construct the accounting modules which consist of multiple modules, each representing a production process of cotton clothing and including an inventory of inputs under that process, such as cotton cultivation (water, fertilizer, pesticides), and spinning (electricity). It can ultimately be used to flexibly invoke one or more modules to calculate the environmental impact of cotton textiles. Moreover, returning carbonized cotton straw to the field can retain about 50 % of carbon, thus having a certain potential for carbon sequestration.

Emergy synthesis of decoupling and recoupling crop-livestock systems under unified system boundary and modified indices

Sustainability assessment of integrated crop-livestock system was crucial for regulating and improving the complex agricultural system. Emergy synthesis (ES) is a suitable tool to assess the sustainability of integrated crop-livestock systems. However, the inconsistent system boundaries and limited assessment indicators caused to subjective and misleading results when comparing the recoupling and decoupling croplivestock models. Therefore, this study defined the rational system boundary of emergy accounting for the comparison of recoupling and decoupling crop-livestock complex systems. Meanwhile, the study designed an emergy-based indices system based on "3R" principles of circular economy. An integrated crop-livestock system including sweet maize cultivation and cow dairy farm in South China was selected as the case to compare sustainability of recoupling and decoupling models under the unified system boundary and modified indices. Results showed that the new ES framework could provide more rational assessment results when comparing the recoupling and decoupling crop-livestock systems. In addition, this study illustrated, through scenario simulation, that the recoupling maize-cow model could be further optimized by regulating the material flow between subsystems and adjusting the system structure. This study would promote the application of ES method in the field of agricultural circular economy.

Life cycle assessment of concrete structures with reuse and recycling strategies: A novel framework and case study

In the construction industry, reuse and recycling strategies help reducing waste, saving energy and cutting down emissions by converting construction and demolition (C&D) waste into resources. This study proposes a novel framework to guide the life cycle assessment (LCA) of concrete structures with reuse and recycling strategies. The material flow in recycling strategies is clarified explicitly. A new definition of degradation rate is introduced to set a nonlinear allocation rule for reusable components based on the durability feature of concrete structures. Reusable rate and replacement percentage are adopted to provide a convenient way to adjust the type and level of the strategies. As a result, a unified system boundary and corresponding indicator functions can be established for various strategies, combing the closed-loop analysis and the open-loop analysis. In the case study, design for deconstruction (DfD) and recycled aggregate concrete (RAC) are taken as examples of reuse and recycling strategies, respectively. With the proposed framework, LCA of various strategy combinations are conducted considering the global warming potential (GWP) and abiotic depletion potential (ADP) indicators. Results show that the maximal environmental benefit of DfD is 1.8-2.8 times compared to that of RAC. When adopting DfD and RAC simultaneously, the environmental benefit level of each strategy will decline, whereas the overall benefits will be increased. LCA with the proposed framework avoids some assumptions in conventional LCA and provides more reliable results for various strategy combinations.

Engineering ethics within accident analysis models

The purpose of this paper is to further investigate engineering ethics and its gap within accident analysis models. In this paper, at first, the role of human factors in the occurrence of accidents is presented. Then engineering ethics as an element of human factors is proposed. It is suggested that engineering ethics can provide engineers with the necessary guidelines to avoid possible accidents arising from their decisions and actions. In addition, the Challenger and Columbia space shuttle case studies that demonstrate the role of engineering ethics in the prevention and occurrence of accidents are discussed. Then sequential, epidemiological, and systemic accident analysis models are briefly investigated and negligence of engineering ethics as a gap in the accident analysis models is described. At the end, we suggest that by implementing engineering ethics as a controller within the system boundary in systemic accident models we may be able to identify and prevent the ethical causes of accidents.

Understanding urban water performance at the city-region scale using an urban water metabolism evaluation framework

Water sensitive interventions are being promoted to reduce the adverse impacts of urban development on natural water cycles. However it is currently difficult to know the best strategy for their implementation because current and desired urban water performance is not well quantified. This is particularly at the city-region scale, which is important for strategic urban planning. This work aimed to fill this gap by quantifying the water performance of urban systems within city-regions using 'urban water metabolism' evaluation, to inform decisions about water sensitive interventions. To do this we adapted an existing evaluation framework with new methods. In particular, we used land use data for defining system boundaries, and for estimating natural hydrological flows. The criteria for gauging the water performance were water efficiency (in terms of water extracted externally) and hydrological performance (how much natural hydrological flows have changed relative to a nominated pre-urbanised state). We compared these performance criteria for urban systems within three Australian city-regions (South East Queensland, Melbourne and Perth metropolitan areas), under current conditions, and after implementation of example water sensitive interventions (demand management, rainwater/stormwater harvesting, wastewater recycling and increasing perviousness). The respective water efficiencies were found to be 79, 90 and 133 kL/capita/yr. In relation to hydrological performance, stormwater runoff relative to pre-urbanised flows was of most note, estimated to be 2-, 6- and 3- fold, respectively. The estimated performance benefits from water sensitive interventions suggested different priorities for each region, and that combined implementation of a range of interventions may be necessary to make substantive gains in performance. We concluded that the framework is suited to initial screening of the type and scale of water sensitive interventions needed to achieve desired water performance objectives.

Life Cycle Assessment for desalination: a review on methodology feasibility and reliability

As concerns of natural resource depletion and environmental degradation caused by desalination increase, research studies of the environmental sustainability of desalination are growing in importance. Life Cycle Assessment (LCA) is an ISO standardized method and is widely applied to evaluate the environmental performance of desalination. This study reviews more than 30 desalination LCA studies since 2000s and identifies two major issues in need of improvement. The first is feasibility, covering three elements that support the implementation of the LCA to desalination, including accounting methods, supporting databases, and life cycle impact assessment approaches. The second is reliability, addressing three essential aspects that drive uncertainty in results, including the incompleteness of the system boundary, the unrepresentativeness of the database, and the omission of uncertainty analysis. This work can serve as a preliminary LCA reference for desalination specialists, but will also strengthen LCA as an effective method to evaluate the environment footprint of desalination alternatives.