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Tea is the second most popular beverage in the world after water, and the potential environmental problems during the entire life cycle stages of its production have not been thoroughly discussed. This study aims to investigate the overall environmental impact of green tea production as a typical perennial crop in China with the system boundary from "cradle to gate". Scenario analysis is carried out to investigate the factors of green tea processing scales and packaging methods on the overall environmental impact level of green tea production in China. Results showed that the average overall global warming potential of procuring 1 kg dry green tea in China ranges from 10.4 to 15.6 kg CO 2 eq, depending on different processing scales and packaging methods. The processing stage is the dominant contributor to the overall environmental impact of producing 1 kg dry green tea product due to the use of electricity. Electricity consumption in the processing stage and chemical fertilizer application in the planting stage are identified as the environmental hotspots throughout the life cycle of green tea production in China. Optimizing energy structure and improving energy use efficiency in the processing stage, as well as reducing the amount of chemical fertilizer application are the critical measures needed to mitigate the environmental emissions of green tea throughout the life cycle. [ABSTRACT FROM AUTHOR]

The sustainable management of WEEE (Waste Electrical and Electronic Equipment) can contribute to the defense of the ESBs (Earth System Boundaries) and achievement of the UN SDGs (United Nations Sustainable Development Goals). This work conducted reasonable generation estimation and critical metals quantity assessment of retired mobile phones in Japan with the sales&new method. The generation estimation is based on the statistical data including sales and quantity of the subscribers. The result shows that there are 31.20 million of mobile phones retired in 2021, comparing 32.83 million in 2008. The calculated lifetime have minimum and maximum value in 2008 and 2019, which is 3.36 and 7.58, comparing 6.42 in 2021. 17 metals are selected as critical metals, with which the quantity and dynamic are also calculated. The replacement from feature phones to smart phones demand less of 11 metals, which shows the critical metals savings leading by the technological innovation. [Display omitted] • Conducting the valid generation estimation of retired mobile phones in Japan. • Calculating the critical metals quantity of retired mobile phones in Japan. • Assessing the dynamic of critical metals quantity by technological progress. [ABSTRACT FROM AUTHOR]

We investigated the effects of air purifiers and ventilation on the particulate matter PM 2.5 concentration of a semi-outdoor bus terminal using computational fluid dynamics (CFD) simulations. As per the numerical simulation results, the air purifiers alone significantly reduced the PM 2.5 concentration of the bus terminal. The effect of mechanical ventilation units on the PM 2.5 reduction is positive without air purifiers but negative with air purifiers. To understand the role of ventilation on the PM 2.5 reduction, a simple theoretical model was derived based on the mass conservation of the PM 2.5. This model considered the effects of traffic-related PM 2.5 emission, air purifiers, and ventilation. The PM 2.5 concentrations predicted by the proposed model showed good correlation with those from the CFD simulations. Using the model, we suggested that the ratio of the mass emission rate of PM 2.5 to the clean air delivery rate of air purifiers is an important value in determining the effect of ventilation. Moreover, when the background PM 2.5 concentration is higher than this value, the ventilation should be limited to reduce the PM 2.5 concentration of the bus terminal. An additional CFD simulation showed that limiting the ventilation using walls can reduce the PM 2.5 concentration of the bus terminal by 28.6% on average and up to a maximum of 44.2%. The present approach may be useful in improving the health of many commuters by designing openings of bus terminal and efficiently operating mechanical ventilation units. • Reduction of PM 2.5 concentration in a semi-outdoor bus terminal. • Combined effects of air purifiers and ventilation. • Strategies for an efficient operation of mechanical ventilation units. [ABSTRACT FROM AUTHOR]