Quantified Hong Kong’s building material stock and flow changes from 1910 to 2050.
Building material stock and flow comply with an S-curve pattern shaped by industrialization and deindustrialization.
Hong Kong has achieved and sustained an advanced economy via a more material-efficient pathway.
Since the construction industry is one of the major sectors responsible for the overexploitation of natural resources and the production of greenhouse gases, there is an urgent need to adopt a sustainable and environmental friendly approach to mitigate climate degradation. Research has explored the potential of recycled aggregate (RA) as a viable alternative to natural aggregate in concrete production. Currently, several treatment methods are being employed to enhance the efficient incorporation of RA into concrete, aiming to address this issue. However, the effective utilization of RA in place of NA remains uncommon. In this study, an effort has been made to develop a low-carbon recycled aggregate concrete by utilizing 100% carbonation treated recycled coarse concrete aggregate (CRCCA) in place of natural coarse aggregate (NCA) and alccofine as mineral admixture. A comprehensive analysis was performed, comparing the properties of CRCCA to those of untreated recycled coarse concrete aggregate. This analysis covered changes in weight, bulk density, water absorption, crushing value, and microstructure. Furthermore, five different concrete mixes were prepared, each varying in the proportion of natural coarse aggregate (NCA), untreated RCCA, and CRCCA. These mixes also incorporated alccofine as a mineral admixture. The evaluation process involved assessing the effectiveness of carbonation treatment and alccofine addition through tests on the workability, water absorption, density, and compressive strength of the concrete mixes. The study demonstrated that carbonation treatment of RCCA resulted in substantial improvements in crushing value and water absorption of CRCCA, alongside enhanced workability, reduced water absorption, and increased density in CRCCA concrete. Moreover, CRCCA concrete exhibited notable compressive strength gains at both 28 and 90 days compared to untreated RCCA concrete. Furthermore, the use of CRCCA and alccofine contributed to reducing GHG emissions associated with cement production, emphasizing the environmentally friendly attributes of this low-carbon concrete formulation.
Fully considering income inequality (ICIE) and its potential environmental effects can help achieve the goal of reducing carbon emissions. Based on this, to effectively explore the nexus between ICIE and carbon dioxide (CO2) emissions, we first deduce the theoretical framework and then empirically check the spatial impact of ICIE on greenhouse effect based on a global dataset from 1995 to 2016. In addition, this study also conducts the regional heterogeneous analysis and further detects the causal mediating route (i.e., indirect route) between variables. The findings suggest that: (i) Rising ICIE affects CO2 emissions positively; in other words, narrowing income gap can effectively mitigate greenhouse effect across the globe; (ii) In countries with high gross domestic product (GDP) level, expanded ICIE will exacerbate the greenhouse effect, while in low-GDP countries, ICIE is negatively correlated with CO2 emissions; and (iii) ICIE can indirectly influence greenhouse effect through substantial economic and technical routes, while the composition route is insignificant. Finally, this paper highlights policy suggestions for carbon reduction by adjusting income distribution, formulating targeted strategies in various countries, and promoting technical innovation.
Ordinary Portland cement is a construction material that is widely utilized all over the world. Aside from deforestation and fossil fuel combustion, the cement manufacturing industry contributes significantly to carbon dioxide emissions, which questions the viability of using Portland cement (PC) in concrete construction. Therefore, finding an alternative to the existing one becomes crucial. Geopolymer concrete (GPC) is a relatively advanced and innovative form of concrete that can be prepared without the use of PC. The present research emphasizes the assessment of the strength and durability of GPC containing fly ash (FA), ground-granulated blast furnace slag (GGBS), and dolomite as binders. The control mix consists entirely of FA as a binder, while five additional mixes are prepared by replacing 20% FA with either GGBS or dolomite or in varying combinations. The slump test is used to assess the workability of the concrete. Key mechanical properties such as compressive strength and split tensile strength are also determined, along with non-destructive tests including ultrasonic pulse velocity and electrical resistivity. To assess GPC durability, initial surface absorption and capillary suction absorption tests are conducted at various curing ages. The findings demonstrate that incorporating GGBS and dolomite into FA-based GPC results in notable improvements in both strength and durability. However, this enhancement reduces the workability compared to the control mix. The addition of GGBS and dolomite yields remarkable enhancements in compressive strength, showing an impressive surge of up to 67%, and a substantial reduction in initial surface absorption, up to 65%, as compared to the control mix over a period of 56 days. The most favorable results in terms of both strength and durability are achieved when FA is replaced with 20% of GGBS. Also, the mix containing a combination of 10% GGBS and 10% dolomite yields comparable results to the mix with 20% GGBS, making it a cost-effective alternative.
Integration of photovoltaic modules into greenhouse roofs is a novel and intriguing method. The cost of products grown in greenhouses is particularly high because of their high energy consumption for heating and cooling, and at the same time the increase in demand for available land, increasing its cost and creating spatial issues, the integration of photovoltaics on the roof of greenhouses is a highly viable solution. Simultaneously, the use of solar radiation is critical to maintain optimal crop development, while also being a renewable energy source. However, photovoltaics reduce the incoming solar radiation in the greenhouse, due to their shade. Shading can be either beneficial for the crops or not, depending on the crop type, thus it is vital to find the shading caused by photovoltaics both temporally and spatially. In this study, a model calculating the shading in a greenhouse due to roof-integrated photovoltaics is developed, based on the Sun position, the geometry of both the greenhouse and of the roof-integrated photovoltaics and their position on the greenhouse roof. Calculating the coefficient of variation of radiation data, for the shaded and unshaded areas using the proposed algorithm, it was found the coefficient of variation for the shaded areas is lower than that for the unshaded areas for a least 76% of the time. Also, the radiation values under the shaded area are more uniform. The proposed model is a tool for PV designers, operators, and owners, in order to optimize the potential of their solar panel installations.
This study assessed the effect of implementing multiple circuit connections and operating parameters (hydraulic retention time (HRT), organic loading rate (OLR), and external resistance) on the improvement of up-flow constructed wetland-microbial fuel cell (UFCW-MFC) in treating the mixed azo dyes wastewater and bioelectricity generation. The multiple-circuits UFCW-MFC facilitated the organic substrate degradation, which improved the removal efficiency of dyes by 8% and COD by 7%, as well as power production by 6.5 times, compared to single-circuit UFCW-MFC. The prolonged HRT from 1 to 3 d extended the interaction time between the pollutants and microbes, which further enhanced the removal efficiency of dyes by 9% and COD by 6%. The decrease in power generation by 1.3 times could be ascribed to the lower OLR at a higher HRT (0.864–0.288 g COD/d when HRT extended from 1 to 3 d) as the utilization of electrons was prioritized for decolorization compared to bioelectricity generation. The increase in OLR (0.288 to 0.754 g COD/d) with the same HRT (3 d) exhibited an improvement of 4% in decolorization and 2.4 times in power generation. This could be attributed to more electron production from the higher COD removal. The lower external resistance benefited the UFCW-MFC performance, where the best performance was obtained at 200 Ω as it approached the internal resistance (150 Ω).