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• Evaluated the environmental impacts of plastic wastes management strategies by LCA. • Industrial incineration is the most potential preferential strategy for Hong Kong. • Mechanical recycling is the second most environmentally sustainable strategy. • Reusing plastics in construction is not an environmental-friendly solution compared to others. • The integrated alternative scenarios can lead to 64–97% reduction of the total impacts. Considering the volume of plastic generation and its persistence in nature, the management of plastic wastes has gained increasing attention globally. To select the most environmentally sustainable solution, insights in the environmental impacts of different management strategies are crucial. This study thus aimed to evaluate different plastic waste management strategies such as mechanical recycling, incineration, industrial incineration, construction and landfill, and exemplified with potential case demonstrations in Hong Kong. The environmental impacts of the developed strategies are comparatively evaluated by the lifecycle assessment (LCA) technique in order to identify the most environmentally preferable strategy. The LCA results indicate that industrial incineration is the most potential preferential strategy for Hong Kong, as it can potentially consume the generated waste locally and substitute the imported coal for the cement industry. Mechanical recycling is the second preferential strategy for the city, as it conserves secondary resources significantly. Grate incineration for generating electricity is the third preferable solution, while the use of recycled plastics in construction may not be a benign environmental strategy for Hong Kong. The findings of this study could help policy makers to design strategic direction for environmentally sustainable management of plastic wastes locally based on the circular economy principle. [ABSTRACT FROM AUTHOR]

Considering the significant consumption of energy in existing building stocks, effective retrofitting has great potential for reducing such consumption and promoting sustainability in existing buildings. This study aims to develop a sustainable retrofit decision-making mechanism for high-rise buildings in Hong Kong, China, by uncovering the optimum set of retrofit solutions based on the local climatic conditions, building features and cost. Based on a prototype building in Hong Kong, the study employed the net present value (NPV) to unveil the most suitable solutions to maximise the energy efficiency of existing buildings and minimise their retrofit costs, integrating the energy simulation. This study revealed that it is desirable to adopt an optimal set of measures for achieving a 40% energy improvement since the energy conservation can be as much as 82 (kWh/m2)/year with the optimal NPV of more than US$3300 over a 20 year life span. However, the cooling system, building energy management system and thickness of wall insulation are the most influential factors to the optimum NPV and energy conservation in Hong Kong. The identified optimal set of cost-effective retrofit measures can be effectively implemented for sustainable retrofit projects in the existing building, and the developed methodological framework can be suitably adapted for sustainable building retrofit projects in different climatic zones. The decision-making model is validated by the process of calculating energy consumption, selecting practical retrofit measures and analysing retrofit benefits when taking the local building standards into account. [ABSTRACT FROM AUTHOR]

• Comprehensive methodological approach was provided for identifying sustainable material sourcing regime. • Identified hotspots of existing construction material and product sourcing in Hong Kong. • Proposed alternative scenario for sustainable material sourcing based on developed decision matrix. • Alternative scenario reduced 28% of the total GHG emissions than the base scenario. While the assessment of environmental impacts of different construction materials is widely studied globally, the development of robust mechanisms for material sourcing as an integral step to transit into a sustainable supply chain is still sparse. Integrating environmental performance into an industry level supply chain is indeed a challenging task due to the absence of standardized methodology. This paper presents a methodological approach for sustainable construction material sourcing by highlighting the greenhouse gas (GHG) emissions. The proposed approach is then adopted to 12 case construction materials and products which are commonly used in to Hong Kong, and the hotspots for existing sourcing of the selected materials and products are identified while the GHG emissions are assessed based on their sourcing locations. Alternative scenarios for sourcing are identified based on a decision matrix developed according to this methodological approach. The results demonstrate that sustainable sourcing of the 12 selected materials and products by adopting the alternative scenarios can reduce 28% of the total GHG emissions compared to the base scenarios. As the scope of emission reduction for resource-scarce high-density city like Hong Kong is limited, sustainable sourcing of materials may significantly influence the emission reduction target of the construction industry. The proposed approach can help underpin sustainable sourcing of materials which can be effectively adopted in other regions to enhance the sustainability performance of the industry. [ABSTRACT FROM AUTHOR]

The importance of the building industry on environmental impacts, especially global warming potential (GWP) impact due to greenhouse gases emissions is undisputed. Thus, significant efforts have been devoted to minimize environmental impacts and waste management problems from building construction globally. Numerous studies have particularly focused on assessing the environmental impacts of buildings based on materials, construction processes and whole building systems. However, less attention has been given on some critical features, especially on temporary works (e.g., hoarding system). But the temporary works also consume considerable amounts of materials and generate significant amounts of waste due to its short service life time. Therefore, this study evaluated the environmental impacts of hoarding systems as a case study in Hong Kong with the aim to identify the areas of impacts reduction and improvements in its waste management system. A case-specific structured questionnaire survey was conducted to the relevant stakeholders to identify the essential materials, and construction, deconstruction and waste management processes of hoarding systems, whereas life cycle assessment was employed to assess the associated environmental impacts. The findings demonstrated that more than 3 tonnes of CO 2 eq GWP and 39 GJ of non-renewable energy consumption impacts were associated with 1 m of hoarding construction. This is mainly due to the use of large amounts of steel products and concrete in the construction of the hoarding system. This results and analysis can help the building industry to identify the opportunity for reducing environmental impacts, and facilitate resource-efficient and effective design of hoarding systems. [ABSTRACT FROM AUTHOR]

Cement is traditionally regarded as an energy and emission intensive construction material. The reduction of environmental impacts in the cement industry has gained increasing concern worldwide for environmental sustainability. As a resource-scarce city, cement production in Hong Kong is associated with high CO 2 emissions, thus contributing significantly to the high environmental impacts in the construction industry. This study herein has been conducted to comprehensively assess the energy consumption and global warming potential impacts of different types of cement manufactured in Hong Kong using life cycle assessment (LCA) techniques. Two sustainable strategies for the reduction of energy consumption and greenhouse gases emission in the cement industry were then proposed. The LCA results showed that ordinary Portland cement production has high environmental impacts mainly due to the import of associated raw materials and burning of fossil fuel. The use of alternative material, such as fly ash would help to reduce the environmental impacts. Significant impacts reductions associated with cement production can be further achieved by strategies such as the use of glass powder from locally generated waste glass bottles as part of the raw materials, and the use of a bio-fuel produced from locally generated wood wastes as a co-fuel with coal. The assessment results indicated that about 12% of the total greenhouse gases emission and 15% of energy consumption can be reduced from the cement industry in Hong Kong by using waste materials to replace virgin materials (clinker/coal). [ABSTRACT FROM AUTHOR]

With the promotion of environmental protection in the construction industry, the mission to achieve more sustainable use of resources during the production process of concrete is also becoming important. This study was conducted to assess the environmental sustainability of concrete slurry waste (CSW) management by life cycle assessment (LCA) techniques, with the aim of identifying a resource-efficient solution for utilisation of CSW in the production of partition wall blocks. CSW is the dewatered solid residues deposited in the sedimentation tank after washing out over-ordered/rejected fresh concrete and concrete trucks in concrete batching plants. The reuse of CSW as recycled aggregates or a cementitious binder for producing partition wall blocks, and the life cycle environmental impact of the blocks were assessed and compared with the conventional one designed with natural materials. The LCA results showed that the partition wall blocks prepared with fresh CSW and recycled concrete aggregates achieved higher sustainability as it consumed 59% lower energy, emitted 66% lower greenhouse gases, and produced lesser amount of other environmental impacts than that of the conventional one. When the mineral carbonation technology was further adopted for blocks curing using CO 2 , the global warming potential of the corresponding blocks production process was negligible, and hence the carbonated blocks may be considered as carbon neutral eco-product. [ABSTRACT FROM AUTHOR]

Substantial amount of resources is consumed by pavement systems, which have resulted considerable environmental impacts. Understanding the environmental impacts would provide opportunity for reducing resource consumption and informing decision-makers in the process of designing sustainable pavement. There is a lacking of comprehensive and comparative sustainability assessment of pavement systems in highly urbanized context currently. Therefore, this study aims to design and comprehensively evaluate the environmental performance of the commonly adopted pavement systems in highly urbanized context using lifecycle assessment (LCA) technique through a case in Hong Kong. According to the codes and practices of Hong Kong, two pavement systems including flexible and rigid pavements were designed based on the same road section. After that interviews with structured questionnaire were conducted to collect relevant practical information of pavement construction and maintenance from the relevant professional bodies and experts for the subsequent LCA of such designs. The LCA results reveal that the two mid-point impacts of global warming potential and mineral extraction are 21% and 54% higher for rigid pavement than for flexible pavement. Yet, the end-point results indicate that flexible pavement is associated with 64%, 65%, and 69% higher human health impact, ecosystem quality damage, and resource damage, respectively. Material production and transportation contribute significantly to the total impact in the two pavement systems. For instance, it is about 57% and 97% of the total global warming potential for flexible and rigid pavements, respectively. The overall results demonstrated that 49% higher total impact was found for flexible pavement than rigid pavement. Therefore, the use of more recycled and environmentally friendly materials can potentially enhance the environmental sustainability of both pavement systems. The findings should provide useful information to the design and selection of sustainable pavement structures in resource-scarce highly-urbanized cities. [Display omitted] • Designed two commonly used pavement systems based on the existing practices in Hong Kong. • Evaluated the environmental sustainability of pavements in an urban context using LCA. • Considerably higher impact was associated with frequent maintenance in flexible pavement. • About 49% higher total impact was found for flexible pavement than the rigid pavement. [ABSTRACT FROM AUTHOR]

• Stabilization/Solidification (S/S) for hazardous materials was evaluated by life cycle assessment. • Sediment and municipal solid waste incineration fly ash remediation was studied with 17 S/S scenarios under five strategies. • Alternative binders and recycled materials reduced the overall environmental impacts. • This decision-support process could facilitate the design of sustainable remediation. Proper management of hazardous materials arouses widespread environmental concerns due to its enormous ecological and health impacts. The development of green stabilization/solidification (S/S) technology for resourceful utilization of hazardous materials, as well as the immobilization of potentially toxic elements is of great scientific interests. Cement-based S/S is often considered a low-cost and highly efficient technology, but the environmental sustainability of a broad spectrum of S/S technologies has yet to be evaluated. Therefore, this study assessed the environmental sustainability of S/S technologies for managing two common types of hazardous wastes, i.e., contaminated marine sediment and municipal solid waste incineration fly ash (MIFA) by using life cycle assessment (LCA). A total of 17 scenarios under three strategies for sediment and two strategies for MIFA S/S technologies were comprehensively evaluated. The LCA results identified the most preferable S/S technology in each strategy. In particular, Scenario 1 (mixture of sediment with a small percentage of ordinary Portland cement and incinerated sewage sludge ash) of Strategy 1 (use as fill materials) would be the preferred option, as it reduces about 54% and 70% global warming potential compared to those of Scenarios 2 and 3, respectively. This is the first initiative for evaluating the environmental impacts of a wide range of recently developed S/S technologies using green/alternative binders for diverting hazardous wastes from disposal. The results can serve as a decision support for the practical application of the environmentally friendly S/S technology for sustainable remediation. [ABSTRACT FROM AUTHOR]

In recent years, considerable efforts have been devoted to minimizing the environmental consequences from building industry globally, as the industry is notorious for its significant resource consumption and environmental emissions. However, due to a lack of data representativeness in many parts of the world, considerable variations were observed among studies, and thus makes life cycle assessment (LCA) results difficult for the decision-making purpose. In addition, the selection of low impact materials and the management of end-of-life building waste are the most important concern. By considering several strategies including data representativeness, low carbon material, and end-of-life building waste management, this study aimed to enhance the accuracy of such assessment and sustainability performance of building. An integrated LCA framework is proposed for implementing those strategies through a case specific high-rise residential building in Hong Kong. Based on case-specific/regional data, carbon emission of building was evaluated with a cradle-to-construction system boundary with the functional unit of 1 m2 of gross floor area using the IMPACT 2002+ method, and then compared to that of selecting generic databases under different scenarios. The results demonstrate that the application of case-specific and generic data would significantly influence the outcomes of the case study, as the deviations of certain magnitudes were mostly derived from different building materials that it can lead to an underestimation of carbon emissions of up to 28%. Along with using alternative materials, the adoption of the proposed materials cycling and resource recovery approach at the end-of-life building could lead to a reduction of 14% of the total emissions (i.e. excluding the use and renovation of building). The results would support data selection for accuracy of evaluation which can be used as benchmark where recognized database is not available and promote sustainability performance of buildings locally, while the proposed framework could be adopted for comprehensive evaluation globally. • Proposed integrated framework for enhancing accuracy and sustainability of building. • Data representativeness is a prerequisite for the accuracy of building LCA. • Representative data induced significantly higher carbon emission than generic data. • Using alternative materials for concrete reduced building's carbon emission. • Adopting resource recover approach in EoL significantly reduced carbon emission. [ABSTRACT FROM AUTHOR]