Search

Turning waste-to-resources is one of the key scientific interests in recent years, especially within industrial symbiosis networks in order to reduce the waste management problem and associated environmental consequences, improve materials efficiency and conserve natural resources. Considering global concern over fossil fuel burning and CO 2 emission, engineered fuels are increasingly used in cement production. The techno-environmental feasibility of using post-consumer wood derived fuel (WDF) in practical application is rarely reported. This study comprehensively evaluated the process feasibility and environmental compliances of utilizing WDF as an alternative fuel in the co-combustion process. The results revealed that physical parameters of WDF met the required fuel standards, and the air emissions by continuous emission measurements also met the specified limits and comparable to the baseline. The stack emission parameters monitored including particulates, dioxin, mercury, cadmium and thallium, and other heavy metals were about 60%, 2%, 21%, 6% and 7% of the specified limits. In addition to significantly reducing CO 2 emission (16% for using 20% WDF as co-fuel), the characteristics, of the flue gas as monitored by continuous emission monitoring and periodic stack emission at the cement plant, and the produced clinker quality were also not affected by the use of WDF. These have demonstrated the suitability of WDF as co-fuel for cement production. • Techno-environmental feasibility of bio-fuel derived from wood waste was evaluated. • Comprehensively reported the practical application of co-combustion process in the cement industry. • WDF was suitable in the co-combustion based on compliances in emission and process parameters. • About 16% reduction of GHGs emission was observed for 20% replacement of coal by WDF in the plant. [ABSTRACT FROM AUTHOR]

Abstract Waste timber formwork from construction sites was used as fibre to prepare wood-magnesium oxychloride cement (MOC) board. The effect of wood fibre content, pulverized fly ash (PFA) and incinerated sewage sludge ash (ISSA) on the mechanical and durability properties of wood-MOC board was investigated. Greenhouse gases (GHGs) emission, one of the representative and most globally concerned environmental impacts, for the production of different types of composite boards was assessed and compared by using lifecycle assessment (LCA) technique. The 'cradle-to-gate' system boundary with 1 kg of board production was considered as the functional unit in this assessment. The result showed that the wood-MOC composites prepared with a higher content of wood fibre had a lower thermal conductivity, higher flexural strength, higher residual flexural strength after exposure to high temperatures and water immersion, and better noise reduction effect. Even though the water absorption was increased with the increase of wood fibre content, it can still be considered to be low. The wood -MOC composites incorporating ISSA showed higher flexural strength, better high temperature resistance and better water resistance than other composites. In addition, the production of the wood MOC board induces lower GHGs emission than plywood and lower human toxicity than conventional resin-based particleboard. [ABSTRACT FROM AUTHOR]

Abstract A rapid development of building environmental research from the globe is witnessed in recent years to deal with the environmental issues, especially in terms of energy consumption and carbon emissions, due to the substantial environmental burdens associated with the building industry. Thus, numerous scientific efforts have been devoted to buildings through environmental assessment like a life cycle assessment (LCA) and a methodological framework development. Concerning the rapid growth of buildings, LCA is increasingly used for assessing and mitigating the associated environmental impacts from material selection to the whole building systems. This study aims to comprehensively review the LCA implication on buildings by discussing the contemporary issues related to the development of this research field. The study considers a wide range of literature including case studies, reviews and surveys, and these articles are critically examined according to the predefined criteria developed. An in-depth analysis is also conducted on selected studies to unveil the criticality of the assessments and results under different considerations. In addition to demonstrating the research gaps for comprehensive assessment of buildings, the adoption of a circular economy (CE) concept is highlighted by providing a comprehensive framework. The findings show that resource recovery and resource-efficient building construction are seldom considered in prevailing studies. As a result, the framework proposed in this paper should help support a paradigm shift towards a comprehensive research for increasing the accuracy and practicability by introducing the CE principle to the building industry for enhancing its sustainability performance. Highlights • Literature related to building-environmental research was critically analyzed. • LCA implication on buildings was comprehensively reviewed by discussing the contemporary issues. • Selected papers were critically analyzed to unveil the research trends and practices. • Knowledge gaps for comprehensive assessment of buildings under the CE principle are identified. • Comprehensive framework based on the CE principle was proposed for comprehensiveness building LCA. [ABSTRACT FROM AUTHOR]

The management of a large amount of wood waste generated from construction activities is a challenging issue. However, wood waste is an inherently renewable resource that can be recycled and utilized for the production of green products and renewable energy. In order to minimize the environmental impacts and to provide a scientific basis for the decision-making process on the wood waste management systems, a life cycle assessment (LCA) approach was employed in this study to evaluate the potential management systems from an environmental point of view. Three alternative scenarios, including the recycling and reusing of wood waste to produce organic polymer based particleboard, cement-bonded particleboard and energy were compared with the current disposal strategy (landfill disposal), with the functional unit of 1 tonne of wood waste within a cradle-to-grave system boundary. The LCA results showed that significant reductions of environmental impacts were observed for the production of particleboard (scenario 1) and wood-cement composite (scenario 2) from wood waste compared to that of using virgin wood. However, the results also showed that scenario 3 (energy generation from bio-fuel derived from wood waste) was the best strategy, as this technology reduces more than 1 tonne of CO 2 eq greenhouse gases compared to the energy generation from coal. The analysis conducted in this study can serve as guidelines to design a sustainable and resource-efficient wood waste management system. [ABSTRACT FROM AUTHOR]

The possibility of recovering energy from biomass residues has attracted a lot of research interest due to the environmental problems associated with burning coal. Wood wastes generated from construction and demolition activities and other wood product wastes can be a good potential source of renewable energy. The present study was conducted by using Hong Kong as an example to assess the environmental sustainability of converting recycled wood wastes (from construction and demolition activities and other wood product wastes) to produce wood pellets for direct energy generation. The chemical and physical characteristics of different types of wood product wastes were tested. An attributional lifecycle assessment approach was used to assess and compare the environmental impacts and sustainability for heat generation from the pelletized bio-fuel and coal. The test results showed that the energy content, chemical compositions and the trace metal concentrations all met the relevant standards. The results also showed that significant impacts on health, ecosystem, climate change and resources damage can be potentially avoided by using wood pellets instead of coal for energy generation. The overall findings demonstrated that the proposed “energy recovery” approach for using wood pellets as a bio-fuel in Hong Kong is environmentally sustainable, which can provide an alternative route for managing wood product wastes with the added benefits of energy recovery, and may be more applicable in mega cities especially when city-based incineration is a concern. [ABSTRACT FROM AUTHOR]

Sustainable building retrofitting has attracted serious research attention in recent years as it can significantly reduce energy consumption and thus help achieve energy reduction targets set by governments around the world. In this paper, a sustainable retrofit decision-making model is developed to uncover the optimal set of retrofit solutions according to local climatic conditions, building features, and retrofit costs. Net present value (NPV), a common method for analyzing the feasibility of a building retrofit solution, is used to determine the optimal retrofit solution of existing high-rise residential buildings in a temperate zone and hot summer-cold winter zone, involving prototypical 1990s apartments of 116 and 53 m2 floor areas respectively. This reveals that the lighting system, wall insulation, and upgraded window glazing are essential optimal retrofit measures for the temperate zone, whereas the heating system and shading devices are also essential for the hot summer-cold winter zone. The results indicate that the optimal NPV can be obtained by pursuing a 40% energy saving, as it can result in energy saving of up to 50 kWh/m2/year and 95 kWh/m2/year at an average retrofit cost of approximately USD 1.30 and 3.20 m2/year in the temperate and hot summer-cold winter zones respectively. The sensitivities associated with the most influential optimal NPV and energy savings input parameters are critically analyzed; these can be used by decision-makers to determine the risks and uncertainties related to various cost-effective retrofit measures. The model can help in devising the most suitable sustainable retrofit measures for existing buildings commensurate with the energy reduction targets of policy and decision-makers in the two climate zones. It is also amenable to being adapted for other climatic zones to identify the most appropriate sustainable building retrofit for particular local climatic conditions and building characteristics. [ABSTRACT FROM AUTHOR]

Over the past three decades, life cycle assessment (LCA) has been increasingly employed to evaluate the environmental impacts of products and buildings. However, the reliability of LCA is frequently weakened by the practice of arbitrary omission of processes and materials and the problem of insufficient data, both leading to inconsistencies in the LCA results. This study proposes an Index of Completeness (IoC) to account for the completeness of an LCA study for a variety of impact categories. An IoC calculation tool is developed to cover the entire life cycle of buildings, including stages of product, construction, use and end-of-life as well as the benefits from recycling and reuse. The IoC helps to identify and remove the inconsistencies in LCA and to enhance its comparability. Residential building projects are tested as case studies. It is found that the IoCs of most impact categories are as high as 98%–99%, whereas of the category of human toxicity the IoC is 85%, mainly due to the fact that plywood formwork was not included in the original model. Sensitivity analysis reveals that dataset changes in an LCA model can not only affect the impact assessment results, but also possibly have influence on the completeness of the LCA model. The LCA practitioners are suggested to combine the newly developed IoCs with the standard four phases of LCA when applying to complex products. Future research should focus on case studies implementing the IoC calculation tool, inclusion of more impact categories in the IoC model, and continuing development to include other complex products. Image 1 • An Index of Completeness (IoC) is proposed to describe to what extent the processes and data are included. • An IoC calculation tool is developed for the building sector. • The case study of a residential building project is conducted. • The IoC of human toxicity is as low as 85%, caused by the exclusion of plywood formwork in the original model. [ABSTRACT FROM AUTHOR]

Ability to forecast the waste electrical and electronic equipment (WEEE) generation can help formulate a robust future WEEE management system. Previous studies applied forecasting models, such as the grey model and artificial neural networks, to predict WEEE generation from a country perspective, leading to less accurate forecasts due to huge socio-economic differences in rural and urban areas. Additionally, there has been the incompatibility of a single forecasting model for all WEEE types, and this remained a research gap. Taking advantage of respective forecasting models, this study presents a hybrid model, Grey Artificial Neural Network, to forecast the WEEE generation of 31 province-level regions in China while evaluating the socio-economic analysis of seven WEEE types via Pearson correlation analysis. More than 70% of WEEE from province-level regions strongly correlates (R > ±0.8) with the gross domestic product and the population, whereas some top WEEE-generating province-level regions (i.e., Tianjin and Shanghai) correlate weakly to moderately. The root mean square error and mean absolute error of the developed Grey Artificial Neural Network hybrid model are the lowest at 8.29 and 6.48, compared to the grey model (13.53 and 11.13) and back-propagation neural network (9.21 and 7.22). Though the Grey Artificial Neural Network hybrid model has the lowest error, posterior mean square deviation ratio analysis indicates that this hybrid model is only suitable for washing machines, refrigerators, color televisions, and personal computers (urban area), while the back-propagation neural network is suitable for monochrome televisions, air conditioners, and personal computers (rural area). Compared to 2019, it is projected that an additional 32.92 M units of WEEE will be generated by 2025, suggesting that China should build at least 15 extra recycling centers (14% more based on 2016) to handle the increased WEEE generation. This study provides policy implications for effective WEEE monitoring and collection systems to build resilient WEEE management. [Display omitted] • Grey artificial neural network hybrid model with higher accuracy is developed. • Province's socio-economic correlation and e-waste prediction are conducted. • Top e-waste-generating province-level regions exhibit different socio-economic correlation. • China's e-waste will reach 286 M units in 2025, 13% more than in 2019. • Policy and strategy are recommended for the increased e-waste generation. [ABSTRACT FROM AUTHOR]