Developing efficient circularity for construction and demolition waste management in fast emerging economies: Lessons learned from Shenzhen, China

Developing a regional scale construction and demolition waste landfill landslide risk rapid assessment approach

In recent years, construction and demolition waste (CDW) landfills landslide accidents have occurred globally, with consequences varying due to surrounding environmental factors. Risk monitoring is crucial to mitigate these risks effectively. Existing studies mainly focus on improving risk assessment accuracy for individual landfills, lacking the ability to rapidly assess multiple landfills at a regional scale. This study proposes an innovative approach utilizing deep learning models to quickly locate suspected landfills and develop risk assessment models based on surrounding environmental factors. Shenzhen, China, with significant CDW disposal pressure, is chosen as the empirical research area. Empirical findings from this study include: (1) the identification of 52 suspected CDW landfills predominantly located at the administrative boundaries within Shenzhen, specifically in the Longgang, Guangming, and Bao'an districts; (2) landfills at the lower risk of landslides are typically found near the northern borders adjacent to cities like Huizhou and Dongguan; (3) landfills situated at the internal administrative junctions generally exhibit higher landslide risks; (4) about 70 % of these landfills are high-risk, mostly located in densely populated areas with substantial rainfall and complex topographies. This study advances landfill landslide risk assessments by integrating computer vision and environmental analysis, providing a robust method for governments to rapidly evaluate risks at CDW landfills regionally. The adaptable models can be customized for various urban and broadened to general landfills by adjusting specific indicators, enhancing environmental safety protocols and risk management strategies effectively.

Method development and empirical research in examining the construction of China's "Zero-waste Cities"

At the current stage, >100 cities in China are in the process of constructing "Zero-waste Cities" (ZCs). However, the absence of a unified quantitative evaluation method hinders the real-time display, assessment, and analysis of the progress and effectiveness of construction in various cities. Based on China's "Zero-waste City" (ZC) construction index system, a five-dimensional evaluation approach of transforming the city's construction index system into an evaluation index system is proposed, and an evaluation method for examining the construction of China's ZCs is developed. Meanwhile, the obstacle analysis model is employed to identify ZC's advantages and weaknesses. Following this evaluation framework, empirical research was conducted on Shenzhen. Results showed: 1) Shenzhen's ZC scoring result increased significantly from 58.9 to 108.3 by implementing the pilot project; 2) The dimensions of Management Measure, Support Capacity, and City Characteristic had achieved or approached full scores, but the dimension of Management Level still need improvement. 3) While industrial waste management reached an excellent level and agricultural waste proved manageable, domestic waste landfill and construction waste disposal still existed challenges. This method takes into account the uniformity of evaluation methods in nationwide and the diversity of solid waste environmental issues in cities. It can achieve a quantitative assessment of the ZC construction level for all cities in China, and providing a scientific basis for the horizontal comparison of the construction effectiveness of each city.

Automatic identification of illegal construction and demolition waste landfills: A computer vision approach

Dozens of landslide accidents are reported at construction and demolition waste (CDW) landfills worldwide every year. Those accidents could be avoided via timely inspection in which the identification of illegal CDW landfills at a large scale plays a critical role. Traditional field surveys are time-consuming, labor-intensive, which is not effective in large-scale detection of landfills. To address this issue, a methodology is proposed in this study for the automatic identification of CDW landfills in large-scale areas by utilizing semantic segmentation of remote sensing imagery. Deep learning is employed to achieve automatic identification and a case study is conducted to showcase the models. The results shown that: (1) The model proposed in this study can effectively identify CDW landfills, with an accuracy of 96.30 % and an IoU of 74.60 %. (2) DeepLabV3+ demonstrated superior performance over Pspnet and HRNet, though HRNet approached DeepLabV3+ in performance with appropriate optimizations. (3) Case study results indicate the potential existence of 52 CDW landfills in Shenzhen, includng 4 official landfills and 48 suspected illegal CDW landfills, mainly in Longhua, Guangming, and Baoan districts. The method proposed in this study provides an effective approache to identify large-scale illegal CDW landfills and has great significance for supervising CDW landfills.

Waste management practices in developing countries: a socio-economic perspective

Growing populations, expanding economies, industrialisation, and urbanisation pose a problem for waste management in developing countries. Their waste management methods, on the other hand, are not as efficient as they could be. Most developing countries' current waste management practices do not fully conform to developed countries' best practices for meeting socioeconomic goals. As a result, the importance of waste management in developing countries has grown in recent years. In order to highlight the socioeconomic perspectives of waste management practices, the present study examines the existing literature, policies, information, and records on waste management in developing nations. The findings indicate that essential socioeconomic factors such as finances, population density, per capita income, education level, policies, and technology have a significant impact on waste management, which encompasses waste generation, collection, composition, and disposal/treatment. Nonetheless, waste management has a number of economic benefits, including financial stability, job creation, and community cohesion. This study will inspire further research on the need for developing nations to consider the socioeconomic benefits of proper waste management and to develop a policy plan to achieve these benefits.

Utilization of electron beam irradiated carboxymethyl cellulose/polyvinyl alcohol/banana peels composite film for remediation of dyes from wastewater

In this work, polymeric composite films were fabricated utilizing stable, non-toxic, soluble, low-cost, good mechanical, and biocompatible polymers such as CMC and PVA with the waste of one of the most current fruits consumed worldwide banana peel waste (BP) as a filler. Sequences of carboxymethyl cellulose/polyvinyl alcohol/banana peel (CMC/PVA/BP) composite films with various amounts of BP utilizing eco-friendly technique (electron beam) (EB) irradiation were prepared to eliminate common hazardous organic pollutants such as methylene blue (MB) dye from its solutions. Physical characteristics like; swelling and gel % were examined. The chemical structure, thermal stability, and surface morphology were examined utilizing FT-IR, TGA, DSC, XRD, EDX, and SEM. Additionally, the UV/Vis spectroscopy study was investigated to study the impact of the various parameters such as irradiation, contact time, pH, temperature, adsorbent dosage, and initial concentration on removal efficiency % of MB dye onto the prepared composite films. The adsorption process fitted with the Langmuir model, pseudo-second-order kinetic model, endothermic, favorable, and spontaneous. The adsorption capacity of MB dye onto the CMC/PVA/BP composite film was 19.6 mg/g at the optimum conditions: irradiation dose = 20 kGy, contact time = 120 min, pH = 10, temperature = 25 °C, adsorbent dosage = 0.1 g and initial conc. = 10 mg/L.

Economic benefit analysis of the carbon potential of construction waste resource management based on a simulation of carbon trading policy

The need for safer and cleaner environments for all humankind remains a topical issue that cannot be overemphasized. To provide an updated perspective, this study analyzes the carbon potential of construction waste resource management based on carbon trading policy. In this study, the system dynamics principle was used to establish a carbon potential model of construction and demolition waste (C&DW) resource treatment by taking the regeneration project of Xiancun Village as an example. The results showed that the use of construction waste for recycling and resource treatment can generate enormous opportunities to reduce carbon emission. The implementation of the carbon trading policy can create significant benefits in terms of reducing carbon emission, while the total reduction of carbon emission in the baseline scenario can reach 100.66% when compared to the scenario without a carbon trading policy. Moreover, the findings shows that the combination of the carbon trading policy of "carbon price + free allowance ratio" can improve the return on investment of resource utilization companies and the carbon reduction benefits of the combined policy are greater than those of the single policy, but only if the level of the carbon price or free allowance ratio in the combined policy is accepted by the carbon trading subjects. The results of this research contribute to the theory of construction waste resourceization management, provide the theoretical basis for government departments to introduce carbon reduction policies for construction waste resourceization, and provide guidance for the management of companies' carbon reduction.

Stakeholders' purchase intention of products with recycled content: a combination of SEM and BPNN approach

The rapid urban renewal progress has generated a large amount of construction and demolition (C&D) waste in China. According to the concept of circular economy (CE), producing products with recycled content (PwRC) is an effective solution to achieve sustainable C&D waste management. However, the low market acceptance of PwRC affects stakeholders' purchase intention, which hinders the development of the PwRC industry. In order to clarify the stakeholders' purchase intention and investigate the influencing mechanism of stakeholders' purchase intention, a novel method which combines structural equation modeling (SEM) with a back-propagation neural network (BPNN) is proposed. The method makes full use of the causal analysis ability of SEM and the nonlinear characteristics of BPNN to simulate and to verify the path of product cues, perceived value, and behavioral intention of stakeholders. The results reveal that the brand and materials of PwRC can affect stakeholders' perceived value, and in turn, affect their purchase intention. Focus on the brand and materials of PwRC will help recycled product manufacturers and governments to promote stakeholders' purchase intention and the development of the C&D waste recycled products market.

Developing a hierarchical framework for assessing the strategic effectiveness of sustainable waste management in the Somaliland construction industry

This study contributes to develop a hierarchical framework for assessing the strategic effectiveness of waste management in the construction industry. This study identifies a valid set of strategic effectiveness attributes of sustainable waste management (SWM) in construction. Prior studies have neglected to develop a strategic effectiveness assessment framework for SWM to identify reduce, reuse, and recycle policy initiatives that ensure waste minimization and resource recovery programs. This study utilizes the fuzzy Delphi method to screen out nonessential attributes in qualitative information. This study initially proposes a set of 75 criteria; after two rounds of assessment, consensus regarding 28 criteria is achieved among experts, and the 28 criteria are validated. Fuzzy interpretive structural modeling divides the attributes into various elements. The modeling constructs a six-level model that depicts the interrelationships among the 28 validated criteria as a hierarchical framework, and it finds and ranks the optimal drivers for practical improvement. This study integrates the best-worst method to measure the weights of different criteria in the hierarchical strategic effectiveness framework. The findings reveal that waste management operational strategy, construction site waste management performance, and the mutual coordination level are the top aspects for assessing strategic effectiveness in the hierarchical framework. In practice, the waste reduction rate, the recycling rate, water and land usage, the reuse rate, and noise and air pollution levels are identified to assist policymakers in evaluation. The theoretical and managerial implications are discussed.

Urban mining from biomass, brine, sewage sludge, phosphogypsum and e-waste for reducing the environmental pollution: Current status of availability, potential, and technologies with a focus on LCA and TEA

Rapid industrialization, improved standards of living, growing economies and ever-increasing population has led to the unprecedented exploitation of the finite and non-renewable resources of minerals in past years. It was observed that out of 100 BMT of raw materials processed annually only 10% is recycled back. This has resulted in a strenuous burden on natural or primary resources of minerals (such as ores) having limited availability. Moreover, severe environmental concerns have been raised by the huge piles of waste generated at landfill sites. To resolve these issues, 'Urban Mining' from waste or secondary resources in a Circular Economy' concept is the only sustainable solution. The objective of this review is to critically examine the availability, elemental composition, and the market potential of the selected secondary resources such as lignocellulosic/algal biomass, desalination water, sewage sludge, phosphogypsum, and e-waste for minerals sequestration. This review showed that, secondary resources have potential to partially replace the minerals required in different sectors such as macro and microelements in agriculture, rare earth elements (REEs) in electrical and electronics industry, metals in manufacturing sector and precious elements such as gold and platinum in ornamental industry. Further, inputs from the selected life cycle analysis (LCA) & techno economic analysis (TEA) were discussed which showed that although, urban mining has a potential to reduce the greenhouse gaseous (GHG) emissions in a sustainable manner however, process improvements through innovative, novel and cost-effective pathways are essentially required for its large-scale deployment at industrial scale in future.

Effects of biochar on plant growth and hydro-chemical properties of recycled concrete aggregate

Biochar has been used as a sustainable amendment to mitigate environmental risks, improve plant growth and soil properties. This study conducted laboratory column tests to investigate the effects of plant-biochar interactions on shrub growth, hydraulic properties and nutrient contents of recycled concrete aggregates (RCAs). In total, three test conditions, namely, vegetated RCA without biochar (R), with 5 % biochar (R5) and 10 % biochar (R10) were subject to drying. With biochar application, total N, P and K of RCA increased by >100 %, 200 % and 31 %, respectively, while pH reduced to 8.3. With shrub growth, the lowest RCA pH was reduced to 7.8. The leaf area index (LAI) of shrub increased by 51 % due to biochar amendment, while the differences in shoot height were insignificant. The water retention capacity of RCA was enhanced by improving the saturated water content and air-entry value by 27 % and 100 %. The slope of the soil suction-LAI correlation for biochar amend cases was 1.6 times lower than R. This indicates that biochar may limit the increase of matric suction and prevent excessive water loss during drying. However, the differences between R5 and R10 were not significant. Therefore, 5 % biochar amendment is highly suggested as it can substantially improve plant growth and soil hydraulic properties during drying.

Exploring the restrictive factors for the development of the construction waste recycling industry in a second-tier Chinese city: a case study from Jinan

Recycling construction waste in urban cities has attracted wide attention in the government department and building industry worldwide owing to numerous benefits in economics, the environment, and society for sustainable development. Most of the research was focused on the scope of first-tier/new first-tier cities. At the same time, less attention has been paid to second-tier cities, which should be further considered because of their significant potential for increasing construction waste. Jinan is one of the pilot cities for construction waste treatment in China. This city has been chosen as the case in this study to explore critical restrictive factors for developing the construction waste recycling industry (CWRI) in second-tier cities with the adoption of combined methods of the DEMATEL-ISM-EWM. It was revealed by the results that (1) the government is the main stakeholder. In addition, the legislation, management system, incentive/support for stakeholders, and technical standards were closely associated with CWRI development in Jinan. Low landfill fees and natural ore tax rates are unique and vital restrictive factors that should receive more attention. (2) Other key restrictive factors that should be given priority were (i) the lack of green design for designers, (ii) poor classification and management of construction waste for constructors on site, (iii) tight operating funds and insufficient publicity for recycling enterprises, and (iv) insufficient research funds for research institutions. Finally, a comparison of the similarities and differences of the restrictive factors on CWRI development between second-tier and first-tier/new first-tier cities was conducted, and a series of reasonable suggestions were provided, considering the perspective of stakeholders. The research will offer a valuable reference for industry practitioners and academics interested in CWRI.

From prospecting to mining: A review of enabling technologies, LCAs, and LCCAs for improved construction and demolition waste management

Knowledge gained from anthropogenic resource prospecting can shed light on the theoretical potential of secondary resources stored in anthropogenic systems. Among others, secondary resources accumulated in the built environment account for a big fraction of anthropogenic resources, indicating great potential for urban mining. However, realizing these opportunities and developing urban mining strategies will require a comprehensive understanding of the technical viability of urban mining technologies, and how their implementation will affect the technical, economic, and environmental performance of a construction and demolition waste (C&DW) management system. To address these important issues, this review summarizes (1) current and emerging technologies that can enable the transition from anthropogenic resource prospecting to anthropogenic resource mining, (2) Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) results to date on various C&DW management systems, (3) key parameters that govern the technical, economic, and environmental performance of a C&DW management system, and (4) opportunities for improving the methodology of LCAs and LCCAs for future C&DW management. We find that enhancing the utility of extant LCAs and LCCAs in guiding technology deployment and policy decisions can be achieved by considering key parameters governing the techno-economic and environmental performance of C&DW management. In addition, it is critical to adopt and upscale emerging technologies to increase the added value of materials or products recovered from C&DW.

Characterization of Three Types of Recycled Aggregates from Different Construction and Demolition Waste: An Experimental Study for Waste Management

Achieving sustainable management and efficient use of natural resources stands out as one of the goals included in the Goals for Sustainable Development in the 2030 Agenda. The construction sector is currently far from presenting an efficient model in terms of treating waste generated by it. Variations in the physical and chemical properties of recycled aggregates coming from construction and demolition waste are one of the main reasons of their limited use in the production of construction materials. This research presents a physicochemical characterization of three different types of recycled aggregates coming from different types of waste: concrete, ceramic and mixed. Physical characterization shows that recycled concrete aggregate has better physical properties compared with mixed recycled aggregate and ceramic recycled aggregate, which makes it more suitable for use in masonry mortars and concrete, due to its higher dry density (2210.33 kg/m3), its lower content of fines (5.17%), its lower friability coefficient (24.60%), and its water absorption coefficient (6.70%). Chemical characterization shows that none of the tested recycled aggregates contains traces of harmful chemical agents that exceed the limits established by the reference regulations. Finally, the statistical analysis shows good homogeneity for these raw materials, obtaining low coefficients of variation and values within the recommended in each of the calculated confidence intervals.

Exploration of the Dynamic Evolution of Online Public Opinion towards Waste Classification in Shanghai

Shanghai is one of the fastest-growing metropolises and the first city in China to implement mandatory waste classification. Waste classification policy of Shanghai has attracted widespread attention since its implementation in July 2019. However, previous papers have not focused on online public attitudes surrounding the implementation of a waste classification policy in Shanghai. In order to fill this gap, this paper explored the dynamic evolution of online public attitudes towards waste classification in Shanghai by using sentiment analysis technology and topic modeling technology. It was found that the proportion of negative posts each month was about 20%; therefore, online public sentiment towards waste classification in Shanghai was generally positive. Compared with the first three months of policy implementation, the public sentiment towards Shanghai's waste classification became more positive, with the exception of two special periods. Negative posts in July 2019 mainly discussed waste's environmental hazards and policy provisions. New topics in negative posts in later months focused on some specific problems, including the process of throwing away wet waste, the allocated throwing times, the number of waste cans, takeaway meal disposal, and gathering activities. Improving the factors causing the negative sentiments in the posts will help the government better implement the policy. The paper will help the government to receive higher public support for the waste classification policy in Shanghai. The present findings also have great reference significance for other cities.

Responsibility disengagement or sharing? Cooperative fulfilling mechanism of solid waste management in the remanufacturing supply chain

Due to limited resources and meager profits, collectors have insufficient motivation to fulfill their responsibilities, resulting in severe secondary pollution in the recycling process. Therefore, it is necessary to focus on the interests of collectors to motivate them to fulfill their solid waste management (SWM) responsibilities better. This paper focuses on remanufacturers' altruistic behavior in the context of collectors' compliance. Based on the Stackelberg game method, this paper constructs decision-making models for remanufacturers concerned or not concerned about the interests of collectors and compares the optimal decision-making outcomes of each model. The study finds that (1) based on remanufacturers' altruistic concerns, a coordination mechanism for sharing responsibility-fulfilling costs for collectors can motivate them to fulfill their responsibilities and improve the performance of the remanufacturing supply chain. (2) The proportion of the remanufacturer's share of the responsibility cost for the collector should not be too low, which is not conducive to encouraging the collector to fulfill the responsibility. However, the sharing proportion should not be too high, as this will increase the burden on the remanufacturer. This paper demonstrates the applicability of remanufacturers to moderately share responsibility costs for collectors to incentivize collectors to fulfill their responsibilities. The findings bridge the gap in research on SWM in remanufacturing supply chains. The management insights from this paper are expected to help remanufacturing supply chain companies establish a reuse behavior model that addresses the challenges that SWM faces to improve remanufacturing supply chain performance.

Sustainable approach for valorization of solid wastes as a secondary resource through urban mining

The incessant population has increased the production and consumption of plastics, paper, metals, and organic materials, which are discarded as solid waste after their end of life. The accumulation of these wastes has created growing concerns all over the world. However, conventional methods of solid waste management i.e., direct combustion and landfilling have caused several negative impacts on the environment (releasing toxic chemicals and greenhouse gases, huge land use) besides affecting human health. Therefore, it is requisite to determine sustainable alternative technologies that not only help in mitigating environmental issues but also increase the economic value of the discarded solid wastes. This process is known as urban mining where waste is converted into secondary resources and thereby conserves the natural primary resources. Thus, this review highlights the technological advancements in the valorization process of discarded wastes and their sustainable utilization. We also discussed several limitations of the existing urban mining processes and further the feasibility of valorization techniques was critically analyzed from a techno-economical perspective. This paper recommends a novel sustainable model based on the circular economy concept, where waste is urban mined and recovered as a secondary resource to support the united nations sustainable development goals (SDGs). The implementation of this model will ultimately help the developing countries to achieve the target of SDGs 11, 12, and 14.

Management system for engineering and decoration waste: An exploratory study in Shenzhen

Rapid urban development and renewal have caused large amounts of engineering and decoration waste to be produced. These wastes pose serious risks to the environment. Disposal and management of this waste have become problematic. A mean of 11.4 × 10⁶ m³ of engineering and decoration waste will be produced each year in Shenzhen between 2018 and 2035. Engineering and decoration waste are currently mainly sent to landfill, but this requires large amounts of land and can cause serious environmental pollution. There are problems including irregular emissions, a disorderly transportation market, and inadequate disposal facilities, so policies for managing engineering and decoration waste need to be established. In this study, a hybrid approach was used to develop a system for managing the whole engineering and decoration waste system (generation, collection & transportation, and disposal). The system was developed after determining waste emission and disposal requirements through site visits, clarifying problems involved in waste collection and transportation through interviews, identifying suitable management practices in an expert seminar, and developing a management system through desktop surveys. It was found that new buildings produce 0.02-0.04 (m³ waste)/(m² building) and 0.11-0.13 (m³ decoration waste)/(m² building) and that emission limits are required. Construction enterprises employ private trucks to transport waste, and illegal dumping occurs. Directed collection and transportation is required. Public welfare requires a mechanism for managing engineering and decoration waste with clear responsibilities. Government-authorized construction and operation should be explored and implemented. A propagable engineering and decoration waste management system is proposed with three management modules, generation, collection & transportation, and disposal, to act as a strategy for improving engineering and decoration waste.

Promoting construction and demolition waste recycling by using incentive policies in China

In the recent two decades, construction and demolition (C&D) waste is becoming a major source of municipal waste which causes severe damage to the environment. To solve the problem, waste recycling measures are gradually used to turn waste into treasures. Meanwhile, several kinds of policies such as waste disposal charging fees have been issued to stimulate stakeholders' behavior to take waste recycling measures to promote the C&D waste recycling industry. However, the C&D waste recycling rate is still too low in China. In order to promote C&D waste recycling industrial development, this paper aims at introducing subsidy and environmental tax policies to promote C&D waste recycling. Based on system dynamics method, this study establishes a model to determine the proper subsidy and environmental tax range. According to the simulation results, three kinds of incentive policies are obtained, namely, single subsidy policy, single environmental tax, and combined incentive policies. Optimal single subsidy and environmental tax are in the interval, [10, 30] and [20, 60], respectively. The best combination strategy is subsidy = 10 yuan/ton and environmental tax = 20 yuan/ton. The results from this paper could be a foundation for government to establish incentive policies to promote C&D waste recycling.

Exploring spatial heterogeneity and factors influencing construction and demolition waste in China

Natural disasters, new urbanization, and urban renewal activities generated a large amount of construction and demolition waste (C&DW), and managing C&DW has become an urgent problem to be solved in the construction of "Zero-waste cities." Based on the calculation of C&DW generation in China from 2005 to 2019, this study explored spatial heterogeneity and factors influencing C&DW in China by Exploratory Spatial Data Analysis (ESDA) and Geographically Weighted Regression (GWR) method. The results showed that C&DW generation in China increased every year, and the overall distribution was characterized as "high in the east and low in the west," with distinct regional differences. The generation intensity of C&DW in China showed a decreasing trend every year. The regions with rapid growth of C&DW generation were concentrated in the eastern coastal areas, and there was significant spatial heterogeneity in the growth trend. There is a significant spatial autocorrelation in C&DW generation in China. The factors of population size, per capita gross domestic product, and the scale of the construction industry played a positive role in promoting C&DW generation in each province, whereas labor efficiency played a negative role inhibiting C&DW generation, which has a significant temporal and spatial heterogeneity. The results extend C&DW management theory and help the policy maker to formulate regional differentiation policies as China and developing country.

Identifying the Barriers to Sustainable Management of Construction and Demolition Waste in Developed and Developing Countries

The construction industry is a vital part of every nation’s economy. Construction activities influence the social, environmental, and economic aspects of sustainability. There are so many barriers to sustainable construction and demolition waste management (C&DWM). This study aims to identify barriers for effective sustainable C&DWM in developed and developing countries. To achieve the objective, 11 barriers have been selected and identified based on an excessive and comprehensive literature review, and then reviewed by experts. These reviewed barriers were further examined by various experts within different organizations using a questionnaire survey. Ranking of the barriers was carried out using the Relative Importance Index (RI), and the results were statistically analyzed using Statistical Package for Social Sciences (SPSS). Practical solutions were proposed to overcome the identified barriers. The overall ranking of barriers by RI indicates that insufficient attention paid to C&DWM, lack of law enforcement, lack of regulation, and financial constraints represent the four major barriers to sustainable C&DWM in these countries. The findings of this study and the proposed solutions are enablers for decision-makers to develop effective strategies to tackle construction and demolition wastes in sustainable manners.

A holistic assessment of the use of emerging recycled concrete aggregates after a destructive earthquake: Mechanical, economic and environmental

This study aims to examine the mechanical, environmental, and economic properties of recycled aggregate concretes produced using emerged recycled concrete aggregates from the buildings that were demolished in a controlled way after the 24 January 2020, Elazig-Sivrice earthquake. For this purpose, 24 series of recycled aggregate concretes were produced, water-to-cement ratios of 0.30-0.35-0.40-0.45-0.50, and cement dosages were chosen as 320-370-420 kg/m³. 100% recycled concrete aggregate was used in the prepared concrete mixtures. Analyses were made on the response surface method using the mixture ratios and test results of 24 series. The effectiveness of the developed models was examined on 6 Control recycled aggregate concrete. Then, Energy Consumption, Global Warming Potential, Waste Generation, and Abiotic Depletion were considered to assess the environmental impacts of recycled aggregate concretes. In order to make environmental and economic comparisons of recycled aggregate concretes and natural aggregate concretes according to these impact categories, 4 different scenarios were developed. Then, a detailed feasibility analysis was made for 4 different scenarios, and the economic results of recycled aggregate concretes and natural aggregate concretes were evaluated. Regarding the arisen millions of tons of waste materials and newly constructed buildings after the earthquake, recycling waste materials is considered crucial. Therefore, a holistic assessment was taken with this study, and the usability of recycled concrete aggregates was examined in detail.

Strategies for Enhancing Construction Waste Recycling: A Usability Analysis

Prior works have suggested various strategies to increase construction waste recycling (CWR) rates. However, choosing the strategies is challenging without a lateral comparison. Therefore, this study aims to compare the usability of various strategies that target the enhancement of CWR implementation. To achieve this purpose, thirteen CWR enhancement strategies were identified from a systematic literature review. Then, questionnaire survey data were collected from 106 construction project managers. The collected data were analyzed via mean score ranking, normalization, overlap analysis, agreement analysis, and factor analysis. Additionally, the data were analyzed using a proposed formula for computing usability indexes using the cost, easiness, and effectiveness values. The results show that three strategies have high usability indexes: organize temporary bins in each construction zone, identify construction activities that produce recyclable materials, and enhance company policies related to CWR. These strategies with high usability indexes are consistent with the overlapping cheap, effective, and easy strategies. This study provides researchers and practitioners with optimal strategies for enhancing CWR implementation. Effective CWR enhancement strategies can improve CWR rates in construction projects. Future researchers can also adopt this study’s approach in computing usability indexes through questionnaire surveys.

Multicriteria analysis of the environmental and economic performance of circularity strategies for concrete waste recycling in Spain

Construction and demolition waste (CDW) is identified by multiple circular economy (CE) policies as a key sector for implementing circularity strategies due to the high volume of waste produced and the large consumption of raw materials. However, CE is not widely applied in the sector because of the lack of solid estimations on its environmental and economic viability. The main aim of this study was to propose a set of methodological steps to identify the optimal circularity alternatives for CDW products based on a multicriteria analysis of their environmental and economic performance. This methodology is applied to evaluate concrete waste. In specific, high-grade applications of concrete waste were analyzed comprising the processing into recycled coarse aggregates (RCA) for their use in structural and non-structural concrete. Multiple scenarios with different RCA replacements (20%, 30% and 100%) and different types of sorting and recycling (on-site and off-site) were evaluated in accordance with the specific site conditions of the region of Catalonia, Spain. The Life Cycle Analysis methodology (LCA) was used to perform the environmental analysis, while a detailed cost analysis was conducted for the economic aspect. The multicriteria method VIKOR was used for the selection of alternatives considering three different criteria. The results of this study showed environmental and economic advantages of CE scenarios based on the use of RCA over conventional concrete, mainly due to the influence of landfilling and transport distances. RCA produced on-site showed a better performance than RCA from fixed plants.

Drawing a Path towards Circular Construction: An Approach to Engage Stakeholders

The activities conducted in the building and construction sector should be guided by circular economy principles, which will result in the implementation of greener practices fostering both the development of economy and protection of the environment. This work proposes and discusses an innovative approach based on a concerted strategy between stakeholders to accelerate the transition to a circular construction paradigm, which involves, as sustainable development, the definition of three dimensions to guide the process: (a) the assignment of key roles to the government and construction professionals; (b) the improvement of the industry to perform a proper management of construction and demolition waste; and (c) the development of sustainable practices at the construction site. In addition to the discussion about the different stakeholder partnerships that must exist, key ideas that should be adopted by industry to deliver recycled materials and products to the building and construction sector are proposed in this work. Moreover, measures to assist in the management of both the traditional and innovative materials and products incorporating recycled waste at the construction site are suggested targeting the implementation of more sustainable practices within this context. A broad use of the ideas proposed in this work in the building and construction sector may lead to encouraging outcomes in the next decade.

A BIM-GIS-IoT-Based System for Excavated Soil Recycling

The increasing excavated soil from construction projects has become a big problem in the sustainable development of megacities worldwide. Even though excavated soil management concerns are receiving increased attention, low rates of excavated soil recycling remain a barrier to the continuous improvement of the construction industry. Nowadays, Building Information Modeling (BIM) technology has gained popularity for construction and demolition (C&D) waste management purposes. However, few studies and cases of recycling excavated soil using BIM technology have been found. This paper gives a BIM-GIS-IoT-based excavated soil recycling system to effectively integrate BIM and Internet of Things (IoT) technologies into a geographic information system (GIS) to achieve scientific and reasonable recycling for excavated soil. The system mentioned above could collaboratively manage information from the government, developers, construction enterprises, transportation companies, and recycling facilities to meet the requirement for the specific communication, analysis, decision-making, and recycling plan preparation of the excavation project. In addition, it provides a systematic method and applies relevant information technology required to recycle the excavated soil effectively in the excavation project. The system is intended to provide a fundamental digital construction model for excavated soil recycling, regardless of whether it is invoked by the existing application software or a program tailored to the demands of a specific organization or stakeholders. It makes excellent use of the rich information stored in digital information models, may create a mapping to the input data required by the application, or automatically convert the basic model to facilitate the specific analysis. This system can not only serve as an excavation project simulation tool before construction, but also serve as a tool to recycle the excavated soil and cost evaluation. The developed model is applied via case studies within an excavation project. Different plans are described and compared in detail in several aspects of the schedule, revenue, and contract, finding that actual benefits will differ depending on the project’s limiting conditions. The result indicates ample opportunity for the advantages of the BIM-GIS-IoT-based excavated soil recycling system in the excavation project.

Evaluation of the Techno-Economic Feasibility for Excavated Soil Recycling in Shenzhen, China

The existing recycling chain of construction and demolition waste generally considers soil inert solid waste to be sent to landfills. As the most significant component of C&D (construction and demolition) waste, excavated soil occupies approximately half of landfills. Currently, excavated soil is a big issue in China’s Pearl River Delta. This paper investigated the composition and quantity of excavated soil in Shenzhen, China. In particular, the potential market demand for critical recycled sand (a key recycled material extracted from the excavated soil) was estimated. Furthermore, the technical analysis for excavated soil recycling takes an entire excavated soil recycling process’s perspective, delving into the process flow for the excavated soil and the recycled sand’s physicomechanical properties. Then, two mainstream and legitimate models of excavated soil recycling were considered: stationary plant recycling and on-site recycling. Each model’s financial and economic viability was assessed. The financial analysis focuses on investors’ perspectives, whose primary goal is to assess their investment profitability. The economic feasibility of the excavated soil stationary plant recycling and on-site recycling models in Shenzhen were then compared via benefit and cost analysis during the lifetime of the recycling equipment. A comprehensive, complete cost calculation and investment analysis revealed that Shenzhen’s excavated soil recycling business is profitable under the current market conditions. This study investigates scaled and effective excavated soil recycling and gives a technically and economically viable reference to the global excavated soil issue.

RGB-D fusion models for construction and demolition waste detection

The development of urbanization has brought a large amount of construction and demolition waste (CDW), which occupy land and cause adverse ecological effects. To effectively solve the negative impact of CDW, it needs to be recycled. Accurate waste classification is key to successful waste management. However, the current waste classification methods mainly use color images to classify, which cannot meet the needs of accurate classification. This paper built an RGB-depth (RGB-D) detection platform, using a color camera and a laser line-scanning sensor to collect RGB images and depth images. In order to use RGB images and depth images for feature fusion more effectively, this paper proposed three fusion models: RGB-D concat、RGB-D Ci-add and RGB-D Ci-concat. All these models based on an instance segmentation network called mask region convolutional neural network (Mask R-CNN), which can accurately segment the contours of each object while classifying them. The experimental results show that the mAPs of the RGB-D Ci-add / concat model are 1.33% to 1.72% higher than those of the RGB model, and the classification accuracy is 1.92% ∼ 2.27% higher. In addition, all the proposed models can meet the real-time requirement of online detection. Due to the excellent comprehensive performance of the RGB-D Ci-concat model, it can be regarded as the final detection model of the robot, which can improve the sorting efficiency of CDW further.

Environmental impacts of hazardous waste, and management strategies to reconcile circular economy and eco-sustainability

The rise in living standards and the continuous development in the global economy led to the depletion of resources and increased waste generation per capita. This waste might posture a significant threat to human health or the environmental matrices (water, air, soil) when inadequately treated, transported, stored, or managed/disposed of. Therefore, effective waste management in an economically viable and environmentally friendly way has become meaningful. Prominent technology is the need of the day for circular economy and sustainable development to reduce the speed of depletion in resources and produce an alternative means for the future demands in the different sectors of science and technology. In order to meet the potential requirements for energy production or producing secondary raw material, solid waste may be the prime source. The activities of living organisms convert waste products in one form or another in which electronic waste (e-waste) is a modern-day problem that is growing by leaps and bounds. The disposal protocols of the e-waste management need to be given proper attention to avoid its hazardous impacts. The e-waste is obtained from any equipment or devices that run by electricity or batteries like laptops, palmtops, computers, televisions, mobile phones, digital video discs (DVD), and many more. E-waste is one of the rapidly growing causes of world pollution today. Plenty of research is available in the scientific literature, which shows different approaches being set up and followed to manage and dispose of waste products. These strategies to manage waste products designed by the states all over the globe revolves around minimal production, authentic techniques for the management of waste produced, reuse and recycling, etc. The virtual survey of the available literature on waste management shows that it lacks specificity regarding the management of waste products parallel to ecological sustainability. The presented review covers the sources, potential environmental impacts, and highlights the importance of waste management strategies to provide the latest and updated knowledge. The review also put forward the countermeasures that need to be taken on national and International levels addressing the sensitive issue of waste management.

Circular Economy in Construction and Demolition Waste Management in the Western Balkans: A Sustainability Assessment Framework

Population growth, consumerism and linear (take-make-dispose) economy models have been piling up waste for decades. The construction industry is also based primarily on linear economy models, but the good news is that most of the waste can be re-used or recycled. So far, numerous models for managing construction and demolition waste in a sustainable way have been developed, but only a few models have included circular economy approaches. The main objective of this study is to propose an integrated framework for the sustainability assessment of CDW management. Apart from the economic, environmental and social aspects of sustainability, this model also includes circular economy principles. The proposed framework is based on the integration of existing methods: bottom-up materials stock approximation; cost–benefit analysis for criteria calculation; and scenario and multi-criteria decision-making analysis for sustainability. It is suggested that the European average recovery rates should be used for future scenario development. With higher re-use and recycling rates, the potential for the circularity of the recovered waste grows. In an effort to increase circularity in the region, particular attention was devoted to customize the framework and examine its potential for use in the Western Balkan countries. The framework may also be useful in countries with immature construction and demolition waste management.

Application of Sustainable Procurement Policy to Improve the Circularity of Construction and Demolition Waste Resources in Australia

The sustainable management of construction and demolition (C&D) necessitates efficient waste minimisation policies. Sustainable procurement of recycled waste products (RWPs) is an encouragement-based policy approach that can serve this purpose. This policy aids stakeholders in enhancing the circular economy (CE) in the built environment (BE) sector. However, this procurement method is yet to be successfully adapted globally or in Australia. Hence, this study was conducted to shed light on the use of sustainable procurement in the Australian BE sector. Based on a mixed-methods methodology, 49 relevant academic, industry and government publications were analysed during the review process. The findings reveal that the two most significant obstacles are the lack of supportive organisational culture and uncertainty about RWP quality. In addition, implementing clear and supporting regulations and maintaining transparency and good governance are identified as the two most important enablers. A model was proposed to facilitate the adoption of sustainable procurement, based on the research findings. The study includes a number of suggestions to encourage the acquisition of C&D RWPs for construction projects. This review is anticipated to contribute to three areas: sustainable procurement theory, policy development, and BE sector practice.

Willingness to pay for construction and demolition waste from buildings in Chile

In order to encourage increased rates in respect of sorting, recycling and the diversion of construction and demolition waste (C&DW), the world's more advanced economies have developed innovative new technologies and studies to improve the creation of sustainable societies. To achieve this, it is important to dedicate greater efforts to the elaboration of tariff schemes and studies to determine society's disposition to improve the management of C&DW. This study analyzes willingness of construction companies in Chile to pay (WTP) to improve the C&DW management, through the contingent valuation method (CVM). This aims to provide analytical background and market information to circular business models and, in turn, provide information which can be used to define public policies governing the subject, as a contribution to future regulatory developments. The Chilean construction industry was surveyed and a total of 57 valid questionnaires were collected. The results show that the average WTP for inert C&DW, non-inert C&DW, mixed C&DW with a greater quantity of inert waste and mixed C&DW with a greater quantity of non-inert waste was 8.77 (US $/ton), 7.73 (US $/ton), 7.98 (US $/ton) and 8.22 (US $/ton), respectively. Additionally, the cost of waste removal and disposal had an average value of 9.68 (US $/ton). Through multiple regression analysis, it was discovered that the variables related to knowledge about circular economy, state actions, management of C&DW and productivity have a significant effect on WTP. These results provide new evidence for the development of appropriate public policies to address the problem of C&DW and improve management in Chile.

A Synthesis of Express Analytic Hierarchy Process (EAHP) and Partial Least Squares-Structural Equations Modeling (PLS-SEM) for Sustainable Construction and Demolition Waste Management Assessment: The Case of Malaysia

Construction and demolition waste (CDW), as the main consequence of construction and demolition (C&D) activities, has severely affected our sustainability needs. However, construction and demolition waste management (CDWM) lacks the integration of sustainability concepts. Thus, there is a great need to include sustainability dimensions in CDWM to reach sustainable construction and demolition waste management (SCDWM). This study aims at empirically investigating SCDWM by analyzing the impacts of factors that contribute to sustainability aspects of CDWM on waste management hierarchy (WMH), including reduce, reuse, recycle, and disposal strategies. According to the literature, 26 factors were initially identified and grouped under four categories, namely environmental, economic, social, and administrative, that contribute to sustainability aspects of CDWM. Subsequently, a pilot test was performed to assess the significance and applicability of these factors in the Malaysian construction industry by implementing the express analytic hierarchy process (EAHP). Then, a questionnaire survey was performed to collect data from 132 construction companies involved in CDWM. Partial least squares-structural equation modeling (PLS-SEM) was used to test the hypothetical relationships by applying SmartPLS software. Results demonstrated that the economic aspect of CDWM (main category) and “public environment contamination due to illegal waste dumping” (sub-category) were the most influential factor in SCDWM in Malaysia.

Tackling the "last mile" problem in renovation waste management: A case study in China

Solid waste generated from building renovation, called "renovation waste" in this study, represents a major waste management problem. A particular difficulty is sourcing renovation waste arising sporadically from discrete sites for central processing. This can be characterized as a "last mile" problem in renovation waste management (RWM). This study reports good practice for dealing with the RWM last mile problem in a city in China. We conduct qualitative research comprising site investigations and interviews, organized in an in-depth case study. We discover that the city effectively solved the last mile problem by developing a multi-layer, nested waste management system, empowered further by various smart technologies and concerted collaboration from multi-stakeholders coordinated by a determined government. Nevertheless, the longevity of the RWM is contingent on confronting several challenges, including (a) achieving cost and benefit balance, (b) defining clearer standards and policies, and (c) raising stakeholders' awareness of waste management. A general RWM strategy is recommended to establish fluent channels through which to source and qualify renovation waste for central treatment. The study delves into the much neglected world of RWM and provides a valuable reference for tackling similar problems.

Estimating construction waste generation in the Greater Bay Area, China using machine learning

Reliable construction waste generation data is a prerequisite for any evidence-based waste management effort, but such data remains scarce in many developing economies owing to their rudimentary recording systems. By referring to several models proposed for estimating waste generation, this study aims to develop a reliable and accessible method for estimating construction waste generation based on limited publicly available data. The study has two objectives. Firstly, it aims to estimate construction waste generation by focusing on the Greater Bay Area (GBA) in China, one of the world's most thriving regions in terms of construction activities. Secondly, it aims to compare the strengths and weaknesses of various waste quantification models. 43 sets of annual socio-economic, construction-related and C&D waste generation data ranging from 2005 to 2019 were collected from the local government authorities. By analyzing the data using four types of machine learning models, namely multiple linear regression, decision tree, grey models, and artificial neural network, it is found that all calibrated models, with their respective strengths and weaknesses, can produce acceptable results with the testing R² ranging from 0.756 to 0.977. This study also reveals that the 11 cities in the GBA produced a total of about 364 million m³ of construction waste in 2018. The result can be used for monitoring the urban metabolism, quantifying carbon emission, developing a circular economy, valorizing recycled materials, and strategic planning of waste management facilities in the GBA. The research findings also contribute to the methodologies for estimating waste generation using limited data.

Self-fulfillment degree of construction and demolition waste management capability based on the Triple-balance theory: A case study of Guangdong-Hong Kong-Macao Greater Bay Area

Construction and demolition waste (C&DW) has become part of the largest waste stream globally and many cities are facing the shortage of management capability to treat C&DW. These cities seek to transport their C&DW to their neighbor cities for recycling or landfilling, which is recognized as the cross-regional management of C&DW. However, there were few studies to investigate the mechanism of cross-regional mobility in C&DW field. This study developed a model to evaluate the self-fulfillment degree of C&DW management capability at regional level based on the Triple-balance theory. Guangdong-Hong Kong-Macao Greater Bay Area (GBA) was selected as the study case, and the data was collected through on-site surveys, expert interviews, and desktop surveys. The results showed that the self-fulfillment degree of C&DW management capability of the cities, such as Guangzhou, Zhuhai, Foshan, Dongguan, Jiangmen, and Zhaoqing was high, which meant these cities could well manage the C&DW generated within the regions under current situation. The self-fulfillment degree of management capability of Macao, Huizhou, and Zhongshan was evaluated as medium; while the indicators of Hong Kong and Shenzhen fell into low category, which meant they needed to transport surplus C&DW to other cities for further treatment. The research is significant as it provides an innovative evaluation model considering the cross-regional mobility for C&DW management performance assessment. Besides, the findings could assist the waste management sectors to plan the C&DW treatment facilities in GBA, while other cities could also benefit from this study regarding to the cross-regional mobility management of C&DW.

Decision-making interaction among stakeholders regarding construction and demolition waste recycling under different power structures

The market power and competition scenario of recycling enterprises and landfills may change in the future due to the environmental pressure caused by landfills and the environmental potential of construction and demolition waste (C&DW) recycling. In this context, how these changes will affect the economic performance of enterprises and the environmental performance of the whole society remains unclear, along with how the willingness to pay and the environmental awareness of contractors will affect the pricing decisions of recycling enterprises and landfills. This study investigates the charging and recycling problem under different power structures in the reverse supply chain of C&DW, which is composed of waste generators (construction contractors) and two disposers (recycling enterprises and landfills). The interactive decisions of three stakeholders are discussed and the optimal charge fee, profit, and recycling ratio are obtained. Results indicate the following (i) The environmental preference of contractors directly increases the charge fee of recycling enterprises, and indirectly increases the charge fee of landfills. (ii) An increase in contractors' environmental preference will reduce the recycling ratio of C&DW and increase landfill and illegal dumping ratios. (iii) From the perspective of environmental benefits, illegal dumping and recycling ratios experience the worst scenario in the Recycling-Stackelberg game model and the best scenario in Nash game model because recycling enterprises take advantage of their dominant market position and set higher charges than those that contractors can afford. This theoretical study bridges the research gap on the effects of the market power on the environmental and economic performance of stakeholders in the field of C&DW management. The findings also help policy makers understand the behavior of stakeholders under different power structures to formulate the most effective intervention strategies.

Financial and economic evaluation of construction and demolition waste recycling in Hanoi, Vietnam

Increasing waste generation and the absence of a formal recycling industry are exacerbating the inadequacy of Construction and Demolition Waste (CDW) management in Hanoi, Vietnam. This study assesses potential CDW recycling in Hanoi by estimating the prospective supply of and demand for CDW recycling plants and evaluating their likely costs and benefits. Supply of concrete waste was calculated based on the weight-per-construction-area method whilst demand for recycled concrete aggregates (RCA) was determined by estimating the amount of aggregates for road construction in Hanoi from 2013 to 2017. Two potential models of CDW recycling plants were considered: a stationary plant and a mobile plant, with capacities of 1,000 and 360 tons/day, respectively. Our findings reveal that demand for RCA exceeds waste concrete supply, suggesting a promising market for RCA. Positive Net Present Value and Internal Rate of Return values of the stationary plant indicate its feasibility as an investment option. Meanwhile, the introduction of mobile recycling plants might require governmental intervention to internalize recycling positive externalities. Supporting policies might include a combination of a virgin material tax, green public procurement, and quality standard development.

Influence of Recycled Aggregates on the Mechanical Properties of Synthetic Fibers-Reinforced Masonry Mortars

The construction sector is one of the main consumers of raw materials and generates a high volume of waste within the European Union. The search for new materials that are more sustainable and respectful of the environment has become a challenge for countries with a high degree of industrialization. In this work, a study of the most relevant properties of masonry mortars made with recycled aggregates and reinforced with synthetic fibers was carried out. Three types of aggregates were used—natural, concrete recycling and ceramic recycling—and two types of reinforcing fibers: polypropylene and polyolefin. In this way, various tests of physical-mechanical characterization and a statistical analysis of the results were carried out. It has been shown that the mortars made from aggregate recycled concrete and reinforced with polypropylene fiber are the ones with the best properties for application in the construction sector, although without improving the properties of traditional mortars made from natural aggregate and without fibers.

GHG Emissions Assessment of Civil Construction Waste Disposal and Transportation Process in the Eastern Amazon

The urbanization process represented by an increased supply of housing and transport infrastructure has taken place at an accelerated rate in several regions of Brazil, especially in the metropolitan areas of the Brazilian Amazon. Despite the existence of environmental policies that guide the proper disposal of civil construction waste (CCW) in Brazil, the impacts of these policies are still negligible, pointing to the need to establish other metrics such as the measurement of greenhouse gas (GHG) emissions in CO2eq associated with civil construction waste. This work aims to evaluate, in the second-largest city in the Brazilian Amazon, the environmental impact generated by the transportation of CCW to disposal sites, having as indicators the volume of this waste and the CO2 emissions produced during a whole year. A literature review on life cycle carbon emissions assessment in building construction and CO2 emissions in transportation are provided to establish the background of the research methodology. Data collection was carried out by searching large generators of construction waste, the companies responsible for transporting construction waste, and the types of vehicles used. Calculation of GHG emissions from CCW transportation was based on the method described in the 2006 IPCC Guidelines. The study identified a volume of waste of around 1244 m3/month, with a generation of 40,440 kgCO2/year, only from small and large generators. Besides the damage identified in this study, there is also the dumping of CCW into urban streams in the city which is causing negative impacts on sanitation and drainage systems. The results point to the need to strengthen local policies to mitigate the impacts of the existing CCW to contribute to a more sustainable city.

"Looking beneath the surface": A visual-physical feature hybrid approach for unattended gauging of construction waste composition

There are various scenarios challenging human experts to judge the interior of something based on limited surface information. Likewise, at waste disposal facilities around the world, human inspectors are often challenged to gauge the composition of waste bulks to determine admissibility and chargeable levy. Manual approaches are laborious, hazardous, and prone to carelessness and fatigue, making unattended gauging of construction waste composition using simple surface information highly desired. This research attempts to contribute to automated waste composition gauging by harnessing a valuable dataset from Hong Kong. Firstly, visual features, called visual inert probability (VIP), characterizing inert and non-inert materials are extracted from 1127 photos of waste bulks using a fine-tuned convolutional neural network (CNN). Then, these visual features together with easy-to-obtain physical features (e.g., weight and depth) are fed to a tailor-made support vector machine (SVM) model to determine waste composition as measured by the proportions of inert and non-inert materials. The visual-physical feature hybrid model achieved a waste composition gauging accuracy of 94% in the experiments. This high performance implies that the model, with proper adaption and integration, could replace human inspectors to smooth the operation of the waste disposal facilities.

Stakeholder-Associated Factors Influencing Construction and Demolition Waste Management: A Systematic Review

Construction and demolition (C&D) activities generate a large amount of waste and have significant impacts on the environment. Thus, it is necessary to implement C&D waste management (WM), which requires the involvement of stakeholders and is influenced by a variety of factors. This study aims to undertake a systematic review of the stakeholder-associated factors influencing C&D WM. The Scopus search engine was used in a literature search, and two rounds of screening were performed. Only journal articles or reviews that were published in English after 2000 were used in this study. A total of 106 journal articles were reviewed. The review identified 35 stakeholder-associated factors influencing C&D WM and categorized them into six groups: regulatory environment, government and public supervision, advances in technologies, recycling market, knowledge, awareness, attitude, and behaviour of stakeholders, and project-specific factors. All the 35 factors are discussed in detail with considerations into relevant stakeholders. Although there have been studies focused on the factors influencing C&D WM, few have attempted to take stakeholders’ perspectives into consideration. This study expands the C&D WM literature by mapping the influential factors with relevant stakeholders and enables the practitioners to clearly understand their roles and responsibilities and make better informed decisions in the C&D WM process.

Key Factors of Opening Gated Community in Urban Area: A Case Study of China

Gated communities are the most popular residential pattern in the urban areas of China. However, along with the increasing population density in urban areas, this pattern may have negative influences on people's daily lives, such as traffic jams. To avoid the negative influences, the government has encouraged residents to open their gated communities; however, few positive actions have been taken. With this background, this study aims to explore the key factors in residents' willingness to open their gated communities. To start with, a total of 26 potential factors were identified based on a comprehensive literature review. Then, a questionnaire was designed and distributed to collect empirical data. Furthermore, logistic regression was employed to analyze the collected data. Based on the derived results, it was revealed that concerns are different between male and female residents. Male residents regarded "community safety" and "property management" as having a significant impact on their decision to open a gated community, while female residents paid more attention to the factor of "proprietary equity". The results of this study could provide valuable references that enable the government to better understand residents' underlying concerns and to make relevant policy decisions.

Attitude of Chinese public towards municipal solid waste sorting policy: A text mining study

With the acceleration of urban development, the amount of municipal solid waste (MSW) has increased dramatically. In order to recycle MSW more efficiently, a compulsory policy of sorting MSW has been enacted in China. According to the existing literature, attitude is an important factor affecting public's MSW sorting behavior. To explore the Chinese residents' emotional tendency towards the MSW sorting policy, this study analyzed the data of Sina Weibo users and their comments on related popular posts. Meanwhile, text mining technology was employed to analyze the collected data. Results showed that although a large proportion of the Chinese public has a positive attitude towards the MSW sorting policy, the proportion of people with negative emotions reached nearly half. In addition, it was found that the Chinese people in different regions pay different attentions to the MSW sorting policy. Results further revealed that the main reasons for the public's negative emotions were fines, MSW sorting rules, fees, timing of throwing waste, and irregular recycling procedures. By providing the public sentiment analysis of MSW sorting, this study can serve as a policy guide for practitioners and policy-makers to link current research areas into social development.

An analytical framework of "zero waste construction site": Two case studies of Shenzhen, China

Around the global construction industry, there is an emerging trend to pursue a "zero-waste" goal at the site level, but little is known about it. This paper aims to shed insights on the waste management concept of "zero waste construction site" by delineating its meaning, system boundary, assessment period, and operation strategies, which are further formulated in an analytical framework. Owing to the nascent nature of the concept, we adopted a qualitative approach including archival study, a series of semi-structured interviews, and two in-depth case studies in Shenzhen, China to sketch the analytical framework. Meanwhile, an analogy between "zero waste construction site" and "net zero building" is continuously made to fine-tune and finalize the framework. This research demonstrates that the zero-waste goal is challenging but achievable on individual construction sites. The system boundary to examine the zero-waste goal is contingent on the project scope, be it a new construction, renovation, or demolition project. The assessment period is dependent on the duration of the construction project. However, it would be too costly, if not entirely impossible, to achieve a "zero waste construction site" by treating it as a closed system. Rather, one needs to consider open, off-site strategies, e.g., engaging third-party recycling services, reusing recycled materials in subsequent projects, or trading it in to a recycled material market. The analytical framework can be utilized to scrutinize existing construction waste management practices. In the long term, the research will contribute positively to a "zero waste" society.

A four-quadrant conceptual framework for analyzing extended producer responsibility in offshore prefabrication construction

Prefabrication has been widely advocated as a green production strategy to minimize the adverse environmental impacts of construction. Amid economic globalization, prefabricated construction materials are commonly sourced offsite and even offshore. As an issue emerging alongside offshore prefabrication, extended producer responsibility (EPR) is yet to be clearly identified, allocated, and implemented. This research develops a conceptual framework using a design thinking process, through which EPR associated with offshore prefabrication can be analyzed, agreed upon, and allocated. By considering the scope and scale of the responsibility and the procurement methods, the framework comprises four quadrants representing four typical scenarios for implementation of the EPR principle. It is applicable for both short-term and lifelong EPR analysis, in both traditional and integrated project delivery contexts. The framework will be particularly useful for devising public policies to achieve an onshore and offshore stakeholder win-win situation.

From Circular Economy to Circular Ecology: A Review on the Solution of Environmental Problems through Circular Waste Management Approaches

(1) Background: The application of concepts linked to the circular economy (CE) has led to a sudden development of studies in numerous fields. However, the level of environmental sustainability of CE strategies could be improved and this topic deserves more attention by the scientific community. This research addresses this gap and aims at presenting a new concept, named circular ecology (CEL), and its application to the field of waste management. (2) Methods: The paper presents a literature review on the criticalities of CE and on examples of studies that implement the CEL principles. (3) Results: The review highlights that CEL principles are widely applied to several fields of waste management, showing promising opportunities to export the results to other geographical contexts. (4) Conclusions: If supported by governments, CEL approaches may allow solving multiple environmental problems at once, with clear economic, time, resources, and emission savings.

Traffic Safety Perception, Attitude, and Feeder Mode Choice of Metro Commute: Evidence from Shenzhen

Like many other transit modes, the metro provides stop-to-stop services rather than door-to-door services, so its use undeniably involves first- and last-mile issues. Understanding the determinants of the first- and last-mile mode choice is essential. Existing literature, however, mostly overlooks the mode choice effects of traffic safety perception and attitudes toward the mode. To this end, based on a face-to-face questionnaire survey in Shenzhen, China, this study uses the two-sample t-test to confirm the systematic differences in traffic safety perception and attitudes between different subgroups and develops a series of multinomial logistic (MNL) models to identify the determinants of first- and last-mile mode choice for metro commuters. The results of this study show that: (1) Walking is the most frequently used travel mode, followed by dockless bike-sharing (DBS) and buses; (2) Variances in traffic safety perception and attitude exist across gender and location; (3) Vehicle-related crash risks discourage metro commuters from walking to/from the metro station but encourage them to use DBS and buses as feeder modes; (4) DBS–metro integration is encouraged by the attitude that DBS is quicker than buses and walking, and positive attitudes toward the bus and DBS availability are decisive for the bus–metro and DBS–metro integration, respectively; and (5) Substantial differences exist in the mode choice effects of traffic safety perception and attitudes for access and egress trips. This study provides a valuable reference for metro commuters’ first- and last-mile travel mode choice, contributing to developing a sustainable urban transport system.