Construction and Demolition Waste Recycling Plants Revisited: Management Issues

CODD: A benchmark dataset for the automated sorting of construction and demolition waste

This study presents the Construction and Demolition Waste Object Detection Dataset (CODD), a benchmark dataset specifically curated for the training of object detection models and the full-scale implementation of automated sorting of Construction and Demolition Waste (CDW). The CODD encompasses a comprehensive range of CDW scenarios, capturing a diverse array of debris and waste materials frequently encountered in real-world construction and demolition sites. A noteworthy feature of the presented study is the ongoing collaborative nature of the dataset, which invites contributions from the scientific community, ensuring its perpetual improvement and adaptability to emerging research and practical requirements. Building upon the benchmark dataset, an advanced object detection model based on the latest bounding box and instance segmentation YOLOV8 architecture is developed to establish a baseline performance for future comparisons. The CODD benchmark dataset, along with the baseline model, provides a reliable reference for comprehensive comparisons and objective assessments of future models, contributing to progressive advancements and collaborative research in the field.

Assessment of the mechanical and physical characteristics of PET bricks with different aggregates

Construction and demolition waste, along with discarded PET plastic bottles, have evolved into a widespread global resource. However, their current disposal in landfills poses a significant environmental pollution challenge. This research is centered on evaluating the performance of cement mortar composed by larger PET particles in conjunction with sand, construction and demolition waste, and lightweight expanded polystyrene aggregates. The primary objective of this study is to formulate a blend suitable for non-structural elements that can be easily manufactured for social housing construction. This modified blend extends upon the original certified mixture employed at CEVE for brick production, which encompasses cement and 3 mm-long PET particles. The experimental analysis revealed that blend containing 8 mm-long PET particles, in combination with fine aggregates of construction and demolition waste, attained a required mechanical strength of 2 MPa, while preserving the bulk density and hydric properties of the initial PET bricks developed at CEVE in Argentina.

Sustainable building materials-recycled aggregate and concrete: a systematic review of properties, modification techniques, and environmental impacts

Resource utilization of construction and demolition (C&D) waste has great potential to significantly reduce the consumption of natural resources and improve the environment. Meanwhile, establishing a sound policy system and reducing production are the key ways to solve the problem of C&D waste. Numerous studies on C&D waste, recycled concrete aggregate (RA), and recycled aggregate concrete (RAC) have been reported in the literature, with few systematic summaries. From a global perspective, this paper assessed the current situation of C&D waste and the countermeasure of several major economies. Then, this paper systematically introduces the composition structure and characteristics of RA. Modification techniques from macro and micro perspectives of RA and its effect on RAC were also presented. Paper also reviews the environmental impacts of RA and RAC. The results showed that bonded mortar was the most significant defect of RA than natural aggregate (NA). Thus, RA weakened RAC's microstructure, workability, mechanical properties, and durability. The research on the modification of RA mainly focused on removing bonded mortar and enhancing bonded mortar containing physical or chemical methods. Enhancing bonded mortar was a more effective method than removing bonded mortar. Carbonation and microbially induced calcium carbonate precipitation were highly efficient and environmentally friendly for RA modification. Research progress in quantifying the environmental impacts associated with concrete from waste materials through the LCA methodology is presented. Suggestions and an outlook were given on the critical issues facing RA and RAC. We expect that this work can provide more technical support for C&D waste utilization.

Management of the construction and demolition waste (CDW) and determination of the best disposal alternative by FAHP (Fuzzy Analytic Hierarchy Process): A case study of Tehran, Iran

The study focused on the management of the final disposal of Construction and Demolition Waste (CDW) generated in Tehran and the determination of the best disposal method. For this purpose, three of final disposal alternatives such as reusing, recycling and landfilling were selected. Moreover, three effective criteria (environmental, economic and socio-cultural) and 16 sub-criteria were considered. A group of experts participated in the questionnaire in order to create a database. FAHP (Fuzzy Analytic Hierarchy Process) was used to determine the final disposal alternative considering to the sustainable development approach. The results obtained from the FAHP model showed that the weight of the environmental, economic and socio-cultural criteria was 0.330, 0.544 and 0.126, respectively. In the view of the environmental, the weight value of the sub-criteria of recyclable, water pollution, air pollution, soil pollution and natural resources protection were 0.035, 0.127, 0.069, 0.042 and 0.055, respectively. In terms of economic, the weight value of the sub-criteria of raw materials cost, land occupancy rate, profitability, mutual interests, exploitation cost and initial investment were 0.108, 0.045, 0.063, 0.083, 0.094 and 0.149 respectively. In addition, from the point of view of socio-cultural aspect, the weight value of the sub-criteria of community acceptance, government cooperation, people's awareness level, security in construction and employment were 0.015, 0.050, 0.011, 0.022, and 0.026, respectively. The reuse alternative with a weight of 0.439 was selected as the best disposal method and the recycling (0.312) and landfilling (0.250) were second and third alternatives, respectively. The results also indicated that the generated CDW in Tehran was mostly composed of reusable components such as metals, plastics, wood, glass and gypsum. Therefore, with the selection of this alternative as a final disposal method, the costs of raw materials and the pollution originated from landfilling can be significantly reduced.Implication: The main purpose of this study is to provide a framework in which the priority of criteria and sub-criteria and alternatives in CDW management in Tehran, Iran is determined. The novelty of this method included providing an efficient management method in CDW management, because the production of this type of waste in Iran has become a major problem. The most important part of this method was the decision of local experts to provide the best disposal alternative, since solving problems related to CDW management is achieved by participation and collaboration with experts working in the same system. The obtained results showed that reusing is the first priority in terms of all the studied criteria and sanitary landfilling is the last priority. Sanitary landfilling is currently in place in the study area and respondents are well aware of its disadvantages. The results in terms of each criterion show that economic criteria are the most important criteria. Investment cost in terms of economic criteria, public acceptance in terms of social criteria and water pollution in terms of environmental criteria as the most effective sub-criteria according to the main goal. Various complex factors affect CDW management systems and therefore the use of practical decision-making techniques such as FAHP to deal with the complexity of CDW management will be useful and valuable.

Industrial Waste Pretreatment Approach for 3D Printing of Sustainable Building Materials

The large volume of industrial by-products and wastes from the construction, timber and paper industries has become a serious challenge worldwide. Recycling these industrial wastes as functional materials in the construction industry is an efficient approach for sustainable development. This study presents a pretreatment approach for recycling construction and demolition waste (CDW) and industrial side-streams (such as green liquor sludge, fiber waste, flotation sand and fly ash) in order to produce a geopolymer for the 3D printing of construction materials. A treatment approach was developed for screening the residues from CDW with a maximum size of 16 mm and for a combined line treatment for industrial side streams. The treatment processes utilized suitable and economical separation techniques for the recycling of waste materials. The crushing of the screened residues resulted in a homogeneous material size that facilitates the separation of mixed wastes and simplifies the classification of materials. The combined plant enabled the cost-effective treatment of various industrial wastes in a single process unit. The results show that the economic and environmental impact of the chosen techniques, in terms of their energy consumption, is highly dependent on the treatment line, separation technique and quantity of the individual waste that is processed. These recycled industrial wastes can be used as sustainable materials for the production of geopolymer concrete, contributing to the sustainability of the construction industry.

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.

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.

Building demolition waste management through smart BIM: A case study in Hong Kong

Hong Kong's construction industry, known for its massive building infrastructure, produces an enormous amount of waste every year, the vast majority of which is disposed for landfills. Therefore, some effective operational measures and waste management policies have been implemented. However, enormous waste remains a concern for stakeholders and exert pressure on the limited capacity of Hong Kong's landfills. Though previous research discusses Building Information Modelling (BIM) application for construction waste management enhancement, the BIM model has not been widely implemented for building demolition with waste management. Hence, as a response to the aforementioned shortcomings, this paper develops a conceptual framework that allows collecting, maintaining, and analyzing comprehensive information through Smart BIM that uses advanced technologies such as Internet of Things (IoT) and capable of reacting to user activities such as waste quantitative assessment, demolition process planning, optimal disposal route selection, and waste management strategy are executed. The advantages of the proposed framework are shown in a case study benefit-cost analysis based on three planned reuse and recycling-rate scenarios that explain on- and off-site recycling methods. The results show that the proposed framework will pave the way for generating sustainable waste disposal practices by providing technical and decision-making support functionalities to engineers and planners in the construction industry.

Conceptualising the Circular Economy Potential of Construction and Demolition Waste: An Integrative Literature Review

Traditionally, construction and demolition waste (CDW) materials have been considered to be unwanted, surplus, or wastage materials or materials with zero value. Such a conceptualisation only embraces a negative aspect, which underpins the disposal of reusable and recyclable CDW materials in landfills, thus damaging the circular economy and the environment. The scope of this research was to conceptualise the circular economy potential of non-hazardous construction and demolition waste, which can be used as a resource for advancing the circular economy and sustainability in the built environment. Thus, the abbreviation ‘CEPCDR’ is used for this purpose. The study employs an integrative literature review to understand in depth whether the rationale in the existing CDW definitions advocates for the circular economy. Instead, the literature showed that the current definitions mainly support quantitative, economic, or classification needs, respectively. That is because they lack consideration of the dynamic nature of CDW materials, which embraces the spatial and temporal dimensions. The former involves the geographic context in which the CDW phenomenon eventuates, while the latter concerns the lifecycle of materials. This study contributes to the body of knowledge by conceptualising the CEPCDR using a holistic approach that includes five dimensions: the social, economic, environmental, spatial, and temporal perspectives. Furthermore, the study seeks to drive future research in measuring the CEPCDR.

Construction and Demolition Waste Recycling through Conventional Jig, Air Jig, and Sensor-Based Sorting: A Comparison

The paper presents a comparison of the concentration methods conventional jig, air jig, and sensor-based sorting to treat construction and demolition waste. All tests were made with concrete, brick, and gypsum particles and the tests aim to separate these materials into different size ranges, depending on the method. The equipment tested, conventional jig, air jig, and sensor-based sorting present good results to concentrate construction and demolition waste particles, with different concentrations and mass recoveries. The results show particularly good mass recoveries and particle concentration for conventional jig, especially for concrete and gypsum particles. Sensor-based sorting should preferably use concentration circuits for best results.

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.

Current Applications of Recycled Aggregates from Construction and Demolition: A Review

A literature review comprising 163 publications published over a period of 26 years from 1992 to 2018 is presented in this paper. This review discusses the generation and recycling of construction and demolition waste (CDW) as well as its main uses as raw materials for the construction engineering sector. This review pays attention to the use of CDW aggregates for sand, pavements/roads, bricks, ceramics, cementitious materials, and concrete productions, as well its uses as eco-friendly materials for water decontamination. The physical-chemical and mechanical characteristics of recycled aggregates play an important role in their correctly chosen applications. The results found in this literature survey allow us to conclude that recycled aggregates from CDW can be successfully used to produce construction materials with quality comparable to those produced with natural aggregates. We concluded that the use of CDWs as raw materials for manufacturing new construction materials is technically feasible, economical, and constitutes an environmentally friendly approach for a future construction and demolition waste management strategy.

Modelling of mineral construction and demolition waste dynamics through a combination of geospatial and image analysis

As the construction sector is shifting towards circular economy models, the role of mineral construction materials as main waste fraction in terms of volumes is crucial. A characterization of this mineral stock, as well as the waste derived from it is decisive in ensuring the application of the best practices of circular economy. This paper describes a methodology for assessing the mineral building stock through a combination of geospatial and image analysis. By analysing old topographic maps, buildings are grouped according to their building age into different typologies and based on these maps the construction and demolition activity is evaluated. The mineral stock is assessed and estimations of the mineral construction and demolition waste (CDW) is generated for different stochastic scenarios. This methodology is applied exemplarily on the country of Luxembourg. It was found that the total mineral construction stock for Luxembourg is 276.75 Mt and has been growing at a rate of 20.81%-24.39% in the last 30 years. Furthermore, the study identified a mean age of the urban building stock of about 60 years and a typical maximum building lifetime of 122 years. Based on the stochastic projections the mineral CDW generated from the existing building stock is expected to be up to 226.9 Mt by 2100, while if future building scenarios are considered, it can be as high as 885.3 Mt. The annual CDW production is expected to be sufficient for a viable concrete recycling activity if regulations on the waste volume flows are made available.

Thermoset Polymer Matrix Composites of Epoxy, Unsaturated Polyester, and Novolac Resin Embedding Construction and Demolition Wastes powder: A Comparative Study

Composite materials that consisted of a polymer resin as matrix (PMCs), filled using construction and demolition (C&D) wastes powder of different grain sizing in micro-scale were manufactured and studied. Three different kinds of resins were used as the matrix for the purposes of this study. More specifically, composites made of epoxy and unsaturated polyester resins purchased from the market and phenolic resin (novolac) laboratory synthesized, were produced. The morphological and elemental analysis of these materials was performed through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Additionally, mechanical performance and thermal insulating efficiency of these materials were examined through bending and shear strength tests according to the three-point method and via determination of the thermal conductivity coefficient λ. C&D wastes have undergone the appropriate processing in order to prepare filling products of the required granular size in pulverized form. In this research study, construction and demolition waste-based thermosetting polymer composites were produced with flexural strength in the range 20-60 MPa, shear strength in between 1-8 MPa, and thermal conductivity coefficients in the range of 0.27-1.20 W/ m K. The developed materials embedded 30-50% w/w C&D wastes, depending on the resin used as the matrix.

Implementing on-site construction waste recycling in Hong Kong: Barriers and facilitators

Construction and demolition (C&D) waste recycling constitutes an indispensable component in the overall waste management strategy. Unlike the traditional recycling approaches whereby C&D waste is transported to off-site facilities for treatment, construction managers are actively exploring the possibility of on-site recycling where C&D waste is treated directly at source. This study reports the barriers and facilitators of implementing on-site C&D waste recycling by contextualizing it in Hong Kong. It does so by adopting a mixed-method approach combining case study, site visits, and interviews. It is discovered that the barriers include (1) site space constraints, (2) narrow window of opportunity to trade recycled products, (3) vulnerable business case, (4) lack of support from off-site recycling, and (5) lack of government policy support. A series of facilitating measures are also proposed, including (1) developing customized on-site recycling equipment, (2) establishing a demand-supply information-sharing platform, (3) developing more thriving off-site recycling, and (4) providing more government support. This study probes into the real-life on- and off-site waste recycling practices in Hong Kong's prominent C&D management system. It can also provide useful references for others in developing their own C&D waste recycling strategies by rationally deploying on- and off-site recycling.

Challenges in current construction and demolition waste recycling: A China study

China produced a large amount of construction and demolition (C&D) waste, owing to the rapid development of construction industry. Although a set of policies and regulations are being drafted in China for promoting C&D waste recycling, execution of these policies in practice seems to be far from effective. Currently, approximately 75% of Chinese cities are still surrounded by large volumes of C&D waste. Therefore, identification of challenges in the development of C&D waste management, specially recycling, is essential. This paper employs site visits to 10 recycling plants in 10 Chinese cities (Shanghai, Hangzhou, Suzhou, Chongqing, Chengdu, Xi'an, Changsha, Shenzhen, Nanjing, and Zhoukou) and interviews with 25 industry practitioners for examining the challenges. Eight challenges are identified: (1) unstable source of C&D waste for recycling, (2) absence of subsidies for recycling activities and high cost for land use, (3) insufficient attention paid to design for waste minimisation, (4) absence of regulations on on-site sorting, (5) unregulated landfill activities, (6) a lack of coordination among different government administration departments, (7) a lack of accurate estimation of waste quantity and distribution, and (8) a lack of an effective waste tracing system. Recommendations to address these challenges are presented. The results of this study are expected to aid policy makers in formulation of proper C&D waste management in China and provide a useful reference for researchers who are interested in C&D waste recycling industry.

Using Recycled Construction and Demolition Waste Products: A Review of Stakeholders’ Perceptions, Decisions, and Motivations

While the increasing rate of urbanisation is a critical concern for socio-environmental reasons, this also leads to more extraction of natural raw materials and the generation of significant quantities of construction and demolition (C&D) waste. Although the use of recycled C&D waste products is technically feasible and regulated, and positive application examples are evident, it is still unclear how to engage key stakeholders to leverage this opportunity in construction projects. Previous research has shown that there is some level of resistance to the reuse of recycled C&D waste products in construction projects. This highlights a critical need to identify the roles of key stakeholders and the barriers they face when using recycled C&D materials. This paper therefore investigates the type of stakeholders influencing the use of recycled C&D waste products and the main factors affecting stakeholders’ decisions to use recycled C&D waste products through a systematic literature review. The authors present an emergent enablers and barriers for recycled C&D waste products model and provide commentary on how stakeholders’ perceptions, decision and behaviour influence the use of recycled C&D waste products. The authors also contribute to the body of knowledge with insights into the factors that various stakeholders believe influence the market for recycled C&D waste products and provides a reference point for authorities to consider these behavioural insights for policy reform.

Multi-agent evolutionary game in the recycling utilization of construction waste

The recycling utilization of construction waste (CW) is of great importance to reduce waste discharge and protect natural resources. This study investigated the evolutionary decision making process and stable strategies among three stakeholders, including the government agency (GA), waste recycler (WR) and waste producer (WP), involved in CW recycling industry based on the game theory. The main factors that affected the strategies of the stakeholders were analyzed and the tripartite evolutionary game model is provided. The evolutionary stability strategy and stability conditions were analyzed subsequently. A numerical simulation illustrated the effectiveness of the proposed method, with which the evolutionary decision making process and stable strategies among the three stakeholders are simulated. It is shown that the GA plays different roles in different stages of the development of CW recycling industry. In the early stage, the supervision and policies of the GA are critical to improve the proportion of enterprises that implement the recycling strategy. With the mature of the CW recycling industry, it is profitable for enterprises to implement waste recycling, and a high proportion of enterprises choose to implement recycling strategy. Under this circumstance, the GA will gradually decrease their interventions to enterprises, and finally evolve into no supervision. Besides, it also concludes that low penalties and subsidies are not conducive to the evolution of the optimal strategy among the three participants, and excessive supervision costs will reduce the regulatory willingness of the GA, hindering the enthusiasm of WRs and WPs to implement the recycling strategy.

Economic and Environmental Assessment of Carbon Emissions from Demolition Waste Based on LCA and LCC

In China, urban renewal and renovation projects generate a large amount of demolition waste every year, the disposal of which has certain impacts on the environment. Therefore, more effective policies should be implemented for the management of demolition waste. This study combines life cycle assessment (LCA) with life cycle costing (LCC) to analyze the environmental and economic drivers of three different waste disposal scenarios in Guangzhou, China, in the context of carbon trading: S1 (landfilling), S2 (recycled aggregate), and S3 (recycled powder). In this study, the carbon emissions of demolition waste were obtained by LCA, and the carbon emission cost was calculated based on the carbon price in the carbon trading market of Guangdong Province. The LCA results showed that waste recycling can greatly reduce carbon emissions. The results showed that compared to S1, S2 reduced 6.790 × 108 kg CO2 eq. Additionally, S3 reduced 4.172 × 108 kg CO2 eq. compared to S2. The LCC results show that waste recycling can greatly reduce the total costs of the demolition sector, while the production of recycled powder can generate 57.35% of the revenue from recycled aggregate to the recycling plant. This study combines LCA and LCC, and considers environmental factors to assess the economic results using carbon emissions cost, thereby forging a new exploration method in the field of life cycle theory. The findings of this study could provide a basis for the formulation of a new demolition waste management policy. In the case of the gradual implementation of carbon trading, it could also provide new ideas for current demolition waste treatment from economic and environmental perspectives.

Potential for pellet manufacturing with wood waste from construction in Costa Rica

The construction sector in Costa Rica produces approximately 100 kg per square meter of residues, of which wood waste comprises 30%. Utilization of these wastes is still limited, but options are being sought and biomass is one of them. The aim of this work was to evaluate the characteristics of biomass produced from wood waste from construction, its energy potential, and its appropriateness for pellet manufacturing by determining its energy, physical, and mechanical characteristics. It was found that wood waste from construction is composed of different species with densities below 0.5 g/cm³, 26% moisture content, and 10% ash content; contamination with cement and nails can reach 6%. The process of pellet manufacturing can adapt adequately to using wood waste from construction, with an efficiency or yielding of 33%. Pellets presented a calorific value of 19573 kJ/kg, a bulk density of 1.25 g/cm³, an apparent density of 700 kg/m³, a failure force in compression of 467 N, and durability of 94.28%. According to different standards, the results obtained for biomass from wood waste are within the range established for pellet quality; therefore, wood waste from construction can be used to produce pellets, despite the disadvantage of it presenting high ash content.

Construction and demolition waste applications and maximum daily output in Spanish recycling plants

The pursuit of construction sustainability has driven the use of partially or wholly waste-based eco-materials. New applications are being sought for recycled aggregate (RA) to further the use of this material and ensure the survival of the construction and demolition waste (C&DW) industry. RA, currently used in the construction of pavements, fills and embankments and only incipiently to manufacture structural or non-structural concrete, is a mere 8.99% of the total aggregate extracted in EU countries where RA is produced. Against this backdrop, the utility of this study lies in the overview afforded of RA typology, the application of the product in bound or unbound materials, the pursuit of new applications, structural or otherwise, and the assessment of daily maximum output by C&DW recycling facilities in Spain. The findings show that irrespective of its origin, RA most commonly adopts the form of wet mix macadam, gravel or sand used primarily in unbound applications with only dubious quality standards. Plant managers contend that RA from clean waste can feasibly be used in bound applications that require higher-performance materials. Maximum daily output varies widely, with capacity under 200 t d^-1 in 30% of the plants. One of the conclusions drawn is that the current business model is in need of revision, with an emphasis on aggregate quality control (certification) and the adoption of technology for separating out impurities, pollutants and undesirable materials to improve the quality of RA.

Innovations in Construction Waste Management: Case of Latvia

The environmental concern has become the top trend nowadays and the ideas of environmental protection, green orientation and green innovation, highly concern from the last few decades in all research areas. The construction industry is one of those that has a very strong impact on the environment. Air, water, noise and vibration, as well as soil pollution caused during construction processes, negatively impact on the environment and its natural ecosystems, as well as on humans at a global level. Construction waste generated during the construction, renovation and demolition process occupies huge landfills due to significant volumes. It may also contain substances that are hazardous to the environment and human health. This paper summarizes the research results on the possibilities for more efficient construction waste management as well as the experience of companies operating in the construction sector with a purpose to reduce the causes of pollution. The data obtained within the framework of the survey on people’s understanding in the field of construction pollution and waste in Latvia have been analyzed. The main goal of the study is to present the main findings of the authors’ survey and to discuss the current construction waste management challenges and potential innovations in Latvia. The authors used the following research methods: literature review, analysis of statistical data; questionnaire creation and conduction a survey; interviews with waste management companies. The research was conducted during the period from October 2019 to July 2020. The obtained results showed that there was a huge potential for innovation because the current situation was far from ideal. The results of an empirical analysis demonstrated that the collection of sorted construction waste on construction sites currently was practically impossible, as the industry points to the human factor in the waste sorting process. Although the data obtained within the framework of the survey clearly indicated the interest of employees in sorting construction waste already on the construction site, waste industry companies currently consider such a practice impossible also due to the influence of other side factors related to economic considerations. It is necessary to develop a normative framework for the implementation of the construction waste certification system to promote the reuse of construction waste in construction as efficiently as possible. Keywords construction waste, management of technological innovation, environmental management, Latvia, sustainable development.

Recommendations for the management of construction and demolition waste in treatment plants

The construction and demolition waste is one of the heaviest and most voluminous waste streams generated in the European Union. It comprises approximately one third of the waste generated. Recycling this stream waste will provide ecological and sustainable benefits. The recycled aggregates from the construction and demolition waste are beginning to be used in civil construction, as substitutes for natural aggregates. The possible applications of recycled aggregates in the infrastructure construction projects will mainly depend on the quality of the recycled aggregates. This will be determined by the nature and the origin of the construction and demolition waste, and the treatment system used. It requires a comprehensive response by part of the processing agents, mainly construction and demolition companies, and above all public administrations. This work proposes recommendations for the handling of the construction and demolition waste, both in the demolition and in the treatment plants. A quality control system is suggested too.