Sustainable Material Recovery from Demolition Waste: Knowledge Management and Insights from a Public Sector Building Renovation

Abstract

The utilization of knowledge management (KM) assists construction companies in planning for waste management. This study applies KM in the material recovery of a public sector building renovation, focusing on aluminum composite panels (ACPs). The cost/benefit analysis (CBA) method examines suitable scenarios, where costs and benefits cover economic, environmental, and social perspectives. The cost/benefit (C/B) ratios reveal that the repurposing scenario, where ACP waste is repurposed as signboards, is the most suitable scenario, with a C/B of 0.96. The refurbishing scenario, in which ACP waste is refurbished as new facades, may be considered if the labor cost could be reduced through training. The repurposing scenario is further examined with a sensitivity analysis and the Leadership in Energy and Environmental Design certification, and it is found that implementing this scenario serves as a beginning step toward green certification and aligns with Thailand’s national strategies for green building promotion and the long-term Net Zero 2065 target. The study results serve as a guideline for Thailand’s transition toward a low-carbon and resource-efficient construction sector. Future studies are recommended to examine the complex relationships between costs and benefits and to track dynamic changes in the C/B ratio over time.

1. Introduction

The construction industry is one of the largest global raw material consumers and waste generators. Construction and demolition (C&D) activities are estimated to generate up to 40% of the global solid waste annually [1,2,3]. This significantly burdens landfills, resource extraction, and carbon-intensive waste processing systems [4,5,6]. In Thailand, rapid urbanization has led to a significant increase in C&D waste generation. Bangkok, Thailand’s most populous and urbanized city, has traditionally produced a significant share of the country’s C&D waste, estimated at approximately 25% of the national annual total of 1.5 million tons [7,8]. Predominant fractions of concrete, steel, tiles, glass, decorative materials like aluminum composite panels (ACPs), tempered glass, and wood remain in the waste stream, primarily due to inefficient onsite management and material handling practices [9]. Specifically, ACPs are widely used in building construction due to their light weight and esthetic versatility for facade cladding and interior decoration. In Thailand, the consumption of new ACPs is expected to be 700,000–1,000,000 m²/year [10]. Conversely, this results in high ACP waste, as LDPE materials require a complicated recycling process. As a result, ACP waste mostly ends up in landfills.

Landfilling remains the primary disposal route in Thailand, constrained by poor waste segregation systems, limited recycling infrastructure, and the weak enforcement of C&D waste regulations [11]. Despite the growing policy interest in circular economy (CE) frameworks, national demolition practices remain predominantly linear, with minimal waste recovery or reuse. The effective management of waste materials remains insufficiently integrated into sustainability agendas due to fragmented data systems, weak market incentives, and inadequate technical expertise [12,13,14]. Consequently, the environmental impacts of unmanaged C&D waste, such as landfill scarcity, hazardous material disposal, and greenhouse gas (GHG) and CO₂ emissions, persist.

In response to these persistent challenges, green building certification frameworks have emerged as viable tools to promote sustainability across the building lifecycle. Internationally recognized systems, such as LEED, the Building Research Establishment Environmental Assessment Method (BREEAM), and the Thai Rating of Energy and Environmental Sustainability (TREES), play a significant role in encouraging waste minimization [5]. Specifically, the LEED standard is commonly implemented in Thailand, where two of its core criteria are C&D waste management planning and building lifecycle impact reduction. These criteria urge stakeholders targeting this standard to quantify and reduce waste outputs during demolition and renovation [15]. While green building adoption remains uneven across Southeast Asia due to barriers like data fragmentation and limited cross-sectoral collaboration, Thailand has emerged as one of the region’s most progressive adopters after Singapore. Several flagship projects in Thailand, including the Park Ventures Ecoplex, SCG Headquarters, the Energy Complex, and the Thai Health Promotion Office, have achieved LEED Platinum certification [15].

Building on the role of green certification in driving sustainable demolition practices, knowledge management (KM) emerges as the operational backbone for the achievement of waste reduction targets. KM involves systematic knowledge acquisition, sharing, utilization, and storage processes to drive continuous learning and organization [16]. In the C&D context, KM transfers data and best practices from completed to future projects, enhancing efficiency and reducing redundancy [17]. KM enhances stakeholder coordination, supports adaptive policy implementation, and translates fragmented technical knowledge into actionable strategies. For example, Fuentes-Ardeo et al. [18] demonstrated how structured KM systems improved project responsiveness, digital knowledge retention, and strategic planning [18]. Similarly, Korkmaz [17] found that integrating KM into construction workflows significantly enhances waste avoidance behaviors and resource recovery efficiency [17]. Khoa and Chinda [19] empirically demonstrated that KM processes strengthen construction competitiveness through immediate operational gains and long-term digital transformation [19].

Addressing C&D-related challenges through economic, environmental, and social perspectives for sustainable development is essential in ensuring holistic and responsible waste management. Mismanaged C&D waste disposal generates severe gaseous pollutants and health impacts [20]. Decisions driven solely by operational efficiency may overlook critical factors, such as environmental impacts, long-term economic costs, and community well-being [21,22,23]. Integrating these dimensions within KM frameworks enables organizations to develop C&D waste strategies that balance resource recovery with the principles of social equity, ecological sustainability, and economic resilience, fostering more ethical and sustainable outcomes in the construction sector.

This study utilizes KM practices to develop sustainable approaches for C&D waste recovery—specifically, decorative materials like aluminum composite panels (ACPs)—as a beginning step toward green certification in a public building renovation. Criteria related to sustainability concepts (i.e., economic, environmental, and social perspectives) are examined with a cost/benefit analysis (CBA) to suggest long-term sustainable approaches. The research steps, activities, and expected outputs in the KM process and scenario evaluation are presented in Figure 1.

The scope of the study is as follows:

• This study considers ACPs as demolition waste for material recovery.
• The data used in the analysis come from a case study in Bangkok, Thailand and secondary sources in the construction-related literature.
• All units in this study are calculated in kg of ACPs.
• This study reuses 70% of ACP waste in refurbishing and repurposing scenarios (based on interviews), and the rest is sold at second-hand shops. The 70% recovery rate is consistent with other studies. For example, in the U.S., regulations for C&D waste recovery require at least 70% of C&D waste to be reused [24]. Caro et al. [25] estimated that 70% of aluminum achieved from demolition waste can be recycled. Saez and Osmani stated that the C&D waste recovery rate could be up to 95%, depending on regional conditions and the availability of recycling technologies.
• In the landfilling scenario, all ACP waste is dumped in landfills, and, in the reselling scenario, it is sold to a second-hand shop.
• The reselling scenario includes ACP dismantling and transportation to second-hand shops and does not include operations at the second-hand shops.
• The refurbishing scenario includes ACP dismantling, transportation to the refurbishing facility, and the refurbishing process to achieve new facades. Refurbished ACP facades maintain similar shapes and sizes to the old ACP facades; thus, only grinding, painting, and adhesive are required in the refurbishing process.
• The repurposing scenario includes dismantling ACPs, transportation to the repurposing facility, and the repurposing process to create signboards.
• The landfilling scenario includes ACP dismantling, transportation to landfills, and landfill preparation, but it does not include operations at the landfills.
• The economic-related data cover the virgin material (aluminum) extraction process, ACP waste management, transportation, and sales of second-life products.
• The environmental-related data cover virgin material extraction and the avoidance of new virgin materials and does not include impacts incurred during ACP and signboard production.
• The social-related data cover new employment, corporate social responsibility (CSR) campaigns, reimbursement, and medical bills from ACP waste management, as well as legal permissions.
• Landfill space is explicitly purchased to dispose of C&D waste.
• Carbon credit refers to environmental-related savings achieved from the end-of-life management of ACP waste, while carbon tax refers to an environmental-related cost from the refurbishing and repurposing processes.

2. Literature Review

2.1. C&D Waste Situation in Thailand

Thailand faces challenges related to C&D waste regarding the volume generated and the environmental consequences of traditional disposal methods, such as landfilling and incineration [26]. Traditional approaches strain the limited landfill capacity in urban areas and contribute to GHG emissions, soil and groundwater contamination, and long-term land degradation [27]. The lack of effective waste management and recycling infrastructure leads to resource inefficiency and losses of valuable construction materials that could be reused and recycled [28].

C&D waste in Thailand is primarily generated from urban development, infrastructure expansion, demolition, and renovation [29]. Specifically, building demolition generates various types of waste, such as concrete, metal, and decorative materials like ACPs, glass, and wooden boards. Without proper management, this waste is disposed of in landfills, causing several environmental impacts. ACPs, specifically, pose severe impacts among decorative materials, such as CO₂ emissions and resource depletion, due to their composite structure, which consists of two thin layers of aluminum bonded to a polyethylene core, making them complicated to recycle [30,31].

2.2. KM Practices in the Construction Industry

Over the years, KM has attracted considerable scholarly interest within the construction sector, given its potential to enhance organizational performance and project outcomes [32]. Various construction-related studies have conceptualized and operationalized KM in diverse ways. For instance, Kokkaew et al. [33] examined the impacts of KM components—knowledge acquisition, knowledge creation, knowledge storage and retrieval, and knowledge transfer and utilization—on organizational performance in Thailand. The results show that KM indirectly influences organizational performance through human resource management. Cerezo-Narvaez et al. [34] delineated the structural and procedural mechanisms that facilitate data conservation into actionable knowledge. They proposed a prototype for KM models comprising four categories: storage, access and transfer, technology, and sociocultural. These categories underscore the multifaceted nature of KM, encompassing both technological infrastructure and human-centric dimensions, to leverage lessons from past projects for future strategies and innovation. Ferrada et al. [35] developed a KM framework to optimize the selection of construction methods within the project environment. It was concluded that the systematic application of KM principles can substantially enhance project performance by facilitating informed decision making and minimizing knowledge loss across project phases. Khoa and Chinda [19] identified five key KM criteria—knowledge dissemination, responsiveness, storage, utilization, and acquisition—and explored their interrelationships to enhance construction competitiveness in Vietnam. They further examined the effects of management support on knowledge-based competitiveness. The results suggested that management focuses on knowledge utilization and dissemination to increase competitiveness quickly and commits to enhancing human- and technology-related activities through knowledge storage, acquisition, and responsiveness to achieve long-term success [36].

Following Khoa and Chinda [36], this study utilizes knowledge acquisition, dissemination, and utilization to quickly enhance the material recovery of building demolition and renovation. Activities within these KM criteria, such as gathering client insights through direct feedback and interaction, applying industry benchmarking results through collaborative discussion and analysis, applying team expertise to resolve operational challenges, enhancing business operations through best practices, facilitating feedback sessions between teams, and coordinating cross-departmental meetings for work updates, are applied to achieve effective plans for material recovery [37]. For instance, meetings among key stakeholders of the building renovation project, such as the main contractors, sub-contractors, demolition companies, and designers, should be organized to plan effective demolition processes in order to achieve good-quality demolition waste for reuse, refurbishment, and recycling. The meeting reports are shared and distributed among team members for timely incorporation. The challenges of waste utilization in building renovation are brainstormed to solve issues like additional costs, utilization, and demolition steps. Details of green certifications, i.e., LEED, are used as guidelines for material recovery practices.

2.3. LEED Certification

LEED certification, developed by the U.S. Green Building Council, is a globally recognized standard for the promotion of sustainability across the building lifecycle [37]. It is a comprehensive framework designed to drive the market toward a near-zero carbon reality and promote the wise and safe use of all resources. For certification with LEED version 4.1, nine categories of scoring are considered. Specifically, the materials and resources (MR) category comprises seven assessment criteria, with two focusing on C&D waste management and planning, aiming to minimize waste, promote material reuse, and support circular building practices [15]. The project team must identify multiple waste streams, set diversion targets (typically 50–75%), and prioritize reusing structural and non-structural elements to reduce embodied carbon [5,15]. These align with global sustainability targets, such as the EU’s waste framework directive, prioritizing the waste hierarchy (i.e., reduce, reuse, recycle) and embodied carbon reduction [15,38].

In the C&D waste management category, credits may also be given through diversion using recycled materials and reducing total waste materials. In building demolition and renovation, 75% of the total waste must be recycled [39]. In summary, the 15 credit areas in the MR section are as follows [37]:

• MR Credit 1—Building Lifecycle Impact Reduction: Encouraging whole-building lifecycle assessment (LCA) to inform design choices and reduce environmental impacts.
• MR Credit 2—Construction and Demolition Waste Management: Diverting C&D waste from landfills through reuse and recycling.
• MR Credit 3—Materials Reuse: Encouraging the reuse of existing building materials in renovations or new constructions.
• MR Credit 4—Recycled Content: Using products with recycled content and reducing the demand for virgin materials.
• MR Credit 5—Regional Materials: Using building materials extracted, processed, and manufactured within a defined radius of the project site.
• MR Credit 6—Rapidly Renewable Materials: Using materials with short harvest cycles or rapidly renewable wood.
• MR Credit 7—Certified Wood: Using wood products certified by the Forest Stewardship Council or other approved certification programs.
• MR Credit 8—Furniture and Medical Furnishings: Using furniture and medical furnishings that meet specific sustainability criteria.
• MR Credit 9—Material Ingredients: Optimizing ingredients for building products, including transparency and health assessments.
• MR Credit 10—Whole-Building LCA: Assessing the environmental impacts of building materials over their entire lifecycles.
• MR Credit 11—Health Product Declaration: Using health product declarations.
• MR Credit 12—Sourcing Raw Materials: Sourcing raw materials by considering extraction practices and social impacts.
• MR Credit 13—Material Ingredient Optimization: Optimizing material ingredients through manufacturer-led initiatives.
• MR Credit 14—Product Transparency and Optimization: Supporting transparency in material sourcing.
• MR Credit 15—Design for Flexibility: Designing for future adaptability and deconstruction to minimize waste.

2.4. Circular Economy and Sustainability Concepts

The increasing concern regarding global environmental challenges, material scarcity, and social inequalities has led to the introduction of the concept of sustainability across all industries [40]. This concept involves three key aspects: economic, environmental, and social [41]. In C&D waste, decorative materials, such as ACP waste, are often disposed of in landfills. ACPs are widely used as facade materials due to their durability, light weight, and esthetic qualities [42]. Large volumes of ACP waste are generated when buildings reach their service lives. The traditional disposal method of landfilling poses serious environmental and resource efficiency concerns, especially in countries like Thailand, where the landfill capacity is limited and no major environmental policies are in place [43]. The CE and sustainability concepts are essential to achieve sustainable development in the long term. From an economic perspective, ACPs’ end-of-life management processes, such as refurbishing, repurposing, and recycling, can reduce the reliance on virgin aluminum, lowering the production and material costs. From an environmental perspective, waste reduction, resource recovery, emission control, and pollution prevention contribute to long-term environmental degradation [44]. By shifting ACP waste from landfilling to circular processes, circular economy strategies, such as refurbishing, repurposing, and recycling, can significantly reduce GHG emissions, energy consumption, and virgin material requirements [43]. For example, recycling aluminum from ACP waste can save up to 95% of energy consumption compared to the original aluminum production [38]. Similarly, refurbishing and repurposing extend the material’s life span for long-term uses and conserve finite resources. From a social perspective, implementing ACP end-of-life management can generate new employment in manufacturing, logistics, and materials processing, particularly in local businesses [45]. These practices support informal workers and promote skills development. Furthermore, by reducing waste and contributing to cleaner urban environments, ACP waste management enhances public health and livability in local areas [46]. Integrating the social aspect into business development ensures a balance between environmental protection and economic feasibility, contributing to long-term sustainability.

2.5. Details of Case Study

2.5.1. Background of Case Study

Figure 2 shows the case study before the renovation. The buildings are located in Bangkok. They comprise a car park and the main buildings. Both are undergoing major renovation both inside and outside, which started in 2024 and is expected to be completed in 2026. The parking building has six stories, and the main building has eight stories. Their exteriors are decorated mainly with glass and ACPs. The ACPs have been removed and will be replaced with a new pattern, as seen in Figure 3. The dismantled ACPs are considered in this study for end-of-life management.

2.5.2. Details of ACP Waste in This Case Study

Based on the bill of quantities of the renovation project, the amount of ACP material before the renovation is 353 m² and 3763 m² for the parking area and main buildings, respectively (a total of 4116 m²). ACPs comprise four main layers; see Figure 4. The outside skin facing the exterior environment is the surface finish, followed by the front aluminum skin layer of 0.5 mm, the fire-retardant core, which is an LDPE layer of 3 mm, and the back aluminum skin layer of 0.5 mm, making the total thickness 4 mm. Given a standard unit weight of 2700 kg/m³ for aluminum and 930 kg/m³ for the LDPE core, the total weight of ACP waste is as shown in

Table 1. Weight of ACP waste in the case study.

Building	Area (m2)	Unit Weight (kg/m2)	Total Weight (kg)
Parking	353	5.49	1937.97
Main	3763	5.49	20,658.87
		Net weight	22,596.84

. It is noted that this ACP waste amount represents about 3.5% of the architectural materials and about 0.5% of the total waste of the project (based on interviews and site observations).

ACP waste may contribute to environmental hazards when incinerated or disposed of in landfills. Specifically, the LDPE core, when incinerated, can release benzene and toluene, which are harmful to the surrounding environment [47]. This issue was discussed among stakeholders to find suitable solutions for its end-of-life management. Knowledge from past projects was retrieved and brainstormed to search for suitable solutions. Several scenarios were discussed and studied to cover economic, environmental, and social perspectives, including using ACPs as new facades, interior decorations, and signboards due to their lightweight properties, esthetics, and ease of installation (see Figure 5). Following the discussion, the contractor adjusted the dismantling plan, from hoist and crane to manual handling, to retain the shape and quality of the ACPs for end-of-life management. During the demolition phase, good-quality ACPs (i.e., a few scratches and wrinkles) were stored onsite at allocated locations. In contrast, unusable ACPs were temporarily stored onsite before transporting them to landfills (see Figure 6).

3. Materials and Methods

The KM and CBA approaches are used in this study to examine scenarios suitable for ACP waste management.

3.1. The Use of KM to Achieve ACP Waste Recovery Scenarios

Many strategies may be used to recover materials from ACPs. For example, Schützenhofer et al. [48] utilized the refurbishing process to extend the service life of ACPs in building applications. Charlotte et al. [49] studied various refurbishment techniques and concluded that surface restoration and recoating make refurbished ACPs compatible with new panels. Boyd et al. [50] evaluated different uses of repurposed ACPs and found that their structural integrity makes them ideal for secondary applications, such as partition walls, signboards, and interior finishes. Jayakody et al. [51] introduced the repurposing process as a viable strategy to reduce ACP waste and conserve embedded energy and materials. Minunno et al. [52] used lifecycle assessment to evaluate the environmental benefits of repurposed ACPs in modular construction. They concluded that the user demand, panel condition, and building codes are key to successful adoption. Milad [53] developed a business model for ACP recycling to help manufacturers and local governments to optimize waste management systems. Brough and Jouhara [54] mentioned that recycled ACPs offer a valuable secondary source of aluminum to meet the growing material demand. Brough and Jouhara [54] reviewed the current ACP recycling technologies and concluded that aluminum layers can be recovered through mechanical or thermal separation, while polymer cores can be processed through incineration or plastic reprocessing.

In this study, knowledge about the material recovery of ACPs was collected through stakeholder meetings and onsite visits (i.e., the case study). Stakeholders included the owner (the government representative), main contractor, demolition company, designers, waste transport service provider, and project consultant. The meetings were held three times onsite to brainstorm possible methods of ACP waste utilization, additional costs from recovery processes, and savings from using recovered ACPs. Data from other projects published online were shared and discussed in the meetings to determine the strengths and weaknesses of waste recovery. The knowledge acquired from the meetings was then compared with the literature, screened, and documented for future use.

A summary of KM implementation to achieve ACP waste recovery is as follows:

• The literature related to demolition waste and its end-of-life uses in Thailand and abroad is reviewed and discussed with team members to gain knowledge of current practices.
• Key stakeholders, including the owner, contractors, designers, and demolition companies, meet regularly to brainstorm possible means of and challenges in recovering and reusing demolition waste in building renovation.
• Challenges and lessons learned from previous projects are also discussed among stakeholders to find the best solutions.
• Data required for the analysis, including the end-of-life management scenarios, implementation processes, costs, and benefits, are collected from secondary sources, onsite interviews, and observations. Primary data—mostly confidential data related to the costs and benefits of ACP waste recovery—must be safely stored and assigned access permissions. They could be recorded in Google Docs and shared among stakeholders.
• Possible scenarios are examined with the green standard, specifically LEED, to plan future steps for certification.
• The study results are published as reports and manuscripts. They are expected to be used as guidelines for implementation in future projects.

3.2. ACP Waste Recovery Scenarios

Based on the above KM practices, four scenarios are set in this study to effectively recover ACPs from building demolition, reduce the environmental footprint associated with ACP production and disposal, conserve valuable raw materials, promote sustainable practices, and follow the circular economy concept [55]. Reselling (Scenario 1) represents the current (as-is) scenario. Refurbishing for new facades (Scenario 2), repurposing for signboards (Scenario 3), and landfilling (Scenario 4) are also examined to recommend the most suitable scenario to reduce waste, promote material recovery, and achieve a preliminary step toward green certification.

3.2.1. Scenario 1: Reselling

In Thailand, valuable demolition waste is mainly sold to second-hand shops. This is an appealing end-of-life management option due to its quick turnaround, low processing requirements, and immediate financial returns [14]. This scenario does not add significant value to the waste stream, despite diverting valuable materials from landfill disposal. Witik et al. [56] stated that ACP waste may be sold at only 5% of its original market value, reflecting material degradation and the absence of value-adding processes like refurbishment or repurposing. The reselling strategy may be a cost recovery tactic rather than a sustainable waste management strategy.

The reselling process is shown in Figure 7. ACPs are extracted, inspected, and documented from the building to assess their sizes and conditions. Cranes are used for mechanical extraction. The removed ACPs are sorted and segregated before being transported to second-hand shops. Waste logging is performed to record the quantity and condition of the ACPs. At the second-hand shop, the ACPs are cleaned to remove dust, adhesives, and debris. Damaged edges are trimmed, and minor bends are straightened to restore usability. They are measured and recorded in the inventory system, followed by size sorting, quality checking, packaging, and labeling. They may be sold directly to customers or specific buyers seeking low-cost ACPs for budget-conscious activities and construction projects [14]. While this method reduces the immediate disposal costs and extends the lives of some materials, it lacks the resource efficiency and environmental benefits associated with more circular approaches, such as refurbishing, repurposing, and recycling [42].

3.2.2. Scenario 2: Refurbishing

The refurbishing process is designed to restore and reuse ACPs. Several studies have explored the refurbishing process across different industries. For example, Metin and Tavil [57] compared the environmental impacts of various facade materials, including ACPs, fiber cement boards, and natural stone, throughout their lifecycles. They found that ACPs have a lower environmental impact during installation than heavier materials like stone but show higher embodied energy and emissions during the production phase. ASKIN Performance Panels [58] analyzed case studies of refurbishing existing building materials, especially ACPs and other non-compliant materials. The study covered practical aspects, such as material removal, panel replacement or refurbishment, compliance upgrades, and building code alignment. The analysis shows that effective workflows and communication in retrieving data from demolition sites could reduce project timelines and material waste.

In this study, the refurbished ACPs are used as new facades. The refurbishing process is shown in Figure 8. ACPs are extracted from the old building, inspected, and documented to assess their sizes and conditions [59]. Cranes are used for mechanical extraction, followed by the manual unscrewing or cutting of the panels [60]. The removed ACPs are segregated based on their conditions and transported to refurbishing sites. The refurbishment process involves several restoration steps. At the facility, the ACPs are inspected for scratches, dents, and oxidation and then cleaned using water or solvents [60]. The surfaces are treated by sanding scratches and applying fillers to repair dents and bends. After the surface and condition treatments, they are repainted and cured in ovens to ensure durability [61]. The ACPs that pass the quality check are packed and labeled for transportation. The refurbished ACPs are sorted and prepared according to size and color requirements and installed as facades in new projects.

3.2.3. Scenario 3: Repurposing

In this scenario, rather than discarding ACP waste from damaged facades, these panels are adapted and used in other applications, such as signboards, furniture, interior cladding, and temporary structures [62]. The repurposing process extends the material’s functional lifespan and helps to reduce landfill use and conserve resources. Several studies support this end-of-life management process. For instance, Borges et al. [63] repurposed composite panels as temporary structures, representing low-load applications. Nadoushani et al. [64] proposed guidelines for the architectural reuse of facade materials, especially ACPs. Manelius et al. [65] demonstrated the potential of integrating repurposed cladding materials into signboards and wayfinding systems, particularly in urban and commercial areas.

In this study, ACPs are repurposed and used as signboards. The repurposing process is shown in Figure 9. After being extracted from the old building, the ACPs are inspected and cleaned to remove surface contaminants, such as dust, paint, and adhesive residues. After this, they are cut to specific dimensions according to the design requirements of the intended signboards. Precision cutting tools, such as CNC cutters and panel saws, are used to ensure clean edges and accurate sizing. They then undergo grooving, a process in which V-shaped channels are machined into the rear sides of the ACPs to allow for bending or folding into shapes, frames, and other multidimensional forms. In addition, drilling is performed to create holes to mount hardware, lighting fixtures, or fasteners. Depending on the application, the surfaces of the panels may be coated to improve their adhesion for screen printing. After fabrication, the finished ACP signboards are assembled, labeled, and packaged for distribution to the construction site.

3.2.4. Scenario 4: Landfilling

Landfilling is the traditional method for solid waste disposal. The landfill space in Thailand is limited, and the environmental regulations are tightening. Reliance on this method risks violating sustainability policies, increasing compliance costs, and undermining Thailand’s national waste reduction targets [66]. ACPs, composed of non-biodegradable aluminum and plastic layers, occupy long-term landfill space [67]. They do not degrade naturally, contributing to the waste burden. Moreover, the disposal of ACPs in landfills leads to the leaching of polymer additives and degradation products under the tropical climatic conditions, raising concerns about soil and groundwater contamination [68].

Figure 10 shows the landfilling process’s steps, from land preparation to monitoring. This scenario begins with land preparation, which involves site selection based on environmental regulations, soil stability, and the distance from demolition sites. The selected site is leveled and lined with impermeable materials, such as high-density polyethylene geomembranes, to prevent leachates from reaching the soil and groundwater. A drainage system is installed to collect and treat the leachate. After the ACPs are extracted by cranes, they are transported to the designated landfills by trucks. Upon arrival, they are unloaded into designated cells and appropriately stacked to minimize settlement. Forklifts or bulldozers are used to position and compress the ACPs. After the landfill reaches capacity, it is covered with a soil layer to reduce wind dispersal and surface runoff [69]. Landfills may be continuously monitored to avoid potential contamination [68].

3.3. Cost/Benefit Analysis

This study utilizes CBA to examine the possibilities of the ACP waste management scenarios. It is a technique for the evaluation of a project or investment by comparing the economic benefits with the costs of the activity. Ortega [70] stated that CBA is commonly used to decide whether a project is justifiable by deciding whether its benefits prevail over the costs, and it provides a benchmark for project evaluation by suggesting projects with the best cost/benefit ratios. A cost/benefit ratio of less than 1 means that the costs of a project outweigh the benefits.

In this study, all costs and benefits, from economic, environmental, and social perspectives, must be quantified and converted into monetary values to calculate the project’s net benefit to society. Based on the literature, costs associated with ACP waste management may include investment, labor, material, storage, overhead, material handling, environmental-related (e.g., carbon tax and water depletion from the end-of-life management processes), and social-related (e.g., workers’ health and risk) costs [71,72]. For example, Tastet and Alsayyed [73] stated that fuel and transportation represent significant operational costs of the recycling process. They reported expenses of USD 660/load to transport recyclables to sorting facilities. In contrast, through various strategies (e.g., refurbishing and repurposing), ACP waste management benefits the project. The benefits may include, for instance, sales of refurbished ACPs and the use of ACPs as signboards, thus saving the original materials, as well as the selling of aluminum as a raw material for other production processes, carbon credits due to reduced material extraction, and an increased GDP from new business opportunities. For example, aluminum has high market value of USD 1231/ton [73]. ACP waste incurs a carbon credit of USD 0.0052/kg CO_2eq [38].

3.4. Data for the Analysis

CE and sustainability concepts are considered to effectively manage ACP waste, emphasizing economic, environmental, and social perspectives. Each scenario offers different degrees of contribution to these sustainability dimensions, and selecting the optimal pathway depends on balancing these outcomes. The data used in the CBA comprise secondary and primary data. Secondary data are collected from international journals, company reports, government reports, and case studies. They cover a 10-year period (i.e., from 2015 to 2025). Meanwhile, primary data are collected from meetings, interviews, and onsite observations.

3.4.1. ACP Waste-Related Data

The ACP waste data are collected from the case study. An example of the data is the amount of ACP waste collected from a demolition site, amounting to about 22,596.84 kg. The reusable ACPs constitute about 70%. On the other hand, data related to electricity consumption, truck capacity, production processes, and fuel consumption are retrieved from the literature. For example, ACPs are refurbished as new facades in the refurbishing process. The production process includes orbital sanding, drying between sanding cycles, painting, and coating. These require an average of 0.26 h/kg of ACP waste [74]. On the other hand, the repurposing process to create signboards includes sizing and cutting, mounting, painting, finishing, and adhesive; these all require roughly 0.21 h/kg of ACP waste [75].

3.4.2. Economic-Related Data

For ACPs, a sustainable economic approach involves identifying pathways that reduce the disposal costs and recover the material’s economic potential through material recovery. The economic-related data for ACP waste management vary by scenario and are based on labor, transportation, equipment, and material recovery. The reselling scenario involves ACP dismantling and transportation to second-hand shops. The economic cost data mainly reflect labor, crane rental, and transportation. While reselling generates direct revenue through the sales of second-hand ACPs, amounting to USD 0.31/kg, this scenario provides no additional benefits to the company due to the lack of reuse of the ACPs and no savings for the environment or community. In contrast, refurbishing and repurposing scenarios may provide greater value through value-added products (i.e., refurbished ACP facades and repurposed signboards) and reduce environmental-related costs. However, these scenarios require additional work to dismantle, cut, grind, shape, and paint new products. These incur extra costs, such as materials, machines, and labor. Based on the interviews, painting incurs an additional cost of USD 1.04/kg and a labor wage of USD 1.3/h. Investment in refurbishing and repurposing equipment and tools totals USD 1515 and USD 2513, respectively. Although these processes incur additional costs, the sales of second-life products (i.e., facades and signboards) may generate high profits. The landfilling scenario requires several activities, as land must be prepared specifically for ACP waste disposal. Costs may include land purchase, legal permission, and site preparation. For example, 22,596.84 kg of ACP waste requires 33 m² of space for disposal, costing USD 606/m². Legal permission, with a cost of approximately USD 74/m², is also required for landfill operations.

3.4.3. Environmental-Related Data

Different scenarios of ACP waste management affect the environment differently. Chayutthanabun and Chinda [38] stated that refurbishing extends the material’s life without reprocessing, thus conserving resources and reducing construction waste. Repurposing supports environmental goals by keeping materials in use and avoiding raw material extraction, while reselling provides short-term reuses of materials [76]. Based on the construction-related literature, ACP production may affect the environment as follows.

• CO_2eq emissions: CO₂ emissions are from aluminum extraction, diesel combustion during transportation, and electricity generation using fossil fuels. For example, the carbon footprint from manufacturing virgin aluminum is estimated at 13.5 kg CO_2eq/kg of aluminum. Avoiding 1 ton of virgin aluminum production can save 13.5 tons of CO_2eq emissions [77].
• Particulate matter (PM): The improper burning and mechanical cutting of ACPs can release PM, endangering workers and nearby communities. Johnson et al. [78] indicated that an increase in PM2.5 raises the respiratory illness rate by 5% per 10 µg/m³ exposure, leading to higher healthcare burdens and lost productivity. In this study, the release of PM occurs through ACP dismantling, diesel combustion, fossil fuel electricity generation, and aluminum extraction.
• Water depletion: Primary aluminum production requires significant water for ore processing and cooling systems, estimated at 115 L/kg of aluminum [79]. In addition, ACP production consumes water, particularly during bauxite mining, alumina refining, and cooling stages in aluminum smelting [80].
• Metal depletion: Aluminum mining requires large-scale bauxite extraction and chemical processing. Every ton of virgin aluminum consumes about 4 tons of bauxite and produces 2 tons of red mud, a hazardous byproduct [81].
• Fuel depletion: Fuel is required in transportation, refurbishing, and repurposing processes. Primary aluminum production consumes about 15 MWh/ton of electricity [82]. This is crucial in Thailand, as much of the electricity generation is still based on fossil fuels. Renewable energy, such as biomass and solar power, may reduce the fossil fuel dependency and GHG emissions [83].
• Landfill disposal: ACP disposal in landfills consumes landfill space and may generate groundwater contamination from leachates [84].

ACP waste management may bring several environmental benefits and costs due to the end-of-life management processes (four scenarios in this study). The end-of-life management of ACPs avoids using virgin materials, saving about USD 1/ton CO₂ [79]. The management of ACP waste may demonstrate compliance with environmental, social, and governance (ESG) standards, increasing investor confidence and reducing sustainability reporting risks under emerging disclosure laws [66].

3.4.4. Social-Related Data

Social-related costs from ACP waste management include health risks (i.e., reimbursement and medical bills), CSR campaigns, new employment, and legal permission. Leachates from landfilled ACPs, particularly those with polyethylene cores and aluminum coatings, may release microplastics and volatile organic compounds into soil and groundwater [84]. These substances have been associated with respiratory diseases, dermatitis, and even long-term cancer risks. Many studies examine the potential costs related to social activities to broaden the materials that align with the concept of sustainability in the C&D industry. For example, in India, a comparable case in the Ghazipur landfill recorded compensation of up to USD 570/household after leachate-related illness outbreaks [85]. In a more serious case, environmental class action lawsuits in China have led to court-ordered reimbursements exceeding USD 306,213 to cover health impacts and relocation expenses [86].

While easily accessible, ACP reselling lacks quality assurance and may transfer degraded materials to informal markets without safety oversight [87]. The lack of traceability and quality assurance in ACPs could compromise user safety and long-term product reliability. However, refurbishing and repurposing ACP waste offers new job opportunities, specifically for small and medium enterprises, by repairing, fabricating, and redesigning products [88]. These practices create economic opportunities and encourage skill development and local economic circulation. Moreover, they support the growing market for eco-friendly construction materials, aligning with the 18% annual increase in demand for green-certified buildings [89]. E-conscious building materials are expected to contribute up to 4% of total GDP growth in the construction sector by 2030 [89]. As government incentives for low-carbon buildings expand, this shift could inject approximately USD 30 million into local supply chains, attract foreign investment, and generate long-term employment, sustaining environmental management and social development in C&D companies in Thailand [90]. Landfilling always raises social concerns. The improper disposal of ACPs, especially those with polyethylene cores and metallic coatings, can release toxic leachates [84]. The Department of Pollution Control [91] estimated that medical treatment for one community affected by toxic leachates costs over USD 1584/person, covering hospitalization, outpatient treatment, and medicine subsidies. Integrating ACP waste management into green construction supports Thailand’s GDP and sustainability goals. With government incentives on the rise, green practices in C&D industries are forecasted to contribute up to 4% of the country’s construction GDP by 2030, potentially injecting USD 30 million into domestic supply chains [89]. These sustainable waste practices mitigate social and health risks and drive long-term socioeconomic growth in the Thai community.

The cost and benefit data used in the CBA analysis are given in Appendix A and Appendix B.

3.5. Flow of ACP Waste Management

Figure 11 shows the flow of ACP waste in different scenarios. ACPs are first dismantled from old buildings using cranes or manual handling. The quality of the ACP waste is checked to separate it into usable and unusable parts. Usable ACPs are stored onsite for detailed examination. On the other hand, unusable ACPs are transferred to landfills or second-hand shops using 6-wheel trucks.

All scenarios require trucks for transportation (i.e., to landfills, factories, and second-hand shops), with a rental cost of USD 152/trip, for four trips. The refurbishing and repurposing scenarios provide sustainable alternatives; however, the processes may incur additional costs. In these scenarios, ACPs are manually extracted, increasing the labor costs. Nevertheless, the refurbishing and repurposing processes contribute to job creation and business opportunities, raising the industry and the country’s GDPs. After manual dismantling, ACPs are temporarily stored at a rented facility before undergoing treatment. In the refurbishing scenario, ACPs are refurbished as new facades. The initial investment is estimated at USD 1515 for the initial equipment requirements (i.e., pressure washers, orbital sanders, saw cutters, and spray guns), with the surface treatment involving painting at USD 1.04/kg [92]. The overhead cost is estimated at 10% of the total cost. The refurbished ACPs can be sold as new ACPs with an average price of USD 1.85/kg. Environmental benefits are also incurred through avoided emissions and resource extraction, such as savings from purchasing carbon tax at USD 0.0052/kg CO_2eq, savings from PM generation at USD 0.45/kg PM_eq, and reductions in water, fuel, and metal depletion [38]. The repurposing process requires a higher investment cost of USD 2423 compared to the refurbishing scenario. Costs related to the production process are USD 0.91/kg for adhesive, USD 1.40/kg for graphic filming, USD 0.75 for LED light, and USD 0.56/kg for polyurethane framing [92]. Material handling requires forklifts, adding USD 606/month [93]. Finished signboards yield an average price of USD 4.54/kg, offering a favorable return on repurposed ACPs [92].

In the landfilling scenario, ACPs are extracted using a crane to minimize the demolition time, labor, and material handling costs. The crane rental cost is approximately USD 485/month. The ACP waste is then transported to landfills located on the outskirts of Bangkok, about 20.6 km from the demolition site. According to the Pollution Control Department [94], landfills must be designed to ensure that the trench base is at least 1 m above the groundwater level. Hydrogeological and geotechnical site investigations are required, and landfill component layouts must be documented in plans at a scale of no larger than 1:2500. In addition, the stacking height for landfills in Thailand is approximately 2.5 m, not exceeding 10 m high per landfill [95]. Based on Appendix A, a landfill space of 20.01 m² is required for an ACP waste amount of 22,596.84 kg, at a land cost of USD 749.79/m² around the Bangna Industrial Zone area [96]. From an environmental perspective, this scenario incurs significant hidden costs through CO_2eq emissions, resource depletion, and PM. Moreover, social-related risks, such as nearby community protests, may urge construction companies to initiate CSR campaigns, such as community health checks and tree planting. These may add up to USD 9164/year on average.

4. Analysis Results

4.1. CBA Results of Scenario 1 (Reselling)

The costs of Scenario 1 cover the economic, environmental, and social aspects (see Appendix A). The total cost of this scenario is USD 23,969.83. It is calculated from the following.

• Investment in equipment and tools: This includes pressure washers and an edge trimming machine, which are estimated at USD 305.02.
• Labor: Laborers are required to load ACPs onto trucks for transportation. This process takes about three months.

  o

  Manual dismantling takes three months and three laborers, costing 3 × 349 × 3 = USD 3141.

  o

  According to Appendix A, seven laborers are required at the second-hand shop for the ACP preparation process. Preparing one kg of ACPs takes 0.15 h at a labor rate of USD 1.3/h. With 22,596.84 kg of ACP waste (usable ACPs), it costs 0.15 × 1.3 × 22,596.84 = USD 4406.38.

  o

  The total labor cost is then 3141 + 4406.38 = USD 7547.38.

• Transportation: ACP waste is transported to second-hand shops, and the cost comprises truck rental and fuel consumption.

  o

  For truck rental, the cost is calculated from the number of trips and the truck rental fee: 4 × 152 = USD 608.

  o

  The fuel cost is calculated from the distance between the demolition site and the second-hand shop, the fuel consumption rate, the fuel price, and the number of trips: 78/4.5 × 1 × 4 = USD 69.33.

  o

  This yields a total transportation cost of USD 677.33.

• Material handling: ACP dismantling uses a crane. The crane is rented for USD 485/month for three months, or USD 485 × 3 = USD 1455.
• Carbon tax: CO_2eq emissions occur during diesel combustion, with an emission factor of 2.68 kg CO_2eq/L.

  o

  Transportation to the second-hand shop requires 69.33 L.

  o

  Cranes consume fuel at 10 L/h. With a maximum of 160 h working/month and a three-month working period, the fuel consumption is 10 × 160 × 3 = 4800 L.

  o

  The carbon tax is then (69.33 + 4800) × 2.68 × 0.0052 = USD 67.86.

• PM: PM is generated from demolition activities and diesel fuel combustion.

  o

  For ACP dismantling, PM is generated at 22,596.84 × 0.00214 = 48.36 kg PM (see Appendix A).

  o

  PM is generated at (69.33 + 4800) × 0.0013 = 6.33 kg for diesel combustion.

  o

  The PM-related cost is (48.36 + 6.33) × 0.45 = USD 24.61.

• Fuel depletion: Fuel depletion is calculated by converting diesel consumption to oil equivalents.

  o

  Four trips of ACP waste transportation to the second-hand shop consume 69.33 L of diesel fuel.

  o

  The fuel consumption for cranes is 10 × 160 × 3 = 4800 L.

  o

  According to Appendix A, about 0.85 kg of oil_eq is equivalent to one liter of diesel. With USD 0.26/L, the total fuel depletion cost is (69.33 + 4800) × 0.85 × 0.26 = USD 1076.12.

• Water depletion: Water depletion is calculated from the water used to clean the ACP waste. Using 0.00071 m³ per kg, the water depletion cost is 22,596.84 × 0.00071 × 0.58 = USD 9.31.
• Reimbursement and medical bills: These costs arise from occupational health risks during ACP dismantling. According to the Office of Social Security [97], the average direct reimbursement per injury is USD 1584. With approximately 2.3 injuries per project, it incurs a reimbursement cost of 1584 × 2.3 = USD 3643.2.
• CSR: This cost, approximately USD 9164, covers a community health check, dust mitigation, and tree planting activities.

This scenario’s benefit is achieved through the sales of ACP waste. The average selling price of USD 0.31/kg yields 22,596.84 × 0.31 = USD 7005.05 (see Appendix B). Figure 12 shows the costs and benefits of this scenario. The C/B is then calculated as 23,969.83/7005.05 = 3.42. This makes this scenario less attractive for implementation, although it provides a quick financial return for companies.

4.2. CBA Results of Scenario 2 (Refurbishing)

The total cost of this scenario is USD 101,715.84.

• Investment in equipment and tools:

  o

  The refurbishing process requires pressure washers, orbital sanders, saw cutters, and spray guns, which are estimated at USD 1515.

  o

  Unused ACPs are sold at second-hand shops that require pressure washers and edge trimming machines for their operations. The equipment cost is estimated at USD 305.02.

  o

  The total investment cost is 1515 + 305 = USD 1820.02.

• Labor: Laborers must extract ACPs from old buildings (manual dismantling) and load them onto trucks for transportation. They are also required for the refurbishing process.

  o

  Manual dismantling takes three months and three laborers, costing 3 × 349 × 3 = USD 3141.

  o

  According to Appendix A, seven laborers are required in the refurbishing process. Refurbishing one kg of ACPs takes 1.82 h at a labor rate of USD 1.3/h. With 15,817.79 kg of ACP waste (usable ACPs), it costs 1.82 × 1.3 × 15,817.79 = USD 37,424.89.

  o

  The labor cost at the second-hand shops for operating 6779.05 kg of ACP waste (usable ACPs) is 0.15 × 1.3 × 6779.05 = USD 1321.91.

  o

  The total labor cost is 3141 + 37,424.89 + 1321.91 = USD 41,887.8.

• Electricity: At a consumption rate of 0.0194 kWh/kg, the electricity cost for the refurbishing process is 0.0194 × 15,817.79 × 0.13 = USD 39.89.
• Transportation: Usable ACP waste is transported to facilities for refurbishment, while the unusable amount is transferred to second-hand shops.

  o

  For truck rental, transporting 15,817.79 kg of ACP waste requires three trips and one trip to a second-hand shop. One truck rental trip is USD 152. This incurs 4 × 152 = USD 608 for 6-wheel truck rental.

  o

  The fuel consumption for travel from the demolition site to the refurbishing facility is about 41.8 km/trip. With fuel efficiency of 4.5 km/L and a fuel cost of USD 1/L, this incurs a cost of 41.8/4.5 × 1 × 3 = USD 27.87. A trip to a second-hand shop, with an average distance of 78 km/trip, costs 78/4.5 × 1 × 1 = USD 17.33.

  o

  The total transportation cost is then 608 + 27.87 +17.33 = USD 653.2.

• Material handling: The forklift handles ACP waste in a refurbishing facility. With a rental cost of USD 606/month and a three-month processing period, this incurs a material handling cost of USD 606 × 3 = USD 1818.
• Materials: Paints and adhesives are used for refurbishing ACPs, costing (1.04 + 0.91) × 15,817.79 = USD 30,844.69.
• Storage: Temporary storage is required before ACPs are transported to facilities. This costs 137 × 3 = USD 411.
• New ACP facades: To produce new facades, 30% of new ACPs (i.e., 6779.05 kg of unusable ACP waste) must be purchased. At the ACP cost of USD 1.85/kg, this incurs a cost of 1.85 × 6779.05 = USD 12,541.24.
• Carbon tax: Carbon tax is calculated from new aluminum extraction, diesel combustion, and electricity generation.

  o

  New aluminum materials are required to create new ACP facades (i.e., 6779.05 kg of unusable ACP waste). The extraction of aluminum materials emits approximately 13.9 kg of CO_2eq/kg of new facade [98]. CO_2eq emissions are calculated as 6779.05 × 13.9 = 94,228.8 kg of CO_2eq.

  o

  Transportation to refurbishing facilities requires 45.2 L of diesel, which has an emission factor of 2.68 kg CO_2eq/L. This generates CO_2eq emissions of 45.2 × 2.68 = 121.14 kg CO_2eq.

  o

  According to the Energy Policy and Planning Office [99], electricity generation in Thailand produces emissions of 0.399 kg CO_2eq/kWh. This electricity consumption (306.87 kWh) is for refurbishing equipment. This incurs CO_2eq emissions of 0.399 × 306.87 = 122.44 kg CO_2eq.

  o

  The carbon tax is calculated as (94,228.8 + 121.14 + 122.44) × 0.0052 = USD 491.26.

• PM generation: PM is generated during ACP dismantling, diesel combustion, electricity generation, and aluminum extraction.

  o

  PM is generated at 22,596.84 × 0.00214 = 48.36 kg PM for ACP dismantling.

  o

  Transportation to the refurbishing facility consumes 45.2 L of diesel, equivalent to 45.2 × 0.0013 = 0.059 kg PM.

  o

  According to the Energy Policy and Planning Office [99], Thailand’s electricity generation generates 0.006 kg PM/kWh. Electricity consumption of 306.87 kWh may produce 0.006 × 306.87 = 1.84 kg PM.

  o

  Aluminum extraction produces 0.00586 kg of PM/kg of ACP; thus, producing 6779.05 kg of ACPs generates 6779.05 × 0.00586 = 39.73 kg PM.

  o

  The PM-related cost is then (48.36 + 0.059 + 1.84 + 39.73) × 0.45 = USD 40.49.

• Water consumption: Water is used in new ACP facade production and operations at second-hand shops.

  o

  With 6779.05 kg of new ACP production, the water cost is USD 786.37 × 0.2 × 0.58.

  o

  The operations at second-hand shops incur a water cost of 6779.05 × 0.00071 × 0.58 = USD 2.79.

  o

  The total water consumption cost is USD 789.16.

• Metal depletion: Aluminum extraction for new ACP facades (equivalent to 6779.05 kg of Fe_eq) contributes to the irreversible depletion of finite mineral resources. This incurs a cost of 6779.05 × 0.25 = USD 1694.76.
• Fuel depletion: Fuel consumption occurs in transportation and refurbishing processes.

  o

  According to Appendix A, about 0.85 kg of oil_eq is equivalent to one L of diesel. The trip to the refurbishing facility costs 45.2 L of diesel, resulting in fuel depletion of 45.2 × 0.85 = 38.42 kg oil_eq.

  o

  About 1.1 kg of oil is consumed per kg of new ACP production, resulting in 6779.05 × 1.1 = 7456.96 kg.

  o

  In Thailand, electricity is generated mainly from natural gas and coal, with fossil fuels. Fuel consumption is estimated at 0.3 kg oil/kWh. With 306.87 kWh required for refurbishing, fuel depletion is 0.3 × 306.87 = 92.06 kg of oil.

  o

  The fuel depletion cost is calculated as (38.42 + 7456.96 + 92.06) × 0.26 = USD 1972.73.

• Reimbursement and medical bills: Reimbursement is from ACP dismantling and aluminum extraction.

  o

  Aluminum dismantling costs USD 3643.2 for reimbursement, on average.

  o

  According to Carlos-Rivera et al. [100] and Fontcha et al. [101], the average medical cost of aluminum extraction (non-fatal injuries) is USD 266/case, with an average of four cases/project. With only 30% of aluminum extracted for unusable ACP waste, this may cause 4 × 0.3 = 1.2 cases, with a reimbursement cost of 266 × 1.2 = USD 319.20.

  o

  The total reimbursement cost is 3643.2 + 319.2 = USD 3962.40.

• CSR: Aluminum extraction (for unusable ACP waste, i.e., 30% of ACP waste) generates environmental impacts, and the company needs to compensate the communities through health checks and tree planting campaigns, which cost approximately 9164 × 0.3 = USD 2749.20.

This scenario’s total benefit is USD 89,156.52. It covers economic, environmental, and social benefits (see Appendix B).

• Savings from refurbished facades: Refurbished ACPs can be used as facades, avoiding the production of new facades. This saves 1.85 × 15,817.79 = USD 29,262.91.
• Sales of ACP waste: With ACP waste of 6779.05 kg, it can be sold at second-hand shops for 0.31 × 6779.05 = USD 2101.51.
• Carbon credit: The recovery of 15,817.79 kg ACPs can reduce CO_2eq emissions by 15,817.79 × 13.9 = 219,867.28 kg CO_2eq, incurring a carbon credit of 219,867.28 × 0.0052 = USD 1143.30.
• PM reduction: ACP recovery reduces PM by 15,817.79 × 0.00586 = 92.69 kg PM and saves 92.69 × 0.45 = USD 41.71.
• Water savings: Water saved from ACP recovery is 15,817.79 × 0.2 × 0.58 = USD 1834.86.
• Metal savings: With an estimated depletion saving rate of USD 0.25/kg Fe_eq, the metal savings are 15,817.79 × 0.25 = USD 3954.45.
• Fuel savings: Material recovery saves fuel by 15,817.79 × 1.1 = 17,399.57 kg oil_eq. This saves 17,399.57 × 0.26 = USD 4523.89.
• Savings in reimbursement and medical bills: Material recovery (from usable ACPs) reduces medical bills by 4 × 0.7 = 2.8 cases, thus saving 266 × 2.8 = USD 744.8 [100,101].
• Savings in CSR cost: Material recovery (usable ACP waste) promotes a green image of the company and reduces the CSR cost by 9164 × 0.7 = USD 6414.80.
• New employment: Refurbishing usable ACPs creates job opportunities equivalent to 15,817.79 × 1.82 = 28,788.38 h. The labor rate of USD 1.3/h means that the benefit from new employment is 28,788.38 × 1.3 = USD 37,424.89.
• Savings from legal permission: Refurbishing reduces the use of landfills. Legal permission for land use and impacts to the community costs about USD 74/m². Refurbishing 15,817.79 kg of ACPs saves landfill space by 23.1 m², bringing the savings to 74 × 23.1 = USD 1709.40.

Figure 13 shows the costs and benefits of this scenario. The C/B is then calculated as 101,715.84/89,156.52 = 1.14, making it unattractive for implementation. This is mainly due to the high labor and material costs in refurbishing.

4.3. CBA Results of Scenario 3 (Repurposing)

The total cost of this scenario is USD 158,856.76, calculated using the data in Appendix A.

• Investment in equipment and tools:

  o

  The repurposing process requires pressure washers, saw cutters, spray guns, hole saws, hot glue guns, mounting equipment, and a sticker-format printer, which are estimated at USD 2513.

  o

  Unused ACPs are sold at second-hand shops that require pressure washers and edge trimming machines for their operations. The equipment cost is estimated at USD 305.02.

  o

  The total investment cost is 2513 + 305.02 = USD 2818.02.

• Labor: Laborers must extract ACPs from old buildings (manual dismantling) and load them onto trucks for transportation. They are also required at the repurposing facility.

  o

  Manual dismantling takes three months and three laborers, costing 3 × 349 × 3 = USD 3141.

  o

  Seven laborers are required in the repurposing process. At a labor rate of USD 1.3/h, repurposing one kg of ACPs takes 1.47 h. With 15,817.79 kg of ACP waste (usable ACPs), it costs 1.47 × 1.3 × 15,817.79 = USD 30,227.8.

  o

  Seven laborers are required in the second-hand ACP preparation process. With 6779.05 kg of ACP waste (usable ACPs), it costs 0.15 × 1.3 × 6779.05 = USD 1321.91.

  o

  The total labor cost is 3141 + 30,227.8 +1321.91 = USD 34,690.71.

• Electricity: At a consumption rate of 0.013 kWh/kg, the electricity cost for the repurposing process is 0.013 × 15,817.79 × 0.13 = USD 26.73.
• Transportation: Usable ACP waste is transported to repurposing facilities, while the unusable amount is transferred to second-hand shops.

  o

  For truck rental, transporting 15,817.79 kg of ACP waste requires three trips and one trip to the second-hand shop. One truck rental trip is USD 152. This incurs 4 × 152 = USD 608 for a 6-wheel truck rental.

  o

  The fuel consumption for travel from the demolition site to the repurposing facility is about 41.8 km/trip. With fuel efficiency of 4.5 km/L and a fuel cost of USD 1/L, this incurs a cost of 41.8/4.5 × 1 × 3 = USD 27.87. A trip to a second-hand shop, with an average distance of 78 km/trip, costs 78/4.5 × 1 × 1 = USD 17.33.

  o

  The total transportation cost is then 608 + 27.87 +17.33 = USD 653.2.

• Material handling: A forklift handles ACP waste in a repurposing facility. With a rental cost of USD 606/month and a three-month processing period, this incurs a material handling cost of USD 606 × 3 = USD 1818.
• Materials: Adhesives, graphic films, LED light, and polyurethane framing are used for ACP repurposing, costing (0.91 + 1.4 + 0.75 + 0.56) × 15,817.79 = USD 57,260.39.
• Storage: Temporary storage is required for three months before ACPs are transported to the facilities. This costs 137 × 3 = USD 411.
• Signboards: In total, 30% of new LED signboards (equivalent to 6779.05 kg of unusable ACP waste) must be purchased. At a cost of USD 7.3/kg, this incurs a cost of USD 7.3 × 6779.05 = USD 49,487.07.
• Carbon tax: Carbon tax is calculated from new aluminum extraction, diesel combustion, and electricity generation.

  o

  New aluminum materials are required to create new signboards (i.e., 6779.05 kg of unusable ACP waste). The extraction of aluminum materials emits approximately 13.9 kg of CO_2eq/kg of new signboards [98]. CO_2eq emissions are calculated as 6779.05 × 13.9 = 94,228.8 kg of CO_2eq.

  o

  Transportation to repurposing facilities requires 45.2 L of diesel, which has an emission factor of 2.68 kg CO_2eq/L. This generates CO_2eq emissions of 45.2 × 2.68 = 121.14 kg CO_2eq.

  o

  Electricity consumption of 0.013 × 15,817.79 = 205.63 kWh is required for equipment utilization to repurpose ACPs. This incurs CO_2eq emissions of 205.63 × 0.399 = 82.05 kg CO_2eq.

  o

  The carbon tax is calculated as (94,228.8 + 121.14 + 82.05) × 0.0052 = USD 491.05.

• PM generation: PM is generated during ACP dismantling, diesel combustion, electricity generation, and aluminum extraction.

  o

  PM is generated at 22,596.84 ×0.00214 = 48.36 kg PM for ACP dismantling.

  o

  Transportation to the repurposing facility consumes 45.2 L of diesel, equivalent to 45.2 × 0.0013 = 0.059 kg PM.

  o

  Electricity consumption of 205.63 kWh may produce 0.006 × 205.63 = 1.23 kg PM.

  o

  Aluminum extraction produces 0.00586 kg of PM/kg of ACP; thus, producing 6779.05 kg of ACPs generates 6779.05 × 0.00586 = 39.73 kg PM.

  o

  The PM-related cost is then (48.36 + 0.059 + 1.23 + 39.73) × 0.45 = USD 40.22.

• Water consumption: Water is used in new ACP production and the operations at the second-hand shops.

  o

  With 6779.05 kg of new ACP production, the water cost is USD 786.37 × 0.2 × 0.58.

  o

  The operations at the second-hand shops incur a water cost of 6779.05 × 0.00071 × 0.58 = USD 2.79.

  o

  The total water consumption cost is USD 789.16.

• Metal depletion: Aluminum extraction (equivalent to 6779.05 kg of Fe_eq) contributes to the irreversible depletion of finite mineral resources, which incurs a cost of USD 1694.76 (6779.05 × 0.25).
• Fuel depletion: Fuel consumption occurs in transportation and repurposing processes.

  o

  A trip to the repurposing facility costs 45.2 L of diesel, resulting in fuel depletion of 45.2 × 0.85 = 38.42 kg oil_eq.

  o

  About 1.1 kg of oil is consumed per kg of new ACP production, resulting in 6779.05 × 1.1 = 7456.96 kg.

  o

  With 205.63 kWh required for repurposing, fuel depletion is 0.3 × 205.63 = 61.69 kg oil_eq.

  o

  The fuel depletion cost is (38.42 + 7456.96 + 61.69) × 0.26 = USD 1964.84.

• Reimbursement and medical bills: Reimbursement is from ACP dismantling and aluminum extraction.

  o

  Aluminum dismantling costs USD 3643.2 for reimbursement, on average.

  o

  In total, 30% of aluminum is extracted for unusable ACP waste; this carries a reimbursement cost of 266 × 4 × 0.3 = USD 319.2.

  o

  The total reimbursement cost is 3643.2 + 319.2 = USD 3962.4.

• CSR: Aluminum extraction (for unusable ACP waste, i.e., 30% of ACP waste) generates environmental impacts, and the company needs to compensate the communities through health checks and tree planting campaigns, which costs approximately 9164 × 0.3 = USD 2749.2.

This scenario’s total benefit is USD 168,166.39, covering the following economic, environmental, and social benefits.

• ACP signboards: Using repurposed ACPs as signboards avoids the production of new signboards, saving USD 7.3 × 15,817.79 = USD 115,469.87.
• Sales of ACP waste: With ACP waste of 6779.05 kg, it can be sold at second-hand shops for 0.31 × 6779.05 = USD 2101.51.
• Carbon credit: The recovery of 15,817.79 kg ACPs can reduce CO_2eq emissions by 15,817.79 × 13.9 = 219,867.28 kg CO_2eq, incurring a carbon credit of 219,867.28 × 0.0052 = USD 1143.3.
• PM reduction: ACP recovery reduces PM by 15,817.79 × 0.00586 = 92.69 kg PM and saves 92.69 × 0.45 = USD 41.71.
• Water savings: Water saved from ACP recovery is 15,817.79 × 0.2 × 0.58 = USD 1834.86.
• Metal savings: With an estimated depletion saving rate of USD 0.25/kg Fe_eq, the metal savings are 15,817.79 × 0.25 = USD 3954.45.
• Fuel savings: Material recovery saves fuel amounting to 15,817.79 × 1.1 = 17,399.57 kg oil_eq. This saves 17,399.57 × 0.26 = USD 4523.89.
• Savings in reimbursement and medical bills: Material recovery reduces medical bills by 266 × 4 × 0.7 = USD 744.8.
• Savings in CSR cost: Material recovery (usable ACP waste) promotes a green image of the company and reduces the CSR cost by 9164 × 0.7 = USD 6414.8
• New employment: Refurbishing usable ACPs creates job opportunities equivalent to 15,817.79 × 1.47 = 23,252.15 h. The USD 1.3/h labor rate generates a benefit of 23,252.15 × 1.3 = USD 30,227.8.
• Savings from legal permission: Refurbishing reduces the use of landfills. The legal permission for land use and impacts to the community costs about USD 74/m². Refurbishing 15,817.79 kg of ACPs saves landfill space by 23.1 m² and brings the savings to 74 × 23.1 = USD 1709.4

Figure 14 shows the costs and benefits of this scenario. The C/B is then calculated as 158,856.76/168,166.39 = 0.94, making it an attractive implementation scenario (as the costs are lower than the benefits). The greatest benefit is from using repurposed signboards, representing 68.66% of the total benefit. This scenario may be investigated for LEED certification to plan for further accreditation.

4.4. CBA Results of Scenario 4 (Landfilling)

The total cost of Scenario 4 is USD 54,061.35. It is calculated from the following.

• Land purchase: Based on the interviews, the company must purchase land for ACP waste disposal. With 22,596.84 kg of ACPs at a density of 5.4 kg/m², the area required is 22,596.84/5.4 = 4184.6 m². A panel thickness of 4 mm results in a landfill volume of 4184.6 × 0.004 = 16.74 m³. With an average stacking height of 2.5 m, the area needed is 16.74/2.5 = 6.67 m². In addition, a 200% additional area is required to accommodate road access, safety zones, and handling operations, increasing the required area to 6.67 × 3 = 20.01 m² [95,96]. The land cost is 20.01 × 675.79 = USD 13,522.56.
• Labor: Laborers are required to load ACPs onto trucks for transportation from the demolition site to the designated landfill. They must also extract ACPs from old buildings (manual dismantling) and load them onto trucks for transportation. They are also required at the repurposing facility.

  o

  Manual dismantling takes three months and three laborers, costing 3 × 349 × 3 = USD 3141.

  o

  Five laborers are required for landfill operations. The landfilling process takes three months, costing 5 × 349 × 3 = USD 5235.

  o

  The total labor cost is 3141 + 5235 = USD 8376.

• Transportation: ACP waste is transported to landfills, and the cost comprises truck rental and fuel consumption.

  o

  The truck rental cost is calculated from the number of trips and the truck rental fee: 4 × 152 = USD 608.

  o

  The fuel cost is calculated from the distance between the demolition site and landfill, the fuel consumption rate, the fuel price, and the number of trips: 47.2/4.5 × 1 × 4 = USD 41.96.

  o

  This yields a total transportation cost of USD 649.96.

• Material handling: ACPs are dismantled using a crane. Forklifts and bulldozers transport ACP waste to landfills.

  o

  The crane is rented for USD 485/month for three months, or USD 485 × 3 = USD 1455.

  o

  The forklift is rented for USD 463/month for three months, costing USD 606 × 3 = USD 1818.

  o

  The bulldozer is rented at USD 3399/month for three months, costing 3399 × 3 = USD 10,197.

  o

  This yields a total material handling cost of 1455 + 1818 + 10,197 = USD 13,470.

• Carbon tax: CO_2eq emissions occur during diesel combustion.

  o

  Truck transportation to landfills requires 41.96 L.

  o

  A crane requires 10 L/h, with a maximum of 160 working hours/month for three months; the diesel consumption is then 10 × 160 × 3 = 4800 L.

  o

  A forklift requires 2 L/h, with a maximum of 160 h/month for three months; the diesel consumption is then 2 × 160 × 3 = 960 L.

  o

  A bulldozer requires 12 L/h, with a maximum of 160 h/month for three months, yielding diesel consumption of 12 × 160 × 3 = 5760 L.

  o

  The carbon tax is then (41.96 + 4800 + 960 + 5760) × 2.68 × 0.0052 = USD 161.13.

• PM generation: PM is generated from demolition activities, diesel fuel combustion, and landfill preparation.

  o

  PM is generated at 22,596.84 × 0.00214 = 48.36 kg for ACP dismantling.

  o

  Diesel combustion generates PM at (41.96 + 4800 + 960 + 5760) × 0.0013 = 15.03 kg.

  o

  For landfill development, landfill preparation releases approximately 1.5 kg of PM/m². With the required space of 20.01 m², this becomes 20.01 × 1.5 = 30.01 kg of PM.

  o

  This incurs a PM-related cost of (48.36 + 15.03 + 30.01) × 0.45 = USD 42.03.

• Fuel depletion: The fuel depletion is calculated by converting diesel consumption to oil equivalents.

  o

  Using 41.96 L of diesel in truck transportation causes fuel depletion of 41.96 × 0.85 = 35.66 kg oil_eq.

  o

  The fuel depletion of a crane is 10 × 160 × 3 × 0.85 = 4080 kg oil_eq.

  o

  The fuel depletion of forklifts is 2 × 160 × 3 × 0.85 = 816 kg oil_eq.

  o

  The fuel depletion of bulldozers is 12 × 160 × 3 × 0.85 = 4896 kg oil_eq.

  o

  The total fuel depletion cost is (35.66 + 4080 + 816 + 4896) × 0.26 = USD 2555.19.

• Reimbursement and medical bills: ACP dismantling causes a reimbursement cost of USD 3643.2.
• CSR: This cost, approximately USD 9164, covers a community health check, dust mitigation, and tree planting activities.
• Legal permission: Landfill operations require official approval from relevant government authorities, such as the Department of Industrial Works, Office of Natural Resources and Environmental Policy and Planning, and Pollution Control Department [99]. The permits cover land use, environmental compliance, and pollution control to protect nearby communities. The legal cost for obtaining such permissions is USD 74/m². The total legal permission cost is 33.48 × 74 = USD 2477.52.

The landfilling process yields no benefit because no new jobs are created. Figure 15 shows the costs of this scenario. With only costs incurred, this is the worst implementation scenario, with no financial return to the companies.

5. Discussion

5.1. CBA Result Discussion

The CBA results of the four scenarios could be arranged from the best to the worst; see

Table 2. C/B ratio results.

Scenario	Total Cost (USD)	Total Benefit (USD)	C/B Ratio	Rank
Repurposing	158,856.76	168,166.39	0.94	1
Refurbishing	101,715.84	89,156.52	1.14	2
Reselling	23,969.83	7005.05	3.42	3
Landfilling	54,061.35	-	-	4

. The repurposing scenario is the only scenario with a C/B less than 1 (i.e., 0.96), reflecting the feasibility of its implementation. In the repurposing scenario, the greatest benefits from the economic-, environmental-, and social-related perspectives are for ACP signboards, fuel savings, and new employment. In contrast, the most significant costs of this scenario are from new ACP production for signboard creation (economic-related), fuel depletion (environmental-related), and reimbursement and medical bills (social-related). To further enhance the C/B of this scenario, it is suggested that other types of waste (e.g., acrylic and glass) be considered to replace the new ACP production for unusable ACP waste.

The refurbishing scenario is not feasible (C/B = 1.12), mainly due to high labor and material costs. Currently, seven laborers are required for the refurbishing process. Skill training and incentives may reduce the labor costs due to less rework and better productivity. The C/B of 2.59 for the reselling scenario proves that this scenario, which is the current practice, is not recommended, although it provides quick and easy ACP waste management. Because this scenario is not environmentally friendly, several campaigns, such as health checks, dust mitigation, and tree planting, must be activated, resulting in high implementation costs. Landfilling is the worst solution for ACP waste management and should be avoided. ACP waste must be disposed of in specific landfills; this may lead to protests from nearby communities. Moreover, disposing of ACP waste in landfills incurs long-term environmental impacts, such as toxic gases, soil and water contamination, and leachates.

Several studies support the use of ACP waste as signboards and facades or recycling to produce aluminum materials. For example, Stacbond [102] mentioned that ACP waste could be recycled or reused as signage, banners, facades, and decorative materials. Alubuild [103] stated that ACPs may be used as facades, column coverings, balcony cladding, and esthetic elements.

5.2. Sensitivity Analysis of the Repurposing Scenario

The results show that the repurposing scenario is the best scenario for ACP waste management. This is based on 70% reusable ACPs from the demolition site. Nevertheless, the reusable percentage can range from 50 to 90% [24,25]. Different reusable percentages of ACPs are examined with a sensitivity analysis to confirm the suitability of this scenario. The results are shown in

Table 3. C/B ratios of the repurposing scenario with different ACP reusable percentages.

Reusable Percentage (%)	Cost	Benefit	C/B Ratio
50	168,499.36	124,654.27	1.35
70	158,856.74	168,166.39	0.94
90	145,954.7	211,678.47	0.69

. The results show that the reusable percentage of ACP waste highly affects the C/B ratio. In this study, at least 70% of ACP waste should be considered in the end-of-life management process to achieve economic benefits. The results reveal the importance of the demolition and material handling practices to maximize the ACP recovery rate.

5.3. The Use of KM to Integrate the Repurposing Scenario with LEED Certification

The repurposing scenario is further mapped with the materials and resources section of LEED certification using various KM activities.

• The group meetings summarize details of the selected repurposing scenario to pinpoint key cost- and benefit-related activities.
• Data from this scenario are shared between team members using Google Docs and updated regularly.
• Meetings with contractors are organized to finalize the selected scenario. Team members share experiences from past projects regarding LEED certification to set action plans for certification. Tentative action plans are checked with the LEED criteria to ensure their integrity and the possibility of implementation.
• The analysis steps and results are shared between stakeholders and stored in the project’s files for future reference.

Table 4. Mapping the repurposing scenario with the LEED criteria (MR credits).

Credit	Detail	Explanation	Supported by the Repurposing Scenario?
1	Building lifecycle impact reduction	Up to 5 points could be earned through one of four options—reuse of building elements, renovation, historic building preservation, or whole-building LCA—with ≥ 20% reduction in global warming potential and ≥ 10% reduction in two other impact categories.	No (only 1 point could be earned from reusing 70% of ACPs as signboards in renovations).
2	Environmental product declarations (EPDs)	Up to 2 points could be earned: 1 point for using at least 20 products with EPDs and one additional point for optimization.	No: ACPs do not come with EPDs unless newly purchased.
3	Sourcing of raw materials	Up to 2 points could be earned: 1 point for using at least 20 products with recycled, reused, or certified content; 1 additional point for optimization.	Yes: Repurposed ACPs are counted as reused materials. If their cost is documented, they could contribute toward the 25% threshold by cost.
4	Material ingredients	Up to 2 points could be earned: 1 point for using at least 20 different permanently installed products from at least five manufacturers; 1 additional point for material ingredient optimization.	No: Repurposed ACPs lack ingredient disclosure documentation.
5	C&D waste management	Up to 2 points could be earned by diverting ≥ 50% or ≥75% of C&D waste from landfills, with no material stream minimum required.	Yes: ACP waste used as signboards diverts up to 70% of C&D waste from landfills through repurposing.

shows the results of the brainstorming meetings. It shows the preliminary steps toward green certification by implementing the repurposing scenario.

Although ACP waste represents a small percentage (i.e., 0.5% of the total waste or 3.5% of architectural materials), its end-of-life management through repurposing plays a crucial role as an example of sustainable waste management onsite, considering economic, environmental, and social perspectives. It may be used as a guideline for other types of demolition waste to proceed to certification.

6. Conclusions

Improper C&D waste management poses several impacts on the environment. Many types of waste should be recovered, processed, and used as second-life products to achieve sustainable development and gain green recognition. This study focuses on recovering ACP waste, previously used as facades in an old public sector building. Four scenarios for end-of-life management are considered: reselling (as is), refurbishing, repurposing, and landfilling. Cost and benefit data related to economic, environmental, and social perspectives are input into the CBA to rank the most suitable scenarios. The results reveal that the repurposing scenario is the only scenario with a C/B ratio of less than 1 (i.e., total cost less than total benefit), confirming its suitability for implementation. The greatest benefit is from using repurposed ACPs as signboards in the new building, while materials contribute the highest cost portion of this scenario. Closer examination reveals that fuel depletion is a significant concern from an environmental perspective. This is because Thailand still relies heavily on fossil fuels for electricity generation. Increasing the portion of renewable energy in power generation may further improve the feasibility of this scenario.

In contrast, the C/B ratio of the refurbishing scenario is slightly over 1 (i.e., 1.12), making it unfavorable in implementation. Reducing the labor costs in this scenario may assist in lowering the C/B ratio. The results show that the current ACP waste practice (i.e., the reselling scenario) is not recommended, although it is a quick and easy method to manage C&D waste. This is due to a huge opportunity loss from material recovery. Lastly, landfilling is the worst scenario, does not generate any benefits, and may pose several long-term environmental problems and health risks to nearby communities.

A sensitivity analysis was conducted by varying the reusable percentages of ACP waste in the repurposing scenario. The results reveal that high recovery rates bring better C/B ratios, pinpointing the importance of the ACP dismantling process to support end-of-life management.

• This study contributes to the body of knowledge as follows:
• The study integrates the use of KM into C&D waste management, making it effective for sustainable planning and development.
• Several scenarios are proposed for waste management. The results are presented by C/B ratios, making them easy to understand and facilitating planning for implementation.
• This study’s cost and benefit data cover the economic, environmental, and social perspectives, representing a complete sustainability concept.
• The selected end-of-life management scenario is mapped with the LEED criteria—specifically the MR credits—guiding the preliminary steps toward green certification.

There are limitations and recommendations for future studies. The primary data were from interviews and site observations of an old public sector building renovation. In contrast, the secondary data were from the literature, not specifically reflecting the Thai context. Primary data collection from second-hand shops, facilities, and landfills may enhance the data accuracy. Future studies are recommended to examine the complex relationships between the cost and benefit data and develop models that can capture changes in data in a dynamic environment. ACPs have a wider range of applications, such as rooftops, tabletops, wardrobes, and mosaics, which can be explored in future studies. The engineering properties of demolition waste may be examined utilizing various methodologies [104].