A BIM–WMS Management Tool for the Reverse Logistics Supply Chain of Demolition Waste

Abstract

In the construction industry, the reverse logistics supply chain (RLSC) is one of the measures used to effectively manage demolition waste. However, there are still many problems associated with its operation, including inaccurate calculation of demolition waste supplies and insufficient interaction between supply and demand information, and waste suppliers usually choose transportation alternatives associated with high carbon emissions to obtain economic benefits. These issues have hindered the sustainable development of the RLSC. This paper proposes a waste recycling facility selection system (WRFSS) that integrates building information modeling (BIM), web map service (WMS), and an application programming interface (API) plug-in. Compared to the actual transportation scenario, the transportation distance of the WRFSS was reduced by 30.6 km and the amount of carbon dioxide emissions were reduced by 0.0259 tons. This selection system realizes an optimal selection mechanism for waste recycling facilities and develops the shortest transportation plan, thereby reducing carbon emissions during transportation and achieving sustainable development.

1. Introduction

The RLSC is considered a useful management tool that enables a large amount of demolition waste to be recycled rather than simply disposed of [1]. In reverse logistics, materials are transferred to recycling parties after their original use value has been exhausted to retain their value [2]. As a result of its high efficiency in recycling resources, this technology is widely used.

However, there have been some problems with the use of the RLSC in the construction industry. First, the demolished volume (expected quantity) is usually determined by constructors using their experience or visual estimation, which may create significant errors in supply and demand information. Second, there is no effective information integration mechanism for recycling facilities in RLSC operations, with waste suppliers cooperating with waste recycling companies only via phone or network within their social scopes, but this match between supply and demand information is one-sided and information is not sufficiently exchanged. Additionally, with the renewal of cities, the amount of greenhouse gases generated by waste transportation is no longer negligible [3].

Recently, several major considerations in the management of the RLSC have emerged, including the calculation of construction and demolition waste (CDW) production, route planning for landfill, and reuse of CDW. Recent studies have used BIM technology to measure the production of CDW [4,5,6], and different types of elements have been identified and classified within the BIM model. Then, the corresponding algorithms are used to predict waste production. When compared to traditional waste management methods, the use of BIM technology can result in a cost reduction of 57%. According to Ge et al. [7], drones and cameras can be used to photograph the building, and then, 3D point cloud images are used to reconstruct the BIM model in order to estimate the quantity of construction waste more precisely. Furthermore, the concept of the nD-BIM model has been proposed as the application of the BIM functionality deepens, and more and more factors are being considered as a part of a BIM model, such as cost management, equipment management, the sustainability plan (construction waste reuse plan) [8,9,10], greenhouse gas emissions, and route planning [11,12].

Despite extensive research into the BIM-based RLSC, there still remain some issues that require further investigation. First, most studies focus only on the prediction of CDW and do not consider the management of both upstream and downstream companies in reverse logistics as a whole, such as the flow of information along the entire supply chain. Second, BIM and WMS are used separately in the construction field, with no direct connection between them. Through the integration of BIM and WMS development via API, the management process for the RLSC can be fully automated. Third, there is lack of consideration of sustainable development of RLSC management, meaning that a decision tool is needed to consider carbon emission, economic benefit, distance, and time.

According to the analysis above, this study applied BIM and WMS technology to develop a waste and recycling facilities selection system (WRFSS). Through the implementation of this WRFSS, a transportation plan with the shortest transportation distance between demolition waste and recycling parties was developed. This system is based on BIM–WMS technology and provides timely and accurate information on demolition waste, transportation costs, carbon emissions, and waste recycling prices. Then, the corresponding economic benefits and carbon emission data were calculated, providing information technology support for building demolition projects. In addition, this system can assist government departments in collecting and managing information related to demolition waste. This paper consists of six parts: (1) an introduction of the concepts related to the RLSC for demolition waste; (2) a literature review of related research; (3) development of the BIM-WMS model; (4) development of the WRPSS; (5) validation of the developed system by a case study; and (6) conclusion and discussion.

2. Literature Review

2.1. Research on Demolition Waste Management and Disposal Methods

The U.S. Environmental Protection Agency (EPA) defines CDW as “waste from the construction, renovation, repair, and demolition of buildings.” Demolition waste needs to be sorted first and then disposed of in different ways, depending on the type of demolition waste. Normally, demolition companies use mobile shredding equipment to crush buildings on construction sites [13]. They then sort and collect different types of waste including recycled concrete aggregates, recycled steel, and disposed waste by manual work or with machines, after which, the demolition waste that meets the standard is transported to recycling companies, road base projects, reclamation depots, etc. [14].

To estimate the volume of CDW, Lu [15] divided construction-related waste into three categories according to the type of construction activity: construction, demolition, and decoration waste. To estimate the total volume of urban CDW, the corresponding floor areas of three different types of construction activities are multiplied by the waste generation index.

In real demolition projects, inert waste is usually pre-stacked, transported, and reprocessed centrally; however, a disposal model does not permit an accurate classification of demolition waste. Meanwhile, the measured concrete or brick production does not provide much information to demolition companies. Therefore, if inert waste is categorized according to the types of waste recycling companies at different disposal sites, it will provide valuable information on the expected quantity of demolition facilities.

2.2. RLSC in the Architecture, Engineering, and Construction (AEC) Industry

According to Govindan [16], in a typical forward-logistics supply model, the disposal of products at the end of their life cycle is not considered, which is not conducive to resource sustainability. Thus, he proposed the concept of a “closed-loop” supply chain and introduced the concept of reverse logistics into the field of logistics engineering [17]. Unlike forward logistics, reverse logistics involves the recycling, remanufacturing, and disposal of a wide range of waste products, as well as collection, storage, transportation, and other logistics activities [18]. The emergence of reverse logistics (RL) has provided a cost-effective solution for waste recycling [19]. The RLSC can efficiently recover and reprocess demolition waste. As soon as a building has been demolished, the demolition debris is sorted and segregated at the construction site. Different grades of waste are then sent to landfills or secondary markets after testing and grading by machines or human work [20,21].

The potential to optimize and promote the sustainability of products has led to the application of RLSC engineering in the construction industry. A quantitative model has been proposed to describe the factors influencing the RLSC [22]; through a regression analysis based on the structured equation modeling analysis technique, all potential influencing factors are ranked in terms of importance, allowing practitioners and researchers to determine the degree of influence of different factors on the RLSC in the construction industry. The importance of reverse logistics and what factors influence its implementation has been emphasized in most studies. However, few studies have been conducted to reduce the transportation cost and carbon emissions of the RLSC from a practical perspective.

2.3. Application of Information Technology in the RLSC

With the introduction of BIM and green buildings (GB), more practitioners have chosen information technology to achieve sustainable development in the ACE industry [23,24]. Wu et al. [25,26] optimized the floor tile layout workflow by combining building information modeling (BIM), parametric design (PD) methods, and optimization algorithms to achieve a reduction in construction waste production.

Traditional reverse-logistics methods are inefficient in terms of construction engineering. It has been suggested that waste management is not well integrated with the information flow, which leads to fragmentation and uncertainty in the infrastructure, and the use of information technology can facilitate innovation and intelligence in RLSC operations [27]. To manage reverse logistics, a well-organized and well-subscribed repository of information should be established [1]. Yu et al. proposed a model based on the waste generation rate (WGR) and cross floor area (GFA) to predict the demolition waste production in the urban renewal process. The WGA was calculated via on-site measurements and existing industry standard data, while the GFA was obtained by image recognition technology and Google Earth [28]. Cheng et al. developed a BIM-based web services framework, which implements three important functions related to green building design: energy simulation, code checking, design, and updating the building model. It also integrates the information required for green building design, automates the assessment of building designs, and enables effective information exchange among stakeholders.

BIM and WMS technologies can integrate the required information effectively, such as determining the amount of waste to be recycled and planning transportation routes [29]. Based on web service APIs and BIM, Li et al. developed a tool to evaluate publicly available diverse uses and transportation that fulfills the “Access to Quality Transit and Diverse Uses” criterion in LEED v4 [30]. A conceptual model has been proposed that effectively addresses the information needed for demolition waste after its dismantling, testing, grading, and reprocessing [4]. A decision support tool has been developed to meet the needs of different construction departments by integrating WMS and BIM technologies [11]. This tool was developed as a BIM-integrated plugin to select the source of construction materials by measuring and comparing the cost of different materials, delivery times, and location-related credits in some green building standards. The majority of studies have employed BIM technology to obtain accurate predictions of demolition waste through the automatic extraction of materials and automatic calculation of waste generation. There are also studies utilizing WMS technology to select construction materials. However, few scholars have applied WMS technology to the RLSC in the construction industry to provide more accurate traffic information and route-planning solutions for demolition waste.

2.4. Carbon Emission Study of the Transportation Industry

Currently, automobiles are one of the largest sources of greenhouse gas emissions. In 2019, the transportation sector contributed 24% of the global carbon emissions, making it the second-largest source of emissions in the world. China’s transportation sector accounted for 18% of the country’s total carbon emissions in 2018, making it one of the top three contributors [31]. In Japan, 17.9% of the carbon dioxide emissions originate from the transportation sector, with 86.2% coming from passenger vehicles [32]. Li et al. [33] investigated the carbon emissions of the transportation industry in 30 Chinese provinces from 2005 to 2019, using the Tapio decoupling index mode to synthesize the demographic, economic and social factors and derive the impact of these factors on carbon emissions. He proposed that when the energy efficiency is below the threshold of 473,000 yuan/t, carbon emissions are reduced by 0.818% for every 1% increase in energy efficiency. When the energy efficiency is higher than the threshold value of 473,000 yuan/t, a 1% increase in the energy efficiency results in a 0.926% reduction in carbon emissions. Wang et al. [34] used the spatial analysis module of ArcGIS (Geographic Information System) software to predict the trends of CO₂ emissions generated by major transportation modes (electric motors, buses, and cars) in major cities in China and India. He concluded that with the current growth rate of CO₂ emissions in Xi’an, the total emissions of electric motors, buses, and cars will increase from 135 × 10⁶ t in 2012 to 961 × 10⁶ t in 2030.

According to the International Energy Agency, each liter of gasoline produces 2.348 kg of carbon dioxide, and, as vehicle emission standards vary from country to country, this study assigned carbon dioxide emissions per liter of diesel as 2.7 kg/L. Because of the introduction of a carbon emissions index, transportation alternatives can be assessed more intuitively in terms of their contribution to carbon emission reductions [35]. The above literature indicates that CO₂ emissions from transportation cannot be ignored and must be considered in the RLSC management.

3. Methodology

With the integration of WMS, BIM technology, Revit secondary development, and other related technologies, this model provides the basis for comprehensive research on the use of information technology, the improvement of supply and demand information, and optimal path planning.

3.1. Application of BIM Technology to Calculate the Demolished Volume

3.1.1. Calculation Method for the Waste Generation Rate

Currently, demolition waste is transported to mobile shredding plants or recycling companies for reprocessing. Before a building’s main structure is dismantled manually or mechanically, non-inert construction waste that is easier to recycle, such as glass, metal, wood, plastic, and paper, is already disposed of at the appropriate waste and recycling facilities. Therefore, this study only considered the main structure of the building, including the walls, floor slabs, and stairs in the building structure, which is directly crushed by the demolition company at the construction site, and then transported to recycling enterprises or shipped to the road paving projects for backfilling according to the grade of the salvaged materials. In this model, demolition companies process waste to produce recycled coarse and fine aggregates to be delivered to municipal roads or recycling facilities, and waste that does not meet the standard is transported to landfills. Currently, there is no calculation formula available for specific waste types, particularly for types of waste that are used by waste recyclers, such as recycled coarse and fine aggregates and inert waste. This paper employed a questionnaire to collect data from demolition companies utilizing mobile shredding equipment, as well as stakeholders related to demolition waste.

Table 1. Respondents’ positions and types of business.

Interviewee Numbers	Organization	Total Employees	Registered Capital (CNY)	Assets	Role	Years of Experience	$\mathbf{Production} \mathbf{Factor} \left({\mathit{R}}_{\mathit{r}\mathit{a}}\right)$
4	Demolition company	143	30,000,000	6 mobile shredding plants; 15 transport vehicles	Project Manager	15–25	60%
16	Demolition company	40	20,000,000	15 excavators; 10 transport vehicles	Demolition Worker	10–15	70%
6	Salvaging company	88	1,000,000,000	2 recycling centers; housing estates	General Manager	20–25	63%
5	Landfill	25	37,847,500	5 excavators; 4 crushing machines; 4 compactors; 1 garbage classifier	Manager	20–23	\
5	Reclamation depot	8	300,000	1 steel bar bender; 1 steel bar shearing machine; 3 transport vehicles	Worker	10–15	\

shows the profiles of the selected interviewees.

In order to obtain the production factor of standard-compliant recycled coarse and fine aggregates ($R_{ra}$) for brick and mortar building structures, because of the differences in building structure, demolition methods, and building types, the $R_{ra}$ values ranged from 60% to 70% in this study Consequently, an equation for calculating the supply of recycled coarse and fine aggregates ($V_{ra}$) required for demolition waste disposal sites was developed [4]:

$$V_{ra}={\varnothing }_v\times V_t\times R_{ra}$$

(1)

where $V_t$ is the total volume of the masonry, ${\varnothing }_v$ is the coefficient of change in the volume of the demolition waste (

Table 2. Volume change factor for construction and demolition wastes.

Types of Materials	$\mathbf{Coefficient} \mathbf{of} \mathbf{Volume} \mathbf{Change} \left({\varnothing }_{\mathit{v}}\right)$
Concrete; masonry; cement	1.1
Steel	1.02

), and $R_{ra}$ is the production factor.

Additionally, an equation for calculating the supply of residual inert waste $(V_r$) required by recycling companies was established.

$$V_r={\varnothing }_v\times V_t-V_{ra}$$

(2)

Finally, an equation was developed to calculate the total mass of scrap rebar ($M_s)$ required at the reclamation depot:

$$M_s=V_s\times {\rho }_s$$

(3)

where $V_s$ is the total volume of the actual scrap steel in the demolished building, and ${\rho }_s$ is the density of the scrap steel. Based on the above equations, a theoretical basis for calculating waste supply could be established, and the validity of the formula was verified in a test case.

3.1.2. Application of BIM to the Calculation of Demolished Volume

The actual volume of masonry from a demolished building must be determined to calculate the amount of recycled coarse and fine aggregates. Additionally, the model utilizes Dynamo visual programming to extract building material information and calculate the demolished volume, as shown in Figure 1.

The first stage was demolition of the building. A BIM model can extract information related to reprocessed materials (concrete and steel) required by recycling enterprises or reclamation depots, and parameters related to the component volume can be extracted by invoking material takeoff schedules. Moreover, the components in each Revit family are organized into three categories in Dynamo: “volume of recycled concrete aggregate,” “volume of disposed waste,” and “weight of recycled steel”. In the second stage, according to the information extracted from the material takeoff schedules, three categories of materials are calculated using Equations (1)–(3). In the third stage, Dynamo imports the calculated demolished volume into a specified Excel file to display the results.

To achieve the function of extracting waste supply into Revit, the Dynamo file of the waste supply extraction function is integrated with the Ribbon UI command button utilizing the Revit API (Figure 2), thereby facilitating the use of its function by users. To calculate the amount of demolished waste, the Ribbon button can be used with the External Tools in Revit’s Add-in module.

3.2. Application of WMS Technology in RLSC Operation

In this section, WMS technology is used to obtain RLSC information, comprising driving distance, driving time, and path identification from the demolition project site to waste and recycling facilities (demand side). Baidu Maps serves as the provider of WMS technology, owing to its localization advantage, and a web browser such as Internet Explorer is utilized to implement the path planning functionality, which requires users to input initial information about their starting point to complete the process. With the application of WMS technology, path planning solutions can be acquired from demolition project sites to multiple waste and recycling facilities. Baidu Maps JavaScript API provides three interfaces: DrivingRoute, DrivingRouteResult, and RoutePlan. DrivingRoute is used to obtain a driving route plan, DrivingRouteResult is used to display the route navigation results, and RoutePlan is used to display a driving, walking, or cycling route plan. To obtain information on the route planning of the demolition waste supply, the three interfaces enable research on the routes between the demolition project site and the demand sides and provide information such as traffic route planning, driving distance, and time. Finally, by integrating the theory of the BIM API with the WMS API, the supply of demolition waste, route planning, and corresponding traffic route information can be calculated and displayed.

4. The BIM–WMS-Based Waste and Recycling Facilities Selection System

4.1. Analysis of the WRFSS Requirements

In the RLSC of demolition waste, due to the problems of closed supply and demand information flow and a single mechanism for selecting waste and recycling facilities, waste suppliers may decide to illegally dump or landfill demolition waste, or choose transportation routes with high economic benefits, but higher carbon emissions. Through the use of information technology, this study was able to optimize the RLSC of demolition waste, streamline the internal flow of information regarding supply and demand, and find an optimal path for transportation.

BIM and WMS technology provides waste and recycling facilities with information on demolition volume, route planning, and transportation distance. The matching of supply and demand information and the shortest path are used as constraints to form an optimal selection mechanism. Finally, this study concludes that the key tasks for each stage of WRFSS are:

• During the supply allocation stage, the demolished volume generated at the demolition site should be assessed.
• During the identification of the demand-side information stage, information about the demolished volume of the demand-side, transportation distances, carrying capacities of the transport vehicles, transport costs, and prices of waste recycling should be collected from each waste and recycling facility.
• During the decision-making stage, the supply and demand information, as well as the optimal transportation path, should be considered as constraints to select waste and recycling facilities with the shortest driving distance and demand requirements.

Based on the above mechanisms, this chapter clarifies the functional requirements of waste recycling party selection and establishes the workflow of the WRFSS based on BIM and WMS.

4.2. Development of the BIM-WMS Plug-in

To realize human–computer interaction between the supply and demand information matching function and the geospatial information query function, the system requires a medium that can combine the demolished volume by the BIM model, demand information, transportation cost, and recycling price information with the driving distance information obtained through WMS. Then, human–computer interaction is accomplished through the use of the Winform graphical user interface (GUI). Moreover, WMS is integrated with BIM to develop prototype software and add a plug-in through the Revit API.

4.2.1. Functional Modules and System Chart

To obtain an optimal transportation plan for waste, the supply of demolition waste and the demand for salvaged materials are matched based on the functional requirements of the WRFSS, while using WMS to obtain information about driving distances. To achieve its functions, the system consists of three main functional modules (Figure 3).

BIM Module

Dynamo is used to extract the data from the BIM model. As shown in Figure 4, the Categories block and the All Elements of Category component are used to select the target elements. Then, the GetParameterValueByName block is used to extract the value of the element’s volume. To determine the actual total volume of inert waste, all parameter columns are summed using the Math.Sum block. Then, the supply function of recycled coarse and fine aggregates is set through the Code block. Finally, the corresponding data are imported into an Excel table (Figure 5) through the Excel.WriteToFile block to realize automatic extraction of the demolished volume.

WMS Module

WMS technology is used to obtain transportation information, which includes the shortest driving distance, driving time, and path identification from the demolition site to the recycling facility (demand side). With the three interfaces of DrivingRoute, DrivingRouteResult, and RoutePlan provided by the Baidu Maps JavaScript API, the path search from the demolition project site to the demand party can be realized. Additionally, the path planning function from the demolition project location to multiple demand parties is developed by cyclically executing the search method within the DrivingRoute interface, resulting in a path planning function from the demolition project location to multiple demand parties.

Transportation Module

The demolished volume is matched with the demand information, the demander with the shortest transportation distance is selected, and the economic efficiency and carbon emissions are calculated based on the solution.

The program block diagram of the WRFSS obtained by integrating the three modules above is shown in Figure 6.

Step 1:

After the BIM model is constructed, the Revit API is used to calculate the volume of recycled concrete aggregate and recycled steel; then, the expected volume is used as input information for the next step.

Step 2:

The location of the demolition site and the demolished volume are input into the WRFSS, and the information about the waste and recycling facilities is imported to an Excel sheet. The WMS engine is then used to match the route from the project site to the demanders.

Step 3:

Path matching is performed using the shortest path as the constraint, and a combination of waste and recycling facilities that can fully accept the waste supply is screened. The transportation route for each demand facility is displayed on the map layer according to the screened supply solution, and the results are listed in a table.

Step 4:

The selection of transportation vehicles, such as the type and capacity of trucks, may result in different transportation paths, costs, times, and carbon emissions. Two stages are involved in the transportation of demolition waste. In the first stage, the trucks transport debris to the waste and recycling facilities, while in the second stage, the trucks return to the demolition site without any debris.

Step 5:

According to the transportation scheme, the total transportation cost can be calculated and the volume of renewable concrete aggregates or the weight of recycled steel obtained from the BIM model is combined with the price of waste recycling to determine revenue. Subsequently, the comprehensive cost and carbon emissions are calculated.

5. Test Case

5.1. Description of the Demolition Project

In this study, a self-built brick house Revit model was used as an engineering example to demonstrate the effectiveness of the WRFSS. The superiority of the developed model was verified by comparing two options.

Scenario 1: The actual transportation route.

Scenario 2: The shortest transportation route.

To obtain an accurate total volume of a multi-story masonry building, only the major structure of the existing building was included in the model, as detailed in the following building information:

The construction area of this three-story brick building was approximately 411 m² composed of brick walls, structural columns, ring beams, and hollow floor slabs. Based on the statistics of the waste transport company and reclamation depot, the volume of inert waste from the demolition of the building (bricks and concrete) was approximately 253 m³, of which approximately 167 m³ could be processed into recycled coarse and fine aggregates, while the rest of the inert waste was approximately 86 m³ and 5.42 tons of scrap steel.

5.2. Applications of the WRFSS

5.2.1. Calculation of the Demolished Volume

To calculate the demolished volume of the brick building, component information was extracted from the BIM model using the Revit plug-in and then the data were imported into an Excel file. The table represents the extraction results of the waste supply to the resource utilization company, landfill, and reclamation depot, respectively. As shown in

Table 3. Comparison results between the BIM model and actual project.

	Demolished Volume (BIM Model)	Demolished Volume (Actual Project)	Relative Error
$\mathrm{Supply} \mathrm{of} \mathrm{recycled} \mathrm{coarse} \mathrm{and} \mathrm{fine} \mathrm{aggregates} ({\mathrm{m}}^3)$	153.47	167	8.10%
$\mathrm{Supply} \mathrm{of} \mathrm{inert} \mathrm{waste} ({\mathrm{m}}^3$)	83.37	86	3.06%
Supply of scrap steel bars (t)	5.28	5.42	2.58%

, the demolished volume of recycled concrete aggregate was 153.47 m³, the volume of disposed waste was 83.37 m³, and the weight of recycled steel was 5.28 t. Subsequently, the extraction results were input into the WRFSS.

5.2.2. Results of the Transportation Scenarios

Scenario 1:

In the actual project, demolition waste suppliers took the transport solution with the greatest economic benefit, as shown in Figure 7. The Chinese characters in Figure 7 are landmark information of Yue yang City, Hunan Province, China. The green circle icon of the map is the start point of the transportation path, and the red circle icon is the end of the transportation path.

According to the results of scenario 1, the total distance of transportation was 252.4 km, the total transportation cost was USD 344.68, the economic benefit was USD 1847.26, and the total carbon emissions were 0.2342 tons.

Scenario 2:

The results matched by the WRFSS are shown in Figure 8. The Chinese characters in Figure 8 are landmark information of Yue yang City, Hunan Province, China. The green circle icon of the map is the start point of the transportation path, and the red circle icon is the end of the transportation path.

According to the results of scenario two, the total distance of transportation was 221.8 km, the total transportation cost was USD 305.41, the economic benefit was USD 1681.86, and the total carbon emissions were 0.2083 tons.

5.2.3. Analysis of the Results

The WRFSS involves a multi-objective decision problem, which takes into account both supply and demand information pairing and the physical distance between the suppliers and the demanders. BIM and WMS technologies can provide sufficient information for RLSC management in order to assist in the selection of waste recycling parties. Based on the results in Table 3, the relative error between the waste supply extracted by the BIM API and the actual waste supply did not exceed 10%, indicating that the error between the supply extracted by the BIM model and the actual supply was relatively small. Consequently, the production of recycled coarse and fine aggregates for brick structures and related calculation formulas are applicable and valid.

Furthermore, based on the developed plugin, the results of the evaluations of both transportation options are shown in

Table 4. Transportation results of the WRFSS and actual project.

Transportation Scenario	Demanders	Total Driving Distance (km)	Carbon Emissions (t)	Supply (m3)	Economic Benefit (USD)
Actual scenario	Landfill(A)	105.6	0.0998	83.37	1816.31
WRFSS	Landfill(A)	105.6	0.0998	83.37	1816.31
Actual scenario	Company(G) Company(J) Company(A)	41.4 44.8 52	0.0391 0.0423 0.0491	55.00 49.00 49.47	1099.77 1249.14 1247.59
WRFSS	Company(G) Company(H) Company(I)	41.4 34.8 37.2	0.0391 0.0329 0.0352	55.00 49.00 49.47	802.77 796.19 817.13
Actual scenario	Reclamation depot(G)	8.6	0.0039	5.28 (ton)	10,642.59
WRFSS	Reclamation depot(A)	2.8	0.0013	5.28 (ton)	10,543.91

. The distance of the WRFSS transport was reduced by 30.6 km (12%) and the amount of carbon dioxide emission was reduced by 0.0259 tons (11%). The above data indicate that the WRFSS played a significant role in reducing carbon emissions during transportation. However, at the same time, the economic benefit of the WRFSS decreased by USD 165.4. The WRFSS reduced the carbon dioxide emissions by reducing the transportation distance, thus contributing to carbon neutrality and achieving carbon peak targets. However, the primary goal of construction companies is to pursue higher economic interests [30], and they are more concerned about the economic gains of the company than about the social and environmental impacts [31]. As the price of material recovery varies, the reduction in transportation costs and distance does not necessarily equate to an increase in economic efficiency on the supply side. Instead, the economic benefits could be reduced, causing waste suppliers to choose disposal options that require greater transport distances and generate higher carbon emissions, or even illegal dumping or landfilling of demolition waste. Therefore, to achieve green development of the RLSC of demolition waste, government departments can either increase the recycling price of waste by increasing the recycling subsidy of demolition waste or subsidize the transportation fee for the shortest transportation scheme in order to reduce transportation costs, so as to achieve a balance between the economic benefits and carbon dioxide emissions.

6. Discussion

6.1. Application of the WRFSS in Demolition Waste Management

Transportation is an important factor in RLSC management. The WRFSS has made a great contribution to the integration of information from upstream and downstream enterprises, the estimation of demolition waste, vehicle tracking, and route planning. The user group of the WRFSS includes project managers and managers of resource recovery companies and managers of transport vehicle companies. At the current stage, the WRFSS only considers truck transportation; if Baidu Maps can incorporate air and sea transport into the model and add their carbon emission calculation models to the WRFSS [36,37], it can further extend the scope of model coverage.

Furthermore, this paper only considered the main structure of the building, including the walls, floor slabs, and stairs in the building structure because of their difficulty in recycling and resource utilization. However, other parts of the building can also be considered in future research, including plumbing and wiring lines, heating ducts, and other demolition waste. In the future, the carbon pricing mechanism can be applied to the transportation of demolition waste, and a carbon tax can be introduced to increase the marginal cost of waste transportation [32] to accomplish the aims of not only meeting the economic needs of the waste supplier and avoiding illegal dumping, but also achieving savings in energy and carbon emissions.

6.2. Application of the RLSC for Demolition Waste

In recent years, RLSC management has been divided into three operation modes: self-built, associates, and outsourcing reverse logistics from the perspective of construction enterprises [38]. Its main participants include construction material suppliers, construction waste recycling and treatment enterprises, logistics enterprises, and construction enterprises. The self-built model refers to a construction enterprise’s own construction waste reverse logistics recycling system, which only serves the enterprise’s own construction waste recycling business. The associates mode refers to two or more related enterprises, which, through certain agreements of cooperative operation, set up a complete demolition waste reverse logistics system to provide reverse logistics services for cooperative or non-cooperative enterprises. The outsourcing model refers to the contracting of a construction enterprise to assign part or all of its demolition waste recycling work to an enterprise specializing in logistics activities. The characteristics of the three operation modes are shown in

Table 5. Comparison of three management modes.

	Self-Built	Associates	Outsourcing
Logistics cost	Highest	High	Low
Professionalization	Low	Middle	High
Information feedback	Quick	Slow	Extremely slow
Financial risk	High	Middle	Low

.

The three different modes of RLSC management have their own advantages and disadvantages, such as the slow rate of information feedback in the associates and outsourcing mode, and the high logistics costs in the self-built and associates mode. With the introduction of the WRFSS, different management modes can be greatly improved. For example, through the WRFSS, a platform can be established so that the relevant companies in the associates and outsourcing mode can track the progress of logistics in real-time. Meanwhile, through BIM technology, project managers of construction companies can also estimate the amount of demolition waste generated in advance to verify the cost and supply chain management plan. All WRFSS users can work in the following ways: Architects can use the BIM tool to model demolished buildings accurately; project owners and/or project managers can use the BIM–WMS tool to estimate the amount of demolition waste generated in advance and enter the amount of demolition waste, project location, etc. into the WRFSS system for matching; the manager of recycling facilities can provide data related to material or resource requirements, location, cost, transportation methods, etc.; the government can collect data on reverse logistics operations through the WRFSS platform and can improve the sustainability of reverse logistics service providers, etc., through policies and other means.

7. Conclusions

This study provided a new way of thinking for research on the optimization of the RLSC for demolition waste, innovatively integrated BIM and WMS technologies with information on supply and demand, transportation costs, and recovery prices of waste, and then constructed a BIM-WMS-based waste recycling facility selection system. With the use of BIM technology, the BIM model of demolished buildings was used as a source of information about waste supplies, and a waste extraction model was developed to estimate the various demolished volumes produced by demolished buildings. The information extracted on a single platform can help dismantle planners and recycling companies to design downstream operations. In addition, WMS technology was used to obtain information about the shortest paths (path planning, distance, and driving time) between supply and demand. The selection system realizes an optimal selection mechanism for waste recycling facilities and develops the shortest transportation plan, thereby reducing carbon emissions during transportation, optimizing the RLSC for demolition waste, and achieving sustainable development.