Abstract
The construction sector in Europe is among the biggest waste generators, producing 370 million tonnes of construction and demolition waste (CDW) every year, which contain important secondary materials. Quantification of CDW is important from their circular management and environmental impact point of view. Thus, the overall objective of this study was to develop a modelling methodology for estimating demolition waste (DW) generation. The volumes (m3) of individual construction materials contained in 45 residential buildings in Greece were accurately estimated using computer-aided design (CAD) software and the materials were classified according to European List of Waste. These materials will become waste upon demolition, with a total estimated generation rate of 1590 kg m−2 of top view area and with concrete and bricks representing 74.5% of total. Linear regression models were developed to predict the total and individual amounts of 12 different building materials based on structural building characteristics. To test the accuracy of the models, the materials of two residential buildings were quantified and classified and the results were compared with the model predictions. Depending on the model used, the % differences between models’ predictions and CAD estimates for total DW averaged 11.1% ± 7.4% for the first case study and 2.5% ± 1.5% for the second. The models can be used for accurate quantification of total and individual DW and their management within the framework of circular economy.
Keywords
Introduction
Quantification of construction and demolition waste
Over the last years, many countries around the world (e.g. European Union (EU), China, Japan, Canada, UK) have promoted the circular economy (CE) as the only sustainable economic system (Korhonen et al., 2018). The three basic pillars of CE are the economy (e.g. less use of raw materials, energy saving), society (e.g. new employments) and environment (e.g. less waste, reduced carbon dioxide emissions, preservation of the natural resources) (Saidani et. al., 2017). For this purpose, EU adopted plans to transform into a CE society and identified construction and demolition waste (CDW) as a priority waste stream (European Commission, 2015). Over the last years, EU implemented many actions and set targets to improve the management of CDW. The Waste Framework Directive 2008/98/EC (Vardopoulos et al., 2021; Zorpas and Lasaridi, 2013) introduced the waste hierarchy and was amended by Directive (EU) 2018/851 strengthening the transition from a linear to the CE model, which would close loops by applying reduce–reuse–recycle activities, thus preventing the generation of wastes and converting them into resources (Zhang et al., 2022). However, the transition to the CE model does not prove to be easy, as there are still several obstacles until it can be fully adopted. Oluleye et al. (2022) classified those obstacles into seven categories and considered governments, industry, media and institutions responsible to implement the CE. Also, actions have been proposed on how to improve efficiency of CDW management and reduce disposal (Shooshtarian et al., 2022) or ways to improve the knowledge of those involved in CDW management (Pappas et al., 2022).
Construction, renovation and demolition activities are the main sources for production of the CDW, which are classified in the European List of Waste (LoW) in Chapter 17. The construction industry in EU-28 produced 372 million tonnes of CDW in 2018, representing 35.9% of total waste generated (Eurostat, 2022). CDW contain important secondary raw materials, including concrete, steel, glass, wood and bricks (Akhtar and Sarmah, 2018) that could be used to replace part of the primary raw materials in new activities, for example, in the pavement and road construction or for light reinforced sections (Puthussery et al., 2017; Tuladhar et al., 2020). They also contain materials with high market value, for example, concrete, metals, wood and ceramics (Zheng et al., 2017). Sometimes, hazardous materials (e.g. asbestos and lead-based paints) are also included in CDW that can cause health problems or release harmful substances into the environment (Kim and Yu, 2014). All hazardous materials must be recognized and removed from the waste stream, as they need special handling or treatment before CDW management (Bonifazi et al., 2019; Wu et al., 2022).
The accurate quantification and classification of CDW are of great importance, as they will provide necessary information for reuse, recycling and disposal, leading to effective circular management and utilization in individual project cases or at the regional and country levels (Wu et al., 2014). It can also be used to assess environmental impact under field conditions and emergency situations, such as after earthquakes and war. Wu et al. (2014) classified the methods that had been used for CDW quantification into six main categories: (1) site visit (Hoang et al., 2020; Lafayette et al., 2018; Poon et al., 2004), (2) generation rate calculation (Banias et al., 2011; Cha et al., 2017; Fatta et al., 2003; Lu et al., 2015; Ram and Kalidindi, 2017), (3) lifetime analysis (Huang et al., 2013; Kalcher et al., 2017; Marinova et al., 2020; Wu et al., 2016), (4) classification system accumulation (Coelho and de Brito, 2011; Kim et al., 2017; Llatas, 2011; Solís-Guzmán et al., 2009), (5) variables modelling (VM) (Kern et al., 2015, 2018; Lu et al., 2021; Teixeira et al., 2020) and (6) others (Shi and Xu, 2006), but many researchers have used a combination of two or more of the above. Another approach for the estimation of CDW is building information modelling which provides building designs and data from a project in digital form, yielding geometric and semantic information for waste quantification (Cheng and Ma, 2013; Guerra et al., 2019; Hu et al., 2022; Su et al., 2021).
The VM method can estimate CDW generation using numerous relevant variables (Wu et al., 2014). For this purpose, machine learning (ML) models, such as linear regression (LR), artificial neural networks (ANNs), decision tree and grey models (GM), have been used to quantify generation of various solid waste streams (Dai et al., 2011; Duman et al., 2019; Golbaz et al., 2019; Wei et al., 2013). Several studies also used ML models to estimate individual materials or total CDW at the project, region or country level. Supplemental Table S1 lists some of these studies and includes information about the method, the input data needed, the output and the performance of each model. These studies are summarized as follows:
Three studies (Kern et al., 2015, 2018; Teixeira et al., 2020) used LR for estimating total construction waste (CW) at the building level in Brazil.
One study (Islam et al., 2019) developed LR models for estimating total CW, total demolition waste (DW) and individual components at the country level in Bangladesh.
One study (Coskuner et al., 2021) used ANN for estimating total CDW at the country level in Bahrain.
One study (Lu et al., 2021) used different ML models for estimating total CDW at the region level in China.
One study (Song et al., 2017) created a hybrid GM-support vector regression model and estimated total CDW and seven individual construction materials at the country level in China.
One study (Cha et al., 2022) developed four different ML and hybrid ML models to quantify total DW at the building level in South Korea and compared their performance.
Two studies (Akanbi et al., 2020; Cha et al., 2020) developed ANN and Random Forest models for estimating total DW and individual components at the building level in UK and South Korea, respectively.
Based on the above and Supplemental Table S1, the LR method has not been used specifically for DW at the building level. The latter is important and useful to professional engineers and contractors dealing with management of demolition projects.
In this study, to quantify DW generation at the building level in Greece, we chose LR, which is a widely used technique for model development, based on multiple parameters relevant to the modelling objective (Abdallah et al., 2020). LR has the advantage of simple mathematics, the well-developed statistical theory (Abbasi and el Hanandeh, 2016) and does not require very large amount of data, as other methods do (e.g. ANN) (Xu et al., 2021).
Along these lines, the objectives of this study were as follows: (1) to develop LR models to estimate the individual and total quantities of 12 materials contained in Greek urban residential buildings, (2) to estimate waste generation rates upon building demolition and (3) to provide guidance using case study examples on the use of the developed models, not only for waste generation, but also for estimating recycling cost. The implicit assumption is made that the construction material contained in a building will become waste upon demolition. Actual field measurement of these materials is difficult, because of the large volumes and bulky materials being produced upon demolition. To overcome this obstacle, the volume of construction materials contained in a known geometry residential building was accurately calculated using computer-aided design (CAD) software.
The novelties of this paper are the following: (1) It uses volumes of individual construction materials contained in residential buildings in Greece, estimated by CAD software. Field measurements of these materials are difficult, time-consuming and expensive. (2) Using regression analysis, equations have been developed to predict the quantities of 12 individual materials, some of which (plaster, insulation and marble) have not been reported by previous LR studies (Islam et al., 2019). In the past, Fatta et al. (2003) estimated total CDW generation at the country level in Greece, using data from construction and demolition licenses and, later, Banias et al. (2011) developed a web-based application to estimate DW for different types of Greek buildings.
The LR models developed in this study can be used by professionals and researchers for accurate quantification of total and individual DW, which is important information in management and decision-making. These models cannot be applied for DW prediction in countries with different construction codes but the methodology developed here can be used for creating similar models.
Building construction in Greece
Estimation of DW in Greece is an interesting case study, with DW generation affected by environmental factors. Specifically, Greece is a highly seismic country and throughout history earthquakes have caused heavy damage to buildings (Riga et al., 2021). Inland areas experience low temperatures in winter and high temperatures in the summer, which affects building integrity (Papamanolis, 2005). Most urban residential buildings are multi-storey apartment buildings, containing three to five floors with basements and balconies, and the height of each floor is a little less than 3 m (Papamanolis, 2005). The regulations of building construction were established initially in 1959 with the first ‘Greek Seismic Code’, which was updated in 1984, and the most recent one in 1995. Reinforced concrete was the main construction material for the frame while bricks and plaster were used for the walls. Another important regulation in building construction was the ‘Thermal Insulation Code’ in 1979, which brought the use of thermal insulation materials to reduce energy consumption. Based on the Greek construction codes, the time period in which a building was constructed has important implications on the total quantities of materials contained into it.
Many urban areas were mostly developed between 1970 and 1990 (Theodoridou et al., 2011). In the following years, the expected gradual replacement of these buildings will generate an increased amount of DW. In 2020, Greece generated 3.4 million tonnes of non-hazardous and 0.69 million tonnes of hazardous CDW, respectively, representing 14.1% of total waste (Hellenic Statistical Authority, 2022). Regarding CDW management, Greece adopted Directive 2008/98/EC with Greek Law 4042/2012 (Vardopoulos et al., 2021; Zorpas and Lasaridi, 2013) and most recently Directive 2018/851/EU with Law 4819/2021.
Materials and methods
Data collection
The initial raw data were obtained in 2019 from the departments of urban planning of three different areas (Thessaloniki, Kavala and Xanthi) in Greece and contained licenses of buildings constructed during the period 1955–1997. This period was chosen because of the increase in urbanization after the war, which also resulted in the construction of many buildings (Zambon and Salvati, 2019).
Building licenses contained construction drawings and technical reports. A total of 45 urban residential buildings were used, and their main characteristics or parameters are presented in Supplemental Table S2. Using CAD software (AutoCAD, 2016), the three-dimensional (3D) building models were created (Supplemental Figure S1) over the period 2019–2021. Then, the volume (m3) of each component material (concrete, iron, bricks, plaster, wood, glass, ceramic tiles, insulation, roof tiles, mortar, marble and aluminium) contained in the building was calculated. It was decided to include only those building characteristics that could be more easily available in a demolition project. When a building license did not contain sufficient data (in some old building licenses, some details were missing), reasonable assumptions were made after discussion with experts in the field. For example, ceramic tiles thickness was set to 2 cm, plaster thickness on walls to 2 cm and on ceilings 1.5 cm, and for concrete reinforcement, stirrups were set with a diameter of 8 mm and spacing of 400 mm in columns and 300 mm in beams. The component materials were shown in the drawings or the technical report that accompanied the building license. Visual inspection of the buildings’ exteriors was performed before creation of the 3D models.
Regression analysis
The depended variable of the problem is the material volume and the independent variables are the building characteristics or parameters, listed in Supplemental Table S2. To examine whether correlations existed between variables, the Pearson Correlation coefficients were calculated, using the Minitab v.17 software. If the absolute value of these coefficients is close to 1, then the relationship between the two variables is strong (Edwards, 1976: 33–46). The same software was used to conduct the regression analysis. Regression models then were created to predict the amount of each construction material contained in a building (equations (1)–(12), Table 1). To select the best regression model, all the parameters were included initially in the equations. Βy sequentially dropping the non-significant terms, the simplest equations were chosen, for which the p value for each term was statistically significant (p < 0.05).
Best reduced regression models with respective code numbers and entry type according the European LoW.
The standard errors of the corresponding coefficients are in parentheses.
LoW: list of waste; MNH: mirror non-hazardous.
p > 0.05 indicates normal distribution of residuals.
Two regression equations were developed that could calculate the total amount of construction materials in a building, in m3. The first equation (equation (13), Table 1) that includes all the surfaces (total area) contained in a building (apartments, basements, common areas, balconies, terraces and foundations) and a second one (equation (14), Table 1) that is more simplified and includes only the closed interior surfaces (apartments, basements and common areas).
Results
Materials distribution in buildings
The quantification of the building materials showed that concrete and bricks contribute 74.5% by volume, with the contribution of plaster, mortar, insulation, wood, marble, ceramic tiles, iron, stone, aluminium, glass and roof tiles being less than 10% per material by volume (Supplemental Figure S2).
Supplemental Figure S3 shows the boxplots of the measured materials, except the stone. The materials originate mainly from three- to five-storey buildings and from one nine-storey building. Stone material appeared only in two buildings with stone walls. These buildings were rebuilt into pre-existing ones and kept their old walls. Supplemental Figure S3 shows that the building materials do not follow normal distribution and are strongly skewed towards higher values, as indicated by the outliers. This distribution resulted in the high standard deviations of Supplemental Table S3. The visual lack of normality was also verified by the Anderson–Darling test (Ramachandran and Tsokos, 2021).
Pearson correlation coefficients
Supplemental Table S4 presents only the statistically significant Pearson correlation coefficients. Concrete and iron coefficients were statistically significant for all measured variables. Bricks, plaster, wood, glass, ceramic tiles, insulation, mortar, marble and aluminium were not significantly associated only with the construction year, while roof tiles were statistically significantly correlated with the total area and the average area.
Regression analysis
The construction materials were classified as mirror non-hazardous according to the LoW and are presented in Table 1 with their respective LoW six-digit code numbers and the different regression equations that were developed for each material (equations (1)–(12)). For the selection of the most proper equation, the method described by Berthouex and Brown (2002) was followed for developing the best reduced models. On each equation, the confidence interval of the estimated regression coefficients was examined and if zero was included in the interval, then that term was removed from the model. Afterward, the residuals were examined to verify if they were normally distributed (p > 0.05), using the Anderson–Darling test. The p values for the normal distribution of residuals are listed in Table 1.
Number of levels, average area and total area are the main variables that were included in most of the regression equations (equations (1)–(10) and (12)) In contrast, construction year, total height, doors, balconies, rooms and windows were included in a smaller number of regression equations (Table 1). Plaster (equation (4)) and roof tiles (equation (9)) had the highest R2, 98.99% and 98.96%, respectively, while marble (equation (11)) and aluminium (equation (12)) had the lowest, 88.48% and 69.51%, respectively. Lastly, three different equations which can estimate the total amount of materials in a building were developed: In equation (13), all the surfaces of the buildings were used and in equation (14) only the closed interior surfaces were used for the analysis. In equation (15), amounts of individual construction materials, estimated by respective regression models, were added (Table 1). The definition and explanation of input parameters of the regression models of Table 1 are presented in Table 2.
Definition of input parameters in the regression equations of Table 1.
Figure 1 compares the estimates of the regression equations of Table 1 with the actual data produced by the CAD analysis of buildings. The respective errors sum of squares are presented in Supplemental Table S5.

Comparison of regression models (Table 1) predictions for each construction material with the actual data produced by CAD analysis of buildings. - - - Regression best fit straight line.
Generation rates for total DW
The implicit assumption was made that the construction material contained in a building will become waste upon demolition. From the total amount of building materials measured by CAD analysis, two different generation rates for total DW were estimated (Table 3). The Generation rate1 was 1.00 tonnes/m2 or 0.51 m3/m2. The Generation rate2 was 1.59 tonnes/m2 or 0.81 m3/m2. The generation rate expressed in m3/m2 refers to the volume of DW produced per m2. Using the densities of the quantified material components (Supplemental Table S6), the total density calculated for DW was 1.95 tonnes/m3 (Table 3). The Generation rate3 was developed in the project ‘Development of best management systems for high priority waste streams in Cyprus’, LIFE03 TCY/CY/000018 and since then it has been used as the main generation rate for demolition projects and reports in Greece. It is listed in Table 3 for comparison.
Comparison of generation rates and densities for total DW in Greece with other countries.
DW: demolition waste.
Comparison of methods for total DW estimation
The predictions of all methods for total waste estimation alongside with prediction of the Generation rate3 method were visually compared in Figure 2, with respect to the actual data produced by the CAD analysis. To select the best estimation method, the models were ranked with increasing values of their error sum of squares (Table 4). Thus, the models were ranked with order of decreasing preference for estimation in m3 (Table 4 top) as follows: Total1 (equation (13)) > Total based on Generation rate1 (Table 3) > Total3 (equation (15)) > Total2 (equation (14)) > Total based on Generation rate3 (Table 3) > Total based on Generation rate2 (Table 3).

Comparison of six different methods for estimation of the amount of total DW in m3.
Ranking of six methods for total DW estimation based on increasing error sum of squares.
DW: demolition waste.
Equations (13)–(15) with respective densities were used in calculations of generation in tonnes.
Using the respective material densities (Supplemental Table S6) and the tonnes/m3 values (Table 3), the estimation methods for total DW in tonnes were ranked in Table 4 (bottom): Total based on Generation rate1 (Table 3) > Total3 (equation (15)) > Total based on Generation rate2 (Table 3) > Total1 (equation (13)) > Total based on Generation rate3 (Table 3) > Total2 (equation (14)).
Case study
To evaluate the models, the construction materials of two residential buildings were quantified by CAD and their results were compared with the predictions of the six methods presented above for total DW and the regression models of Table 1 for individual waste materials. The unit management cost for each material is included in Supplemental Table S7. ‘Building A’ was a seven-floor building, constructed in 1989, and ‘Building B’ was a three-floor building, constructed in 1991. All the input parameters are included in Supplemental Table S8.
Table 5 presents the estimated DW from the two buildings. Building A produced 1679 m3 of total materials as calculated by CAD. The comparison with the predictions of the six methods above showed that the absolute differences were less than 22.7%. Generation rate1 prediction had the highest accuracy (1758 m3) with a 4.7% difference from the CAD value and the Generation rate2 had the lowest accuracy (2059 m3) with a 22.7% difference. The average and standard deviation of the absolute value % differences for total materials was 11.1% ± 7.4%. The regression equations predictions were less than 10% from the CAD values (actual materials) for bricks, plaster, ceramic tiles, insulation and mortar. The exceptions were the predictions for wood (149.6%), glass (31%) and marble (−86.2%) from the CAD values. The total recycling cost to be charged to the producer for non-mixed CDW was 21,504€ and for mixed CDW was 38,071€, that is, an increase of 77% (without including the transport cost to the plants).
Material estimation (m3) and recycling cost estimates for the two-building case study.
Numbers in parenthesis are % differences from the CAD values.
CAD: computer-aided design.
Building B produced 293 m3 of materials as calculated by CAD. The comparison with the predictions of the above six methods showed that the absolute differences were less than 4.6%. Generation rate1 prediction had the highest accuracy (295 m3) with a 0.6% difference and the equation (14) prediction had the lowest accuracy (280 m3) with a −4.6% difference. The average and standard deviation of the absolute value % differences for total materials was 2.5% ± 1.5%. The regression equations predictions were less than 10% from the CAD values for concrete, bricks, iron, glass and aluminium. The exceptions were the predictions for wood (26.8%), ceramic tiles (−28.7%) and insulation (40.9%) from the CAD values. The total recycling cost to be charged to the producer for non-mixed CDW was 4303€ and for mixed CDW was 7685€, that is, an increase of 79% (without including the transport cost to the plants).
Discussion
This study developed LR models for the prediction of 12 materials contained in Greek residential buildings. The main input variables were the number of levels, average area and total area in most of the regression equations. Similar variables were used in many previous studies (Supplemental Table S1). However, the calculation of the Pearson Correlation coefficients revealed that additional variables (e.g. construction year, total height, doors, balconies, rooms and windows) must be considered to achieve a more accurate prediction.
Concrete represents almost half of the total DW generated in Greece (Supplemental Figure S4). Similar percentages for generation of concrete appeared also in Spain (Martínez Lage et al., 2010) and China (Zheng et al., 2017). In all previous studies, concrete was the most abundant DW component, but Ding and Xiao (2014) found that bricks were the most abundant component in China. Inert materials such as concrete, bricks and mortar, contributed over 80% to the total CDW in Greece, similar to Norway (Bergsdal et al., 2007), China (Ding and Xiao, 2014), the United States (Cochran et al., 2007) and Spain (Martínez Lage et al., 2010). Wood was not as abundant as in other countries, where wood is used more extensively as construction material.
Total DW generation rates in Greece ranged between 1.00 and 1.59 tonnes/m2 (Table 3), depending on the estimation method used. It is important to realize that the differences in generation rates reflect different definitions of the reference area adopted by each estimation method. For example, the area considered in Generation rate1 is larger than that of Generation rate2 (Table 2). The highest ranked method, Generation rate1 (Table 4, bottom), is comparable with that of Malaysia (1.04 tonnes/m2) (Table 3). All other countries register higher generation rates. If Generation rate2 (1.59 tonnes/m2) is considered for comparison, this is similar only to Bangladesh (1.62 tonnes/m2) (Table 3, Islam et al., 2019). These differences are probably due not only to the different construction techniques and construction materials used in each country, but also and the definition of reference area used in the respective regression models.
The EU objectives to promote the CE were the smart demolition for the removal of hazardous materials and the collection of high-quality materials, the reduction of CDW generation and the increase in reuse, recycle or recovery of CDW to a minimum of 70% by weight until 2020 (European Commission, 2020). The LR models of this study could be significant tools for CDW management. They can be used by professionals and researchers for accurate quantification of total and individual DW. This will result in more effective management plans in a building demolition project, regarding maximizing material reuse, recovery and revenues and minimizing the operating cost and illegal dumping. Finally, they can be used to estimate gate fees that a CDW recycling plant will charge to the producers.
The methodology developed in this study for residential buildings could be extended to other types of buildings (industrial, commercial, public, etc.) for estimation and management of DW in Greece. In a future study, in addition to LR, other types of ML models could be developed and their performance could be compared.
Conclusions
Quantifying DW is necessary for their management, but a difficult process to implement, due to variation and diversity of their component materials. In this study, DW from Greek residential buildings was quantified and classified according to the European LoW. For this purpose, building licenses from three different areas in Greece were used and the 3D building models were created. Using CAD, the total volumes of the individual construction materials of the buildings were calculated, resulting in a total waste generation rate upon demolition of 1590 kg/m2 of average top view area.
LR models were developed to estimate individual and total quantities of materials contained in Greek urban residential buildings, which will become waste upon demolition. The main predictors were building characteristics, such as number of levels, total area, average level area and total height, and the construction year. Based on material estimates from CAD and model predictions, six different methods for total DW estimation were developed and compared using the ranking of their respective error sum of squares.
LR models were developed for 12 different DW components and compared against the respective CAD estimates.
Two case studies were conducted to test the accuracy of the models. Depending on the model used, the absolute % differences between model predictions and CAD calculations for total DW were <22.7% with an average of 11.1% ± 7.4% for the first case study and <4.6% with an average of 2.5% ± 1.5% for the second.
The total recycling cost charged to the producer for the first case study was estimated at 21504€ if the construction materials were not mixed and 38071€ if they were mixed, and for the second case study, the total cost was estimated at 4303€ and 7685€, respectively.
Although the results of the study pertain to Greek residential buildings and buildings of similar construction, the methodology could be adopted to other countries with similar construction codes.
Similar research could be conducted for buildings with different usage (offices, public buildings, institutional buildings, etc.) to develop prediction models for DW.
Supplemental Material
sj-docx-1-wmr-10.1177_0734242X231155818 – Supplemental material for Modelling of demolition waste generation: Application to Greek residential buildings
Supplemental material, sj-docx-1-wmr-10.1177_0734242X231155818 for Modelling of demolition waste generation: Application to Greek residential buildings by Vangelis Soultanidis and Evangelos A. Voudrias in Waste Management & Research
Footnotes
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.
Funding
The authors received no financial support for the research, authorship and/or publication of this article.
Supplemental material
Supplemental material for this article is available online.
References
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