**1. Introduction**

The natural environment is constantly being exploited. In order to protect natural resources from destructive human activity, the concept of sustainable development was developed. It was first presented on 26 May 1969, by the United Nations (UN) in the report "Problems of the human environment". This report is considered to be a turning point in the perception of the devastating impact of humans on the environment [1,2]. Sustainable development aims to prevent the deepening destruction of the environment while at the same time satisfying the needs of mankind and enabling unlimited progress. The concept of sustainable development should be applied in all areas of human life [3]. The current assumptions of sustainable development were presented during the UN summit in New York on 25–27 September 2015, in a document entitled "Transforming our world: Agenda for Sustainable Development—2030". Sustainable Development Goals have been incorporated into the legislation of UN member states. In the regulation of the European Parliament and the Council of the European Union from 2011, a sustainable construction was introduced as a new basic requirement [4]. Since then, reusing and recycling construction products has not only become a choice but also a necessity. Countries

**Citation:** Białko, M.; Hoła, B. Identification of Methods of Reducing Construction Waste in Construction Enterprises Based on Surveys. *Sustainability* **2021**, *13*, 9888. https://doi.org/10.3390/su13179888

Academic Editors: Carlos Morón Fernández and Daniel Ferrández Vega

Received: 24 July 2021 Accepted: 29 August 2021 Published: 2 September 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

that changed their law according to the new requirements reduced the production of construction waste, which was proven by the analysis of statistics from 2016 performed by Wing-Yan Tam and Lu [5]. Appropriate waste management is included in the 2008/98/EC Directive, which is based on the latest UN assumptions from the 2030 Agenda. The hierarchy of proceeding with waste is written in such a way that the first and most desirable method (reduction) minimizes the amount of generated waste by reducing the use of construction products that cause this waste. The second method (re-consumption) involves the reuse of products that were originally produced as disposable but can still have auxiliary functions. The third principle (recycling) emphasizes the need to recycle the waste that can be processed and used in the production of new construction products [6]. For proper waste management to be as effective as possible, the activities of industrial, research, civic, and public authorities should be combined [7,8]. It has been also proven that the appropriate management of construction waste not only brings environmental, but also economic benefits [9,10].

In the subject literature, construction waste is defined in many ways. One of them is the definition of waste as materials produced "in the process of the production, construction, renovation, or demolition of structures" [11]. A more detailed definition was created by A. Denmark [12]. It reads: "Construction and demolition waste is a complex waste stream that consists of a wide variety of materials such as rubble, earth, concrete, steel, wood and a mixture of materials resulting from various construction activities, including soil removal, demolition, road construction and the modernization of buildings." A European Union (EU) report from 1999 defines construction waste to be a wide range of materials resulting from the complete or partial demolition of buildings or roads, the construction of buildings/roads, the removal of soil, construction works, and building/road restoration works [13]. According to the works of B. Kourmpanis (2008), construction waste differs in individual countries due to the economic and cultural situation of these countries, the characteristics of waste classified as construction waste, and the type of recorded data [14]. Due to divergences in the definition of construction waste in different countries, the EU has developed a European Waste Catalog for its Member States [15]. In the United Arab Emirates (UAE), federal law generally defines waste as all toxic and non-toxic waste, including nuclear waste, which must be disposed of and recycled in accordance with the law. These wastes include solid waste, such as municipal, industrial, agricultural, medical, and construction waste [16]. To sum up, construction waste can be defined as the difference "between the materials ordered and those used to construct a building" [17].

Construction waste can be classified according to the type of material that was used in the production of a construction product [11,13,14,18]. One example includes the division of construction waste in the European Union into concrete, bricks, ceramic tiles, ceramics and gypsum-based materials, wood, glass, plastics, asphalt, tar and tarred products, metals (including metal alloys), soil and earth, insulating materials, mixed construction waste, and hazardous construction waste [15]. Construction waste can also be distinguished according to the properties of the materials, e.g., recyclable and non-recyclable waste, potentially biodegradable waste, waste that is potentially suitable for disposal at a landfill, and waste that is potentially suitable for incineration [11]. Another way to classify construction waste involves the consideration of its origin, e.g., from the construction of a new building, reworks or demolition [11,19,20], or related to the function of a building [21,22] or the source where this waste was generated [23–28].

The knowledge concerning the sources of generating waste facilitates the identification of methods for reducing this waste. The sources of construction waste in the life cycle of a building were first identified by Gavilan and Bernold (1994) during their research carried out in the Netherlands. They distinguished the following sources where construction waste is generated in the production process: (1) design, (2) procurement, (3) handling of materials, (4) operation, (5) residual, including scrap and nonconsumables, and (6) other sources [17]. In 2000, Lingard, on the basis of the research conducted among employees of general contractors, classified four sources of construction waste and added a behavioral theme to the existing knowledge: (1) production and delivery, (2) transport and storage, (3) construction, and (4) culture related [23].

The influence of the behavioral factor on the production of construction waste has been more widely studied and also confirmed in other scientific studies [24,25,29,30]. In 2004, a survey conducted in Singapore among general contractors identified four main sources of construction waste: (1) design, (2) production and delivery, (3) material management, and (4) construction [26]. The results of these both studies, which were carried out in 1994 and 1996, and following ones confirmed that the maximum number of sources of the construction waste occur at the design stage [23,27–29]. Based on a subject literature review [21–28,31–33], 13 methods of reducing the amount of construction waste used in construction companies were found. These methods are discussed in detail in Table 1 in the next chapter.

**Table 1.** The methods of reducing construction waste used in construction enterprises.


The aim of the conducted research and analyses is to find out whether the application of construction waste-reduction methods with regards to selected construction materials depends on the size of the enterprise. In terms of the number of people employed, the enterprises were classified into five groups: (1) from 1 to 9 employees, (2) from 10 to 49 employees, (3) from 50 to 99 employees, (4) from 100 to 249 employees, and (5) 250 employees and more. The analyses were based on the results of a survey conducted among engineers employed in construction companies. The research was conducted in Sharjah, United Arab Emirates (UAE). The analyzes were performed with the use of the SPSS 26 computer program.

#### **2. Materials and Methods**

The methods of reducing construction waste that are used in construction companies, which were identified based on the literature review, are presented in Table 1. The benefits of using each of them are also listed. Research was carried out for the following construction products: steel, concrete, wood, and small-sized (ceramic, concrete) and finishing (ceramic and stone tiles) elements.

#### *2.1. Size and Structure of the Studied Population*

The population of the studied enterprises consists of five subpopulations. Each of them includes enterprises with a certain number of employees. The groups have been derived from the population as per the characteristic of construction enterprises. In Sharjah, construction companies employ a limited number of people to keep low insurance and municipality fees, and they outsource work to subcontractors. The survey was conducted using the technique of personal interviews and telephone interviews due to the possibility of obtaining the most accurate data and immediate clarification of ambiguities in the obtained answers. The research was carried out in 140 enterprises of general contractors. The structure of the population is presented in Table 2.


**Table 2.** Structure of the studied population of enterprises.

Table 2 presents the number and percentage share of the enterprise sizes in the studied population. In the surveyed representative group, 42 enterprises (30%) employ from 1 to 9 employees, 41 enterprises (29%) employ from 10 to 49 employees, 15 enterprises (11%) employ from 50 to 99 employees, 20 enterprises (14%) employ between 100 and 249 employees, and 22 enterprises (16%) employ 250 employees or more. The largest sub-population includes enterprises that employ the least workers.

Research was also carried out with regards to the companies' experience in the market of construction works. The results of the surveys are presented in Table 3.


**Table 3.** Experience in the construction market among the surveyed companies.

Among the surveyed companies, 63 companies (45%) had 16 years or more of experience in the construction market, 42 companies (30%) had 11 to 15 years of experience, 25 companies (18%) had 6 to 10 years of experience, and 10 enterprises (7%) had between 1 and 5 years of experience. To sum up, the most numerous group were the oldest enterprises, with 16 years of experience or more.
