The construction sector is a major economic backbone of most countries. However, construction waste (CW) has been a principal problem in this sector for years. Ebekozien et al. [1] defined CW as any inefficiency that results in the use of equipment, materials, or labor in the construction of a building. USEPA [2] also defined CW as building and site improvement materials and other solid waste resulting from construction, remodeling, renovation, or repair operations. The Government of Hong Kong defined CW as anything which is generated because of construction works, then abandoned, regardless of whether it has been processed or stockpiled [3]. In a nutshell, CW could be defined as an activity or material that adds no value to any production in the construction stage of buildings.

Sharma [4] indicated that waste could be classified either as unavoidable (or natural waste) or avoidable. If the cost of waste is higher than the cost to prevent it, it is classified as avoidable waste. If the necessary investment for its reduction is higher than the economy produced, it is classified as unavoidable waste [4]. Wu et al. [5] grouped waste from the construction field into inert, non-inert, and hazardous categories. Large amounts of waste are generated in the construction sector as compared to other sectors. In 2017, 569 million tons of construction and demolition (C&D) waste was generated in the United States, and this amount of waste is more than twice the amount of municipal solid waste. However, demolition activities account for more than 90 percent of total waste generation, while the portion attributed to construction activities amounts to less than 10 percent [6]. In the European Union (EU), C&D waste accounted for 36.4% of all waste in 2016 [7]. In 2016, 66.2 million tons of non-hazardous C&D waste were reported in the UK and 59.6 million in England [8]. The Ghanaian construction industry has also experienced an enormous range of CW over the years [9]. According to Agyekum et al. [10], there is a wide variation in wastage rates of between 5% and 27% of total materials purchased for construction projects in Ghana.

Research reveals that design decisions contribute more to materials waste generation on construction sites. In addition, materials waste can be produced during the construction and operation stages ^[10][11][10,11]. Project duration, project size, activities during project delivery, as well as worker numbers greatly influence waste generation. Tzourmaklioutou [12] and Amudjie et al. [13] postulated that mistakes, unplanned work delivery, redundant activity, movement, delayed or premature inputs, and products or services that do not meet customer needs comprise the causes of waste on construction sites. According to Agyekum et al. [9] and Salgın [14], the constructability of a project should be considered in the design process to prevent or reduce the generation of excessive waste.

CW has negative effects on the environment and economy, as well as impacting project costs. The high level of waste recorded at construction sites has led to a great demand for construction materials on construction sites. The stage of construction as well as the method of construction practice, influences waste generation in project delivery. This, therefore, tends to lead to devastating effects on the environment [15]. Construction players have roles to play in minimizing CW to bring value for money at the end of construction projects and protect the environment through the usage of circular principles such as the five (5) ‘Rs’ (reduction, re-use, recycle, repair, and recover).

Bajjou and Chafi [16] defined waste minimization as “the understanding and changing of processes in order to reduce waste at source”. Rasanjali [17] also stated that any procedure, method, or action that prevents or reduces waste at its source or facilitates reuse/recycling is considered waste minimization. It could be understood from the above literature that the concept of material waste minimization tackles waste at the initial stages of the construction activity. Jaillon et al. [18] conducted a study to reveal the waste minimization potential of prefabrication usage compared to traditional construction and found that prefabrication provides benefits in waste minimization (approximately 52%) on sites. Mendis [19] argued that there are two waste minimization strategies, i.e., planning and controlling. Lu and Yuan [20] postulated five (5) waste minimization factors at the construction stage of projects, including minimizing waste by government legislation and through design, establishing an effective waste management system, use of low-waste technologies, and improving practitioners’ viewpoints toward waste reduction. Ding et al. [21] developed a system dynamic model for waste minimization at the construction stage to simulate the environmental benefits of CW reduction. Some research shows the importance of workers’ positive attitudes toward CW minimization [22]. According to Salgın et al. [23], the primary cause of waste during the construction stage of buildings is “improper workmanship and practices”. Tam and Tam [24] examined a kind of reward system called the Stepwise Incentive System (SIS), and it was found that 23% less waste was generated when SIS was implemented in a case study project in Hong Kong. According to Khan et al. [25], providing training and education among staff is an important factor in waste minimization. Despite the existence of these strategies, little impact has been felt on the construction industry as far as waste minimization is concerned. It is thought that there is a low level of awareness of key competencies that drive material waste reduction at the construction stage of a project, especially in the setting of a developing country.

The concept of competency has been touched on by various literature works, with Taylor, McClelland, and Boyatzis spearheading it in the 20th century [26]. Competency is the collection of knowledge, skills, and attributes that are capable of influencing an individual’s performance [27]. The Iceberg Theory, as propounded by Spencer and Spencer [28], viewed competency as an iceberg at sea level depicting a visible part and a hidden part. Knowledge and skill form the visible part, while interpersonal, motive/trait/concept, and value/moral forms the hidden part. Prifti et al. [29] defined competency as a behavior that produces successful results through the combination of knowledge, skill, attitude, and value. Competency is a series of skills and traits needed by workers for effective work delivery.

To ensure waste minimization in the construction industry, there is a need to explore the core competencies required by the construction players to ensure effectiveness. Na’im [30] proposed leadership and organization, basic literacy, target management, and emotional intelligence as core competencies that could drive waste minimization. The Project Management Institute [31] categorized competency under knowledge, performance, and personal competencies. This study focuses on skills and knowledge as the main components of waste minimization competencies. This reiterates the position of Spencer and Spencer [23] on viewing competency as an iceberg showing forth a visible part (Skills and Knowledge) and a hidden part (Trait).

Ebekozien [32] defined skill as the capacity to perform a task of a mental or physical nature in order to have a specified outcome. Skills could be easily identifiable or abstract. Zhao et al. [33] and Geoghegan and Dulewiz [34] asserted that the effectiveness of any project’s success depends on the leadership role of the construction professionals. Therefore, in focusing on key competencies that drive waste minimization at the construction stage of a project, leadership skill was targeted. Leadership skill encompasses self-awareness, emotional resilience, intuitiveness, interpersonal sensitivity, influence, motivation, and conscientiousness [33] of the construction professional in waste reduction.

The construction manager or the head in charge of waste minimization at the construction site should be able to efficiently communicate with all parties involved in CW reduction on policies governing waste management to fulfill sustainability goals. According to Li et al. [35], effective communication of organizational waste management policy mobilizes support for the minimization objectives. Wagstaff [36] also postulated that working cooperatively with others as opposed to separately or competitively is a prerequisite for influencing a team to perform in a desirable manner. Effective communication, information sharing, early warning systems, and the early contribution of expertise on CW needs to be enhanced to prevent construction errors, reworks, and waste [37]. Developing and implementing a waste management plan contributes immensely to CW reduction at the construction stage of a project. It helps to identify the forms of waste and their sources and specifies mitigating measures for them. The plan reflects the peculiarities of the project in terms of the nature and amount of waste anticipated and prescribes ways of managing them [15].

According to Tatham [38], supply chain management skills involve the capacity to obtain suppliers’ highest commitment, achieve just-in-time delivery, and enable lean construction in order to avoid waste due to long storage or ordering unneeded materials. The just-in-time delivery approach enables the usage of material as and when needed. This reduces double handling and damage that erupts from long storage. Alvanchi et al. [39] asserted that the implementation of a Material Logistics Plan (MLP) at construction sites is an efficient way to reduce CW. Logistics management involves effective planning of materials ordering and purchase, inbound, materials movement, and storage on construction sites [40]. Waste minimization requires adequate estimation of materials required at different stages of projects in an attempt to reduce the likelihood of materials over-ordering and subsequent leftover, which is a key cause of waste generation [40]. Bearing skills in logistics management ensures efficient waste reduction.

In a nutshell, potential key factors frequently used during the construction phase of building projects to drive CW minimization were derived from existing literature, and twenty-four (24) competencies were identified under two (2) components as knowledge and skill (see Table 1).

Li et al. [41] defined knowledge as the awareness or understanding of facts, rules, principles, guidelines, concepts, theories, or processes needed to complete a task. Most wastes on construction sites happen due to a lack of planning and sequencing of construction activities. Pérez and Bastos Costa [48] asserted that planning and scheduling is a critical factor in the quest to achieve sustainability; hence it needs to be well addressed and reflected in construction schedules to avoid any delays and wastage of materials. The recycled content, as well as the recyclability of construction material, enhances sustainability which eventually contributes to waste reduction. For instance, according to Senaratne et al. [49], steel can be recycled from construction debris, which makes it a commonly recycled building material. Glass is a recyclable construction material, but its separation from a CW is difficult [50]. Using materials that can be recycled reduces the use of raw mater and embodied energy [50]. He further stated that recycling takes less energy than producing a whole new material. Health and Safety Management is critical when focusing on key competencies that drive waste minimization at the construction stage of a project. The construction manager needs to understand the health impact of on-site workers and the danger improper management of CW brings.

Accidents that normally happen from poor site waste management could be reduced through proper health and safety management [43]. Hwang and Ng [43] postulated that construction managers should select parties for construction activities based on their knowledge of CW. In human resource management, practices such as organizing waste management and materials handling, vocational training for operatives, having a dedicated site team or specialist sub-contract package for on-site waste management, the appointment of labor solely for waste management, etc., could enhance the minimization of waste [37]. Modern construction methods, such as the use of prefabricated construction products and modular construction, contribute to CW minimization at the construction stage of a project. Prefabrication makes use of precast components and modules, modular construction technique, and other off-site technologies [37]. Modular construction also refers to factory-produced building units that are delivered and assembled on-site as building elements or volumetric components. The use of precast materials has the potential to reduce the amount of on-site damage and rework, thereby contributing to waste reduction output by up to 84% [37].

In the construction phase of a project, standard material sizes could be opted for to reduce waste during trimming processes. Salgın [51] states that choosing dimensionally coordinated building products with the building helps to avoid the required cut-offs in the construction stage to ensure CW minimization is provided. Mixing of concrete can also be done on-site to readily control the amount needed. These points are supported by Menegaki and Damigos [15] with the claim that minimal CW during installation reduces the need for landfill space and provides cost savings. Sustainability is a concept that aims at protecting our environment, ensuring economic profitability, and creating social awareness [9]. Requisite knowledge of sustainable construction practices ensures effective waste reduction.

Other knowledge competencies cited by researchers include adherence to project design/drawings, waste auditing to monitor the environmental performance, and thorough review of the project specifications by contractors at the construction stage [52]. Hwang and Ng [43] stated delegation and problem-solving as key skills that could drive CW minimization. Shi et al. [44] also added continuing professional learning, on-site practical skill, and personnel quality as skills that should be possessed by construction professionals in waste minimization. Creative thinking, provision of direction to inspire others, and a personal commitment to pursuing an ethical solution to waste minimization are also skills that could drive material waste minimization if portrayed by construction site workers ^[43][44][43,44].