Selection of green suppliers for trigeneration systems using multi-criteria decision-making methods: A case study

Abstract

Due to high demand and unsustainable need for an increasing energy supply, energy efficiency has become crucial. Restricted energy markets have wide effects in areas ranging from household budgets to international relations. Also, one of the primary concerns of the twenty-first century is climate change, which is caused by increased greenhouse gas (GHG) emissions and unplanned resource consumption (UNEP, 2010). Thus, due to their high energy consumption, buildings and construction activities are on the front line of energy efficiency research. The construction industry consumes one-third of global resources, 40% of global energy, 25% of global water, and generates one-third of worldwide carbon emissions, 40% of the global waste by itself (UNEP-SBCI, 2016). Accordingly, it needs a more sustainable approach at all stages in order to reduce its negative effects on the environment. This need has increased the importance of the concept of sustainable supply chain management in construction. Also, environmental and green building grading and certification systems such as LEED, BREEAM, and Estidama provide a measurement for energy efficiency, health, and cost-saving for construction operations and buildings. Also, a lot of green building councils of countries have been started to establish to help construction stakeholders with the aim of sustainability. One of the systems that play a vital role in increasing energy efficiency for some types of buildings is trigeneration systems that produce power, heating energy as well as cooling from a single generator or process. Also, one of the most significant purchasing steps is the selection of the most appropriate supplier (Weber et al., 1991). While the traditional supplier evaluation particularly concentrates on cost-related criteria, green supplier selection focuses on environmental requirements as a priority. Considering all of these, green suppliers have been critical in creating a successful sustainable supply chain by balancing between economic, environmental, and social pillars of sustainability. Therefore, all legal regulations and standards, green project requirements, and companies' sustainability goals make the sustainable supplier selection a complicated process and vital for green supply chain management in construction. Considering all these, the selection of trigeneration systems in a green way is of great importance in terms of energy efficiency and sustainability. In recent years, trigeneration system procurements have been made frequently in the construction of city hospitals, which are large health complexes combining more than one hospital in Türkiye. In this context, the trigeneration selection of a health complex built in one of the big cities of Türkiye is examined as a case study. MCDM methods are used for this green selection problem. Identification of criteria is carried out as a result of literature research and expert opinions specific to the project. The three pillars of sustainability which are economic, environmental, and social aspects, form the three main criteria. The main economic criterion includes eight sub-criteria: cost, quality, delivery, flexibility, financial ability, operation, and maintenance cost, warranty period, and partnership relations. The environmental main criterion has four sub-criteria: energy efficiency of the system, environmental protection management system of the supplier, green products, and consumption of resources. Finally, the social main criterion includes four sub-criteria: safety and health at work, employees' rights, training of employees, and respect of rights and policies. Also, the contractor of the project evaluated the offers of 7 companies from 2 different cities of Türkiye within the scope of trigeneration systems. While AHP, DEMATEL, and BWM are used to determine the criterion weights, TOPSIS, PROMETHEE, and MAIRCA methods are used to rank the green supplier alternatives. AHP, DEMATEL, TOPSIS, and PROMETHEE are some of the most used MCDM methods, and BWM and MAIRCA are relatively newly developed and gaining popularity. Finally, the study evaluates the green suppliers of trigeneration systems for a healthcare complex and compares the different MCDM methodologies used. Constructing a framework for sustainable supplier selection in the construction sector is the main purpose of the thesis. The selection problem of sustainable suppliers takes a great place in sustainable supply chain management. Also, the most important criterion for all green building certification systems is the energy efficiency of the building. Therefore, the study aims to examine the selection problem of the trigeneration system that has a considerable impact on the energy efficiency of large healthcare complexes. Finally, it is aimed to compare different traditional and newly developed MCDM methods.