Evaluation of in-situ technology performance and decision analysis by combining economic and environmental impact analysis for a case study

Abstract: In the contemporary global context, the global focus on reducing environmental impacts in any formats has intensified. This study intends to assess the environmental impacts and life cycle costs associated with the A1-A5 stages (production and construction stages) of the Köping Port project and eight additional proposed scenarios. The Solidification/ Stabilization method along with the in-situ technology was utilized in this project. The study is based on a port with an area of 48,586 m2 located in Köping, Sweden which was stabilized with treated soil, a composition of sediment, cement, slag, and activated carbon. This study was performed in different sequenced steps of data collection, LCA modeling, environmental assessment, economic analysis, and decision analysis. Data collection for the project was conducted by collecting project-specific data regarding the project process, consumed materials, and involved workforce as well as related costs. Data collection process also continued by investigating and selecting the most appropriate EPDs for slag and activated carbon materials. Based on the type of cement and different binder mixtures, 8 scenarios were defined. To investigate the environmental impacts, the Life Cycle Assessment (LCA) was performed by GaBi (LCA for Experts) and Excel files. The next step was assessing the economic aspect by the Life Cycle Costing (LCC) method. Then, by applying the Single-Point Rate (SPR) calculation, a decision analysis was conducted and the best scenario was selected regarding the integration of LCA and LCC. LCA results from four investigated environmental categories (GWP, AP, EP, ODP) in this study, show that there is a similar trend between four different categories. The pattern is that always scenario with a higher amount of cement in the binder mixture (40%) within each distinct cement type has the highest environmental impact which is followed by a scenario with 30% cement in the binder mixture and finally scenario with 20% used cement in the mixture composition. The LCC results underscore the pivotal role of cement in shaping the overall expenditure of the project within the analyzed stages. According to the results, Scenario 2 which includes cement type I, with the binder mixture of 20%-80% for cement and slag respectively, was selected as the optimum scenario. This result was obtained based on all three options that were defined for weighting factors for the LCA and LCC. In fact, this scenario demonstrated almost 29% lower environmental impact and around 1.5 MSEK less initial cost compared to the base case which cement type 1, with the binder mixture portion of 20% cement and 80% slag is utilized.