Optimal supply chain networks for waste materials used in alkali-activated concrete fostering circular economy

Global objectives to mitigate climate change stimulate transformations within construction sector. Alternative binders to carbon-intensive cement are being researched, including alkali-activated materials. However, barriers preventing adaptation of developed solutions include the absence of supply chains and lack of collaborations between waste producers and concrete manufacturers. We propose a methodological framework that combines geospatial analysis and life cycle assessment with linear optimization model to identify the most optimal supply chain networks for waste materials, focusing on transportation between the actors. Two types of waste generated in Switzerland were examined as case studies, one with distributed source locations, such as ashes produced at municipal waste incinerators, and another with scattered source locations, such as mineral wool insulation waste from construction and demolition activities. Results show that direct symbiosis between waste producers and concrete manufacturers results in 68% and 63% lower CO2 emissions and costs of transportation for ashes and mineral wool waste respectively, compared to cement transportation for conventional concrete production. However, considering investment costs, decision-makers might support the centralized supply chain network design.