Circular concrete scenarios and their environmental impacts: A life cycle assessment modelled after a Swedish city

Changing from linear to circular economy is now regularly mentioned as part of the solution to global warming, because resource extraction and processing cause half of the greenhouse gas emissions globally. Concrete is the most used human-made material by weight. In this study, three scenarios were modelled for a mid-sized Swedish city: a baseline scenario with business as usual, and two scenarios with increased circularity. Life cycle assessment (LCA) was used to evaluate their resource use and environmental impacts. The results show that the more circular scenarios correspond to lower resource use and reduced environmental impacts compared to the linear baseline scenario. Reductions for impact categories related to climate change (−35%), fossil fuel energy use (−27%), mineral and metal use (−51%), land use (−53%), and water use (−43%) were found in the most circular scenario, as well as for the other environmental impact categories (17%–39%) that were part of the analysis. Most of the impact reductions to climate change (80%–84%), can be attributed to the reduction in the use of Portland cement in concrete through supplementing it with other (by-)products. The avoidance of the landfilling of concrete waste contributed mostly to the reduction of the fossil energy (47%–54%), land (63%–88%), and water (46%–67%) use impact categories. Using recycled concrete aggregate, instead of natural aggregate as an ingredient in new concrete, contributed to much of the reduction achieved in the mineral and metal use impact category (67%–85%). Even though circular scenarios might increase the need for more transport and processing, which can lead to higher impacts, the results from this study show them unlikely to negate the overall impact reduction achieved by the circular strategies. Although dependent on local variables, this study indicates that more circularity can be achieved in the concrete industry, even for materials that are dealt with in high volumes such as concrete, while simultaneously increasing sustainability in the form of reduced environmental impacts.