Spatiotemporal Model to Quantify Stocks of Metal Cladding Products for a Prospective Circular Economy

The traditional linear economy (LE) approach based on a “take-make-dispose” plan that has been used in building activities over a long period has a significant impact on the environment. In the LE approach, the used materials are usually sent to landfills rather than recycled, resulting in resource depletion and excessive carbon emissions. A circular economy (CE) is expected to solve these environmental problems by promoting material “closed-loop systems”. This study was intended to quantify and analyse the global warming potential (GWP) values of specific metal roofing and cladding products to promote CE thinking. A spatiotemporal model integrated with the life cycle assessment (LCA) tool was used to quantify the GWP value of the steel products in the investigated buildings. The study analysed ten case buildings located in six different cities in New Zealand: Auckland, Wellington, Hamilton, Palmerston North, Tauranga, and Christchurch. The production stages (A1–A3), water processing (C3), disposal (C4), and recycle, reuse, and recovery stages (D) were the focus of the study in analysing the GWP values of the product’s life cycle. The study found that the production stages became the most significant emitters (approximately 99.67%) of the investigated steel products’ GWP values compared to other selected life cycle stages. However, when considering the recycling stages of the steel products, the GWP value was reduced up to 32%. Therefore, by implementing the recycling process, the amount of GWP can be reduced, consequently limiting the building activities’ environmental impacts. In addition, the integration of spatial analysis and LCA was found to have potential use and benefit in future urban mining and the development of the CE approach in the construction industry.