Tradeoffs and synergy between material cycles and greenhouse gas emissions: Opportunities in a rapidly growing housing stock.

Management of building materials' stocks and flows is a major opportunity for circularity and de-carbonization. We examine the relationship between material consumption and associated greenhouse gas (GHG) emissions under different scenarios in Israel, a developed country with an already high population density that expects tremendous growth in its housing stock by 2050. We created scenarios of varying housing unit sizes and additional material efficiency practices: fabrication yield, lifetime extension, material substitution, recycling, and their combination, resulting in 18 scenarios. In each scenario, the material flows and stocks needed to supply the housing demand and the resulting life-cycle GHG emissions are quantified. No single material efficiency practice achieves a reduction in all indicators, suggesting a potential conflict between circular economy and decarbonization policies: The material substitution scenario allows for the biggest reduction in material consumption (12%-40% concrete reduction and 15%-51% steel reduction in 2050 compared with the baseline), while the recycling scenario achieves the biggest reduction in GHG emissions (22%-43% reduction in 2050 compared with the baseline). In the long-term, the life-extension scenario reduces most demolition waste. These findings can help policymakers and stakeholders consider the impacts of raw materials consumption and implement this knowledge in light of their priorities in policy packages. The results suggest a narrow window of opportunity within the next decade to influence material consumption and emissions to 2050. The findings could also shed light on the sustainability trajectories of other countries with similarly rapidly developing building stock, which have received little attention in this field.