Identifying strategies for reconciling human development and climate change mitigation requires an adequate understanding of how infrastructures contribute to well-being and greenhouse gas emissions. While direct emissions from infrastructure use are well-known, information about indirect emissions from their construction is highly fragmented. Here, we estimated the carbon footprint of the existing global infrastructure stock in 2008, assuming current technologies, to be 122 (-20/+15) Gt CO2. The average per-capita carbon footprint of infrastructures in industrialized countries (53 (± 6) t CO2) was approximately 5 times larger that that of developing countries (10 (± 1) t CO2). A globalization of Western infrastructure stocks using current technologies would cause approximately 350 Gt CO2 from materials production, which corresponds to about 35-60% of the remaining carbon budget available until 2050 if the average temperature increase is to be limited to 2 °C, and could thus compromise the 2 °C target. A promising but poorly explored mitigation option is to build new settlements using less emissions-intensive materials, for example by urban design; however, this strategy is constrained by a lack of bottom-up data on material stocks in infrastructures. Infrastructure development must be considered in post-Kyoto climate change agreements if developing countries are to participate on a fair basis.
The architecture, engineering and construction industry is a major producer of waste, and a major consumer of primary materials. This study presents a method for analysing the dynamics of both floor area and material use in residential housing. The population's demand for housing represents the driver in the system, and the subsequent effects on stocks and flows of residential floor area and building materials in Norway are investigated from 1900 to the projected demands for 2100. Results show that knowledge about past activity levels is important in projecting future levels. Scenarios are applied to the input parameters in the dynamic model to investigate the impacts of changes in these, including variations in material usage (concrete and wood) and material density. All but one scenario suggest a continued increase in the residential housing stock, although at diminishing growth rates, and a substantial increase in demolition, renovation and construction activity in the last half of the present century.
Current waste generation from the construction and demolition industry (C&D industry) in Norway is about 1.25 million tonnes per year. This article presents a procedure for projection of future waste amounts by estimating the activity level in the C&D industry, determining specific waste generation factors related to this activity, and finally calculating projections on flows of waste materials leaving the stocks in use and moving into the waste management system. This is done through a simple model of stocks and flows of buildings and materials. Monte Carlo simulation is used in the calculations to account for uncertainties related to the input parameters in order to make the results more robust. The results show a significant increase in C&D waste for the years to come, especially for the large fractions of concrete/bricks and wood. These projections can be a valuable source of information to predict the future need for waste treatment capacity, the dominant waste fractions, and the challenges in future waste handling systems. The proposed method is used in a forthcoming companion article for eco-efficiency modeling within an evaluation of a C&D waste system.
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