Modelling global material stocks and flows for residential and service sector buildings towards 2050

Residential buildings and service sector buildings have an important contribution to climate change, directly via energy use in these buildings and indirectly through construction activities and the production and disposal of buildings materials. In this paper, we introduce a model that looks at total global building stock for 26 regions between 1970 and 2050 and calculates the floor space and building materials both in new buildings and in demolished buildings. For residential buildings, we build upon the work of Marinova et al. (2019, this issue), who used a building material database to come up with scenarios for materials in the residential building stock. This paper adds two things. First, we introduce a new regression-based model for service building floor space, recognizing 4 different types of service-related buildings. Secondly, we use a dynamic stock model, based on lifetime distributions found in literature, to calculate the construction (inflow) and demolition (outflow) of building floor space for both residential and service-related purposes. We combine this with data from the building material database to come up with scenarios for the annual demand for construction materials worldwide as well as an estimation of the availability of waste materials after building demolition towards 2050. The model can thus be used to assess the potential for closing the material cycles in the construction sector, while distinguishing urban and rural areas explicitly. The results show that demand for construction materials will continue to increase in most regions, even in developed countries. Global demand for steel and cement for the building sector is estimated to be 769 Mt/yr and 11.9 Gt/yr respectively, by the end of the modelling period. This represents a respective growth of 31% and 14% compared to today. Drivers behind this are an expected growth of global residential building stock of about 50%, and a growth of about 150% in the building stock for services. Our model projects that by 2050, only 55% of construction-related demand for copper, wood and steel could potentially be covered by recycled building materials. For other materials the availability of scrap may be higher, reaching up to 71% of new demand in the case of aluminium. This means that in most regions urban mining cannot cover the growing demand for construction materials

Report on the current use of critical raw materials

status: publishe

Deep CO2 emission reductions in a global bottom-up model approach

Most studies that explore deep GHG emission reduction scenarios assume that climate goals are reached by implementing least-cost emission mitigation options, typically by implementing a global carbon tax. Although such a method provides insight into total mitigation costs, it does not provide much information about how to achieve a transition towards a low-carbon energy system, which is of critical importance to achieving ambitious climate targets. To enable sensible deep emission reduction strategies, this study analysed the effectiveness of 16 specific mitigation measures on a global level up to 2050, by using an energy-system simulation model called TIMER. The measures range from specific energy efficiency measures, like banning traditional light bulbs and subsidizing electric vehicles, to broader policies like introducing a carbon tax in the electricity sector. All measures combined lead to global CO2 emission reductions ranging between 39% and 73% compared to baseline by 2050, depending on the inclusion of sectoral carbon taxes and the availability of carbon capture and storage (CCS) and nuclear power. Although the effectiveness of the measures differs largely across regions, this study indicates that measures aimed at stimulating low-carbon electricity production result in the highest reductions in all regions.Policy relevanceThe results of the calculations can be used to evaluate the effects of individual climate change mitigation measures and identify priorities in discussions on global and regional policies. The type of fragmented policy scenarios presented here could provide a relevant bottom-up alternative to cost-optimal implementation of policies driven by a carbon tax. We identify overlapping and even counter-productive climate policy measures through an analysis that presents the policy effectiveness by region, and by sector. The set of 16 policy measures addresses the largest emitting sectors and represents options that are often discussed as part of planned policies

Regional differences in mitigation strategies: an example for passenger transport

This paper shows the importance of including region-specific circumstances in long-term climate change mitigation strategies, by example of a modeling exercise of the transport sector. Important emission reduction options in the transport sector include biofuels, electric vehicles and efficiency standards. The most effective combination of these options depends, among others, on the availability of biofuels, the effectiveness of efficiency standards, and the (expected) emission intensity of the power sector—all of which differ between regions. Differences in climate policies between regions influence these factors. For instance, fuel efficiency standards slowdown the long-term transition in regions where plugin hybrid electric cars compete with gasoline cars (such as the USA or Europe) by decreasing the costs for driving gasoline costs and therefore in fact increase long-term emissions. Another example is that promoting electric vehicles is less effective in regions which are expected to rely heavily on fossil fuels for power generation, such as South Africa, China and India. Based on these findings from the TIMER energy model, we introduce an indicative region-specific framework for assessing mitigation strategies for the transport sector up to 2050, for different ambition levels of climate policy

Global construction materials database and stock analysis of residential buildings between 1970-2050

Huge material stocks are embedded in the residential built environment. These materials have the potential to be a source of secondary materials, an important consideration for the transition towards a circular economy. Consistent information about such stocks, especially at the global level, is missing. This article attempts to fill part of that gap by compiling a material intensities database for different types of buildings and applying that data in the context of a scenario analysis, linked to the SSP scenarios as implemented in the global climate model IMAGE. The database is created on a global scale, dividing the world into 26 regions in compliance with IMAGE. The potential use of the database was tested and served as input for modelling the housing and material stock of residential buildings for the period 1970–2050, according to specifications made for the SSP2 scenario. Six construction materials in four different dwelling types in urban and rural areas are included. The material flows related to those stocks are estimated and analysed in a companion paper (also exploring commercial buildings) by Deetman et al. (2019). The results suggest a significant increase in the material stock in housing towards 2050, particularly in urban areas. The results reflect specific patterns in the material contents across the different building types. China presently dominates developments in the global level building stock. The SSP2 projections show a stock saturation towards 2050 for China. In other regions, such as India and South East Asia, stock growth is presently just taking off and can be expected to become dominant for global developments after 2050. The database is created to be used as input for resource and climate policymaking as well as assessment of environmental impact related to residential buildings and assessment of possibilities for urban mining. In the future, we hope to extend it as new data on materials in the built environment become available

Disentangling the ranges: climate policy scenarios for China and India

Greenhouse gas emissions in China and India have been increasing rapidly over the last decade. Scenario studies can provide insight into expected future trends and the emission reduction potential in these regions. The scenarios show that growing population, gross domestic product, and energy demand are likely to lead to a further increase in emissions. At the same time, a decreasing emission intensity would still allow to create decarbonization scenarios in line with the requirements for reaching a maximal warming of 2 °C. There is, however, a wide range of assumptions across these studies. Based on the literature review, this paper observes that key assumptions in scenarios developed by national institutes in China and India differ from those presented by international studies or modeling teams. We explore how this—and other factors like data availability—may influence the interpretation of the scenarios and how international and national modeling groups could learn from each other. Our main recommendation is for more extensive collaboration between national and international research groups, so that national and international scenario studies can be compared in more detail in order to support international negotiations

Disentangling the ranges: climate policy scenarios for China and India

Greenhouse gas emissions in China and India have been increasing rapidly over the last decade. Scenario studies can provide insight into expected future trends and the emission reduction potential in these regions. The scenarios show that growing population, gross domestic product, and energy demand are likely to lead to a further increase in emissions. At the same time, a decreasing emission intensity would still allow to create decarbonization scenarios in line with the requirements for reaching a maximal warming of 2 °C. There is, however, a wide range of assumptions across these studies. Based on the literature review, this paper observes that key assumptions in scenarios developed by national institutes in China and India differ from those presented by international studies or modeling teams. We explore how this—and other factors like data availability—may influence the interpretation of the scenarios and how international and national modeling groups could learn from each other. Our main recommendation is for more extensive collaboration between national and international research groups, so that national and international scenario studies can be compared in more detail in order to support international negotiations

Regional differences in mitigation strategies: an example for passenger transport

This paper shows the importance of including region-specific circumstances in long-term climate change mitigation strategies, by example of a modeling exercise of the transport sector. Important emission reduction options in the transport sector include biofuels, electric vehicles and efficiency standards. The most effective combination of these options depends, among others, on the availability of biofuels, the effectiveness of efficiency standards, and the (expected) emission intensity of the power sector—all of which differ between regions. Differences in climate policies between regions influence these factors. For instance, fuel efficiency standards slowdown the long-term transition in regions where plugin hybrid electric cars compete with gasoline cars (such as the USA or Europe) by decreasing the costs for driving gasoline costs and therefore in fact increase long-term emissions. Another example is that promoting electric vehicles is less effective in regions which are expected to rely heavily on fossil fuels for power generation, such as South Africa, China and India. Based on these findings from the TIMER energy model, we introduce an indicative region-specific framework for assessing mitigation strategies for the transport sector up to 2050, for different ambition levels of climate policy

Scenarios for demand growth of metals in electricity generation technologies, cars and electronic appliances

This study provides scenarios towards 2050 for the demand of five metals in electricity production, cars and electronic appliances. The metals considered are copper, tantalum, neodymium, cobalt and lithium. The study shows how highly technology-specific data on products and material flows can be used in integrated assessment models to asses global resource and metal demand. We use the Shared Socio-economic Pathways as implemented by the IMAGE integrated assessment model as a starting point. This allows us to translate information on the use of electronic appliances, cars and renewable energy technologies into quantitative data on metal flows, through application of metal content estimates in combination with a dynamic stock model. Results show that total demand for copper, neodymium and tantalum might increase by a factor of roughly 2 to 3.2, mostly as a result of population and GDP growth. The demand for lithium and cobalt is expected to increase much more, by a factor 10 to more than 20, as a result of future (hybrid) electric car purchases. This means that not just demographics, but also climate policies can strongly increase metal demand. This shows the importance of studying the issues of climate change and resource depletion together, in one modelling framework