No abstract

No abstract

Producing steel accounts for 25% of industrial carbon emissions. Long-term forecasts of steel demand and scrap supply are crucial for developing roadmaps of how the steel industry could respond to industrialization and urbanization in the developing world while simultaneously reducing its carbon footprint. We present a dynamic stock model that estimates future demand for final steel and the supply of scrap for ten world regions, assuming that per capita in-use stocks will saturate eventually, as evidence from developed 3 countries suggests. We explore the response of the entire steel cycle, in particular the split between primary and secondary steel production.We find that during the 21 st century, steel demand may peak in the developed world, China, the Middle East, Latin America, and India. As China completes its industrialization global primary steel production may peak between 2020 and 2030 and decline thereafter. We develop a capacity model to demonstrate how extensive trade of finished steel could prolong the lifetime of existing Chinese production assets. Secondary production will more than double by 2050, and it may surpass primary production between 2050 and 2060, thus ushering in the global steel scrap age.

ABSTRACT:Industrialization and urbanization in the developing world have boosted steel demand during the recent two decades. Reliable estimates on how much steel is required for high economic development are necessary to better understand the future challenges for employment, resource management, capacity planning, and climate change mitigation within the steel sector. During their use phase, steel-containing products provide service to people, and the size of the in-use stock of steel can serve as indicator of the total service level. We apply dynamic material flow analysis to estimate in-use stocks of steel in about 200 countries and 3 identify patterns of how stocks evolve over time. Three different models of the steel cycle are applied and a full uncertainty analysis is conducted to obtain reliable stock estimates for the period 1700-2008.Per capita in-use stocks in countries with a long industrial history, e.g., the U.S, the UK, or Germany, are between 11 and 16 tonnes, and stock accumulation is slowing down or has come to a halt. Stocks in countries that industrialized rather recently, such as South Korea or Portugal, are between 6-10 tonnes per capita and grow fast. In several countries, per capita inuse stocks of steel have saturated or are close to saturation. We identify the range of saturation to be 13±2 tonnes for the total per capita stock, which includes 10±2 tonnes for construction, 1.3±0.5 tonnes for machinery, 1.5±0.7 tonnes for transportation, and 0.6±0.2 tonnes for appliances and containers. The time series for the stocks and the saturation levels can be used to estimate future steel production and scrap supply.

Identifying strategies for reducing greenhouse gas emissions from steel production requires a comprehensive model of the sector but previous work has either failed to consider the whole supply chain or considered only a subset of possible abatement options. In this work a global mass flow analysis is combined with process emissions intensities to allow forecasts of future steel sector emissions under all abatement options. Scenario analysis shows that global capacity for primary steel production is already near to a peak and that if sectoral emissions are to be reduced by 50% by 2050, the last required blast furnace will be built by 2020. Emissions reduction targets cannot be met by energy and emissions efficiency alone, but deploying material efficiency provides sufficient extra abatement potential.3

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.

Recent high-level agreements such as the Paris climate accord or the Sustainable Development Goals aim at mitigating climate change, ecological degradation and biodiversity loss while pursuing social goals such as reducing hunger or poverty. Systemic approaches bridging natural and social sciences are required to support these agendas. The surging human use of biophysical resources (materials, energy) results from the pursuit of social and economic goals, while it also drives global environmental change. Socio-metabolic research links the study of socioeconomic processes with biophysical processes and thus plays a pivotal role for understanding societynature interactions. It includes a broad range of systems science approaches for measuring, analyzing and modelling of biophysical stocks and flows as well as the services they provide to society. Here we outline and systematize major socio-metabolic research traditions that study the biophysical basis of economic activity: urban metabolism, the multi-scale integrated assessment of societal and ecosystem metabolism, biophysical economics, material and energy flow analysis, and environmentally extended input-output analysis. Examples from recent research demonstrate strengths and weaknesses of socio-metabolic research. We discuss future research directions that could also help to enrich related fields.

As one quarter of global energy use serves the production of materials, the more efficient use of these materials presents a significant opportunity for the mitigation of greenhouse gas (GHG) emissions. With the renewed interest of policy makers in the circular economy, material efficiency (ME) strategies such as light-weighting and downsizing of and lifetime extension for products, reuse and recycling of materials, and appropriate material choice are being promoted. Yet, the emissions savings from ME remain poorly understood, owing in part to the multitude of material uses and diversity of circumstances and in part to a lack of analytical effort. We have reviewed emissions reductions from ME strategies applied to buildings, cars, and electronics. We find that there can be a systematic trade-off between material use in the production of buildings, vehicles, and appliances and energy use in their operation, requiring a careful life cycle assessment of ME strategies. We find that the largest potential emission reductions quantified in the literature result from more intensive use of and lifetime extension for buildings and the light-weighting and reduced size of vehicles. Replacing metals and concrete with timber in construction can result in significant GHG benefits, but trade-offs and limitations to the potential supply of timber need to be recognized. Repair and remanufacturing of products can also result in emission reductions, which have been quantified only on a case-by-case basis and are difficult to generalize. The recovery of steel, aluminum, and copper from building demolition waste and the end-of-life vehicles and appliances already results in the recycling of base metals, which achieves significant emission reductions. Higher collection rates, sorting efficiencies, and the alloy-specific sorting of metals to preserve the function of alloying elements while avoiding the contamination of base metals are important steps to further reduce emissions.