Copper in steel causes metallurgical problems, but is pervasive in end-of-life scrap and cannot currently be removed commercially once in the melt. Contamination can be managed to an extent by globally trading scrap for use in tolerant applications and dilution with primary iron sources. However, the viability of long-term strategies can only be evaluated with a complete characterization of copper in the global steel system and this is presented in this paper. The copper concentration of flows along the 2008 steel supply chain is estimated from a survey of literature data and compared with estimates of the maximum concentration that can be tolerated in steel products. Estimates of final steel demand and scrap supply by sector are taken from a global stock-saturation model to determine when the amount of copper in the steel cycle will exceed that which can be tolerated. Best estimates show that quantities of copper arising from conventional scrap preparation can be managed in the global steel system until 2050 assuming perfectly coordinated trade and extensive dilution, but this strategy will become increasingly impractical. Technical and policy interventions along the supply chain are presented to close product loops before this global constraint.

Unlike conventional energy analyses, exergy analysis considers the quality of energy flows and efficiencies in their conversion. Additionally, conventional energy analyses focus on the primary and final stages of energy flows, and do not capture the last stage of energy transformations to useful enduses. We further develop previous useful work accounting methodologies by considering the sectoral breakdown of electricity end-uses and efficiencies. Also, this paper is the first accounting for useful work covering a full agricultural-industrial-services economic transition, taking Portugal 1856-2009. Portuguese aggregate final-to-useful efficiency remains constant until 1920, slightly increases between 1920-1950 due to heating uses, soars between 1950-1980 due to electrification and industrialization, and stabilizes afterwards due to an increase in motorization and deindustrialization. Strikingly, along this period the ratio useful work/GDP varies by no more than 20% around its average and ends in 2009 at a value quite close to is 1856 value, around 1MJ/2010€.

Food security relies on nitrogen fertilisers, but its production and use account for approximately 5% of global greenhouse gas (GHG) emissions. Meeting climate change targets requires the identification and prioritisation of interventions across the whole lifecycle of fertilisers. Here, we have mapped the global flows of synthetic nitrogen fertilisers and manure, and their corresponding GHG emissions across their lifecycle. We have then explored the maximum mitigation potential of various interventions to reduce emissions by 2050. We found that approximately two thirds of fertiliser emissions take place after their deployment in croplands. Increasing nitrogen use efficiency is the single most effective strategy to reduce emissions. Yet, this should be combined with decarbonisation of fertiliser production. Using currently available technologies, GHG emissions of fertilisers could be reduced up to approximately one fifth of current levels by 2050.

Cement manufacture is responsible for 5-7 % of world CO 2 emissions. Cement is primarily used in concrete, the most used material on the planet and a critical part of any analysis of emissions reduction strategy. To estimate the potential for reducing demand, this work analyses material flow in the cement industry, using the uk in 2014 as a case study. Combining published data, analytic assumptions, and interviews we estimated the material flow of cement from the production to a breakdown of its use in applications. Having broken down the demand for cement into 25 applications, multiple material efficiency techniques were considered: substituting cement for calcined clay and limestone, reducing the cement content of concrete, post-tensioning floor slabs, using more precast building elements, reducing construction waste, and reducing the overdesign in construction. We produce a final estimate of the total reduction in emissions achievable from material efficiency: 51.3 %. Due to overlap and interactions between the methods, the attribution of the carbon abatement depends on the sequence of application. In this analysis, we have applied the reduction of overdesign last, because it is independent of the others, and would require a cultural change. We show then that cement demand from floors, repairs and maintenance, concrete beams, and applications within the transport sector should be targeted. The substitution of cement with calcined clay and limestone has the biggest potential to reduce cement demand (27 %) and carbon emissions in the uk. Reducing the amount of cement in concrete has the next highest * Corresponding author Preprint submitted to Elsevier today potential (10 %), followed by post-tensioning floor slabs (3 %).

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