Stock Dynamics and Emission Pathways of the Global Aluminum Cycle

Efficiency stagnation in global steel production urges joint supply- and demand-side mitigation efforts

“…S 1.1 outlines the key procedures and their linkages of our analytical framework, the detailed description of which can be found in Section S 1 . In accordance with IPCC 66 as well as other studies 29 , 67 , we performed a process-based approach to quantify the total greenhouse gas (GHG) emission of the iron and steel industry (assumed to be the sum of studied processes). Notably, unlike some studies that only focused on at steelmaking (IPCC 66 ), our analysis expanded the system boundary to the entire steel production chain as illustrated in Fig.…”

“… Emission quantification . Following existing approach 29 , 67 , we quantified both direct and indirect GHG emissions per mass unit output (in Fe content) on an annual basis for each steel production technology. The GHG emissions inventory we compiled draws primarily on unit process data from the Ecoinvent v.3 69 , 70 , but also incorporates data from a variety of sources including technical reports, published LCA datasets and existing literature (for details, see Section S 2.2 ).…”

“…S 2.6 . The GHG emissions have been grouped into three scopes: Scope 1 covers direct GHG emissions from the production site, Scope 2 covers indirect GHG emissions from the generation of electricity and heat that are used in the production, and Scope 3 covers GHG emissions associated with all other activities related to steel production (our treatment of process off-gases is similar to the previous studies 29 , 67 ). As both electricity and heat are important inputs for steel processing, the historical development in the distribution of energy carriers used for electricity and heat generation was also considered and assumed to follow the global average trend (see Supplementary Information 1 Tables S2.5 and S2.6 ).…”

The Materials Science behind Sustainable Metals and Alloys

“…The second biggest effect would come from increasing the fraction of recycled material that is used for making new alloys, i.e. switching from primary to secondary synthesis. ,, The third most influential effect could come from replacing any type of fossil fuel currently used along the manufacturing chain by sustainable electricity (such as for instance the fuel used for mining, benefication, heat treatment, etc.). The fourth target of high relevance is the introduction of inert anodes or of low-carbon anode materials, respectively. , …”

“…A first impulse to react to this (growing) emission scenario of the metallurgical sector could be to transform its linear parts (based on new mineral input, use of non-sustainable fossil feedstock as reductant for primary synthesis, and dumping of the waste products) into circular ones (making alloys from scrap instead, called secondary synthesis) (see details in section ). This is exemplarily shown for the case of steel in Figure . ,,− Such a transition could reduce emissions, waste, by-products and energy consumption in part by up to 70% (steels) or even 90% (aluminum alloys). ,, Also, drastically increasing the recycling rate would simply increase the availability of metals, as some of the metal supplies would become otherwise more and more limited, when only taken from mineral resources, Figure . A third option could be to develop re-integrative market elements, also referred to as re-mining, where old deposited industry waste is retuned back into the recycling stream and used as feedstock. − The forth approach is to reuse and repair parts instead of scrapping them, ,− Figure .…”