About life cycle thinking
Life cycle inventory (LCI) is one of the phases of a life cycle assessment (LCA).
LCA is a tool to assist with the quantification and evaluation of environmental burdens and impacts associated with product systems and activities, from the extraction of raw materials in the earth to end-of-life and waste disposal. The tool is increasingly used by industries, governments, and environmental groups to assist with decision-making for environment-related strategies and materials selection.
The initial phase of LCA includes defining the goals and scope of a study, and the collection and calculation of life cycle inventory data. LCI data quantify the material, energy and emissions associated with a functional system (for example, the manufacture of 1kg of hot-rolled coil). This phase precedes the life cycle impact assessment phase (LCIA) which involves the classification, characterisation and evaluation of these data in relation to ecological impacts. The fourth and last phase is the interpretation, where the data resulting from the LCI and LCIA phases are analysed in the context of the scope and study goals and the quality of any study conclusions assessed.
However, LCA is generally an iterative process where each phase has implications for the other phases.
LCA has been a topic of growing interest to the steel and other industries. Several steel companies and associations have already independently carried out LCA studies, each different in purpose, system boundary and methodology. The worldsteel Board of Directors therefore initiated a global ‘LCI on steel industry products’, in order to avoid inconsistency and duplicated effort.
One of the primary aims of the project was to build a database and develop a common worldwide methodology for cradle-to-gate steel product LCIs across a representative sample of member companies within worldsteel. This database may subsequently form the basis for full LCAs across broader boundaries and complete product life cycles.
The purposes of the project were to:
- produce worldwide LCI data for steel industry products
- assist industry benchmarking and environmental improvement programmes
- provide a basis for carrying out impact assessments
- obtain life cycle information requested by customers
- support communication with industry stakeholders
- support responses to environmental claims against steel
- train industry people in the field of life cycle assessment.
The worldsteel LCI study quantifies resources use, energy and environmental emissions associated with the processing of approx. fourteen steel industry products, from the extraction of raw materials in the ground through to the steel factory gate (“cradle-to-gate”), and produced via the blast furnace/basic oxygen furnace and the electric arc furnace routes. The fourteen products included in the original study were: hot rolled coil; pickled hot rolled coil; cold rolled coil; finished cold rolled coil; tinplated coil; tin-free steel; hot-dipped galvanised; electro-galvanised; organic coated flat; plate; tubes; rebar/wire rod; engineering steel and sections. These products represent more than 80 percent of steel production by product category.
In total, 49 sites currently participate in the most recent update, with more sites and companies joining the project. These sites represent most areas of the world and a range of operating configurations. These companies account for approximately 25% of global crude steel production.
The worldsteel LCI study is one of the most comprehensive LCI studies ever carried out for a material, and was probably one of the first completed in accordance with the ISO standards on LCA (ISO 14040 series). It was an exhaustive process to collate some 20,000 items of data from the participating steel companies and to create various models and calculations for upstream processes. Therefore, it offers enormous scope for data analysis, trending, benchmarking and investigating environmental significance.
This approach has been repeated and improved for the update studies, to include key upstream processes. The data quality is excellent: data are recent, from reliable sources and, in general, their range and variance is small. Every item of data is documented and verifiable. Measures were also taken to verify apparent inconsistencies and to ensure the consistent application of the study methodology, including training and technical support to ensure correct procedures for completion of the questionnaires.
The database includes information on whether data were measured, calculated or estimated. The process of generating LCI results is transparent and extensively documented, and therefore reproducible. Finally, independent critical review panels reviewed each study.
As an LCI is a cradle-to-gate study, the database includes upstream data (i.e., iron ore mining, electricity production, etc.). Iron ore mining data was received directly from iron ore operations. Coal data was generated based on the source of metallurgical coal. Electricity production was obtained mainly from commercial databases (TEAM and GaBi).
The inventory includes:
- All non-mass inputs (including electricity, steam, compressed air and water);
- More than 98% of steelworks material inputs (including raw materials, energy and consumables, as well as minor inputs which may have significant environmental burdens). For more than 98% of these inputs, upstream production was accounted for.
Transport was taken into account for the major inputs to the steelworks.
The major material flows covered are quantified and categorised in terms of resource use, including energy and water; air emissions; water emissions; by-products and wastes. The range of data collected from different sites reflects different iron-making and steelmaking practices, energy efficiencies, national power mixes and efficiencies, and the complexity of the finishing operations.
The quality of data input in the LCI study is excellent. As transparency was a fundamental issue of the study, measures were taken to adopt fair assumptions and allocation rules in accordance with ISO standards. The methodological assumptions, boundaries and allocation principles that were made are transparent and fully documented.
Consequently, all results obtained are totally verifiable and reproducible.
The study was designed to represent the real interactions of steel production routes with the environment and avoid unsound theoretical scenarios. Most importantly, it does not result in unfairly favourable or misrepresentative LCI results for the steel industry.
In addition, the software provides the flexibility to analyse and, if necessary, switch off specific scenarios and/or replace them with alternative functional systems. This facility allows sensitivity analysis of different scenarios, and can be adapted to future data inputs or assumptions as required.
However, as for any LCA studies of this magnitude, there is still scope to improve the database, including the improvement of upstream and by-product data, especially where generic databases have been used which do not represent relevant regional/local practices. Data for specific flow categories such as water usage, waterborne emissions, and air emission of particulates can also be improved by extending and more clearly defining site data collection requirements. The database would also benefit from a larger number of participating sites for certain products, since this would provide more reliable averages and statistical confidence. A large programme of work is managed through worldsteel to continue improving and updating the database.
Whether used in the BOF (basic oxygen furnace) or EAF (electric arc furnace) route, there is no doubt that the recycling of steel is beneficial, because it saves raw materials and other resources. Also, scrap recycled via the BOF and the EAF displaces the energy and emissions associated with primary iron production.
The benefits of recycling steel are also provided in the cradle to gate data, incorporating the end of life of the product.
Steel is 100% recyclable. Approximately 35% of world steel production is made from scrap and the infrastructure for scrap recycling is well established. There is no limit to the recyclability of steel. Steel can be recycled repeatedly without loss of quality.
Scrap is used in both the BF-BOF and the EAF steelmaking routes. External or merchant scrap (as opposed to internally arising scrap) can contain some residual (tramp) elements such as copper and tin. Steelmakers are selective in their purchasing of scrap. They manage the input of different quality scraps and use processes to eliminate or reduce the levels of tramp elements. Such treatment is a normal part of the steelmaking process and ensures that all steel recovered can be reused to make new steel.
The EAF and BOF routes both provide essential capacity for scrap recycling and the impacts of converting scrap to steel are similar for each route.
At current levels of demand, there is insufficient scrap supply. Therefore, there is a need to produce steel from virgin material. In life cycle terms, what is essential is that steel recycling is optimised so that the use of virgin material resources can be reduced to make the two routes complementary.
The LCI study is a cradle-to-gate study. The implications of the data collected should be assessed through full LCA studies, including the downstream activities (use and end of life), and LCIA (life cycle impact assessment), which can be undertaken using the data provided by the study.
Data are made available to worldsteel member companies. The full database is held by worldsteel, to be updated as appropriate.
One of the important aims of the study is to provide data to enable LCA studies of steel-containing products. To this end, third parties undertaking such studies can obtain data from the inventory from worldsteel by filling in the request form under 'Contact us'.