Life cycle assessment and steel sustainability
Life cycle assessment and steel sustainability
The steel industry is the second largest industry in the world after oil and gas industry. Steel is used in almost every sector which ranges from building and construction, packaging, transportation industry, and power and renewable energy sector. Use of steel is found everywhere in the present day society. There are practically no materials or products where steel is not present or has not played a role in their production.
Crude Steel production has more than doubled, over the last three decades, with the 2020 production amounting to 1,864 million tons and the 2019 production amounting to 1,869 million tons. Steel continues to be the backbone and enabler of evolution and progress of the society. It makes the world a better place to live. The smart cities of the future are to be built on steel. Steel being an infinitely recyclable and reusable asset, its use helps in reducing the burden on the resources of the earth.
The high level of steel production inevitably makes the steelmaking sector more responsible towards its environmental impact. Hence, it is imperative to analyze the processes of the steel industry in order to give a clear picture of the main environmental impacts together with possible solutions involving the implementation of a circular economy paradigm.
Steel has a combination of properties which are to be taken into account in the decision making process at the design state. These properties include (i) chemical, metallurgical, and mechanical properties, (ii) corrosion resistance properties, (iii) fire resistance properties, (iv) recyclability, (v) long life (vi) maintenance requirements, (vii) hygienic requirements, (viii) aesthetics, and (ix) environmental influence.
Steels can be recycled without loss of quality. Since metallic bonds are restored upon resolidification, steels continually recover their original performance properties, even after multiple recycling loops. This allows them to be used again and again for the same application. By contrast, the performance characteristics of most non-metallic materials degrade after recycling.
Typically steel products made over the integrated route have a returned process scrap content limited to a value ranging from 10 % to 20 % where as the steel products at end-of-life are recycled at rates ranging from 85 % to 95 %. The ‘recycled content’ method only incorporates the environmental benefits realized today, in contrast with the ‘end-of-life’ method which additionally accounts for the future environmental benefits emerging from scrap which is generated at end-of-life. For steel industry, the ‘end-of-life recycling rate’ is the most appropriate indicator, while available volumes of end-of-life scrap are insufficient to match the present demand. Fig 1 shows the life cycle of steel.
Fig 1 Life cycle of steel
The production of primary (virgin) steel typically includes ore mining and concentrating, smelting, and refining to obtain the steel of the specified chemistry, with a number of processing routes available. In each stage, impurities and byproducts are separated and the concentration of the iron in the final product increases. The refining of steel to sufficient purities frequently needs energy-intensive and precisely-controlled melting stages, which are normally based on the use of fossil-fuel inputs directly as a reductant or indirectly for heat and electricity. Iron and steel production accounts for a substantial global industrial carbon dioxide (CO2) emissions.
In the mining and beneficiation area, there are processes which consist of treating ores in liquid solution to concentrate ore by separating it from the associated minerals. In some processes, very high temperatures are not normally needed and the treatment can take place at high pressures which needs energy to maintain the pressures. Further, it is more likely that the energy intensity of the mining and beneficiation processes is going to increase over time as mines shift from high grade to lower grade ores and when starting of mining more complex deposits. The energy consumption can be improved by increased process efficiencies.
Pyro-metallurgy involves treatment of ore concentrates at high temperatures, in order to strip the iron from its associated mineral constituents. This, in turn, necessitates use of fossil fuels in heating furnaces or electricity to power the furnaces. Further, steel industry produces different types of steel products. These different types of steel products can be made in the same steel plant and from the same primary production processes. Each of these products needs different processing routes for the production of the products used by the end consumers. Fig 2 shows principles for life cycle assessment (LCA).
Fig 2 Principle for life cycle assessment
Material scientists and product developers have now a growing number of tools available to them which allow them to consider the environmental implications of their choices of materials, but in general these tools consider a small number of environmental endpoints, and many data gaps remain. However, given the expected increase in global future demand for steel and its importance in the present day technologies, it is important that high reproducible data for life cycle based environmental burdens of steel production is available and that the implications of co-production of several steel products are clearly understood.
Human activities which need material and energy to develop have irreversible effects on ecological systems and environment such as climate change, the depletion of natural resources, waste generation, and pollution etc. Most of these impacts have hazardous consequences for human health and survival and most of these effects have long-termed results. In Brundtland report which was published in 1987, sustainable development is defined as ‘the development that meets the needs of the present without compromising the ability of future generations to meet their own needs’. A subset of sustainable development which has been evolving worldwide for almost 25 years to 30 years, the role of built environment is very important.
The concept of sustained development, as defined in the Brundtland report, is a very complex and dynamical challenge which demands contributions of the most diverse activity sectors. Climate change and the sustainable use of natural resources are among the main challenges for society today. This puts them at the top of the political environmental agenda, where they are likely to remain for the foreseeable future
Sustainability concerns the whole cycle of a product production i.e. from raw material acquisition, through planning, design, construction and operations, to the its use and end of life waste management. It is a big and important challenge for the future in the steel industry. Several efforts have been made by the steel industry to reduce its carbon footprint by increasing recyclability and improving the processes.
In the sustained development, there is encouragement for the development of methods which are economically and environmentally healthy. The production and distribution of the materials are carried out with the minimum of transportation. Also, those materials are used which are available as close as possible.
Steel sustainability consists of three components namely (i) environmental, (ii) social, and (iii) economic.Steel industry is a highly effective industry to improve social, economic and environmentally sustainable development and it is emerging as a highly active industry in both developed and developing countries. The industry needs natural resources from the earth for the production of steel which is used to construct human-made structures such as building, bridges, and roads and in products used in our daily life.
Life cycle analysis of steel is done for determining environmental impact. Three aspects which determine the environmental impact are (i) production of steel product, (ii) use of the steel product, and (iii) recycling of the end of the life material. The environmental impact is influenced by (i) use of natural resources, (ii) environmental management, and (iii) prevention of pollution of air, water, and land by waste gases, liquids, and solids.
The materials efficiency of the steel product is determined by three criteria namely (i) reduce, (ii) reuse, and (iii) recycle. The quantities of raw materials to produce steel are to be reduced by improving process efficiencies for the reduction of the CO2 emissions. After the life of a steel product is over, part of the steel content of the product can be reused without any loss of steel basic properties. This makes the reuse of steel very important. Steel is 100 % recyclable. All the steel scrap is reused in making fresh steel. Further, byproducts produced during the production of steel are used by various industries and this reduces the requirements of raw materials in those industries and hence helps in conservation of the natural resources.
The social impact of steel is quite substantial. The social impact is influenced by (i) standards of living, (ii) education of the people, (iii) community, and (iv) equal opportunity for everyone.
A sustainable material does not harm the people working to produce it, or who handle it during its use, recycling, and ultimate disposal. Steel is not harmful to the people either during its production or its use. For these reasons, steel is the primary material used in several applications. The safety, like injury-free and healthy workplace of the employees, is the key priority for the steel industry. Steel also improves the quality of life by making technical advances possible. That is why people see presence of steel in everything which they use in their daily life. In fact, today life is not feasible without steel.
The economic component of steel sustainability is very important. The factors influencing the economics include (i) production cost, (ii) profit, (iii) cost savings, (iv) economic growth, and (v) generation of revenues for investments is research and development activities.
Life cycle cost (LCC) is an important criterion for the economic component of steel sustainability. LCC is the cost of an asset throughout its life cycle, while fulfilling the performance requirements (ISO 15686-5). It is the sum of all cost related to a product incurred during the life cycle which consists of (i) conception, (ii) production / fabrication, (iii) its use / operation, and (iv) end-of-life. LCC is a mathematical procedure helping to make investment decisions and / or to compare different investment options. Steel is not expensive if the life cycle cost is taken into account. The cost of other materials substantially increases over time while the cost of steel normally remains constant.
Besides environmental, social, and economic aspects for steel sustainability, there are three overlapping areas such as (i) environmental-social, (ii) social-economic, and (iii) economic-environmental. The environmental-social area includes concern for preservation of environment, and natural resources since they have both local and global effects. The social-economic area includes concerns for ethics, fairness, and employees’ health, safety, and welfare. The economic-environmental area includes operational efficiency, energy efficiency, and use of renewable resources. Fig 3 shows all the components of steel sustainability.
Fig 3 Components of steel sustainability
Key to steel sustainability is the recognition that a full life cycle approach is the best way to assess the impact on the environment of a product. Hence, it is also the best way to help society make informed decisions on the use of materials and their economic importance. Focusing solely on one aspect of a product’s life, such as the material production, distorts the real picture since it can ignore increased impact during another life cycle phase, such as the use phase.
Selecting the most appropriate materials for any application depends on the consideration of a range of technical and economic factors including, for example, functionality, durability and cost. A further and increasingly important factor for the people who are specifying the materials, in a world where sustainable development is a key issue, is the associated environmental performance of material applications from the perspective of manufacturing and product performance.
Quantifying the environmental burdens per life cycle stage and the inter-connectedness of the steel products production systems is needed in modeling global changes in technology, material substitution, and products criticality in terms of their supply chain vulnerability and supply risk. A comprehensive understanding allows better managing of the impacts and benefits of steel products and informed sustainable resource use.
Steel is a highly durable material used in many qualified applications. Like all materials, its production and use affect the environment in many different ways. Assessing the overall environmental impact of products needs an integrated approach which considers the product over its entire life cycle. This assessment is known as ‘life cycle assessment (LCA)’.
The evaluation of the sustainability of the projects can be conducted with the help of a number of tools which have been developed over the a period of last few years. One of the most complete and detailed analysis methodologies, based on the concept of the life cycle, is LCA. It considers the entire life cycle of a product or system, from raw material extraction, through material production and energy requirements, to use and end of life treatment. Through such a systematic overview, environmental burdens are identified and possibly avoided. LCA can assist in identifying opportunities to improve the environmental performance of the projects at various points in their life cycle. The objective of a LCA is to create the complete environmental profile of a product over its entire life cycle, showing the results with the aid of environmental indicators in a more understandable way.
The first studies about life cycle concept were done in the periods from the late sixties and early seventies. Life cycle concept of products or function has been developed in USA within the realm of public purchasing. But the first mention of ‘life cycle’ with this name was in a report which is about life cycle analysis of cost prepared by Novick for RAND Corporation in 1959. At that time ‘life cycle analysis’ (not yet assessment) is used for cost of weapon systems including purchasing, use, and end of life operations. Life cycle analysis was also used as a tool to improve budget management by government.
In 1972, the total energy usage in production of various types of beverage containers, including glass, plastic, steel, and aluminum were calculated by Ian Boustead in 1979, which makes his methodology applicable to a variety of materials. Public interest increased and different life cycle studies were held during that era. In 1992, life cycle assessment (LCA) workshops were held by Society of Environmental Toxicology and Chemistry (SETAC), one of these focused on life-cycle impact assessment and the other data quality.
In 1993, guidelines for ‘Life-cycle Assessment: A Code of Practice’ which is also known as ‘LCA Bible” was published. In 1990s, LCA was also studied by various groups which were published various guidelines such as Dutch guidelines on LCA, and Nordic countries namely Swedish, Finnish, Danish and Norwegian authors, published Nordic Guidelines on Life Cycle Assessment. UN Environment Program published ‘the Life -cycle Assessment: What Is and How to Do it’. The European Environment Agency also published ‘Life-cycle Assessment: A Guide to Approaches, Experiences and Information Sources’. The ‘products are defined as good or service in a LCA study. LCA is also sometimes being called ‘life cycle approach’, ‘cradle- to – grave analysis’ or ‘life cycle analysis’. A full cradle-to-grave study looks at the production from raw material (cradle), through the use phase, to end-of-life (grave).
In November 1993, LCA standardization began at ISO (The International Organization for Standardization) with the Technical Committee (TC 207) Subcommittee SC 5 in Paris. The standard was based on the Code of Practice which was developed by SETAC. At present ISO has issued series of standards which is referred to as 14040 series and Technical Reports for LCA. This ISO 14040 series of standards outline the approach and rigor to which the LCA exercise is needed to adhere, including the necessity for independent third parties to critically review the work.
The ISO 14000 series of standards include ISO 14001 on Environmental Management Systems. The ISO 14040 series of standards include ISO 14040 with title ‘Principles and Framework’, ISO 14041 with title ‘Goal and Scope Definition and Inventory Analysis’, ISO 14042 with title ‘Life-cycle impact assessment’ (LCIA), ISO 14043 with title ‘Life-cycle interpretation’, ISO 14040 with title ‘Requirements and Guideline’, ISO 14047 with title ‘Examples of Application of ISO 14042’, ISO 14048 with title ‘Data Documentation Format’, and ISO14049 with title ‘Examples of Application of ISO 14041’. According to ISO 14040 series of standards, LCA is used for product development and improvement, strategic planning, public policy making, marketing, and other purposes.
LCA is a tool for evaluating the environmental aspects of products at all stages in their life cycle. LCA is defined in ISO 14040 standard as the ‘compilation and evaluation of the inputs, outputs and potential environmental impacts of a product system throughout its life cycle’. A product’s life cycle includes all processes from raw material acquisition through material production and manufacturing to use and final disposal including recovery options. Any transportation in these phases is also to be accounted,
LCA includes all phases including transport in production and also operational phase of goods and services. In a comparative LCA study, it is not the products themselves to be compared but also the function of these products are to be included. LCA has a holistic approach, which put the environmental impacts in consistent framework, wherever and whenever they occur.
LCA is at present one of the most widely acknowledged and used sustainability evaluation method. It is based on the collection and management of environmental impact data most frequently drawn from available ‘life cycle inventory (LCI) databases. LCA methodology and LCI data help the industry to (i) provide information to the customers, as well as their customers, (ii) understand the contribution of steel to the environmental performance of product systems in different applications, (iii) support technology assessment (benchmarking, determination and prioritization of environmental improvement programmes), (iv) carry out impact assessments to reduce the impacts of its own processes on the environment and to work closely with its customers to gain knowledge about the total impact of steel-use of the products on the environment, over their complete life cycle, and (v) increase public knowledge of the life cycle environmental benefits of using steel in applications and where it can be effective in improving environmental performance. LCA also plays a vital role in the organizational environmental and greenhouse gas reporting requirements, marketing and sales support, and ensuring compliance with regulations and voluntary initiatives such as environmental product declarations.
There is presently a realization around the world that product design and consumer behaviour can affect the overall environmental performance and efficiency of a product. Organizations making the products are paying closer attention to manufacture, utilization, and end-of-life, which is an increasingly important factor for the designers specifying the materials. LCA is ‘a holistic approach based on robust methodology to convert science into insights by quantitative assessment of environmental impacts of products, throughout their life-cycle’.
Among the tools and methodologies available to evaluate the environmental, social, and economic performance of materials and consumer products (including their impact on climate change and natural resources), LCA provides a comprehensive approach which considers the potential impacts from all stages of manufacture, product use and end-of-life (reuse, recycling, or disposal). It is based on sound methodology and transparent reporting and hence is an important tool to assist with policy-making.
The first step in trying to ‘close the loop’ of product life cycles through greater recycling and re-use is that of effectively and systematically analyzing, in environmental terms, such product systems through LCA.
LCA is a tool to assist with the quantification and evaluation of environmental burdens and impacts associated with product systems and activities starting 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.
LCI is a structured, comprehensive and internationally standardized method. It quantifies all relevant emissions and resources consumed and the related environmental and health impacts and resource deletion issues which are associated with the entire life cycle of products. LCI is one of the phases of a LCA. LCI data quantify the material, energy, and emissions associated with a functional system (for example, the manufacture of 1kg of hot rolled coil). This LCI data is the basis for full LCAs, including LCIA, across broader boundaries and complete product life cycles. In addition, this data can be used to address single issues such as carbon foot printing of products.
A significant study data on the life-cycle wide energy use and wider environmental impacts of steels is available from various LCI databases. Steel is a major constituent material for a wide range of market applications and products, such as in the automotive, construction, and packaging sectors. The steel industry recognized, at a very early stage, the need to develop a sound methodology to collect worldwide LCI data, to support the markets and customers. The LCI data of steel industry, the World Steel Association quantifies ‘cradle to gate’ inputs (resources use, energy) and outputs (environmental emissions) of steel production from (i) extraction of resources and use of recycled materials, (ii) production of steel products to the steelworks’ gate, and (iii) end-of-life recovery and recycling of steel.
The ULCOS (Ultra-Low Carbon dioxide Steelmaking) consortium, composed of European steelmaking companies, energy and engineering partners, research institutes and universities, is currently trying to develop technologies for reducing steel production CO2 emissions and uses LCA as one of its main environmental evaluation tools. The research has so far investigated over 80 technologies for CO2 reduction and has shortlisted some of these and is now evaluating, among other aspects, their environmental characteristics via the use of the life cycle paradigm. Specifically, an LCI of the integrated classical steelmaking route has been combined with process simulation software to model the CO2 emissions of potentially more sustainable processes involving new technologies, reductants and methods for capturing and storing CO2.
LCA allows a product system to be assessed from an environmental point of view by holistically considering all life cycle stages of the product, ranging from raw material extraction to the final disposal of the product. It is normally used as a tool to quantify the system-wide (cradle-to-gate or cradle-to-grave) environmental burdens of products, services, and technologies. Such a tool has been used in the past to evaluate the environmental performance of steel product systems.
LCA drivers are supported by ‘national voluntary guidelines-principle’ since they (i) provide goods and services which contribute to sustainability throughout their life cycle, (ii) assure optimal resource use over the life-cycle of the product from design to disposal, and (iii) ensure that everyone such as designers, producers, value chain members, customers and recyclers is connected and promotes sustainable consumption. LCA also assists in the ‘business responsibility reporting’ since it provides reports on the products or services whose design has incorporated social or environmental concerns, risks and / or opportunities and since it provides details on reduction during in sourcing / production / distribution and usage by consumers in respect of resource (energy, water, raw material etc.) use per unit of product
Typically LCA study starts by the goal and scope definition as the first phase and proceeds to inventory analysis phase, continues to Impact assessment phase and as the last phase, study ends up with the interpretation. LCA is a computational (mathematical) process in which the practitioners can need to go back to other phases such as goal and scope definition. The relationship between these phases is shown in Fig 4 which shows LCA framework which has been adopted from ISO 14040.
Fig 4 Life cycle assessment framework
Life cycle of a product is modeled as a product system which performs one or more defined functions. A product system is defined with its function and subdivided into a set of unit processes which are linked by flows. Unit processes includes inputs and outputs of the product system and generates the outputs for other processes as a result of its activities. A product system also can link other products systems by products flows.
The goal of a LCA study is to include (i) intended application and audience of study, (ii) reasons to carry out the study, and (iii) whether the results of the study is intended to be used in comparative assertions and disclosed to the public. The scope includes (i) definition of product system, (ii) functions and functional aspects, (iii) unit system boundary, (iv) allocation procedures, (v) impact categories, (vi) data requirements, (vii) assumptions, (viii) limitations, (ix) initial data quality requirements, (x) type of critical review, and (xi) whether any type and format of the report required for the study. The scope is to be sufficient in the breadth, depth and detail for the study. The system boundary defines the unit processes which are to be included in the system according to the goal and scope definition of the study.
The primary purpose of the functional unit is to provide a reference system which is measurable. For making it possible and to ensure comparability of LCA result a reference flow is also needed to be determined. The reference flow means the amount of products needed to fulfill the function. For example, when a painted surface is studied then it is not useful to compare two different types of paint with a functional unit of one litre of painting. This is because two different types of paint do not give the same performance. Instead of this, it is appropriate to determine ‘one square meter of painted surface with a particular degree of coating and service life of 10 years’ as a functional unit.
Inventory analysis phase involves collection and calculation of relevant input and output datas of the product system. Inventory analysis is a computational process. While data is being collected and more is being learned about the system then there can occur new data requirements or limitations. Sometimes a revision is needed in the goal or scope of the study. Example of the types of data which needs collection includes raw material, energy inputs, and emissions to air and water, outputs etc. In this phase, dealing with systems which involves a range of products and recycling systems, allocation procedures is to be taken into consideration. It is possible to allocate the inputs and outputs to the different products according allocation procedure. This phase is one of the most time consuming and expensive processes in a LCA study.
Life cycle impact assessment phase is a relative approach based on a functional unit which is to be carefully planned to implement the goal and scope of the study. The aim of this phase is to evaluate the potential environmental impacts of the product or service according to life cycle inventory analysis results at their life cycle. Impact assessment phase includes two elements namely (i) which is mandatory, and (ii) which is optional. Mandatory elements are (i) selection of impact categories, category indicators and characterization models, and (ii) classification and characterization. The optional elements are normalization, grouping, weightage allocation, and data quality analysis.
There are two main methods for impact assessment. These are problem-oriented method (mid-points) and damage-oriented method (end points). The mid-point method involves environmental impacts such as climate change, acidification, eutrophication, potential photochemical ozone creation, and human toxicity. The end points method is a damage-oriented method which classifies flows into various environmental damage groups such as human beings, and resources. The various impact categories and their definitions are given in Tab 1.
|Tab 1 Common impact categories used in a LCA|
|Global warming||Increase in the earth’s average temperature|
|Depletion of minerals and fossil fuels||Consumption of non-renewable energy or material resources|
|Photochemical oxidation (smog)||Emission of substances (VOCs, nitrogen oxides) to air|
|Human toxicity||Human exposure to an increased concentration of toxic substances in the environment|
|Ozone depletion||Increase of stratospheric ozone breakdown|
|Eutrophication||Increased concentration of chemical nutrients in water and on land|
|Water use||Consumption of water|
|Land use||Modification of land for various uses|
|Acidification||Emission of acidifying substances to air and water|
|Ecotoxicity||Emission of organic substances and chemicals to air, water and land|
|Note: LCA – Life cycle assessment, VOCs – Volatile organic compounds|
Life cycle interpretation is the final phase of the LCA, in which the results of study is summarized and discussed. In this phase of LCA, the results of the inventory analysis and the impact assessment are evaluated together. Life cycle interpretation reveals conclusion which is to be consistent with the defined goal and scope and which offers suggestions.
Among the tools available to evaluate environmental performance, LCA provides a holistic approach to evaluate environmental performance by considering the potential impacts from all stages of manufacture, product use and end-of-life stages. This is referred to as the cradle-to-grave approach. LCA is well established as a sound environmental assessment tool which is easy to implement, and cost effective and produces affordable and beneficial solutions for material decision making and product design.
The use of LCA is becoming more widespread since it takes into account the environmental impacts of the manufacturing processes of a product, the extraction of the raw materials used by these processes, the use and maintenance of the product by the consumer, its end–of-life (reuse, recycling or disposal) as well as the various methods of transport occurring between every link of the chain. Presently, there is an increasing number of national or regional databases are available which cover major industrial sectors. Many manufacturing organizations have LCA departments and there are more and more LCA software packages are now available. It is also now a subject which is taught at universities.
In Europe, an environmental product declaration (EPD) is a standardized way of quantifying the environmental impact of a product or system following life cycle analysis. For a steelmaker, it is also strategically important to demonstrate this life-style approach (in terms of governments and policies) so that the long service-life, re-use and multi-recycling characteristics of steel are adequately appreciated and measured.
The LCA data can also be used for other purposes including (i) eco-design / design for recycling applications, (ii) benchmarking of specific products, (iii) procurement and supply chain decisions, (iv) inclusion in ‘Type I Ecolabel’ criteria for products, (v) inclusion in life cycle based ‘Type III environmental product declarations’ for specific products, and (vi) the analysis of specific indicators, e.g. carbon footprints or primary energy consumption.
Thinking in life cycles has an important advantage. With LCA, the whole lifespan of a product can be evaluated i.e. the production, use and disposal at the end of life. Environmental impacts occur along the entire supply chain i.e. at the production site itself as well as in the extraction of raw materials and their transport, and at power plants supplying the energy to the production site. Capturing both direct and indirect impacts can help to avoid shifting environmental burden from one life cycle stage to another. Environmental regulations which only regulate one phase (use) of a product’s life cycle can create unintended consequences, i.e. increased CO2 emissions. Correct modelling of the recycling potential of steel products at the end-of-life phase is critical for our sector to compete with other materials and demonstrate the performance of steel solutions to meet the demand for ‘best in class’ sustainable uses.