Life Cycle Assessment

Synonyms

Cradle-to-cradle assessment; Environmental assessment of products; LCA

Definition

The fundamental principles of life cycle assessment were laid down in the early 1990s in a scientific consensus process under the auspices of the Society of Environmental Toxicology and Chemistry (SETAC) (e.g., SETAC 1993) and later standardized by the International Organization for Standardization (ISO) as elements of the environmental management standard series. The ISO standard for LCA defines a life cycle as: “consecutive and interlinked stages of a product system, from raw material acquisition or generation from natural resources to final disposal” and life cycle assessment as: “compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product system throughout its life cycle” (ISO 2006a). Environmental impacts and their assessment are treated in the (see “Environmental Impact”) and the (see “Environmental Impact Assessment”).

Theory and Application

Theory

Life cycle assessment (LCA) is an analytical method used to assess the environmental impacts of a product or a service throughout its life cycle from the extraction of raw materials over manufacture and distribution to use and maintenance and eventually end of life treatment of the product. The holistic system perspective applied on the life cycle of the product (also referred to as the “product system”) in combination with a comprehensive coverage of environmental impacts caused by the product is a central feature of life cycle assessment. They support a systematic overview that allows identifying and possibly avoiding unintentional shifting of environmental burdens between processes, life cycle stages, or different types of environmental impact.

The main focus of LCA is on the environmental impacts caused by the product system although also social impacts and economic costs are analyzed in a life cycle perspective in some studies, and a framework for life cycle sustainability assessment (LCSA) has been proposed combining environmental LCA, social LCA, and life cycle costing LCC (Klöpffer 2008). The methodology for social LCA is treated by Dreyer et al. (2006, 2010a, b) and Benoît and Mazijn (2009), and LCC is addressed from a life cycle assessment perspective by Hunkeler et al. (2008). These other sustainability dimensions are not treated further in this entry.

The LCA methodology comprises the phases goal and scope definition (G&S), life cycle inventory (LCI), life cycle impact assessment (LCIA), and interpretation.

As visible from Fig. 1, life cycle assessment is an iterative procedure with multiple feedback loops between the phases. The interpretation, which is performed after each phase, includes a sensitivity analysis to determine the influence that choices made in that phase has on its outcome. This insight serves to guide a new iteration with qualification of the choices made and the data collected for central processes in the previous iteration.

Life Cycle Assessment, Fig. 1

The LCA framework. (Based on ISO 2006a)

Goal Definition

The first phase of the life cycle assessment is definition of the goal of the study. This is where the LCA practitioner takes care to get the question right before starting to answer it with the assessment. It is a very important phase influencing central choices to be made in the ensuing scope definition, and framing the interpretation of the results, which should always be done in respect of the defined goal of the study. For further details see the “Life Cycle Assessment: Goal and Scope Definition”.

Scope Definition

Based on the defined goal, the life cycle assessment is scoped in terms of six aspects.

• 1. The product system to be studied

  This is where the boundaries of the product system (example in Fig. 3) are drawn and decisions made on which processes need to be included and which processes can be left out, considering the goal of the study. The choices made when drawing the boundaries are later checked when results of the inventory analysis and impact assessment are available (as illustrated in Fig. 2).

• 2. The functions of the product system and the functional unit of the study

  When the LCA is used for comparative purposes (which is very often the case), it is essential that the compared alternatives are true alternatives, i.e., they are seen as functionally equivalent by the user of the product or service that is studied. This is ensured by anchoring the LCA in a functional unit – a quantitative description of the service to be offered by the analyzed product systems.

• 3. Types of environmental impact to be analyzed

  The LCA practitioner must up front choose which environmental impacts the study should address, so the relevant information about the product system can be gathered during the later inventory analysis. It is a requirement in the ISO standard that the chosen selection of impact categories reflects a comprehensive set of environmental issues related to the product system being studied (ISO 2006b).

• 4. Handling of multifunctional processes (allocation procedures)

  In most product systems, there will be processes that have several valuable outputs (often termed co-products or by-products), of which some are not used by the studied product system (i.e., they do not contribute to the functional unit of the study). This means that not all the environmental impact from the multifunctional process should be carried by the studied product system; other product systems should carry part of the impact. The ISO standard offers a hierarchy of solutions to this challenge (ISO 2006b).

• 5. Fundamental approach to the modeling of the inventory (attributional or consequential)

  Depending on whether the LCA is performed with the purpose (as defined in the Goal definition) to support decisions and choices between alternative products or with the purpose to document the environmental impacts associated with a product or a service, different modeling approaches are recommended in the inventory analysis. The former requires a consequential approach (in simple terms analyzing the consequences of the decision for the product system and the resulting environmental impacts, typically using market information to identify the marginal technologies that are affected by the decision). The latter calls for an attributional approach (accounting perspective, typically applying average data for the involved technologies).

• 6. Type of critical review, if any, and type and format of the report required for the study.

  Considering the complexity of most product systems and the number of choices that are made in an LCA, a critical review by an expert outside the study is normally a good idea. For publicly communicated LCA studies that claim to be compatible with the ISO standard, a critical review is a requirement of the standard that gives guidance on how to perform the review.

Life Cycle Assessment, Fig. 2

LCA proceeds through multiple iterations of each methodological phase (G&S is goal and scope definition, LCI is life cycle inventory, and LCIA is life cycle impact assessment), and within each iteration the work is focused with guidance from the outcome of the previous iteration

Life Cycle Assessment, Fig. 3

Process tree illustrating the life cycle of paper for newsprint or office use. “T” and “W” represent transportation and waste treatment processes, respectively, with life cycle of their own, not shown in the figure

Life Cycle Inventory, LCI

The life cycle inventory phase follows the scope definition and consists in a compilation of input and output flows from all the processes in the product system. The product system can be divided into a foreground system, comprising all the processes under influence of the producer of the product or the provider of the service, and a background system on which the foreground processes draw. The background system comprises processes that are not directly controlled by the producer or immediate suppliers such as raw material extraction, production of materials and standard components, transportation, supplies of electricity and water, and treatment of waste. The concept of foreground and background system is illustrated in Fig. 4.

Life Cycle Assessment, Fig. 4

The product system can be split into a foreground system and a background system according to the influence of the producer or provider of the service

For processes belonging to the foreground system, it is normally possible for the producer of the product to obtain primary data representing the actual processes that are active in the product system. These can be obtained through measurements on own processes and inquiries to suppliers. Depending on the goal of the study, primary data should be sought for the dominating processes in the foreground system.

For processes belonging to the background system, it is generally not possible and often not relevant to decide the precise process that is active in the product system. For commodities traded in a market it may fluctuate with time and location, and often, an average across technologies is used, e.g., for the technology used to generate the electricity or incinerating the waste from the product system.

Unit process databases offer data on input and output for many technical processes presented per functional output of the process (e.g., per kWh for electricity generation, per mass for production of materials like plastics, or per weight and distance for transportation processes). These serve as building blocks that can be scaled to the relevant size when the product system is modeled.

The inventory can be reported per life cycle stage or for the whole product system as a list of elementary flows per functional unit.

Life Cycle Impact Assessment, LCIA

Even for simple product systems, LCI easily comprises hundreds of elementary flows in the form of resource input, land and water use, and emissions to the different compartments of the environment – air, water, and soil. Some flows are large and some are small, and their ability to cause environmental impact can vary dramatically. In order to interpret the outcome of the inventory analysis in accordance with the goal of the LCA, it is necessary to incorporate knowledge about the environmental properties of the elementary flows. This is the objective of the impact assessment phase of LCA.

According to the LCIA framework laid out in the ISO standard, the impact assessment proceeds through a number of steps:

• First the categories of environmental impact to address are defined or – typically – chosen among already defined and developed categories of impact (see “Environmental Impact” for default list of impact categories in LCIA). Then the elementary flows from the inventory are assigned to the different categories of impact, each of which is represented by an impact indicator. This step is called classification of the inventory flows.

• Next step is characterization where a quantification of the contribution of the elementary flows to the total impact score for the category is calculated using characterization factors. A characterization factor is a quantitative expression of the substance’s specific ability to impact on the indicator of the impact category, determined by the inherent properties of the substance. The resulting indicator scores are summed across elementary flows within the impact category, and the collection of category indicator results for the different impact categories is the environmental impact profile of the product.

• The indicator can be chosen anywhere along the impact pathway from inventory result to the final endpoint, human health, natural environment, or natural resources. Figure 5 lists the typical midpoint impact categories (i.e., category indicator chosen at some point between the elementary flow of the inventory and the resulting damage to an area of protection in the form of human health, environment, or resources). It also indicates how each of the impact categories relates to the areas of protection.

• A number of LCIA methods have been developed over the last 20 years. Hauschild and Huijbregts (2015) give a recent and consistent presentation of most of the existing LCIA methods.

• The third and fourth steps of the LCIA are voluntary and support comparison across impact categories. The third step is normalization, where the indicator results from the characterization step are related to a common set of reference information, frequently the current level of impact from society within each impact category. Normalization brings all scores on a common scale, expresses them in a common metric, hereby making it easier to relate them to each other and preparing for the likewise voluntary valuation or weighting.

• Valuation is the fourth and final step of the LCIA. It may be performed in comparative LCAs none of the compared alternatives is the absolute preference, outperforming the others on all category indicator results. It can be done as a weighting assigning quantitative weights to all category indicators, but it can also be a more qualitative ranking or grouping of the category indicators. It involves subjective choices, and in LCA studies supporting comparative assertions disclosed to the public the ISO standard does not allow the use of weighting (ISO 2006b).

Life Cycle Assessment, Fig. 5

Impact categories according to the European Commission’s ILCD guidelines (Hauschild et al. 2013)

Interpretation

The last phase of the life cycle assessment methodology is the interpretation phase where the results of the other phases are interpreted in accordance with the goal of the LCA. Sensitivity and uncertainty analysis are important elements in the interpretation and as illustrated in Figs. 1 and 2, these elements of the interpretation are performed throughout the analysis as the guiding element of the iterative approach that is fundamental in LCA. The conclusions that come out of the interpretation should respect the intentions and restrictions of the goal and scope definition of the study. The interpretation should present the results of the LCA in an understandable way and help the reader evaluate the robustness of the conclusions and understand the weaknesses of the study in light of the identified limitations.

Application

The ability of LCA to quantify environmental impacts of products and services is utilized for various purposes by different sectors in society. Hauschild et al. (2017) reviewed LCA application practices within multiple decision contexts and technological sectors.

Industry

With the growing concern about environmental sustainability and the outsourcing of manufacturing, the responsibility of industry has expanded from its own facilities to encompass the whole value chain. With product stewardship and the focus on circular economy, the environmental performance in the use stage and end of life stage of the product also increasingly becomes the responsibility of the company. Accordingly, sustainability claims have to consider the whole life cycle of the products or services of the company, and this makes LCA a central tool for gauging the environmental sustainability performance of an industry. Important fields of application are product development, product documentation and marketing, and company reporting.

Product development – design for environment. Incorporation of environmental performance in the development of products has long been an important internal use of LCA in many companies. LCA helps determine the environmental impact hot spots in the product and in its life cycle identify focus points for the product improvement and set targets for the product development. During the product development LCA-based tools are used to analyze and compare alternative solutions and document the attained improvements (Fig. 6).

Life Cycle Assessment, Fig. 6

LCA-based insights help focus ecodesign (design for environment, DFE) on the environmental hotspots in the product and its life cycle

Environmental product information and marketing. Companies that want to use the environmental performance attributes in the marketing of products may use Environmental Product Declarations (EPDs), which have the results of a life cycle impact assessment as a core element together with other relevant environmental information about the product (International EPD System 2017).

Company reporting. Outsourcing introduces a risk of problem shifting. The environmental impacts from the company’s own activities are reduced, but impacts from the suppliers may be worse for the same produced output. Through its contracts with suppliers, the company can influence their environmental performance, and this entails a responsibility for this part of the life cycle as well. It is therefore relevant to include the value chain in environmental sustainability reporting, and many companies do that, e.g., in their reporting on environmental performance indicators like the company’s carbon footprint or environmental footprint, taking a life cycle perspective on their activities, and quantifying the associated impacts in a life cycle perspective. Some companies (e.g., Puma sport goods and Novo Nordisk pharmaceuticals) have taken the step to calculate and report on the “true cost” of their products or activities, quantifying the environmental impacts in the value chain (the “externalities” in economic terms), monetarizing them, and including them as economic costs in the economic accounting for the product or the company to reveal its net economic value to society (Trucost 2017).

Authorities

Historically, public regulation of environmental pollution has focused on the most important point sources like heavily polluting industries, mines, or landfills. Some of the most challenging environmental impacts that our societies face today are, however, of a more diffuse nature. They are caused by activities or emission sources that each alone has a very small impact, that can be difficult to trace to the source (hence “diffuse”), but that occur in huge and often growing numbers which causes the problem. An example is climate change impacts where an important cause is our use of fossil-based energy for transportation, use of electrical products, or heating of houses. Another example is the use of ten thousands of chemicals in the products that we find in the market today and the emission of these chemicals to the environment from manufacturing, use, and disposal of the products. Taken one by one, most of these chemicals may not constitute an environmental problem but together they can lead to exposure of ecosystems or humans in exceedance of safe levels. Given the role that consumption of products has in the growth of these environmental problems, it is natural that authorities have looked toward the products and their regulation in search for a way to control them, and the last decades have seen the development of sustainable consumption and production strategies to support sustainable development at the regional as well as the global level (EC 2017; UNE 2017).

For quantitative information about the environmental performance of products LCA is the tool of choice. The European Commission has introduced the term “Product Environmental Footprints (PEFs)” for the results of product life cycle impact assessments. In order to harmonize the results of life cycle assessments and strengthen their use in policy contexts, a PEF guideline has been developed and operationalized in a number of Product Category Rules simplifying and harmonizing the LCA work by stipulating methodological details in the assessment approach to be taken for different product categories (PEF World Forum 2017).

In accordance with the ISO standard for ecolabeling (ISO 1999), life cycle assessments are also used in the development of criteria for ecolabels in many parts of the world. The LCA results are used to identify the most important causes of environmental impact for the product category in question, and determine desirable performance levels for these aspects, so the ecolabel criteria can target them. Together with environmental product declarations (see above), ecolabels are used to inform both professional public purchasers and ordinary consumers.

Consumers

Consumers use LCA-based information to make informed choices among alternative products or services, when they wish to behave as green consumers and favor the producers that offer the greenest products. The information is typically offered in the form of ecolabels but also environmental product declarations and similar information is increasingly becoming available to the interested consumer.

Cross-References

• Environmental Impact

• Life Cycle Assessment: Goal and Scope Definition

• Life Cycle Impact Assessment

• Life Cycle Engineering

• Product Life Cycle Management