Life-cycle assessment


Life cycle assessment, also known as life cycle analysis, is a methodology for assessing the impacts associated with all the stages of the life cycle of a commercial product, process, or service. For instance, in the case of a manufactured product, environmental impacts are assessed from raw material extraction and processing, through the product's manufacture, distribution and use, to the recycling or final disposal of the materials composing it.
An LCA study involves a thorough inventory of the energy and materials that are required across the supply chain and value chain of a product, process or service, and calculates the corresponding emissions to the environment. LCA thus assesses cumulative potential environmental impacts. The aim is to document and improve the overall environmental profile of the product by serving as a holistic baseline upon which carbon footprints can be accurately compared.
The LCA method is based on ISO 14040 and ISO 14044 standards. Widely recognized procedures for conducting LCAs are included in the ISO 14000 series of environmental management standards of the International Organization for Standardization, in particular, in ISO 14040 and ISO 14044. ISO 14040 provides the 'principles and framework' of the Standard, while ISO 14044 provides an outline of the 'requirements and guidelines'. Generally, ISO 14040 was written for a managerial audience and ISO 14044 for practitioners. As part of the introductory section of ISO 14040, LCA has been defined as the following:
LCA studies the environmental aspects and potential impacts throughout a product's life cycle from raw materials acquisition through production, use and disposal. The general categories of environmental impacts needing consideration include resource use, human health, and ecological consequences.
Criticisms have been leveled against the LCA approach, both in general and with regard to specific cases. When the understood methodology of performing an LCA is not followed, it can be completed based on a practitioner's views or the economic and political incentives of the sponsoring entity. In turn, an LCA completed by 10 different parties could yield 10 different results. The ISO LCA Standard aims to normalize this; however, the guidelines are not overly restrictive and 10 different answers may still be generated.

Definition, synonyms, goals, and purpose

Life cycle assessment is sometimes referred to synonymously as life cycle analysis in the scholarly and agency report literatures. Also, due to the general nature of an LCA study of examining the life cycle impacts from raw material extraction through disposal, it is sometimes referred to as "cradle-to-grave analysis".
As stated by the National Risk Management Research Laboratory of the EPA, "LCA is a technique to assess the environmental aspects and potential impacts associated with a product, process, or service, by:
  • Compiling an inventory of relevant energy and material inputs and environmental releases
  • Evaluating the potential environmental impacts associated with identified inputs and releases
  • Interpreting the results to help you make a more informed decision".
Hence, it is a technique to assess environmental impacts associated with all the stages of a product's life from raw material extraction through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling. The results are used to help decision-makers select products or processes that result in the least impact to the environment by considering an entire product system and avoiding sub-optimization that could occur if only a single process were used.
Therefore, the goal of LCA is to compare the full range of environmental effects assignable to products and services by quantifying all inputs and outputs of material flows and assessing how these material flows affect the environment. This information is used to improve processes, support policy and provide a sound basis for informed decisions.
The term life cycle refers to the notion that a fair, holistic assessment requires the assessment of raw-material production, manufacture, distribution, use and disposal including all intervening transportation steps necessary or caused by the product's existence.
Despite attempts to standardize LCA, results from different LCAs are often contradictory, therefore it is unrealistic to expect these results to be unique and objective. Thus, it should not be considered as such, but rather as a family of methods attempting to quantify results through different points-of-view. Among these methods are two main types: Attributional LCA and Consequential LCA. Attributional LCAs seek to attribute the burdens associated with the production and use of a product, or with a specific service or process, for an identified temporal period. Consequential LCAs seek to identify the environmental consequences of a decision or a proposed change in a system under study, and thus are oriented to the future and require that market and economic implications must be taken into account. In other words, Attributional LCA "attempts to answer 'how are things flowing within the chosen temporal window?', while Consequential LCA attempts to answer 'how will flows beyond the immediate system change in response to decisions?"
A third type of LCA, termed "social LCA", is also under development and is a distinct approach to that is intended to assess potential social and socio-economic implications and impacts. Social life cycle assessment is a useful tool for companies to identify and assess potential social impacts along the lifecycle of a product or service on various stakeholders. SLCA is framed by the published in 2009 in Quebec. The tool builds on the ISO 26000:2010 Guidelines for Social Responsibility and the Global Reporting Initiative Guidelines.
The limitations of LCA to focus solely on the ecological aspects of sustainability, and not the economical or social aspects, distinguishes it from product line analysis and similar methods. This limitation was made deliberately to avoid method overload but recognizes these factors should not be ignored when making product decisions.
Some widely recognized procedures for LCA are included in the ISO 14000 series of environmental management standards, in particular, ISO 14040 and 14044. Greenhouse gas product life cycle assessments can also comply with specifications such as Publicly Available Specification 2050 and the GHG Protocol Life Cycle Accounting and Reporting Standard.
File:Life cycle analysis and GHG carbon accounting.jpg|thumb|Life cycle analysis and carbon accounting for greenhouse gas emissions

Main ISO phases of LCA

According to standards in the ISO 14040 and 14044, an LCA is carried out in four distinct phases, as illustrated in the figure shown at the above right. The phases are often interdependent, in that the results of one phase will inform how other phases are completed. Therefore, none of the stages should be considered finalized until the entire study is complete.

Goal and scope

An LCA study begins with a goal and scope definition phase, which includes the product function, functional unit, product system and its boundaries, assumptions, data categories, allocation procedures, and review method to be employed in the analysis. The ISO LCA Standard requires a series of parameters to be quantitatively and qualitatively expressed, which are occasionally referred to as study design parameters. The two main SPDs for an LCA are the goal and scope, both which must be explicitly stated.
Generally, an LCA study starts with a clear statement of its goal, outlining the study's context and detailing how and to whom the results will be communicated. Per ISO guidelines, the goal must unambiguously state the following items:
  1. The intended application
  2. Reasons for carrying out the study
  3. The audience
  4. Whether the results will be used in a comparative assertion released publicly
The goal should also be defined with the commissioner for the study, and it is recommended a detailed description for why the study is being carried out is acquired from the commissioner.
Following the goal, the scope must be defined by outlining the qualitative and quantitative information included in the study. Unlike the goal, which may only include a few sentences, the scope often requires multiple pages. It is set to describe the detail and depth of the study and demonstrate that the goal can be achieved within the stated limitations. Under the ISO LCA Standard guidelines, the scope of the study should outline the following:
  • Product system, which is a collection of processes that are needed to perform a specified function and are within the system boundary of the study. It is representative of all the processes in the life cycle of a product or process.
  • Functional unit, which defines precisely what is being studied, quantifies the service delivered by the system, provides a reference to which the inputs and outputs can be related, and provides a basis for comparing/analyzing alternative goods or services. The functional unit is a very important component of LCA and needs to be clearly defined. It is used as a basis for selecting one or more product systems that can provide the function. Therefore, the functional unit enables different systems to be treated as functionally equivalent. The defined functional unit should be quantifiable, include units, consider temporal coverage, and not contain product system inputs and outputs. Another way to look at it is by considering the following questions:
  • # What?
  • # How much?
  • # For how long / how many times?
  • # Where?
  • # How well?
  • Reference flow, which is the amount of product or energy that is needed to realize the functional unit. Typically, the reference flow is different qualitatively and quantitatively for different products or systems across the same reference flow; however, there are instances where they can be the same.
  • System boundary, which delimits which processes should be included in the analysis of a product system, including whether the system produces any co-products that must be accounted for by system expansion or allocation. The system boundary should be in accordance with the stated goal of the study.
  • Assumptions and limitations, which includes any assumptions or decisions made throughout the study that may influence the final results. It is important these are made transparent as their omission may result in misinterpretation of the results. Additional assumptions and limitations necessary to accomplish the project are often made throughout the project and should be recorded as necessary.
  • Data quality requirements, which specify the kinds of data that will be included and what restrictions. According to ISO 14044, the following data quality considerations should be documented in the scope:
  • # Temporal coverage
  • # Geographical coverage
  • # Technological coverage
  • # Precision, completeness, and representativeness of the data
  • # Consistency and reproducibility of the methods used in the study
  • # Sources of data
  • # Uncertainty of information and any recognized data gaps
  • Allocation procedure, which is used to partition the inputs and outputs of a product and is necessary for processes that produce multiple products, or co-products. This is also known as multifunctionality of a product system. ISO 14044 presents a hierarchy of solutions to deal with multifunctionality issues, as the choice of allocation method for co-products can significantly impact results of an LCA. The hierarchy methods are as follows:
  • # Avoid Allocation by Sub-Division - this method attempts to disaggregate the unit process into smaller sub-processes in order to separate the production of the product from the production of the co-product.
  • # Avoid Allocation through System Expansion - this method attempts to expand the process of the co-product with the most likely way of providing the secondary function of the determining product. In other words, by expanding the system of the co-product in the most likely alternative way of producing the co-product independently. The impacts resulting from the alternative way of producing the co-product are then subtracted from the determining product to isolate the impacts in System 1.
  • # Allocation based on Physical Relationship - this method attempts to divide inputs and outputs and allocate them based on physical relationships between the products.
  • # Allocation based on Other Relationship - this method attempts to divide inputs and outputs and allocate them based on non-physical relationships.
  • Impact assessment, which includes an outline of the impact categories identified under interest for the study, and the selected methodology used to calculate the respective impacts. Specifically, life cycle inventory data is translated into environmental impact scores, which might include such categories as human toxicity, smog, global warming, and eutrophication. As part of the scope, only an overview needs to be provided, as the main analysis on the impact categories is discussed in the Life Cycle Impact Assessment phase of the study.
  • Documentation of data, which is the explicit documentation of the inputs/outputs used within the study. This is necessary as most analyses do not consider all inputs and outputs of a product system, so this provides the audience with a transparent representation of the selected data. It also provides transparency for why the system boundary, product system, functional unit, etc. was chosen.