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Program Brief
Life Cycle Assessment Framework
Environmental Life-Cycle Assessment (LCA) provides a framework, approach, and methods for identifying and evaluating environmental burdens associated with the life cycles of materials and services, from cradle-to-grave. Since the 1970's, there have been several efforts to develop LCA methodology. In the 1990's, the Society for Environmental Toxicology and Chemistry (SETAC) in North America and the U.S. Environmental Protection Agency (USEPA) sponsored workshops and other projects designed to develop and promote consensus on a framework for conducting life-cycle inventory analysis and impact assessment. Similar efforts have been undertaken by SETAC-Europe, other international organizations (such as the International Standards Organization, ISO), and LCA practitioners worldwide. As a result of these efforts, consensus has been achieved on an overall LCA framework and a well-defined inventory methodology.
LCA systematically identifies and evaluates opportunities for minimizing the overall environmental consequences of resource usage and environmental releases. Early research conducted by the USEPA in LCA methodology along with efforts by SETAC led to the four-part approach to LCA that is widely accepted today: 1. Specifically stating the purpose of the study and appropriately identifying the boundaries of the study (Goal and Scope Definition); 2. Quantifying the energy use and raw material inputs and environmental releases associated with each stage of the life cycle (Life Cycle Inventory, LCI); 3. Interpreting the results of the inventory to assess the impacts on human health and the environment (Life Cycle Impact Assessment, LCIA); and 4. Evaluating opportunities to reduce energy, material inputs, or environmental impacts along the life cycle (Improvement Analysis, or Interpretation).
The numbering of the components does not imply that the process is stepwise, proceeding in 1,2,3,4 fashion. LCA works best as an iterative process which always begins with a clear definition of the goal and scope, but may proceed with inventory data collection, or identifying impact categories of particular concern to guide the data collection, or a comparison of improvement options that are being assessed, etc. Because of this interconnectedness of the steps, the LCA process is often depicted by a triangle with Goal and Scope Definition as the centering concept around which inventory, impact assessment and improvement analysis are based.
Defining the Goal and Scope of an LCA
It is clear that the scope and goal definition process is critical. The conclusions of the SETAC document on impact assessment support this view - “The study goal and scope are crucial to managing and coordinating a life-cycle study by bringing together the LCA information needed to make an identified decision and an understanding of the reliability and representativeness of the LCA.” When starting an LCA it is vital that the use for which the study results are intended is clearly identified. Too often this step is only given casual thought before data collection is started. The scope of the study describes the system to be studied and directs how much information is needed, in what categories, and to what level of detail and quality. Further guidance on goal and scope definition can be found in the report by SETAC-NA, “Streamlined Life Cycle Assessment.”
Inventory
Identifying all the process steps within the system being studied is the first step in collecting data for a life cycle inventory. Raw materials use, energy use, the ratio of product to co-products, and environmental releases must all be quantified for each process step that makes up the system. A simple guideline for setting boundaries on data collection is to include operations that make a significant contribution to the entire life cycle.
Again, data collection is driven by the study’s goal. At times site-specific data are needed, such as the data for the manufacture of a certain product being studied. At other times average or commodity data are sufficient, such as when a study is being done at a national level and is not focusing on a particular manufacturer. It is important that the study goal be revisited periodically as data collection progresses to ensure that the goal will be met.
Life cycle inventory has been practiced in Europe and the US for over twenty years leading to a basic methodology that is widely accepted. Practitioners generally agree upon a common system analysis approach for performing inventories, however, obtaining process data that are needed to conduct inventories continues to be difficult due to logistical as well as psychological barriers (such as a fear by industry of sharing data and thereby revealing confidential corporate. Current efforts to make data more available and consistent are explored further in the following section, Future Direction in LCA Development.
Impact Assessment
A life cycle impact assessment describes a system’s effect on human health and the environment. Impact indicators are used to measure the potential for the impact to occur rather than directly quantifying actual impacts. This approach works well to simplify the LCA process making it a more useful tool. A variety of environmental impact indicators and associated indicators have been developed and more continue to be used as LCA methodology evolves. The categories for indicators range from a global level, such as contribution to global warming and ozone depletion, to local impacts, such as photochemical smog formation. As an example, a recent study conducted for the USEPA defines eight impact categories and indicators for: global climate change, stratospheric ozone depletion, acidification, photochemical smog, eutrophication, human toxicity, ecological toxicity, and resource depletion.
ISO 14042 guidelines for impact assessment describe the need for environmentally relevant indicators and emphasize that the results should be clearly stated in terms of the following criteria:
- The ability of the indicator to reflect the consequences of the inventory result on the category endpoint(s), at least qualitatively.
- The incorporation of environmental data or information in
the model, including
- the environmental condition and the intensity of the category endpoint(s),
- the spatial extent of projected impacts on category endpoint(s),
- the temporal aspects, duration, residence time, persistence, timing, etc., of projected impacts on category endpoints,
- the reversibility of projected impacts on category endpoints, and
- the uncertainty of projected impacts with respect to category endpoints.
LCA practitioners and developers around the world continue to explore and improve impact assessment methodology. Further description of life cycle impact assessment methodology, including discussion on what is and is not LCIA, can be found in the 1997 SETAC report, “Life Cycle Impact Assessment: The State of the Art.”
Streamlining LCA
A continuing concern over the cost and time required for LCA encouraged some practitioners to investigate the possibility of “streamlining” or simplifying LCA to make it more feasible and more immediately relevant without losing the key features of a life-cycle approach. When the concept of streamlining was first introduced, many LCA practitioners were skeptical, stating that LCA could not be streamlined. Over time, however, there has been growing recognition that “full-scale” LCA and streamlined LCA are not two separate approaches but are, instead, points on a continuum. Most LCA studies will fall somewhere along that continuum, in between the two extremes. As a result, streamlining an LCA becomes part of the scope and goal definition process.For example, as the study team decides what is and is not to be included in the study, they are engaged in streamlining – in addition to determining what will and will not be included, the study team will determine how to best achieve these requirements. The key is to ensure that the streamlining steps are consistent with the study goals and anticipated uses, and that the information produced will meet the users’ needs. From this perspective, the scope and goal definition process involves determination of what needs to be included in the study to support the anticipated application and decision.
The bottom line is that in order for a study to be called an LCA it must be multi-media (quantify releases to air, water, and land), include all the life cycle stages from cradle to grave (raw material acquisition, manufacture, use/reuse, recycling, and disposal), and include some type of impact assessment upon which the results are interpreted. Further, the interconnectedness of the life cycle stages is an important aspect of interpretation through trade-off analysis.
In addition to comparing the environmental soundness of products, LCA is also being used to assess applications within industrial processes, such as supplementing pollution prevention activities. The following two examples demonstrate how LCA has been used to evaluate options for material substitution and raw material sourcing.
Example 1 - Solvent Substitution Using Aqueous Cleaners
While aqueous cleaners offer a suitable substitution for chlorinated cleaning solvents, energy use with aqueous cleaners may generally be higher than that required for chlorinated solvents. They generally require pretreatment prior to discharge to a POTW in order to adjust the pH, remove oil, grease and solids and to precipitate phosphates and inactive chelating agents. This pretreatment results in the use of energy to run equipment as well as generation of waste streams that must be disposed. Another consideration is that heating may be required during the cleaning process.
Example 2 - Biobased Feedstocks for Chemical Production
An alternative to natural gas-derived feedstock to produce1,4-butanediol (BDO) is a feedstock process that is based on the fermentation of corn-derived glucose to succinic acid, followed by catalytic reduction to BDO. The higher energy use of the alternative process indicates that the overall environmental consequences would be greater than the conventional process. Because electricity generation is inefficient, and energy production in the US is mostly coal-based, the alternative process was analyzed to have a greater potential for impact in multiple impact categories, including global warming, acid rain, smog, water use, particulates, and solid waste (ash) disposal.
Future Direction in LCA Development
While LCA use and activity is constantly increasing, there are several barriers that are prohibiting its wide-spread adoption. The three key barriers are 1. Lack of awareness of the importance of using the life cycle concept, 2. Inaccessibility to life cycle inventory data and a measure of the quality of the data, and 3. Lack of understanding of impact assessment methodology and identifying what type of modeling is appropriate for the specific application.
- Lack of Awareness of the Importance of the Life Cycle Concept. Producers and decision-makers need to be made aware of the life cycle impacts that their activities carry and the importance of going beyond meeting compliance. More importantly, government offices that issue media-based or industry focused regulations and policies need to begin using life-cycle thinking.
- Inaccessibility of Reliable LCA Data. Lack of data has hindered, perhaps prevented, many applications. To make data more easily accessible, several efforts are underway in North America and Europe, such as the work by SPOLD, the Swedish SPINE initiative, and the SETAC- Europe workgroup on "Data Availability and Data Quality.”
- Lack of an Impact Assessment Method.This seems to be more of a barrier in the US than in Europe where several attempts at LCIA have been published. However, there is no consensus on how what methodology should be followed. Although development of LCIA methodology is in the early stages, developers are beginning to recognize that a slate of impact assessment approaches defined by the study goal may be more appropriate than attempting to develop a “one-size-fits-all” approach.
LCA in Environmental Decision-Making
The split between the scientists and engineers who are trying to develop a scientifically-defensible tool and the business managers and policy makers who are trying to make sound environmental decisions is seen clearly within the environmental community in the US. Recently, a SETAC - North America workgroup on environmental decision-making tools and techniques started an effort with the goal of integrating the myriad of decision-support tools and techniques that are available to support decision-making. Initial discussions with decision-makers found that they are not interested in having tools, but instead want the information they need to help them make a decision. The result is the growing realization that the life cycle concept has grown beyond being simply a tool to compare products but is now seen as an essential part of achieving broader goals such as sustainability.
Fortunately, LCA activities can provide a forum for individuals from different parts of the government as well as from different disciplines in both the private and public sectors to work together on particular environmental problems. The results of combining resources and expertise will strengthen the LCA research agenda and lead to a more robust and useful tool.