EME 807
Technologies for Sustainability Systems

2.4. Life Cycle Assessment


2.4. Life Cycle Assessment Methodology

Life Cycle Assessment  (LCA) is a "cradle-to-grave" approach for evaluating products, materials, processes, services, and industrial systems with respect to their environmental impacts. Cradle-to-grave process begins with the extracting of raw materials from the earth to manufacture a product and ends at the point when all materials are returned to the earth in some form. LCA looks at all the stages of the product’s life one by one, estimates various environmental impacts at each stage and, as a result, allows selecting the path or processes that are least impactful based on chosen metrics.

LCA studies help decision-makers select the product, process, or technology that would be "least evil" in terms of its environment footprint, however the final judgment and interpretation of the results always depends on the key metrics and criteria that are most important to specific stakeholders. In that sense, LCA objectives should be set early in the analysis to answer the questions relevant to a particular project or application. Classic LCA deals primarily with environmental impacts, but further can be used with other pieces of information, such as cost and performance data, to find optimal solutions. 

Life Cycle Assessment Objectives: 

  • Support informed decision making for government, industry, and businesses

  • Provide basis for fair comparison between products and alternatives

  • Support recommendations for improving design and lowering impacts

The diagram below illustrates the main lifecycle stages to be considered in LCA:

stages of lifecycle assessment
Figure 2.3: The main stages and typical inflows and outflows considered in lifecycle assessment.
Click to expand to provide more information

This diagram is based around a box-shaped system that includes four processes and is surrounded by a System Boundary. The four highlighted stages are:

  • Raw Materials Acquisition
  • Manufacturing
  • Operation/Use/Maintenance
  • Recycle/Waste Management

System Inputs are shown as arrows on the left of the system, outside the System Boundary. Inputs are represented by Raw Materials and Energy that flow into the system.

System Outputs shown as arrows on the right and at the bottom of the system, outside the System Boundary. Outputs are represented by Main Product and Co-Products (shown at the bottom), and Atmospheric Emissions, Waterborne Waste, and Solid Wastes (shown on the right).

Credit: Mark Fedkin

As you can see in the diagram above, any product or technology would require input of some raw materials and energy at all stages: from acquisition to manufacturing, operation, and finally disposal. All of the mentioned lifecycle stages may produce atmospheric emissions, waterborne and solid wastes, simply because the efficiency of material use and energy conversion is always below 100% - there are losses and by-products, which sometimes can be highly undesirable. LCA helps to keep track of all useful and harmful outcomes, and the diagram in Figure 2.3 provides a guideline to LCA mapping.

Procedure for Life Cycle Assessment

A standard LCA study would consist of several key steps outlined below:

  1. Goal definition and scope: Identify a product / Set system boundaries / Develop LCA map and material flow chart.
  2. Inventory analysis: Collect data / Identify and quantify energy, water, and materials as inputs and emissions as outputs.
  3. Impact assessment: Set impact categories / Develop metrics / Perform calculations and comparative analysis.
  4. Data interpretation: Relate metrics to objectives / Quantify human and ecological effects /  Deliver information to target audience / Issue recommendations

The standardized procedure for the LCA recommended for product and technology assessment in the U.S. is documented in the EPA guidelines referred below. Study this document carefully – some parts of this framework will be used as a basis for technology evaluation repeatedly in this course's assignments.

Reading Assignment:

US EPA Document: Life Cycle Assessment: Principles and Practice, EPA/600/R-06/060, 2006.

This document provides a detailed guideline on how lifecycle assessment should be performed. This is a long document and contains a significant amount of information. While I would like you to look through the entire file, here are a few things that you may want to focus on:

  • Certainly read through Chapter 1, where the basics of the LCA strategy are explained (pp. 1-7).
  • In Chapters 2 and 3, try to mainly understand how the scope and flow diagrams are constructed for a particular project or product. The purpose of those diagrams is to present a big picture and list all the important elements of the life cycle before data analysis is started. Study the examples in Figures 2-1 and 3-2, as you will be asked to do something similar for this lesson assignment. You may scan quickly through the rest of these chapters.
  • Chapter 4 on Impact Assessment is the core of the LCA. Read through entire chapter 4 (pp. 46-53). Take a note of the major environmental impacts that are usually considered in LCA. That will be an important piece of information when we explore different metrics in Lesson 3.
  • You can quickly scan through Chapter 5, taking note of the main steps in LCA interpretation.

In this Lesson, we are going to do an exercise on LCA scoping for a simple product. That would only cover Stage 1 of the entire process. Still, it is a very important step that sets the ground for the entire analysis and provides directions for collecting data and developing metrics during the Inventory Analysis and Impact Assessment stages of the LCA. Please refer to the Canvas Module 2 for specific directions on this assignment.

Examples of LCA Projects

Website: Design Life-Cycle, University of California, Davis, Department of Design, URL: http://www.designlife-cycle.com/  Accessed: May 2020.

This website presents a very versatile collection of LCA studies of consumer products, fashion, architecture, electronics, and other technologies. Studies are presented in the "nutshell" form and enhanced by infographics. Very fun resource to explore!

LCA Limitations

  • LCA thoroughness and accuracy will depend on the availability of data; gathering of data can be problematic; hence a clear understanding of the uncertainty and assumptions is important.
  • Classic LCA will not determine which product, process, or technology is the most cost-effective or top-performing; therefore, LCA needs to be combined with cost analysis, technical evaluation, and social metrics for comprehensive sustainability analysis.
  • Unlike traditional risk assessment, LCA does not necessarily attempt to quantify any specific actual impacts. While seeking to establish a linkage between a system and potential impacts, LCA models are suitable for relative comparisons, but may be not sufficient for absolute predictions of risks.

Even for relatively small systems, LCA is a comprehensive task that requires interdisciplinary knowledge in the technical and economic areas. Hence, LCA projects are typically assigned to teams of experts and can rarely be performed by a single person with sufficient accuracy.

LCA approach has developed over decades, coming from a product-oriented model used to evaluate environmental impact to a bigger framework that elaborates on a wider environmental, economic, and social scale. At the current stage, LCA is being transformed into Life Cycle Sustainability Analysis (LCSA), which links the sustainability questions with the knowledge and research needed to address them. Check out the following article to learn more about the LCA history and background:

More Reading on LCA:

Journal article: J.B. Guinee et al., Life Cycle Assessment: Past, Present, and Future, Environ. Sci. Technol., 2011, 45, 90-96.

This article reviews the history and the most recent advances and trends in the life cycle assessment. It provides some good illustrations of method diversity, which can be both beneficial and challenging in terms of data interpretation and application. The article also exemplifies LCA being linked to policy development and decision making.

This reading is optional, but highly recommended in the context of this lesson. This article can be accessed online through the Penn State Library system database or via link in Canvas.