EME 807
Technologies for Sustainability Systems

2.4. Life Cycle Assessment (LCA) methodology

Life Cycle Assessment (LCA) is a "cradle-to-grave" approach for assessing products, processes, industrial systems, and the like. "Cradle-to-grave" begins with the gathering of raw materials from the earth to create the product, and ends at the point when all materials are returned to the earth. LCA evaluates all stages of a product’s life from the perspective that they are interdependent, meaning that one operation leads to the next. LCA enables the estimation of the cumulative environmental impacts resulting from all stages in the product life cycle and, as a result, allows selecting the path or process that is more environmentally preferable.

LCA approach has developed over decades coming from 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. Read the following article to learn more about the LCA background:

Reading Assignment:

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

This article describes the history and most recent advances and trends in the life cycle assessment. It can be accessed online via the link above or through the Penn State Library system database. It is a good introduction to LCA if you are not too familiar with this concept.

LCA helps decision-makers select the product, process, or technology that results in the least impact to the environment. This information can be used with other factors, such as cost and performance data to find optimal solutions. LCA identifies the transfer of environmental impacts from one media to another (for instance: a new process may lower air emissions, but creates more wastewater, etc.) and between different lifecycle stages. 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 square-shaped system that includes four processes and is surrounded by a System Boundary. The four processes are:

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

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

System Outputs are at right and at the bottom of the system, outside the System Boundary: out the bottom are arrows for Main product and Co-Products, and out the right side of the system are arrows for Atmospheric Emissions, Waterborne Waste, and Solid Wastes.

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 never 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.

A typical LCA project plan includes the following main stages:

  1. Goal definition and scope. Identify a product / process / technology; establish context and system boundaries.
  2. Inventory analysis. Identify and quantify energy, water, and materials as inputs as well as environmental releases as outputs.
  3. Impact assessment. Assess the potential human and ecological effects, quantify metrics.
  4. Data interpretation. Compare data from Inventory Analysis and Impact Assessment stages to select or recommend a preferred product, process, or technology.

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.

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 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 (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.