EME 807
Technologies for Sustainability Systems

5.7. LCA approach to waste management systems

Life Cycle Assessment (LCA) is an analytical framework that is normally focused on resource consumption and on impacts to human health and the environment associated with manufacturing of specific product. The main advantage of LCA is that it alleviates problem-shifting considering the full range of relevant impacts.

Lifecycle assessment (LCA) for waste management systems is designed according to the same principles as LCA for products and processes (as advised by EPA Guide for LCA - see Lesson 2). [Life Cycle Assessment…, 2006]

As you may recall from Lesson 2, the major steps in the LCA of waste management systems are:

  1. scope definition (defining system boundaries and parameters);
  2. inventory analysis (identifying inputs and outputs of all processes in lifecycle);
  3. impact assessment (setting assessment criteria; quantifying the environmental impact);
  4. data interpretation (analyzing and comparing all impacts and performing sensitivity analysis).

With the four above consecutive stages, LCA is still an iterative process; i.e., the results of data interpretation can help fine-tuning the earlier phases of the analysis. [Solid Waste Technology.., 2011]. Refer to the following reading material to study the main steps in LCA of waste management systems:

Reading Assignment:

Solid Waste Technology & Management, Christensen, T., Ed., Wiley and Sons, 2011.

Chapter 3.1. Christensen, T.H., LCA in Waste Management: Introduction of Principle and Method, pp. 113-134.

This book is available online through PSU Library system.

While reading, pay special attention to the assessment criteria commonly used in waste management LCA (Box 3.1.3). What criteria are especially influential or unique to the waste management field? Note that, depending on the goals of the analysis, some of these criteria can be excluded and others can be added.

One of the key stages of LCA is impact assessment, because it generates numerical data that can directly affect conclusions from this assessment. The main four steps in impact assessment are:

  • setting assessment criteria;
  • defining or choosing scoring system (model);
  • normalization of impacts;
  • weighing of impacts.

Based on the above reading, answer the following questions:

Check Your Understanding

What is the purpose of normalization of impact scores?



What is the purpose of weighing impact scores?



Click for answer.

ANSWER:

Normalization is unifying results in common terms for proper comparison. For example, emissions of methane and carbon dioxide both contribute to greenhouse effect. For comparison, methane emissions should be normalized to CO2 equivalents to compare their global warming potentials. Normalization must be done to ensure adequacy.

Weighing is assigning "importance" scores to impacts from standpoint of stakeholders. Weighing is subjective and is done solely to fit the analysis objective. Weighing is optional.

The following material can be used as additional reading on this topic. It provides extended discussion on how LCA is applied to waste management systems and shows some real life examples.

Supplemental Reading

Solid Waste Technology & Management, Christensen, T., Ed., Wiley and Sons., 2011. Chapter 3.2. "Application of LCA in Waste Management", Bjorklund, A., Finnveden, G., Roth, L., pp. 137-159.

This book is available online through PSU Library system.