Several product charts have been updated.

March 2008

Life Cycle Assessment (LCA)

Life Cycle Assessment is gaining popularity as a decision making tool in the sustainable design/build community. LCA takes a product, process, or chemical compound and analyzes its environmental impact throughout its whole life cycle: from the extraction of raw materials through to the afterlife or disposal of the product. A formal LCA requires the gathering of detailed and technical information that is then analyzed, usually using sophisticated computer software. Standards for LCAs have been created by ISO in the 14000 series.

The detailed technical information is called the Life Cycle Inventory(LCI). This is the data that the computer software uses to analyze the product or process. This is usually a large amount of data that is a combination of hard facts, estimations, and assumptions. Subjective value based decisions are a part of deciding what information will be gathered and included in the inventory.

The EPA has created a LCA 101 document which summarizes LCAs like this:

"The LCA process is a systematic, phased approach and consists of four components: goal definition and scoping, inventory analysis, impact assessment, and interpretation...:

  1. Goal Definition and Scoping - Define and describe the product, process or activity. Establish the context in which the assessment is to be made and identify the boundaries and environmental effects to be reviewed for the assessment.
  2. Inventory Analysis - Identify and quantify energy, water and materials usage, and environmental releases (e.g., air emissions, solid waste disposal, waste water discharges).
  3. Impact Assessment - Assess the potential human and ecological effects of energy, water, and material usage and the environmental releases identified in the inventory analysis.
  4. Interpretation - Evaluate the results of the inventory analysis and impact assessment to select the preferred product, process or service with a clear understanding of the uncertainty and the assumptions used to generate the results".

When reviewing an LCA, a few basic questions can help clarify the four categories above:

In summary, the net effect is that

I interpret this to mean that LCA is science based but doesn't give us "the one right" answer or "one best green product or process." LCAs give us the answers we ask it to give us based on the data we value enough to input and based on the assumptions and estimates used. There will always be a level of uncertainty because of the nature of science and the evolution of human knowledge.

EPA: LCA 101 This page at has access to the LCA 101 document that is summarized and quoted in this article. Scroll down and click on the LCA 101 document link to download a copy of the complete LCA 101 report.
by: Sue Norman