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:
"Specifically, LCA is a technique to assess the environmental aspects and potential impacts associated with a product, process, or service, by:
- Compiling an inventory of relevant energy and material inputs and environmental releases
- Evaluating the potential environmental impacts associated with identified inputs and releases
- Interpreting the results to help decision-makers make a more informed decision."
"The LCA process is a systematic, phased approach and consists of four components: goal definition and scoping, inventory analysis, impact assessment, and interpretation...:
- 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.
- Inventory Analysis - Identify and quantify energy, water and materials usage, and environmental releases (e.g., air emissions, solid waste disposal, waste water discharges).
- Impact Assessment - Assess the potential human and ecological effects of energy, water, and material usage and the environmental releases identified in the inventory analysis.
- 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:
- What environmental impacts are being considered? Common ones include: global warming, eutrophication, acidification, and ozone depletion. And what environmental impacts are not being considered?
- What impacts other than directly environmental ones are being considered or left out? Such as human health impacts related to any type of chemical release especially toxics.
- What stages of the life cycle are being considered? All or some?
- What types of resource uses are included? Land, air, water, minerals etc.
- What assumptions or estimates are being used about the impacts in question?
- To clarify the uncertainty issue, it is good to note that the LCA community is examining the question of uncertainty in the LCA standards and in practice.
In summary, the net effect is that
- "LCA can help identify potential environmental tradeoffs. However, converting the impact results to a single score requires the use of value judgments, which must be applied by the commissioner of the study or the modeler. This can be done in different ways such as through the use of an expert panel, but it cannot be done based solely on natural science."