1. Define the goals and scope of the LCA

First, identify the goals your facility wants to achieve through an LCA. What are the questions you want to answer (e.g., Which raw material generates the most emissions when manufactured? How much energy is used to make and sell a certain product?)? Also, determine what data you need to gather to answer the questions.

The goals and data establish the scope of the LCA. Will you evaluate the entire lifecycle of a product, one part of the lifecycle (such as the raw materials used in various products), or something in between?

Consider these common scopes:

• Cradle-to-grave, which assesses a product’s entire lifecycle (raw material acquisition to waste management);
• Cradle-to-cradle, which assesses a recycled or reused product’s entire lifecycle (replaces the waste management phase with a new product lifecycle);
• Cradle-to-gate, which assesses only part of a product’s lifecycle (raw material acquisition to when it leaves the facility); and
• Gate-to-gate, which assesses only one phase of a product’s lifecycle.

Your goals and scope inform every other part of the LCA process.

2. Develop a lifecycle inventory (LCI)

Now it’s time to gather the needed data through a lifecycle inventory (LCI). During this part, you’ll measure the inputs and outputs used in each phase of the product’s lifecycle.

• Inputs refer to the materials and energy used to create a product, including transportation between each .
• Outputs are the things that the process generates: the product itself, coproducts (i.e., outputs that are valuable and not treated as waste, such as industrial scrap sold to other manufacturers), and waste (like air emissions or material waste).

Limit the inventory to inputs and outputs that will help your facility achieve its goals and stay within the established scope. The inventory for each lifecycle process should include:

• Descriptions of the inputs used and the types of outputs generated;
• Quantifiable data for the amounts and kinds of inputs;
• The sources for input and output data (primary and/or secondary data); and
• Quantifiable data for the outputs, including environmental releases.

3. Conduct a lifecycle impact assessment (LCIA)

Using the data from the inventory, evaluate the significance of the environmental impacts that the inputs and outputs (LCI items) have. You’re essentially connecting the product’s materials and processes to their potential effects on the environment to compare their impacts.

Here’s how to conduct a general LCIA:

• Choose the impact categories into which you’ll group the LCI items based on your goals and scope. Each category should focus on one environmental effect (like human toxicity, air pollution, or land use) and contain only the LCI items that have that environmental impact.
• Assign the LCI items to the impact categories (e.g., toxic chemical releases assigned to the human toxicity category). If an LCI item affects multiple categories, you must decide whether the item’s effects are dependent or independent:
  • If an LCI item has two environmental impacts at different times, assign the correct proportions of the LCI item to the two impact categories. For example, a facility with toxic chemical releases (the LCI item) through air emissions in one part of the process and through water discharges in another part of the process would allocate 50 percent of the releases to the air pollution and water pollution impact categories.
  • If the item can have two environmental impacts that occur at the same time, assign 100 percent of the LCI item’s effects to both impact categories. For example, air emissions (the LCI item) can harm human health and air quality simultaneously. In this case, you’d assign 100 percent of the emissions both to the human toxicity and air pollution impact categories.
• Within each impact category, establish and apply characterization (or equivalency) factors to the LCI data to convert the results into impact indicators.
  • Characterization factors allow you to convert all LCI data in an impact category into the same unit of measurement to show the relative impact of each LCI item and calculate the total impact of the category. Whether the characterization factor is based on an established consensus or set by your facility, it must be aligned with your goals and scope.
  • Once you establish the characterization factor, convert the LCI items into impact indicators:
    LCI data X characterization factor = impact indicator
  • With all measurements in the same units, you can now compare the effect each impact indicator has on the impact category. For example, if reducing air emissions is a priority for your facility, you can rank the impact indicators from most to least emissions.

Note: The LCIA process above roughly follows ISO Standards 14040 and 14042, which establish a required process for conducting an LCA, including specific steps for the LCIA. The Environmental Protection Agency includes the ISO standards in its guide Lifecycle Assessment: Principles and Practice (2006).

4. Interpret the results

The ultimate purpose of the interpretation is to address the goals established at the beginning of the LCA. An effective lifecycle interpretation:

• Prioritizes the products and parts of their lifecycles that have the most environmental impact, and
• Translates the results of the LCA into actionable conclusions and recommendation.

Based on the ISO standards, your facility’s lifecycle interpretation should:

• Identify the most significant environmental issues based on the LCI and LCIA;
• Evaluate the completeness, sensitivity, and consistency of the LCA; and
• Include conclusions, limitations, and recommendations.

5. Take action!

Even the most comprehensive LCAs aren’t helpful if you don’t take action. Implement your LCA’s recommendations to help your facility reduce its environmental impacts, conserve resources, and lower costs.