Life Cycle Assessment

With the recent explosion of green claims clinging onto many everyday and building products, consumers are often confused as to which declarations and labels they should believe, and which are greenwashing.  Life cycle assessment (LCA) is a decision support tool that can help manufacturers, organizations, and consumers better assess, understand, manage and optimize the economic and environmental impacts of their products, processes and activities.

A holistic tool that considers influences beyond the scope typically utilized by metrics (which quantify the worth or impact of a product or process), LCA is commonly referred to as cradle-to-grave, cradle-to-cradle, or cradle-to-gate modeling.  The phases for which it determines impacts often include resource extraction, material production, manufacturing, assembly, use, and disposal (reuse, recycling, incineration or landfill).  Based on an assessment of each phase’s environmental effects, improvements can then be made to selected aspects of a product or process’ development to minimize its life cycle footprint.

The American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) have delineated the national and international standards for life cycle assessment with the ISO 14040 environmental management series.  Per ISO, an LCA incorporates a goal and scope definition, life cycle inventory (LCI), and life cycle impact assessment (LCIA).  After each of these steps, interpretation and iteration are also required; thus, each step is redefined repeatedly.  Many LCAs actually stop at the inventory step since impact assessment can complicate the interpretation of results when all concerned decision-makers are not from similarly minded institutions or their goals are inconsistent.  LCIs typically include dozens of inputs and outputs; the former is usually resources and the latter environmental discharges.  LCIA has traditionally evaluated such aspects as land use, ecosystem destruction, and the potential for global warming, ozone depletion, eutrophication, and human toxicity.

The two most common LCA approaches are process LCA and input-output (I-O) LCA.  Process LCAs are based on detailed process model descriptions and corresponding emission and waste data, which can be collected directly from companies, public databases or published studies.  In this method, however, the boundary around the problem is often drawn tightly for practical reasons, inadvertently excluding potentially important upstream and downstream life cycle components.  A good entry point to process LCA (and LCAs in general) is Building for Environmental and Economic Sustainability (BEES®), a tool focusing on building and biobased products.

Conversely, the input-output LCA approach allows for a more inclusive view of the economy, which can also be used to identify processes of principal concern for process LCAs.  I-O LCAs are based on economic input-output data and publicly available resource consumption and environmental discharge data organized by economic sector.  Because data collection for I-O LCAs must be performed on a national level, only a few such models exist.  And there is just one free and open one in the United States: Carnegie Mellon University’s Economic Input-Output Life Cycle Assessment model (EIO-LCA).  Based on public data gathered by the Census Bureau and Bureau of Economic Analysis, EIO-LCA represents the entire U.S. economy with a matrix that considers the contributions and distributions of economic purchases by 491 sectors.  Sample I-O sectors include wholesale trade, truck transportation, oil and gas extraction, child day care services, and tortilla manufacturing.

Both the process and input-output LCA methods have advantages and limitations.  While LCA has been recognized worldwide as an important tool for environmental performance measurement and the management of products and processes, it has also been criticized for being tedious, expensive, and slow to generate results.  The latter is especially true when trying to include all upstream components, which requires working through the hierarchy of process models in the supply chain while trying to match ever-decreasing product development cycles.  Also, due to various assumptions and boundary conditions used in different LCAs, results are sometimes difficult to compare.  Consequently, many recent LCAs have combined the process and I-O strategies to create hybrid life cycle assessments.

It’s good news for product manufacturers that many past LCAs have concentrated on building materials and products.  This precedence means that the life cycle data and understanding surrounding the environmental impacts of building products is sizeable.  Main sources for this information include the U.S. Life Cycle Inventory (U.S. LCI) Database, ATHENA Environmental Impact Estimator, SimaPro, GaBi, and EcoIndicator.  The U.S. LCI Database is publicly available and aspires to be the LCA data depository of the future.

The author of this article, Aurora Sharrard, is the research manager at the Green Building Alliance, most notably working on the organization’s Green Building Products Initiative and the Database for Analyzing Sustainable and High Performance Buildings.  Ms. Sharrard holds a Master’s and Ph.D. in Civil and Environmental Engineering with an emphasis in Green Design from Carnegie Mellon University. She also holds a Bachelor’s degree in Civil Engineering from Tulane University.  


Free Online LCA Resources

Economic Input-Output Life Cycle Assessment Tool,

Process LCA Software, BEES,

LCA Data Source,

Other LCA Resources include ATHENA® Environmental Impact Estimator, EcoIndicator, GaBi (Germany), and SimaPro (Netherlands)

Private LCA Practitioners include First Environment and Five Winds

University LCA Resources include Carnegie Mellon University, Green Design Institute; University of Pittsburgh, Sustainability & Green Design; Arizona State University, Global Institute of Sustainability; University of Michigan, Center for Sustainable Systems; and University of Minnesota, Bioproducts and Biosystems Engineering

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