Carnegie Mellon University

Limitations of the EIO-LCA Method and Models

The factors that make the EIO-LCA method an efficient and robust tool also limit its use for life cycle assessment.

First, the results of an EIO-LCA analysis represent the impacts from a change in demand for an industry sector.  Depending on the model chosen, an industry sector represents a collection of several industry types, and this aggregation leads to uncertainty in how well a specific industry is modeled.  For example, in the U.S. models, one sector represents Power Generation and Supply, which would include coal-fired plants with high levels of CO2 and particulate emissions as well as hydropower plants with virtually no CO2 or particulate emissions.  The results for impacts from the Power Generation and Supply sector thus represent the "average" impacts for generating electricity.  Similarly, a sector such as the Electronic Computer Manufacturing sector produces hand-held computers (PDAs), laptops, desktops, workstations, and mainframe computers.  Since making these products requires similar processes, they are grouped together in a single sector.  So, the method is limited in its ability to model the effects of "producing one laptop" but is good at modeling the effects of the Electronic Computer Manufacturing sector as a whole.  (We like to point out that the U.S. models designate one sector entirely for Tortilla Manufacturing, so the impacts for making tortillas are well-represented.)  Non-U.S. models are more aggregated, with up to only 100 sectors representing all industries.  See the model information for the number of sectors represented in the economy of a given model.

Second, as an LCA tool, the EIO-LCA models are incomplete in as much as a limited number of environmental effects are included.  The EIO-LCA models use as the basis for data only that which is publicly available.  While industry specific data is publicly available for a number of environmental effects, we do not have data for impacts such as habitat destruction, non-hazardous solids wastes, or non-toxic pollutants to water. Some data used in earlier models (e.g., fertilizers) are no longer collected at the national level due to efforts to minimize reporting burden of companies. Other sources and LCA methods will need to be consulted to account for a full range of environmental impacts.

Third, the EIO-LCA method, models, and results represent the inventory stage of the LCA.  The results estimate the environmental emissions or resource consumption associated with the life cycle of an industry sector, but do not estimate the actual environmental or human health impacts that these emissions or consumption patterns cause.  For example, the U.S. models estimate the emissions of particulates to the air, but do not estimate the increased number of hospitalizations or deaths due to these emissions.  Again, other sources and LCA methods will need to be consulted to account for translating the inventory results from an EIO-LCA analysis into impact on the environment.  

Comparison of EIO-LCA with Process-Based Models

(from Hendrickson, C. T., Lave, L. B., Matthews, H. S.  (2006).  Environmental Life Cycle Assessment of Goods and Services:  An Input-Output Approach.  Resources for the Future Press.)

  Process-Based LCA  EIO-LCA 
 Advantages results are detailed, process specific  results are economy-wide, comprehensive assessments 
  allows for specific product comparisons
allows for systems-level comparisons
  identifies areas for process improvements, weak point analysis
uses publicly available, reproducible results
  provides for future product development assessments
provides for future product development assessments
    provides information on every commodity in the economy

setting system boundary is subjective
product assessments contain aggregate data 
  tend to be time intensive and costly
process assessments difficult
  difficult to apply to new process design must link monetary values with physical units
  use proprietary data imports treated as products created within economic boundaries
  cannot be replicated if confidential data are used
availability of data for complete environmental effects
  uncertainty in data
difficult to apply to an open economy (with substantial non-comparable imports)
    uncertainty in data