This paper reviews the origins and methodological framework of the Okala impact factors. Okala impact factors are single figure values that can be used to estimate overall environmental impacts of materials, processes, and overall lifecycle performance of competing product or service systems. System development teams, professional product designers as well as design, business and engineering students use the Okala impact factors.

The factors have been calculated for 240 materials and processes, including major plastics, metals, packaging materials, transportation methods, electricity and energy sources, incineration, landfill and recycling impacts. The Okala Impact Factors comprise the only usably specific palette of values for a broad range of materials and processes assessed with North American methods that is currently available to designers and system planners. System designers need values for a wide range of materials and processes to compare and refine alternative configurations. Okala Impact Factors were developed to meet these needs. We surveyed 95 working product designers (mostly from North America) who informed us for which processes and processes they currently need environmental impact assessment results (4). This paper also lists the types of materials and processes for which companies and designers currently use, or increasingly want to use, but no inventory data is readily available.

This paper outlines methodological components and considerations used to create the Okala Impact Factors. The impact categories, normalization values and weighting values used for the Okala Impact factors are listed in the table below with the appropriate source. These sources were each selected because they are legitimate centers for LCA expertise in North America. This set of values was consistently applied to assess all processes and materials.

Each factor contains the discrete impact values of the ten impact categories prescribed in the TRACI characterization methodology. In a more narrow assessment comparing a few processes, context is essential. But for a palette of process values whose primary function is its ability to be rapidly used in virtually any situation or system, the primary objective is to provide data-derived results based on the best available information.

Normalization values are based on the science from the US EPA. Weighting values are admittedly based on subjective evaluations of NIST. This subjectivity could not be avoided by not weighting. Non-weighting assigns equal weighting of each impact category, which is as subjective as assigning other weighting values. I use the NIST values because NIST is a recognized US authority science and technology; these values are the most legitimate values of which I am aware.

The paper considers challenges to developing more accurate factors through higher quality (less uncertain) process flow data. Uncertainty exists in all forms of impact assessment, including both process flow assessment (such as the Okala Impact Factors) and input/output economic correlation (hybrid) assessment. These impact factors were produced with the awareness that uncertainty exists and should be minimized wherever possible.

It also describes how the Okala Impact Factors have been used in classroom settings in terms of what are the proposed and observed learning outcomes, with suggestions on how best to help engineers, designers and design teams use the factors accurately and in the appropriate context.