Thoughts From LCA XIX: Fossil Fuels Sources of Uncertainty

One of the more interesting sessions at LCA XIX focused on uncertainties associated with Life Cycle Assessment (LCAs) on fossil fuels and their impact on downstream products – fuels and petrochemical-based materials like plastics. 

Although analysts have traditionally used a single number for fossil fuel GHG emissions, it’s clear that no two quantities of crude oil or diesel will have exactly the same GHG profile, for example. Crude oil has many different properties, and the methods used to extract and refine it can vary significantly. Therefore, our LCA results inevitably have great variability due to the data (or lack thereof) used to model the GHG emissions. Our certainty is only as strong as our least-certain link.

How can we improve the situation and reduce these uncertainties for fossil fuels? The obvious first step is to acquire better data about crude oil characteristics and extractions, petroleum movements, refineries, and final product slates.  

Our challenge, as LCA practitioners, is to be able to communicate both uncertain results and our need for better data in flow, model and parameter uncertainties in the tools we use. We need to recognize what level of certainty is required for our study, understand the uncertainty, standardize the uncertainty and carefully communicate this uncertainty to decision-makers in a way that provides them with trustworthy information for important decisions.  

There are many possible next steps, both near- and long-term. Enthusiastic discussion at the session focused on a couple of things, including the need for an agreed-upon glossary of terms.  Some consensus best-practice guidance would be a big help, too: Do we use a scale, put a quantitative value on uncertainty?  A checklist?  Standardize uncertainty factors for certain products (eg. 5% for fossil fuels and 10% for natural gas, and 50% for ethylene glycol)? Use a contribution analysis?  

More work needs to be done, but the conversation at LCA XIX was a good start.

About the Authors:  

Caroline Taylor PhD, EarthShift Global’s Director of Research and Development, conducts and supports rigorous research and analysis for use in strategic sustainability decision-making at companies, governmental bodies and NGOs. Caroline has over 20 years of experience in modeling and analysis, a decade of it in energy and sustainability. She is a member of the Editorial Advisory Board for Global Change Biology: Bioenergy and holds a visiting appointment with Agricultural and Resource Economics at the University of California Berkeley. She has earned Bachelor’s degrees in Classics and Chemistry from the University of California at Irvine and a Doctorate in Chemistry (Chemical Physics) from the University of Chicago, and was a post-doctoral scholar at Cornell University.

Holly O. Harris, Latin American Business Development, heads EarthShift Global’s Latin American Business Development. She has represented EarthShift Global at conferences including CILCA 2015 and 2017, the International Conferences on Life Cycle Assessment in Latin America, where she has co-authored papers, unveiled the Spanish-language version of EarthSmart, and helped conduct training sessions. She is a key participant in EarthShift Global’s Latin American Pathways Challenge Network, which is developing Sustainability ROI data for a support program for small and medium-sized businesses, with funding from the U.S. Department of State and the World Environment Center.

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