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Determine Largest Mobile Greenhouse Gas Emission Sources

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Step 2

For the purposes of portfolio planning, a Federal agency's first data analysis step is to determine which mobile emissions sources represent the largest contributors to the agency's overall greenhouse gas (GHG) emissions. Agencies can use agency-level data to determine which fleets/locations, which vehicle assets (e.g., fleet vehicles, non-fleet equipment, etc.), and which fuel types are producing the largest amounts of emissions.

Based on this analysis, the agency can better define which mitigation strategies will be most effective. For instance, if a single fleet comprises over half of the agency's vehicle and equipment emissions, the agency may choose to work with this particular site to optimize its size and vehicle inventory. However, if a single site or fleet does not emerge as an overwhelming contributor to emissions, agencies may choose to focus mitigation efforts on overarching strategies aimed at, for instance, reducing gasoline consumption or minimizing the number of heavy-duty vehicles operated by the agency.

Figure 1 – An image of a pie chart titled 'Mobile Emissions Sources (Agency total: 135,000 MTCO2e). The slice labeled 'Vehicles and Equipment' shows 44% of emissions. The slice labeled 'Fleet' shows 56% of emissions.
Figure 1. Distribution of Agency ABC emissions
according to mobile source

To illustrate, Agency ABC uses its annual GHG inventory report to determine at a very high level which vehicle assets and fuels warrant the greatest focus for mitigation efforts. Figure 1 shows that over half of the agency's mobile source emissions result from fleets, as compared to non-fleet vehicles and equipment.

Within each category, the agency can further examine which fuels are contributing to emissions. As Figure 2 illustrates, nearly 80% of Agency ABC's total mobile emissions result from three categories of fuel combustion: non-fleet diesel (31%), fleet gasoline (27%), and fleet diesel (20%). Thus, this analysis shows that the agency can potentially achieve the greatest emissions reductions by focusing mitigation strategies at reducing gasoline and diesel consumption across its portfolio of mobile sources, rather than focusing on mitigating emissions specifically in its fleet vehicles.

Figure 2 - An image of two pie charts. One pie chart is titled 'Fleet Vehicles Emissions Share by Fuel (Total: 75,000 MTCO2e).' The slice labeled 'Diesel' shows 39% of emissions. The slice labeled 'Gasoline' shows 53% of emissions. The slice labeled 'Biodiesel' shows 5% of emissions. The slice labeled E-85 shows 3% of emissions. The slice labeled CNG shows 0% of emissions. The other pie chart is titled 'Non-Fleet Vehicles and Equipment Emissions Share by Fuel (Total: 60,000 MTCO2e). The slice labeled 'Diesel' shows 67% of emissions. The slice labeled 'Gasoline' shows 9% of emissions. The slice labeled 'LPG/Propane' shows 3% of emissions. The slice labeled 'Aviation Gas' shows 1% of emissions. The slice labeled 'Jet Fuel' shows 20% of emissions.

Figure 2. Fleet and non-fleet vehicle and equipment emissions
according to fuel consumption

Next Step

For analyzing data to evaluate an emissions profile, the next step is to determine vehicle usage and refueling trends to minimize emissions.

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