New Online Calculator for Fleets Measures GHG Emissions

The crux of our work with corporate fleets is getting them to consider greenhouse gas emissions as one variable when making vehicle purchasing and use decisions. Relatively minor decisions, when multiplied over hundreds of vehicles traveling 20,000+ miles a year can add up to significant differences in emissions. Being able to understand what decisions impact emissions and to track emissions over time are important skills for the 21^st century fleet manager.

Tracking emissions of hundreds to thousands of vehicles dispersed across the country is easier said than done. Medium-to-larger fleets that use a national fuel card typically have good information about the type and volume of fuel their vehicles are consuming. With this information, they can calculate the carbon dioxide (CO₂) emissions from their vehicles. The data required to calculate emissions of the other greenhouse gases from vehicles – nitrous oxide (N₂O), methane (CH₄), hydro fluorocarbons (HFCs) {most commonly HFC 134a}- are a different story.

For N₂O and CH₄, fleet managers need to know the emissions control technology used and miles traveled for each unit. Unfortunately, mileage data is notoriously unreliable for fleets because relying on drivers to code in correct mileage information adds human error. Matching each unit with its specific emissions control technology, such as EPA Tier II or California LEV, is possible. But as they've never had a reason to track this before, most fleets don't have this information readily available. As for HFC emissions from air conditioner leakage, most fleets have no way of tracking these emissions. Getting this information from a dispersed fleet is a data collection nightmare.

Fleets with good fuel data face their own version of the infamous 80-20 rule, except in their case it's more of a 95-5 rule. Carbon dioxide accounts for about 95% of greenhouse gases from passenger vehicles (on a CO₂E basis). With good fuel consumption data, it's straightforward to calculate emissions. The other three gases account for about 5% of the emissions, but – as they are vastly more complex to track – it can take 95% of the effort to track them.

To help fleets overcome this paradox, we created a fleet GHG emissions calculator that estimates total fleet greenhouse gas emissions from fuel consumption data alone. The fuel data is directly used to calculate emissions of CO₂. Emissions of N₂O, CH₄ and HFCs are estimated based on their prominence among greenhouse gas from transportation source as reported in the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006, Table 2-15.

We worked with NAFA Fleet Management Association to develop this calculator and unveiled it at the annual NAFA I&E held in New Orleans in April. Over the two days EDF had the calculator on display, we were visited by a few hundred fleet managers from a wide cross-cut of private and public fleets. An additional fifty fleet managers joined our seminar on measuring greenhouse gases. Based-on the conversations we had in New Orleans and since, it appears that the calculator is filling an important niche.

We encourage fleet managers that have good fuel data to use our tool. For the few fleets that have the more complete data needed to measure non-CO₂ emissions, they might want to follow the more complex calculation protocol put forth by the EPA Climate Leaders program. At minimum, we encourage all fleets to start to create data collection systems

If you have thoughts on ways we can improve on the calculator, we'd love to hear them. The calculator can be found at: http://edf.org/greenfleet. A technical background piece [pdf] is also online.

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