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AskPablo: How can I reduce the emissions of my company’s fleet?

| Monday November 19th, 2007 | 3 Comments

fleet.jpgThis week Jamie asked me about the climate change impact of her company’s vehicle fleet and the options for reducing it. Her company has a vehicle fleet of 738 vehicles that average around 30,000 miles per year each. That adds up to 22,140,000 vehicle miles per year, or 0.00131% of US annual passenger miles (22,140,000 miles / 1,689,240,950,000 miles).
We will assume that the average fuel economy of this fleet is 30 mpg. This means that the company uses around 738,000 gallons of gasoline per year (22,140,000 miles / 30 mpg) at a cost of over $2.2 million (at $3/gallon). In a previous AskPablo I determined that a gallon of gasoline results in 19.56 lbs, or 8.87 kg of CO2 when combusted. So that vehicle fleet is responsible for roughly 6,546 mT of CO2 each year!


So, should they switch to a bio-diesel electric plug-in hybrid hover-car? If costs were no object that would be pretty cool, but sadly it’s not feasible… In another previous AskPablo I discussed corn-based ethanol so let’s see if conversion to ethanol would make sense. I showed that for every unit of fossil fuel energy that is used to make fertilizer, grow corn, and make ethanol, we get 1.34 units of energy out. If we assume that fossil fuel use is correlated 100% with CO2 emissions, this represents a 25.4% reduction in CO2 emissions. Of course the most common high ethanol-content fuel is E85 (85% ethanol) so the actual emissions reductions would be 21.6% or 1,414 mT (6,546 mT *21.6%).
But how much would it cost to convert 738 vehicles to run on E85? Flex Fuel US currently sells the only EPA licensed E85 conversion kit, for use in fleets only. Perfect, right? Well, at $995 for a conversion kit and maybe another $100+ for installation it would cost $810,000 to convert the fleet. If we depreciate the kits over 5 years ($162,000/year) the emissions reductions would cost $114/ton ($162,000 / 1,414 mT). At current Chicago Climate Exchange CO2 rates at $2.10/ton it would be far cheaper to just purchase legitimate carbon offsets. Once a national carbon trading scheme becomes mandatory the price will certainly rise but it will take a long time before it ventures over $100.
What other options are currently available? You could have the vehicles converted to run on natural gas for about $2,000 each. Unfortunately you would achieve no reduction significant reduction in greenhouse gases, only criteria air pollutants (see AskPablo: Clean Natural Gas?).
You could have AC Propulsion convert the vehicles to electric, but that costs around $55,000 per vehicle and is currently only available for the Scion xB. A hybrid gasoline electric conversion would probably cost event more and with an increase to 60 mpg the payback period would be far longer than the projected life of the vehicle.
As outlined in yet another previous AskPablo I showed that there is a point at which it makes more sense, from an ecological perspective, to get a new car than to continue driving your old one. Based on this I would recommend a planned phase-out of current vehicles while replacing them with the latest plug-in hybrids available. At 100 mpg these vehicles will save money, reduce emissions, and serve as a great marketing vehicle to convey a positive message about the company.


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  • Saul Payus

    “We will assume that the average fuel economy of this fleet is 30 mpg”
    Bro – isn’t that info available? I’ll bet that’s actually high. The company ought to have that information no?

  • http://www.AskPablo.org Pablo

    Rather than calculate the actual average fuel economy of all of the vehicles I looked at the fuel economy of the most common ones in the fleet. The weighted average of the entire fleet would be around 30 mpg in this case.

  • Jorene

    Try a natural mineral oil base, EPA registered–other charters (trucks, bus lines) have found success with it