Director, Environmental Dynamics Program
Co-Director, Sustainability Curricula
I had the opportunity to attend the annual conference and exposition of the Association for the Advancement of Sustainability in Higher Education in Nashville, Tennessee on October 6-10, 2013, with Todd Knobbe, a Geosciences graduate student.
Dr. Steve Boss
Participation in the AASHE conference presented an opportunity to conduct an experiment in transportation efficiency. Given that the meeting was within reasonable driving distance from Fayetteville, Knobbe and I decided to track carbon intensity and cost of travel to the conference by private vehicle and compare it to the carbon intensity and cost of travel by air. The objective was to assess the carbon dioxide emissions and cost effectiveness of automobile travel versus air travel to this particular meeting.
Note that we focus exclusively on the carbon emissions and direct transportation costs, discounting entirely an evaluation of wear and tear on the vehicle (which we assume is minimal compared to the anticipated lifetime of the vehicle) or other considerations, such as travel time and relative safety of air travel versus automobile travel.
We drove my 2010 Toyota Prius and, to assist in minimizing travel footprint while in Nashville, transported two bicycles to ride while at the conference to gain additional savings on fuel (and thus, carbon footprint) and money (saving costs for fuel and downtown parking). We parked the car at no cost at the hotel and biked approximately 7 miles daily (round trip) to the downtown conference center.
Todd Knobbe
The total carbon footprint for their travel was estimated from their vehicle mileage and performance characteristics. The round trip from Fayetteville to Nashville totaled 1085 miles. My Prius consumed a total of 20.7 gallons of regular unleaded gasoline for average fuel efficiency of 52.5 miles per gallon. The U.S. Energy Information Administration reports that most unleaded gasoline in the U.S. now contains about 10% ethanol and combustion of 1 gallon of this fuel releases 17.68 pounds (8.02 kilograms) of CO2. Thus, the total CO2 emissions from this road trip were:
20.7 gallons consumed x 8.02 kilograms/gallon = 166.01 kg of CO2.
Of course, since two people were transported, we can divide this total by two to determine a per person transportation footprint of 83.00 kilograms of CO2. The total fuel cost for this trip was $76.98, or $36.99 per person.
For the two of us, total carbon emissions for air travel would have been 844.74 kg of CO2 compared to our actual 166.01 kg of CO2 for vehicular travel and the total cost would have been $1,360 for air travel compared to $76.98 for vehicular travel.
We compare the emissions and cost above to emissions and cost had we traveled by air to this conference. Since there are no direct, non-stop flights from Fayetteville to Nashville, we examine the emissions for the most likely air route we would have used: Northwest Arkansas Regional Airport (XNA) to Nashville, TN (BNA) via the Dallas-Fort Worth International Airport (DFW). The International Civil Aviation Organization maintains an online calculator to determine carbon dioxide emissions for air travel using standard protocols. Using this calculator, the CO2 footprint for these routes was estimated to be:
- XNA-DFW (round trip): 166.09 kg of CO2 per person
- DFW-BNA (roundtrip): 256.28 kg of CO2 per person
- TOTAL: 422.37 kg of CO2 per person
Cost of this round-trip flight would have been $680 per person.
For the two of us, total carbon emissions for air travel would have been 844.74 kg of CO2 compared to our actual 166.01 kg of CO2 for vehicular travel and the total cost would have been $1,360 for air travel compared to $76.98 for vehicular travel. Here we report only the cost of air travel, omitting emissions and costs related to airport transfers in Nashville and travel by private vehicle to and from XNA for departure and return.
Thus, for this trip, the carbon footprint of travel by Prius was 5 times less than the carbon footprint of travel by air. Cost savings were even more dramatic. Air travel was 18 times more expensive than vehicular travel! This experiment demonstrates that for travel within an 8-10 hour driving radius, vehicular travel yields a much smaller emissions footprint than air travel, and is vastly more cost effective. It would be interesting to compare the cost of vehicular travel over air travel as a means of managing emissions for trips shorter than 600 miles one-way.
Feel free to comment or ask questions below!
Related Links:
http://wordpress.uark.edu/sustain/2013/05/13/bike-to-work-week-infographic/
http://wordpress.uark.edu/sustain/2013/07/25/what-is-a-carbon-footprint/
http://www.postcarbon.org/issue/12879-transportation
http://www.epa.gov/climatechange/ghgemissions/ind-calculator.html
What about social capital? Assuming that travel time by car was greater than by air more opportunity for social capital development would exist during the road trip…unlesssssssss one (or God forbid both) traveling companions got up on the wrong side of bed in which case there might no development or worse yet degradation!
Fair point, Stephan! A couple of responses are in order. First, travel from XNA-DFW-BNA would have required approximately 6-7 hours to accommodate waiting at airports for connecting flight, assuming no flight delays. The drive to Nashville was about 8.5 hours, so comparable to travel time by air. Second, Todd was able to work on his presentation on his laptop during the drive, and I was able to give him some advice on the presentation. He was also able to practice it a number of times to refine his speech and timing. So, indeed, the drive provided opportunity for social interaction, mentoring, and learning!
I think this is an interesting calculation and based on your math it seems as if you chose a highly ecologically friendly mode of transport. But have you considered that whether or not you are on the plane, it will be making the flight? Taken in this light, instead of thinking about the difference in the two modes of travel, you must consider the fact that in addition to the total emissions of the planes, you are adding emissions to the atmosphere because while you are choosing an alternative mode of transportation, this does not replace the plane and the plane will fly and emit regardless of your presence aboard it.
Thanks for writing this up – The first thing that comes to mind is that most folks do not have access to cars that reach 52.5 mpg – however, even if you halve that number, it still seems that the numbers would be favorable. Also, I was curious why you included that you were able to bring along the bikes for extra savings because there is the Bcycle program in Nashville and also is possible to rent bikes there, so I do not think that should be figured in to the calculations.
Broadening the discussion, paraphrasing a publication by the Green Car Congress citing research by Dr. Michael Sivak, Director, Sustainable Worldwide Transportation at the University of Michigan Transportation Research Institute (UMTRI), flying is less energy intensive than driving…but only in the case of relatively long driving trips.