UPDATE 3/16: Correction to aviation emissions reductions (56 MMtCO2e NOT 125 MMtCO2e). Additional measures added to Household Energy to compensate for this shortfall.
Last week on this Switchboard blog, my colleague Matt Eisenson introduced the Behavioral Wedge Project, a joint NRDC-Garrison Institute effort to see if it would be possible to reduce U.S. greenhouse gas (GHG) emissions by 1 billion tons carbon dioxide-equivalent (CO2e) below business-as-usual by 2020 if 100% of Americans took a series of simple and low-cost personal actions (in many cases, the actions recommended come with no cost, and of the actions that do have some upfront cost, all pay for themselves over time). The actions fall into four categories: transportation, household energy consumption, food & diet, and waste. In this post, he will focus on the underlying assumptions and methodologies of our transportation analysis:
Passenger transportation accounts for 24% of total U.S. GHG emissions. Local transportation (cars, trains, and buses) accounts for 15% of the total, while long range travel (including airplanes) accounts for 9%. Through small, simple changes like carpooling more frequently, reducing idling, and basic vehicle maintenance, our analysis shows that we can cut GHG emissions by over 160 million metric tons (MMt) of CO2e in 2020. Further, among the 20% of the population that takes 3 or more roundtrip flights per year, eliminating just one of those trips could reduce U.S. GHG emissions by another 125 56 MMtCO2e.
Figure 1: Proposed measures for reducing emissions from transportation.
It is worth briefly discussing how we estimated the behavior baselines, the future size of the vehicle fleet and vehicle emissions factors. Many people, of course, already engage in a number of the behaviors we recommend, and many others are ineligible to participate in certain measures (e.g. someone who does not fly cannot cut back on air travel). In some cases, this baseline is well-documented. For example, there is a wealth of information on commuting and aviation. However, for a few of our smaller-impact items (using the correct grade of motor oil, engine tuning, and removing excess vehicle weight), we made our own conservative baseline estimates to compensate for a lack of available information. We estimated that 10% of the vehicle fleet could upgrade its motor oil, 25% receive a much-needed engine tuning, and 25% remove 100 pounds of excess weight.
From 1950 to 2007, the automobile fleet grew at an average compound annual rate of 3.1%. Between 1997 and 2007, the growth rate was a more modest 2.1%. To be conservative in estimating the size of the future vehicle fleet we are targeting, we cut this most recent growth rate by one third, and projected an annual increase of 1.4% between 1997 and 2020. Thus, we predict that 249 million vehicles in 2007 will grow to 298 million by 2020.
For our emissions factor, we used an EPA estimate of 11.5 kg CO2e/gallon of gasoline, which includes combustion (9.1 kg) and upstream emissions from fuel extraction, refining and delivery (2.4 kg). We did not factor in emissions from vehicle production (approximately 8.5 MtCO2e per car) because our recommendations are limited to vehicle use and maintenance. Upgrading to a more fuel efficient vehicle, while often beneficial in the long term, is too costly an action to be considered in this project.
Figure 2: the share of total projected emissions reductions achieved through each of our recommended transportation measures.
Changing the Way We Drive
In cars across the country, we waste at least 5% of our gasoline idling. Although anti-idling ordinances and automatic shut-off technologies have begun to take root, until regulation and technology put idling behind us, we can cut our idling time through small changes in personal behavioral. Many people incorrectly believe that shutting off and restarting one’s engine causes wear and tear that exceeds the environmental cost of burning extra fuel. The truth: engine wear and tear is negligible and the gasoline used while idling is much greater than the gasoline used restarting your engine. Promisingly, studies show that drivers are particularly responsive to anti-idling educational campaigns. We estimate that if all Americans cut their idling time by 50%, we could reduce U.S. GHG emissions by over 40 MMtCO2e in 2020.
In this automotive nation, where over 75% of the workforce drives alone to work every day, emissions from local transport alone exceed 1 billion tons CO2e. While using public transportation is one of the best ways to significantly reduce your carbon footprint, public transport options for many Americans are limited. For this reason, we estimated the emissions impact if the solo-commuting workforce in the U.S. carpooled two days a week or, for those with more flexible work arrangements, telecommuted one day per week. At an average daily roundtrip commute of 24 miles, this 20% reduction in vehicle-miles traveled would avoid nearly 75 MMtCO2e in 2020 (assuming conservative growth of the vehicle fleet and commuter workforce).
Improving Vehicle Care
As we approach the next item, we brace ourselves for derision. No vocal proponent of tire inflation, from Jimmy Carter to Barack Obama, has escaped without scorn. But consider this: in 2005, according to the Government Accountability Office, underinflated tires wasted 1.2 billion gallons of gasoline, which translates to nearly 15 MMtCO2e. This easily remediable problem produced more emissions than each of the 65 smallest GHG-emitting countries of the world.
Other vehicle maintenance measures, including engine tuning, removing excess weight, and using the recommended grade of motor oil can increase vehicle efficiency by 2-4% each. If adopted by the entire eligible U.S. population by 2020, these measures could reduce U.S. GHG emissions by 30 MMtCO2e.
Flying Less
Although scarcely one-fifth (19%) of Americans take three or more roundtrip flights per year, and a majority (52%) do not fly at all, the emissions impact of air travel is disproportionate to the frequency of its use. A British study recently cited in the New York Times found that the average one-way commercial flight from London to Los Angeles produced more CO2 emissions per passenger than the average British commuter produced yearly by car, train, and subway combined—and this is only half the picture. Due to the high altitude at which it releases the majority of its emissions, an airplane’s contrails (cloud-forming vapor streams) significantly increase its heat-trapping impact. As such, the IPCC recommends multiplying the total CO2 emissions per mile by a radiative forcing index (RFI) of at least 2. [For more information on the emissions impacts of air travel see this report].
While it would be unreasonable to expect those who fly only one or two times per year to give up their flight (that flight could well be their vacation), frequent flyers, and especially business travelers, could take advantage of alternative options like telecommuting to cut down on air travel. The average 1,100-mile one-way domestic flight emits 0.44 kg lbs CO2 per passenger per mile, or 0.88 kg lbs CO2-equivalent with radiative forcing. [For more information, see Bureau of Transportation Statistics here]. The average revenue passenger on a roundtrip flight of this length is thus responsible for 1.92 MtCO2e 870 lbs CO2e(which is nearly 10% 5% of the average American’s annual carbon impact). If those Americans who fly three or more times per year give up just one domestic flight, total emissions savings in 2020 would amount to 125 56 MMTCO2e.
Stay tuned for the next post on reducing home energy use. In the meantime, if you’d like to reduce your own carbon footprint by implementing some of these ideas and track your progress, join the Simple Steps community by going to “My Simple Steps”.
This project is collaboration between NRDC and the Garrison Institute’s Climate, Mind and Behavior (CMB) Project, working to integrate emerging research findings about what drives human behavior into new thinking on climate solutions. It envisions a "behavioral wedge" empowering people to eliminate a gigaton of GHG emissions by simply changing our behavior, starting now, even as we continue to work on other fronts to achieve institutional, regulatory and market changes. CMB is convening leading thinkers and practitioners in the fields climate change and environmental advocacy, neuro-, behavioral and evolutionary economics, psychology, policy-making, investing and social media, working together on ways to shift behavior on a large enough scale to realize this potential 1 gigaton emissions reduction.