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Lifecycle analysis of energy use and pollution from gasoline, CNG and electric vehicles in 6 southwestern states highlights variability of benefits
29 July 2013
|Comparison of greenhouse gas emissions from new vehicles in 2020, EVs by state power mix. Percentages are relative to gasoline baseline. Click to enlarge.|
A report for policymakers issued by the Southwest Energy Efficiency Project (SWEEP) has found that in Arizona, Colorado and Nevada, electric vehicles offer the cleanest ride, while in New Mexico, Utah, and Wyoming that’s not necessarily the case. SWEEP promotes greater energy efficiency in a six-state region that includes Arizona, Colorado, Nevada, New Mexico, Utah, and Wyoming.
The report, “Transportation Fuels for the Southwest”, compared the well-to-wheels energy use and air pollution emitted by vehicles fueled by gasoline, compressed natural gas and electricity in order to determine which fuel is cleanest in each of the six southwestern states.
This report follows an earlier report released by the Southwest Energy Efficiency Project (SWEEP), Policies to Promote Electric Vehicles in the Southwest. The earlier report provided analysis of the policies that have been adopted to support electric vehicles by state governments across the Southwest, and found a wide variation in policy support. This new report identifies the states where electric vehicles offer the greatest emissions benefits. These are the states where supportive policies make the most sense, SWEEP suggests.
What becomes clear is that the emissions benefits of EVs compared to traditional gasoline-fueled and compressed natural gas (CNG) vehicles vary significantly from state to state and are highly dependent upon the fuels used to generate electricity in each state. For instance, today EVs are much cleaner in Arizona and Nevada, which use relatively low amounts of coal to generate their electricity supply, than in Wyoming, which produces almost all of its electricity from coal. Because coal-fired power plants are a major contributor to smog and greenhouse gas emissions in the Southwest, coal’s use in the production of electricity consumed in each state is a key determinant—though not the only one—of whether EVs are cleaner or not.
What’s more, over the next several years the electricity fuel mix in the Southwest is expected to shift towards less coal and more natural gas and renewable electricity. Because of these more efficient and cleaner fuel sources, electric vehicles will use less energy and produce fewer emissions every year they are on the road. During the same time frame, new gasoline, CNG and electric vehicles will also become more efficient. This report considers all of these factors.
...A word of caution on interpreting these results: for emissions that contribute to smog, the location where the pollution is emitted is very important. Gasoline and CNG vehicles driven in urban areas emit pollution directly into urban airsheds; in many cases, the power plants that supply EVs are located outside of these urban areas. For example, we have conducted a more fine-grained analysis of emissions from EVs in Utah, which concluded that EVs provide significant air quality benefits to the Salt Lake City area, because most of the emissions are outside of the urban airshed.—“Transportation Fuels for the Southwest”
SWEEP used Argonne’s GREET model to make a comparison between the life-cycle energy use and emissions of three light-duty vehicle fuels: gasoline, compressed natural gas (CNG) and electricity. The authors analyzed the energy consumption and emissions of the three vehicle fuels in three different scenarios: new vehicles in 2013; 2013 vehicles in 2020; and new vehicles in 2020.
The three scenarios demonstrate the effects of two major trends: the planned improvements in fuel economy for new vehicles, and the shift in the electrical generation sector away from coal and towards natural gas and renewables. While the fuel economy improvements are a federal requirement and therefore expected to be consistent across the southwestern states, the changes in the electrical generation vary considerably by state.
|Summary of best performing vehicle in each state. Click to enlarge.|
Among the findings of the analysis:
In all six states, electric and CNG vehicles offer significant benefits by 2020 in reduced emissions of ozone precursors compared to gasoline vehicles.
By 2020, EVs in Arizona, Colorado and Wyoming provide a greater reduction in NOx emissions compared to CNG vehicles; in Nevada, New Mexico and Utah NOx emissions are relatively similar by 2020.
In all states, EVs have the lowest level of VOC emissions. Thus, policies to increase the use of EVs may be an important component of strategies to reduce urban air pollution and improve public health in all of the southwestern states, the report suggests. This is also important for states that will be required to show compliance by 2020 with an expected new ground-level ozone standard from the EPA.
Emissions of greenhouse gases vary widely between states. SWEEP’s analysis shows significant GHG reductions from EVs in Arizona, Colorado, and Nevada compared to gasoline and CNG vehicles, suggesting that policies designed to increase the use of EVs in these states could be an important strategy to reduce greenhouse gas emissions and mitigate the impacts of climate change.
In Wyoming, New Mexico and Utah, however, electric vehicles tend to have lower emissions than gasoline vehicles and CNG vehicles tend to have lower emissions than electric vehicles. In these states, in order to have a positive climate benefit, policies to increase use of EVs should be coupled with additional efforts to shift electricity generation from coal to natural gas and renewables.
The Southwest Energy Efficiency Project is a public interest organization that advances energy efficiency policy in Arizona, Colorado, Nevada, New Mexico, Utah and Wyoming.
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