Electric vehicles and other alternative fuels get lots of hype for their ability to reduce greenhouse gas emissions. Sales of plug-in hybrid electric vehicles (PHEVs), which run on gasoline and electricity, and zero emission vehicles (ZEVs) which run only on electricity and have no tailpipe emissions, have grown rapidly over the past five years. Considering on-road vehicle emissions account for about 45% of greenhouse gas emissions in California and 30% nationwide, electric vehicle adoption is an important step to combat climate change. But alternative fuels have several other often overlooked benefits. Governor Brown’s executive order B-16-2012 sets a goal of 1.5 million ZEVs on California roads by 2025. What is needed to achieve this and what will the benefits be? In this two-part series, we will look at current air quality in the U.S. and air quality improvements expected through increased ZEV adoption, with a particular focus on San Diego County.
U.S. Air Quality: Past & Present
We tend to think air quality in the U.S. has improved since 1970. Photographs of Los Angeles and other urban centers during severe smog days in the 1950s are surprising reminders that visibility sometimes matched that often experienced in China today. Yet nearly half of Americans still live in regions that don’t achieve annual U.S. Environmental Protection Agency (EPA) air quality standards for ozone. In addition, the U.S. still experiences higher rates of cancer along transportation corridors. Sulfur oxides (SOx) and particulate matter, nitrogen oxides (NOx) and volatile organic compounds (VOCs), which react in sunlight to form ground-level ozone, irritating lungs and decreasing lung capacity. Particulate matter is largely produced by motor vehicles, as well as industrial and agricultural activities. NOx and SOx are also primarily emitted by motor vehicles and industry. Our transportation choices play a central role in visibility and health.
Over the past decade, new vehicle emission standards have contributed to a significant improvement in regional ambient air quality. Particulate matter, NOx, and other vehicle pollutants have also decreased. While many urban areas remain out of compliance with ozone standards, the EPA still plans to tighten standards this October. These standards should encourage continued industrial improvement and innovation. We are doing better, but we can do more.
What Role Can Plug-In Electric Vehicles Play?
Electric vehicles have gained popular support over the last five years as a reliable technology to decrease greenhouse gas emissions, EPA criteria pollutants, and fuel costs. However, all electric vehicles are not equal; the electricity source matters. Electric vehicles powered by coal substantially increase greenhouse gases and air pollutants compared to conventional vehicles. But if the electricity mix is partially renewable energy, switching to electric vehicles can decrease greenhouse gas emissions, air pollutants, and health risks, and improve visibility.
A case study in Texas found that even with an electricity grid mix of 10% renewable energy – below the US average of 20% and a California average of 33%– PHEVs would decrease greenhouse gas emissions and the criteria pollutants NOx, CO and VOCs. They would also offer a modest reduction of carbon monoxide and particulate matter (PM). Compared to conventional vehicles, PEVs have been found to provide a greater reduction of NOx, VOCs and PM than compressed natural gas (CNG) or ethanol 85 (E85) alternative fuels. Vehicles fueled by CNG, E85, and electricity sourced from natural gas all have a lower health impact than conventional vehicles, but PEVs powered entirely by renewable energy are the clear health winner.
An important caveat for air quality is that while electric vehicle adoption can offer a limited to moderate improvement, it may also shift the peak timing and location of emissions. Most electric vehicle owners are encouraged to charge at night, when electricity demand and costs are lower. With widespread electric vehicle adoption, this would increase night-time ozone-forming pollutants while decreasing day-time levels. Similarly, coal-reliant states would experience a regional shift in mercury and sulfate deposition. Total emissions would be slightly reduced, but locations near coal plants could experience an increased exposure.
San Diego County
Increased adoption of electric vehicles can improve air quality, visibility, health, and associated economic impacts. They can also help urban areas meet greenhouse gas and air quality requirements. Part II of this series will look at impacts specific to San Diego County, an early adopter of electric vehicles. The County’s Climate Action Plan includes continued growth of ZEVs as part of its climate change mitigation strategy. How many ZEVs will the County need to contribute its fair share of California’s 2025 ZEV goal? What pollutant reductions might the County see with this level of adoption? Can it act as a model for other US cities, or does it have an advantage others can’t expect to attain?