June 26, 2017

Do electric vehicles actually increase emissions?

In Beijing, the capital of China, there are more than 5.6 million vehicles now which emit nearly one million tons of air pollutants per year. In 2016, there were 39 heavy-polluted days because of high levels of PM 2.5 (particulate matter smaller than 2.5 microns). Vehicle emissions account for more than 30 percent of local pollution in Beijing. In order to make the sky “blue” again, Beijing has come up with many regulations and enacted some laws. Firstly, vehicle emission standards have been more and more strict. In 2017, so-called “the most stringent emission standard,” which is the “Jing-six” emission standard, will be implemented. And many old vehicles are required to be scrapped. It is predicted that in 2022, the total vehicle emissions in Beijing will decrease by 20%, compared to 2017. Secondly, Beijing has imposed a vehicle restriction which forbids people from driving in the Beijing urban area one work-day per week based on the last digit on the vehicle plate. And when important international conferences are held in Beijing, such as APEC (Asia-Pacific Economic Co-operation), Beijing will ban vehicles based on even- and odd-numbered vehicle plates. And thirdly, several years ago Beijing began issuing new vehicle plates via lottery to control the number of vehicles. But if what you want to buy is an electric vehicle, you can not only bypass the vehicle plate restriction but also get a state subsidy toward the purchase. This is rationalized by the believe that electric vehicles can decrease air emissions. But is that true?

As we know, normal gasoline vehicles are powered by fuel combustion at high temperature and pressure and air pollutants generated are emitted through the tailpipe. How about electric vehicles, which electric vehicles are driven by electricity and don’t have tailpipe emissions? The question is: where does the electricity from? From coal, tide, nuclear, wind or something else? Is there pollution made during the production of electricity? If so, how can we calculate that? As secondary energy, is electricity really cleaner or more sustainable than the combustion of gasoline?

In the U.S., researchers have conducted an analysis that combines a theoretical discrete-choice model of vehicle purchase, an econometric analysis of electricity emissions, and the AP2 air pollution model to estimate the geographic variation in the environment benefits from driving electric vehicles. They conclude that across the U.S., accounting for both global and local air pollution, electric vehicles do more environmental damages than comparable gasoline vehicles. But there is also considerable spatial variation around the average. For example, the environmental benefit per mile produced by electric vehicles in Los Angeles, California is 6.3 cents per mile higher than that in Grand Forks, North Dakota. That geographic differentiation is driven the power generation mix. So maybe the clean primary energy is “true answer” to solve environmental problems.

In this research, the marginal emissions factors of the 1,486 power plants which provide electricity for electric vehicles are estimated. And then the electric vehicle emissions data which is relative to comparable gasoline vehicles can be derived. In the analysis of air pollution, the CO2 (carbon dioxide), SO2 (sulfur dioxide), NOx (nitrogen oxides), PM2.5, and VOCs (volatile organic compounds) are taken into account. Then the damages these pollutants do to human health, economy development and more are monetized to estimate the negative effects that different brands electric vehicles have on the environment. It is found that in U.S., no matter what brand they are, the average environmental pollution they make is always higher than that made by comparable gasoline vehicles.

Moreover, in the U.S., the pollution caused by gasoline vehicles doesn’t vary much across the country. The largest urban areas are a little more severe than rural areas, because the population density is higher in urban areas, which means the same amount of pollution can do more damage to human health.

In contrast, the environmental pollution caused by electric vehicles shows obvious regional variation.

Comparing the two figures, the researchers find that in the western part of U.S., the environmental pollution from electric vehicles is less than that from gasoline vehicles. But in the eastern part, the situation is reversed.

In the green area where electric vehicles cause less pollution, the government should provide an “environmental subsidy” for each electric vehicle. But in the yellow and red areas in which gasoline vehicles are eco-friendlier, the government should introduce an “environment tax” on electric vehicles.

The main reason why there is spatial heterogeneity of pollution caused by electric vehicles is due to the electric grid in the U.S. There are three main interconnections: Eastern, Western and Texas. And the three electric grids can operate almost separately with limited flows between them. But the energy-source structure is quite different among them. In the western part, 70% of generation comes from renewables, nuclear, hydro, and natural gas, which means emissions are lower. In the East, there is significantly more coal-fired generation, while Texas generates electricity mainly by natural gas. So, the spatial differentiation of energy-source structure helps electric vehicles in the West get more environmental benefits.

Although this study was conducted in the U.S., the same condition also exists in China. In 2015, 67% of the electricity is generated from fossil fuels in China, which is slightly lower than that in Texas Interconnection but higher than those in Eastern Interconnection and Western Connection. Even if Comparing with Texas Interconnection, China Power Grid uses more coal rather than natural gas. So, the power plants in China actually cause more pollution than those in the U.S., which means the electric vehicles in China also emit more pollutants than traditional gasoline vehicles according to the views put forward in this paper.

For electric vehicles, maybe they can’t reduce the air pollution, but they can still make some environmental benefits for human beings. Because the electric vehicles emit nothing and the pollutants are all from the power plants, which means these pollutants have been centralized. And people can deal with those emissions more easily.

So, the question is, for China which is the largest developing country all over the world, how to balance the economic development and environmental protection. According to the 13^th five-year plan, China will be committed to develop various sources of renewable energy including solar, wind, geothermal, tide and more. Will this be the answer? Let’s wait and see.