Electric Vehicles: Where Do the Emissions Go?

04/04/2011 01:50 pm ET | Updated Jun 04, 2011

By Robert Earley, Dr. Feng An, Liping Kang and Lucia Green-Weiskel

Both the US and China have pledged to put 1 million electric vehicles on the road in the next decade (see here and here), citing the environmental and energy security benefits of this technology. But given that today electricity grids in China and the US are mostly powered by dirty sources of energy such as coal, are electric vehicles really better for the environment?

There is a common misconception that electric vehicles are zero-emission and that their impact on the environment is as non-offensive as the quiet sound of their humming engines.

But electricity doesn't come from nowhere. To charge vehicles with current technology, tons of dirty coal (or sometimes natural gas or uranium) must be consumed at a power plant, generating electricity which then must be distributed to a building or charging station. This process is in and of itself a carbon-intensive one. In the United States and China, most electricity is generated by coal, which, according to the Intergovernmental Panel on Climate Change, has a much higher global warming potential than conventional vehicle fuels like diesel or gasoline.

So when we promote electric cars are we just shifting the emissions from the tail pipe to the power plant?

In the last three months, the Beijing-based policy center, Innovation Center for Energy and Transportation worked on a report commissioned by the United Nations entitled, Electric Vehicles in the Context of Sustainable Development in China.

What we found may surprise many.

We found that pure battery electric vehicles may not always improve environmental impact of transport as much as we would like to expect; in fact, in some regions, electric vehicles are not an environmentally friendlier technology, particularly in terms of GHG emissions, because of the source of electricity which powers them.

Except for one region in China, compared with conventional vehicles, electric vehicles do not significantly reduce emissions -- from a lifecycle point of view. After all, electric vehicles are an energy conversion technology, rather than a clean energy technology. That is to say, if we use dirty energy in our electric vehicles, then the technology is dirty; if we use clean energy in our electric vehicles, then the technology is clean.

In order to generate data that reflects the lifecycle GHG emissions we analyzed the environmental impact of the sequence of events that occur in the production of electricity or gasoline fuel. For electric vehicles, we looked at the emissions associated with the entire lifecycle of electricity, from the mining of coal, to the generation of electric power, to the transportation and storage of energy and finally to the efficiency of the use of electricity in an electric motor.. This is what we call "Mine-to-Wheel" emissions. For a conventional vehicle, we measure the emissions generated during the fuel's life cycle, from the oil well to the tank, then in the combustion of fuel in the car's engine. This is called "Well-to-Tank" emissions.

This analysis points to a clear implication for policy. Electric grids must be made more efficient, be more reliant on renewable sources of energy such as wind and solar (some would also argue nuclear). In China this means replacing coal plants with renewable energy on a large scale, and simultaneously producing what many would call a "smart grid." If renewables aren't commercially viable, then we need to install new technology to burn coal more cleanly or capture the emissions that come from coal. In the US and China (the world's biggest coal-consuming countries) these are existing areas for government led research and development. But there is still a long way to go before so-called clean coal or renewable energy will be economically feasible in order to remake the electricity grids in either country to something we can call "smart." This report adds evidence to the existing pile that electric power and grid reform should be priorities on both governments' agendas.