Few people are fooled by Nissan’s claim that the LEAF is a zero emissions vehicle. Zero tailpipe emissions does not mean zero emissions. “Electric vehicles just shift emissions from the tailpipe to the smokestack,” many critics claim. Both of these claims oversimplify the issue and do not accurately reflect the potential impact of electric vehicles on greenhouse gas emissions.
In reality, electric vehicles shift emissions from the tailpipe to the smokestack, nuclear reactor, hydroelectric dam, wind farm and many other sources of electric power. Ultimately, the impact of electric vehicles on greenhouse gas emissions is a function of the electric generation mix in a given region. In the United States, the generation mix is nearly 50% coal and an additional 22% comes from natural gas and other fossil fuels (see image below, courtesy of MIT Electric Vehicle Team Blog).
With this generation mix, Samaras and Meisterling (2008) report that the average life cycle greenhouse gas intensity of electricity generation in the United States is 670 g CO2-eq/kWh. At this level of greenhouse gas intensity, Samaras and Meisterling estimate that plug-in hybrids produce nearly 40% less lifecycle greenhouse gas emissions than conventional gasoline vehicles (see image below). Even at the greenhouse gas intensity of coal, plug-in hybrids produce less lifecycle greenhouse gas emissions than conventional gasoline vehicles.
In comparison to conventional hybrids, plug-in hybrids produce slightly less lifecycle greenhouse gas emissions. At the greenhouse gas intensity of coal, plug-in hybrids produce more lifecycle greenhouse gas emissions than conventional hybrids. Therefore, in coal dependent states like West Virginia, buying a conventional hybrid as opposed to a plug-in hybrid will lead to a larger reduction in greenhouse gas emissions. See the image below for a state-by-state summary of generation mixes (courtesy of MIT Electric Vehicle Team Blog).
Over the next few years, availability and purchases of electric vehicles will be concentrated in the northeast and west coast, where coal is a small fraction of the generation mix. Most of these states have an average life cycle greenhouse gas intensity of electricity generation lower than natural gas. Therefore, electric vehicles in the United States will lead to significant reductions in greenhouse gas emissions. Electric vehicles are not zero emissions vehicles, but their potential impact on greenhouse gas emissions is significant enough to justify generous government rebates and all the attention they are receiving.
I’m confused. Because California buys and burns it’s coal in other states (the four corners area) that makes it look like we don’t use any coal. 44% of the electricity in LA is generated from coal. And 49% of the electricity in the US is generated from coal. To me the problem is our coal-dependency. And an electric car is great but not really an improvement until we kick coal.
Regarding the “total well to wheel” efficiency the ICE & Electric vehicle solution is really something different.
Not trying to be totally scientific but to give you some indicative levels of “losses” in the chain as follows:
ICE (100 units of energy)
Drilling & Refining -15% (=85 units)
ICE and drive train efficiency -80% (=17 units)
Total WTW ICE efficiency = 17%
EV (100 units of energy)
Power production -10% to -50% (Hydro power, Coal condence =90 or 50 units )
Transmission losses -8% (=83 or 46 units)
Charge & discharge -15% (=70 or 39 units)
Electric motor -10% (=63 or 35 units)
Drive train -10% (=57 or 32 units)
Total WTW EV efficiency = 57%-32%
Which exceeds the ICE system with 2-3 times.
A fuel cell vehicle makes the case worse since electricity is needed to produce the Hydrogen and there are losses in the distribution and compression of hydrogen and also in the fuel cell that once again create electricity…
//Joachim
Joachim,
Would you please explain the 8% transmission lose? The number seems to be very low.
thank you,
Joe
What I meant was transmission losses in the electricity grid.
The figure 8% is no exact figure and is very dependant upon how far away the actual electricity production is located.
With a Solar panel on the roof they are very small but transmitting electricity from the Hoover dam to LA has of course bigger transmission losses.
Josh, good statistics and a worthwhile discussion. Hopefully debates like this will enlighten others and prompt them to consider the true impact of their transportation choices. Factoring in the local varieties of point-source energy inputs and their corresponding emmissions is the only logical thing to do when assessing one’s impact and carbon footprint. I think there should be more discussion about distributing renewable energy sources. In California, for example, we could incentivize large companies to add solar charging stations (do we already?) at work to encourage PHEV use. Matching low (net) emmissions solar to the load (PHEV) during peak production hours is quite ideal. Charging off the grid overnight from home is less ideal. At least here in California, there is great potential to maximize the environmental benefits of electric vehicles.
Well, being 3x more efficient than an internal combustion engine (ICE) car, I would expect electric cars to reduce carbon emissions substantially, needing only one third of the energy to do the same work. Moreover, the electricity grid delivers energy with high efficiencies and its energy can produced with renewable sources.
For example, Costa Rica’s electricity is produced with 95% renewable sources (hydro, geothermal and wind). So every electric system is different and these primary source numbers will vary according to a country or region’s resources and its policies.
Definitely electric cars will lower carbon dioxide emissions.
Mario
We need a lot more discussion of the permutations and possible impacts of auto fleet electrification. I have addressed some of these in a regional context:
http://marylandenergyreport.org/2010/03/31/electric-cars-carbon-dioxide-emissions-and-air-conditioning/
Josh,
Good article, however when I see articles as this one no one mentions this issue of battery life cycles. The life cycle environmental impact of all types of vehicles are going to compared, should not the issue of the electric batteries needs to be part of the discussion? What happens to the batteries after the electric hybrids reaches the end of their life cycle? That is a real concern and one I have not seen (or heard) it discussed. I would hate to see one environmental fix shifted to another environmental issue (or possible disaster)…where are all of these batteries end up? I would hope we don’t see mounds of battery landfills!
Have you heard of any discussions around the issue? I have become very hesitant in accepting electric vehicles because of this point.
Thank you sharing this issue.
Joe,
A lot of people have brought up this issue, although I don’t know of any scientific articles that address it. The article here focuses on greenhouse gas emissions. In general, the environmental movement has shifted towards a focus on greenhouse gas emissions. Many environmentalist now support nuclear power. Much like the byproducts of nuclear power, electric vehicle batteries end up as toxic waste.
The question is, how much of this waste from nuclear power and batteries are we willing to put up with? When does this problem overshadow the global warming problem?
Environmentalists now seem to be willing to put up with a lot of toxic waste, as long as greenhouse gas emissions are significantly reduced.
Josh,
Thank you for responding. I understand the reasoning behind this issue, however with the most resent information coming to light about Global Warming (and I am not trying to stir the pot about GW) I am concerned the baby is being thrown out with the bath water. I am not a big Nuclear Electric Generation advocate for the same reasoning we both mentioned with potential legacy issues with battery disposal. We could be creating a much larger issues for our grand children to address. Just my opinion…I have been leaning more towards NGV’s for fueling of our vehicles for the future.
Thanks again.
It is my understanding that the old lead acid batteries are completely recyclable and also offer the best performance.
What about the CO2 footprint of manufacturing an electric car?
For sure, a hybrid has a higher footprint (all of a gas engine car + all of an electrical -maybe less batteries, though).
I suppose that today’s electric cars also have a much higher CO2 footprint than an equivalent size gas engine car, but that may change.
I have a feeling that most of the CO2 footprint of a car comes from other things than the oil it burns. At least most of the cost of a ‘normal’ car, used ‘normally’, is from other things than oil, thus the CO2 footprint might be somewhere else?
With electric cars, I suppose it will be even more true.
So the key is that electric cars become dirt cheap (low resources i.e. low footprint), that it is made through processes using low CO2 footprint (we’re far from that), and that the electricity source becomes also CO2 free.
We’ll get there, of course… when there are no more fossil fuels cheap enough to burn!
Don’t have numbers at hand, but the CO2 footprint to manufacture an electric car is overall pretty much the same as a gasoline or diesel car. CO2 is higher for batteries, but lower for the electric motor (compared to the more complex ICE). The rest is pretty much the same, as long as you’re comparing similarly sized cars. The electric also doesn’t have fuel system components, and a much smaller cooling system (if it has any cooling system at all).
I was wondering if the transportation costs and impact of gas/diesel are included in the emissions levels from the ICE population. Liquid fuels don’t just show up free of charge at the gas station.
Bio-diesel that is available in my area is made locally so there should be less impact from the local source.
Good point. Articles like this one agonize over the costs and pollutants for electricity while totally ignoring the costs and pollutants for gasoline or diesel fuel. To be fair we need to include exploration, drilling, pumping, manufacturing and transportation costs for petroleum products. We also need to include similar costs of the lubricating and hydraulic fluids required by ICE cars. Anti-freeze too. And we should factor in environmental risks like the major spill happening in the Gulf.
Josh,
I enjoyed your article.
Question: Regarding your statement “Even at the greenhouse gas intensity of coal, plug-in hybrids produce less lifecycle greenhouse gas emissions than conventional gasoline vehicles.” Is this because electrical vehicles are more efficent than ICE vehicles?
I’m not exactly sure why. I based that statement on the above graph, which came from the cited article:
http://pubs.acs.org/doi/pdf/10.1021/es702178s?cookieSet=1
You might be able to find more info there.
What is the conversion from 670 g CO2-eq/kWh to g CO2-eq/mile for electrics and hybrids? That would allow a direct comparison with cellulosic biofuels, which can reduce g CO2/mile substantially compared to gasoline, using life cycle or well-to-wheels analysis. Additionally, biofuels have a much higher energy:volume and energy:weight ratio than batteries (reducing vehicle weight), and are made from plant material formed by photosynthesis from atmospheric CO2 and sunlight. Given the financial and policy emphasis on EVs, it is important to detail these comparisons.
Let’s not overlook the fact that pure electric vehicles are about 50% more efficient than ICE vehicles on the basis of many fewer moving parts & therefore lower friction losses & more energy getting to the wheels.
What a thoutful article. When it comes right down to it, we are seeing the kind of vying for position and attention that comes with any techological progress. Electric, bio-diesel, hydrogen, hybrid. Right now there is no clear way to see which might ended up becoming the main technology used…and perhaps we will have to utilize all of them to effectively reduce our greenhouse gas emmisions. I wonder how hydrogen stacks up? I know that hydrogen is often viewed as energy intensive, but when coupled with solar it might end up being a useful componant. Especially since a hydrogen powered car is capable of much longer distances. I recently read an interesting white paper on a new electrolysis technology which might make on-site hydrogen generating fueling stations a real possibility. If anyone is interested in how hydrogen might end up being used in the new green(er) economy, you might want to look at this white paper out of “Gridshift” in georgia:
http://www.grid-shift.com/white_papers
Thanks again for the interesting article/