Carbon Footprint

Factual Questions
1

Hello, FNG here. :slight_smile:
What has a larger carbon footprint, a gasoline automobile with reasonable mileage, or an all-electric car that’s charged in an area where the grid is powered by coal (as it is here in Utard)? Was always curious about that (I may be buying an electric motorcycle in the near future).
Thanks!

2

Power plant+ electric motor is more still more efficient than an internal combustion engine.

3

You may get different answers based on your assumptions.

  1. Will you count just the carbon footprint regarding the fuel for the vehicle? Or will you also count the carbon footprint of the factory that produced the car in the first place?
  2. Are you assuming that the EV and ICE would both be driven the same number of miles per year? If not, will you figure the carbon footprint per mile driven or per year?
  3. You said that you’re assuming all the electricity comes from coal plants. What assumptions will you make about where the gasoline comes from? Does it contain 10% ethanol?
  4. You mentioned an electric motorcycle, which may give a very different answer from a standard EV.
  5. What do you consider to be “reasonable mileage” for the ICE?

I’m willing to plunge ahead with my own assumptions, but YMMV (pun intended).
I’ll assume we’re comparing a brand new ICE which gets a combined fuel economy of 25 MPG and a brand new EV which gets a combined fuel economy rating of 100 MPGe. From what I’ve seen, these are typical numbers for cars being sold in the US. EVs tend to drive fewer miles because you don’t take them on road trips. But, for an apples-to-apples comparison, let’s pretend that you don’t use the ICE for road trips either, but you always take a train or a bus when you go on vacation. So, let’s say 6,000 miles per year of around-town driving. That’s 240 gallons of gas for the ICE (which would cost $575.76 at $2.399/gal), compared to an amount of electricity equivalent to 60 gallons for the EV, which is 60 x 33.7 KWh = 2022 KWh of electricity (which costs $177.94 in Utah).

1 gallon of gas = 8.887 kg CO2 cite
1 KWh of electricity from a coal plant produces anywhere from 0.8 to 1.0 kg of CO2 cite

So, burning 200 gallons of gasoline produces 2133 kg of CO2.
And, 2022 KWh of electricity from a coal plant produces anywhere from 1618 to 2022 kg of CO2.

So, the EV wins, but not by much. However, that’s assuming all the power comes from coal. In Utah, 81% comes from coal, 15% natural gas, 4% other. And remember that you have the flexibility that, even if your EV were getting its power 100% from coal today, it doesn’t have to stay that way forever. In the future, you might move to a state which has a larger share of renewable energy. But with the ICE, you’re stuck with gasoline no matter what state you move to.

4

How would a CNG Honda Civic compare?

http://automobiles.honda.com/civic-natural-gas/

5

The EPA website says the 2015 Honda Civic CNG emits 0.218 kg CO2 per mile, so for 6,000 miles that’s 1308 kg CO2. But I don’t know what assumptions they’re making about how much of that is city driving, so it’s not a direct comparison.

How about we try it using only the EPA’s numbers (www.fueleconomy.gov), so that way the assumptions are the same across the board. I plugged in Salt Lake City Utah (97101) as the location.

2015 Nissan Leaf (EV) 0 tailpipe + 130 g/mi upstream

2015 Honda Civic CNG 218 g/mi tailpipe + 88 g/mi upstream = 306 g/mi total

2015 Toyota Camry (ICE) 317 g/mi tailpipe + 71 g/mi upstream = 388 g/mi total

2015 VW Jetta 6-spd turbo diesel 283 g/mi tailpipe + 81 g/mi upstream = 364 g/mi total

So the EV wins by a rather wide margin there. But if you live in a different part of the country, the answers aren’t so lopsided. For example, if you live in Galt, Iowa, the Nissan Leaf comes in at 250 g/mi total, which is still better than the Honda Civic CNG but not by as wide a margin.