Friday, 1 June 2012

Is an electric car greener than a gasoline one?

I was having an interesting discussion with my friend Arturo about what´s the real carbon footprint of an electric car, in a country like Mexico, where 76% of the electricity is generated by fossil fuels.  So I made some quick calculations to see if even in that case, an electric car is a greener option.  It seems that it is, but just for a little difference.

BP reported emissions of 135.32 Mtons CO2e in 2010, including extraction, refining and petrochemicals.  For the same year, BP production was 3.81 millions of barrels a day, which means 1389.65 millions of barrels in 2010.

That means 
0.0974 tons CO2/barrel ;  1 barrel =  158.9873 L ;  1 ton = 1000 kg
0.6125 kg CO2/ litre
612.5 g CO2/litre

The Nissan micra has a fuel consumption of 47.5 MPG and average CO2 outpout of 147.8 g/km

47.5 MPG ;  1 mile = 1.61 km ; 1 Gallon = 3.79 litres
Therefore  20.18 km/litre
So, the CO2e for the oil production for the micra will be
30.35 g CO2/km

Total CO2e,  30.35+147.8

178.15 g CO2e/km

Now, for the Nissan Leaf (electric car) , it has a consumption of 0.34 kW·h/mi,  or 0.211 kW·h/km

According to greenpeace,  the total emissions of CO2 for electricity production in 2008 were 112.5 Mton CO2e,  for a total production of 235.87 TW·h

That is 0.4769 kg CO2/kW·h  or 476.9 g CO2/kW·h

Therefore 100.63 g CO2e/km

It's interesting to compare with the USA data.  Again taking the Micra values, we have  (20.18*147.8) = 2982.6 gCO2/litre.  Nissan values for the leaf are 0.024 litre/km of gasoline equivalent, which will mean that in the USA the leaf will be producing  71.58 gCO2e/km

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