How green is my car?

UPDATE (02/10/2018) - Updated to account for upstream CO2e emissions of fuel (i.e., extraction, refinement, and transport).

A few years ago, my wife and I decided that our next car purchase would be an electric vehicle (EV).  We saw three reasons to make this decision:

1. EVs have lower life-cycle greenhouse gas (GHG) emissions compared to petrol or diesel cars;
2. An EV can be charged directly from our solar panels at minimal cost; and
3. We believe that EVs are the future of personal transport and we wanted to be a part of the transition away from cars that burned fossil fuels, even if that meant that we would be paying more money up front to buy electric.

A year later, we bought a fully electric Nissan Leaf.  The car has no exhaust pipe and we plug it into a powerpoint in our garage.  The car is a dream to drive.  It is so quiet, but also very quick.

People seem to be interested in the car and the most common question is, "What is the range?"  We once drove 115 km with a full car and the air-conditioning running and got home with 7km of range remaining.  Having said that, I tend to only charge the car to 80% capacity and rarely drive more than 65 km in a day, so it's not often that I test the limits of its range.  On the odd occasion where I need to top up the battery, I use a free fast-charger located about 10 km from home.  The fast-charger can add about 10 kWh of power in 25-30 min, which is about 70 km range.

I was surprised to find that some folk seem to think that the car is just as bad for the environment as a petrol or diesel car.  Their argument, so far as I can tell, is that the manufacturing process of batteries causes higher greenhouse gas emissions than the manufacturing process for internal combustion engine vehicles (ICEV) plus the fact that most of our electricity is sourced from coal-fired power stations.  I just had to investigate!

I discovered that Nissan produce an annual audit of the greenhouse gas emissions they produce during the production of their vehicles; however, they don't breakdown the data into different models.  According to Nissan (2013), 0.76 t of CO2 are emitted per vehicle produced.  This figure probably does not include the GHG emissions for production of all the parts that Nissan source from other companies.

A paper by Correia and colleagues (2013) compared seven estimates of embodied CO2 equivalent (CO2e) emissions (includes emissions from resource extraction all the way to the finished product) for four vehicles: a 1.2L VW Golf, a 1.6L VW Golf, a hybrid Toyota Prius, and a Nissan Leaf.  According to this analysis, the embodied CO2e emissions of the four vehicles are:

• 1.2L VW Golf, 6.0t;
• 1.6L VW Golf, 6.2t;
• Toyota Prius, 7.4t; and
• Nissan Leaf, 9.2t.

In the last two years of driving, the Leaf has travelled 25,000 km and averaged 15 kWh per 100 km (I have a bit of a lead foot compared to other drivers who get 12-13 kWh per 100 km).  This works out at a total of 1,875 kWh of power per year.  If we assume that 100% of my power came from the grid in Queensland, then my driving would create 1.52t CO2e per year, according to the National Greenhouse Accounts Factors (Department of the Environment, 2014).  I actually pay an extra 5.5c per kWh to my power provider to buy 100% green energy (not to mention the solar when the car is plugged in during the daytime), so I could argue that my driving is totally emissions free, but I am aware that most folk don't pay a premium for their power, so I'll keep the 1.52t per year of CO2e emissions for the sake of the comparison.

Assuming the same annual mileage in a 1.6L Golf, which has a fuel consumption of 8.4L / 100 km, the total amount of petrol for a year is 1,050L.  According to the DoE report (Department of the Environment, 2014) each litre of petrol produces 2.3 kg of CO2e emissions ...

EDIT (02/10/2018) - Some further reading has highlighted a mistake in my calculations.  The Australian Government (DoE, 2014) is only interested in calculating the emissions caused by the combustion of petrol or diesel.  They do not include the emissions from extraction of the raw materials, refinement of the fuel or its transportation.  According to Moretti et al. (2017), these stages account for an additional 22% of CO2e emissions.  This means that each litre of petrol actually produces 2.81 kg of CO2e emissions, (all following calculations have been updated in bold accordingly)

... so the annual CO2e emissions would be 2.95t.  If we consider the more efficient 1.4L TSI turbocharged VW Golf, you can improve your economy to 5.4L per 100 km, which results in annual emissions of 1.8t.

Comparing the options, we can see that the newer, more efficient VW Golf is the better environmental choice compared to the Leaf on grid power, even when you assume the grid is getting greener at 5% per year.  EDIT(02/10/2018) If we assume that the grid will get greener at a rate of 5% per year, the Nissan Leaf beats out the newer more efficient VW Golf after seven years on the road.  If you compare the less efficient vehicle like the 1.6L VW Golf, then the Leaf becomes the greener option after 2.5 years.  Of course, if you get green power through your energy retailer, or from your own solar panels, then the Leaf is clearly the better environmental choice.

There are many other things to consider, of course.  If you need to drive more than 100 km per day, then don't buy any of the first generation of EVs.  The 2nd Gen Leaf will be available in Australia in a few short months and has double the range of the 1st gen Leaf (about 240 km).  Cost is obviously a major consideration too.  The new Leaf will cost about $50k - $55k when it becomes available, compared to the VW Golf, which costs between $25k - $30k; but, the EV is much cheaper to run than the ICEV, both in terms of fuel cost (50% - 100% cheaper) and maintenance cost (about 70% cheaper due to lack of moving parts).  In my opinion, it is worth considering the impact of exhaust emissions on health in our cities.  ICEVs, particularly diesel cars, clearly contribute to respiratory illnesses in cities.  EVs don't have any exhaust fumes at all and they are very quiet, which makes for a more pleasant and healthy city environment.

So, I have to admit my surprise.  I fully expected the EV to come out as the better choice in terms of CO2e emissions.  It seems that the low-emissions ICEVs available at the moment are holding their own when compared to grid-powered EVs.

References:

Correia, G.N., Batista, T.P., Marques, S.S., & Silva, C.M. (2014). How car material life-cycle emissions are considered in environmental rating methodologies? Suggestion of expedite models and discussion. Renewable and Sustainable Energy Reviews, 38, 20-35.

Department of the Environment. (2014). National Greenhouse Accounts Factors. Australian Government: Canberra, Australia.

Moretti, C., Moro, A., Edwards, R., Rocco, M.V., Colombo, E. (2017). Analysis of standard and innovative methods for allocating upstream and refinery GHG emissions to oil products. Applied Energy, 15, 372-381.

Nissan. (2013). Nissan Motor Company Sustainability Report 2013. Retrieved from https://www.nissan-global.com/EN/DOCUMENT/PDF/SR/2013/SR13_E_P118.pdf