A number of articles published this week paint a negative picture of electric cars based on a British study published earlier this month. The study attempts a comparative life-cycle assessment (LCA) of conventional, hybrid and electric cars and prompted “downer” headlines such as, “Electric Cars May Not Be So Green After All” and “More Bad News For The Chevy Volt.”
The report was undertaken by consulting company, Ricardo and was released by the Low Carbon Vehicle Partnership on June 8th. And contrary to the above headlines, the press release was considerably more upbeat, stating: “Electric and hybrid cars create more carbon emissions during their production than standard vehicles – but are still greener overall.” Since the headlines suggest a different view of electric cars than the press release, I’ll attempt an objective view of the report’s findings.
An analysis of the full report reveals the study is based on various assumptions. The authors assume projected 2015 vehicle specifications coupled with an in-use period of 150,000 km (93,750 miles). They also assume an electricity carbon intensity of 500 gCO2/kWh. The life-cycle assessment itself covers four distinct “blocks” of a vehicle’s life :
1) Vehicle production – to assess embedded CO2
2) In-use phase – to assess CO2 incurred during the driving life of the car
3) Disposal at end-of-life, and
4) Fuel production and delivery processes – considering both electricity generation and gasoline production, depending on vehicle type
To cut to the chase, the report concludes the following:
Whole Life Carbon Emissions:
- Standard gasoline vehicle 24 tonnes
- Hybrid vehicle 21 tonnes
- Plug-in hybrid vehicle 19 tonnes
- Battery electric vehicle 19 tonnes
“Not so green” and “more bad news” for the electric vehicle? No so much! The EVs and hybrids come out ahead. But those negative headlines should prompt the critical person to pay attention to details – because the stories behind the headlines do have a point.
The biggest downside for hybrids – and even more so for electric cars – is the embedded CO2 factored into battery pack production. Whereas the report calculates the total embedded CO2 for the production of a conventional car is 5.6 tonnes, it’s 8.8 tonnes for a mid-size EV. And of that embedded CO2, the EV battery production accounts for 43.1% of the total, equating to 3.8 tonnes. That’s pretty significant.
Detractors of EVs point out that these cars won’t get 150,000 km out of a single battery pack and here, they may have a point. Lithium Ion batteries do degrade with age and with repeated recharging, so at some point, an EV might have to undergo battery replacement. When that happens, we would have to factor in further embedded CO2 for replacement battery production – that is, an additional 3.8 tonnes. But having said that, in an experiment carried out at MIT, an EV battery was subjected to 1,500 rapid charging and discharging cycles, and only lost 10% of total battery life. So, if we consider an EV can go 100 miles per charge, and can withstand 1,500 charge cycles – then that exceeds the mileage assumed in the LCA report. But for the sake of argument, if we concede the worst case scenario, and assume EVs may require a second battery pack, the lifetime CO2 increases to 22.8 tonnes – still better than the projection for a conventional car, if not by a huge margin.
Interestingly, the authors of the report do not try to say whether EVs are better than conventional cars in their conclusion. While they do state embedded CO2 during production is becoming an increasing component of total life-cycle CO2, the main take-away is that further work has to be done to obtain common methodologies and data sets.
My conclusion is, there’s no such thing as a free lunch. Both EVs and conventional cars have a considerable carbon footprint – and there’s no way around this today. Today’s EVs can never genuinely claim to be “zero-emissions,” but this report does not conclude, at all, that they are lesser than conventional cars from an environmental standpoint. EVs offer the advantage that their CO2 footprint can be mitigated by increasing the balance of renewable energy for recharging, and let’s not forget, the benefits of EVs extend beyond an assessment of CO2 emissions and climate change. Diminishing our dependance on foreign oil is another good reason to encourage the evolution of electric cars.