At least for now, some electric vehicles (EVs) may generate about as much greenhouse gas (GHG) as some internal combustion engine vehicles (ICEVs) when judged over their entire cradle-to-grave life.
So say researchers from Norway’s Industrial Ecology Programme and Dept. of Energy and Process Engineering, and the Norwegian University of Science and Technology. Writing in the journal Environmental Research Letters, the group assessed the lifecycle GHG emissions of four differently sized EVs. They totaled up not just the GHG emitted to keep the cars on the road, but also that going into their manufacture and end-of-life phases.
From a GHG perspective, EVs equipped with smaller battery packs are more competitive than the heavier EVs with larger battery packs, the group says. However, EVs with small battery packs suffer from shorter driving ranges and depend more heavily on infrastructure in the form of fast charging stations.
The group also says that compared to conventional vehicles, the EV production phase was environmentally more intensive. Yet, depending on the energy source used for charging, the EVs were able to make up for the higher production impact in the use phase.
To make their analysis, the group calculated the lifecycle greenhouse gas emissions per vehicle and over a total driving range of 180,000 km using the average European electricity mix. They considered EVs that used lithium-ion batteries and which were manufactured in Europe (primarily Germany).
For the EV use-phase, the group says they made two key assumptions: lifetime and electricity mix. Industry reports most commonly give EVs a use life of 150,000 km. The researchers assumed a lifetime of 12 years and a yearly mileage of 15,000 km, resulting in a total mileage of 180,000 km. The total mileage and the EV energy requirement were multiplied to find total EV electricity requirement. Researchers assumed the average European electricity mix (521 g CO2/kWh) for the use phase. In addition, sensitivity analysis assessed electricity mixes with different carbon intensities.
The group points out that EV technology is still developing, and there are both near- and long-term opportunities to reduce their lifecycle GHG emissions. Near-term opportunities are mainly available through technology and production improvements. They consider impact reductions due to cleaner electricity more of a long-term opportunity.
The group also found that larger EVs can have higher lifecycle GHG emissions than smaller conventional vehicles. Thus, at the current state of the technology, finding the right balance between battery size and charging infrastructure is an important element in maximizing the climate change mitigation of EVs, they say.