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Curb Your Carbon: What EVs Actually Do to Transportation Emissions

Image courtesy of The Verge

History will likely point to 2021 as an inflection point for electric vehicles. A Silicon Valley luxury entered mainstream conversation, startups with zero revenue gained multibillion-dollar valuations, and a full-throated electrification strategy became playing stakes for traditional automakers.

Amid the hype and clickbait articles proclaiming the EV as either humanity’s savior or a trojan horse for dirty mining, it’s easy to throw your hands up and ignore answering the key question: How much of a dent will EVs actually make when it comes to climate?

Join me in for a quick spin through some VERY basic math — you remember addition and multiplication, right? — so you never have to get confused about this again.

The problem

The first step is to acknowledge transportation’s impact on the environment. As of 2018, this sector accounted for 28% of total greenhouse gas emissions in the United States — about 59% from passenger vehicles, and 23% from heavy-duty vehicles.

Carbon emissions from the transportation sector have grown by about 24% over the last 30 years, and transportation now contributes the largest share of GHG emissions of any sector. (The dip following 2007 was due to reduced economic activity following the Great Recession.)

In particular, road-based transportation, overwhelmingly powered by internal combustion engine (ICE) vehicles, is responsible for 6 gigatons (Gt) CO₂ of global emissions annually. That’s the same mass as 60,000 US aircraft carriers!

A gigaton of ice filling Central Park would extend 341 meters (1,119 feet) high — almost as tall as the Empire State Building. Image courtesy of NASA.

The opportunity

How much can we realistically offset by electrifying transportation? Let’s start by diving into one specific example.

The lifespan of an average vehicle in the US is 13–17 years — to be conservative, let’s assume a sedan is used for 13 years. Each year, the average sedan travels 11467 miles. Assuming an ICE sedan achieves a fuel efficiency of 30.8 miles per gallon, the vehicle will consume 4840 gallons of gasoline in its lifetime. Gasoline combustion emits 8.89 kg CO2 per gallon, so the ICE will directly emit 43 tonnes of CO₂.

Its electric vehicle (EV) counterpart can achieve an energy efficiency of four miles per kWh and consume 37.3 MWh over its lifetime. Assuming average US grid emissions of 0.42 kg CO₂ per kWh, the EV will be responsible for 15.6 tonnes of CO₂¹.

On the other hand, emissions from EV manufacturing are significantly higher than those from ICE manufacturing, due in large part to the battery. From Tesla’s 2019 Impact Report, we can derive that manufacturing a typical ICE generates 8.2 tonnes of CO₂, whereas manufacturing an EV generates 12.2 tonnes. Still, this means an ICE’s lifetime emissions total 51.2 tonnes versus 27.8 tonnes for an EV, leading to a net lifetime emissions reduction of 23.4 tonnes of CO₂ per sedan².

What would be the impact if all new sedan sales were immediately electric? In 2019, sedan sales totaled 4607242 in the US, 8257375 in Europe, and 10471790 in China. Electrifying all these new sedans would save roughly 0.55 gigatons of CO₂ just in these regions (out of 33 gigatons of energy-related CO₂ emissions globally in 2019).

The beautiful thing is that once these vehicles are electrified, any improvement to the grid automatically reduces emissions further. The best-case scenario is a 100% renewable grid. Performing the same calculation for other vehicle types, across the base grid and 100% renewable scenarios, we get:

Notice that the global avoided emissions of 5.89 Gt CO₂ under a 100% renewable grid scenario is suspiciously close to RMI’s estimate of 6 Gt CO₂ from road-based transportation. Our math worked out! (Feel free to play around with the calculations yourself.)

The conclusion

When one of the most ambitious climate investors is requiring their portfolio companies to scale to at least half a gigaton of CO₂ reduction, electrifying transportation is a winning strategy.

Of course, the current fleet of vehicles will take time to turn over, and in the absence of complete bans of ICE sales, some consumers will still decide to purchase ICEs. The International Council on Clean Transportation expects that electric vehicles could make up 10–15% of new vehicle sales globally by 2025. Clearly, we have a ways to go.

[1] This does not account for the additional indirect emissions attributable to the EV through electricity transmission losses or those attributable to the ICE through the production, refining, and transport of gasoline.

[2] As we decarbonize the electricity grid, the manufacturing emission difference will decline. Battery pack materials and manufacturing are responsible for between 61–106 kg CO₂ equivalent per kWh. Based on this and the Model 3’s 82kWh battery pack, the battery is likely responsible for around 5 tonnes CO₂, or about 40% of manufacturing emissions. About half of the battery emissions come from electricity used during the manufacturing process, so as carbon intensity of grid electricity drops so will the emissions from battery pack manufacturing.



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