The Carbon Debt Question: Why a Used EV is the most eco-friendly option for personal transportation.

By Jesse Lore, founder.

If you are like most Americans, climate change is on your mind. According to Pew Research, 54% of voters in the U.S. view climate change as a major threat to our world (the number goes up to 78% for Democrats). But for the critical thinkers among us, the question of how to reduce our carbon footprint related to transportation is a more complicated one. What is the actual impact of an electric vehicle (EV) versus an internal combustion engine vehicle (ICE) on greenhouse gas emissions, from a full-lifecycle perspective? Are EVs really better for the environment?

Transportation makes up the largest part of U.S. greenhouse gas emissions, according to the EPA at 28%. A more detailed breakdown of personal carbon emissions by the Center for Sustainable Systems at the University of Michigan shows us that passenger cars and light-duty trucks make up 58% of transportation emission, with heavy duty trucks, aircraft, ships, rail, and public transit making up the balance. It follows that if we could take the CO2 out of transportation, we could reduce the US carbon footprint by over 15%.

But it’s not that simple. The truth is, production of electric vehicles is much more carbon intensive than the production of internal combustion engine vehicles today, mostly because of battery minerals mining and battery production.  The International Energy Agency (IEA), using data from a 2020 study by the Argonne National Laboratory, published a study showing that EVs are 33% more carbon intensive to manufacture than ICE vehicles, mostly because of battery mineral mining and assembly. However the same study showed that even with EVs being powered by electricity that is generated through a blend of clean and dirty sources, EVs are less than half as carbon-intensive as ICE cars. If you’re powering your vehicle with clean energy, then EVs are more than 80% less carbon intensive than ICE cars (more on this later).

The implications of this study are that after about 19,000 miles, or just under two years of average driving, an EV is carbon neutral to an ICE vehicle. At that point, the EV has paid off its carbon debt, and is a net positive for the planet from that point until end-of-life (15-20 years, according to a study by Recurrent Automotive) when its battery is repurposed for a solar farm, street light, or recycled into another EV, according to Consumer Reports and other sources. So if you are looking to purchase your next car, and you want the choice that is going to have the best impact on your personal carbon footprint, get an EV that has at least 20k miles on it; someone else has paid off that vehicle’s carbon debt, leaving you to drive GHG-free for the next 180k+ miles.

“But wait!” you say. “What about the electricity generation? We’re not driving GHG free if the power to charge our EV comes from a coal-fired power plant.” That is true; in 2022, 79% of energy consumption in the U.S. was from fossil fuels. If you buy an EV, charge it at home, and don’t have solar panels on your roof, then your clean EV just becomes a repository for GHG emissions created elsewhere. 

The best framework to explain this conflict is the Greenhouse Gas Protocol, an international non-profit that develops and deploys accounting and reporting standards for GHG emissions. Under this framework, there are 3 types of emissions: Scope 1, which you create directly through burning fossil fuels; Scope 2, which is from purchased electricity (like home power supply); and Scope 3, also known as value chain emissions, which are emissions that are created by manufacturers of products you buy, or emissions created when you dispose of your products.

For your car, you can think of Scope 1 emissions as your tailpipe emissions, which amount to 8.887 kg of carbon dioxide for each gallon of gasoline you burn. If you own an EV, your emissions that come from charging your vehicle are Scope 2 emissions. Your car’s Scope 3 emissions are the GHGs that are created when the car is manufactured, and its end-of-life emissions. Taking what we have learned from the IEA report, we know that a used EV with 20k miles has worked off its Scope 3 emissions, it has no Scope 1 emissions, and now the only concern is Scope 2 emissions. So how do we reduce our Scope 2 emissions?

If you live in New Hampshire, Maine, or Massachusetts, you get to choose who generates the electricity you buy. You can’t choose your delivery provider – that is the public utility who operates the transmission lines, reads the meters, and sends you your bill. But you can choose who your supplier is, and there are 100% clean and renewable energy suppliers out there! In NH, the Community Power Coalition offers clean power options in over 30 communities throughout the state. Plus there are private companies like Think Energy that offer low-cost, fixed rate clean power options to ratepayers. If you want to be sure that the energy you buy for your EV charging is GHG free, you can explore your options and make the switch to clean power.

If you are looking to maximize your climate impact on your next vehicle purchase, the options are becoming more plentiful and more affordable. And according to the data available today, the most climate friendly option is a used EV with at least 19,000 miles, charged up with 100% clean and renewable energy.