Concentrated spodumene from Greenbushes lithium mine, south west Western Australia. Spodumene contains up to 6% lithium by weight.
"But are EVs actually better for the environment?"
We get this question a lot. Before answering it, perhaps it should be rephrased: “Are EVs better for the environment than petrol or diesel vehicles?” This distinction is important, as it confines the discussion into an assessment of EVs over the incumbent technology – the internal combustion engine vehicle. One can make a solid argument that mankind’s modern life has a generally negative impact on the natural systems which sustain us, so if the goal was zero impact, the better option is to walk everywhere. In Australia, the private automobile is the de facto transport option with more than 70% of trips taken by car. So if you must drive a car, the least-worst option is to drive an EV. It’s not just about greenhouse gases, but also air quality, noise pollution, economics and global conflict. Putting aside the broader impact of modern life on our environment, let’s make a comparison between an electric car and a petrol car.
Environmental Impact at Manufacture
An EV takes about 25 % more energy, results in 30 % more emissions and takes substantially more material resources from the Earth’s crust than an equivalent-sized ICE vehicle. The two vehicles are effectively the same right up until the drive train is added – they both need wheels, a steel chassis, suspension, glass windscreens, air conditioning systems and plastic trims. Steel, aluminium and oil products are present in near-identical proportions. While the EV gets an electric motor stuffed with copper windings and a rotor with a few grams of rare earth metals, the big numbers are in the battery. Weighing up to 600 kg and consisting of a complex mixture of transition metals, polymers, graphite, copper and aluminium, the battery is where the bulk of 'embedded' energy and emissions stem from. These resources must be extracted from the ground and refined into useful chemicals. None of these processes could be described as impact-free; they still take energy, yields greenhouse gases and ultimately displace non-renewable elements from the Earth. It’s worth noting that all of these materials are recyclable, which we’ll get to later.
An EVs electric motor contains up to 10 kg of copper in its stator windings. The battery contains considerably more.
By comparison, the ICE vehicle gets an alloy engine block, hardened steel gears, hundreds of individual moving parts, an empty fuel tank, and an exhaust system which includes rare earth elements in its catalytic converter. The steel chassis, rubber tyres and glass windscreens all have a large embedded energy bill attached to them, but these are no different for an EV or an ICE vehicle. Over the life of the car, many of these components will need to be replaced and repaired, like belts, spark plugs, filters and of course regular oil changes.
When the whole lot gets turned into a 4-door sedan, you have a rolling lump of metal and plastic representing roughly 17 tons of CO2-e and 2.55 MWh of energy. By comparison, the EV will have produced 25 tons of CO2-e and maybe about 3.75 MWh of expended energy. Considering the world makes about 80 million cars a year, that’s a lot of energy and emissions from both the electricity used at the factory, and the processing of ores. Not only this, mineral extraction often leaves a sizeable impact on the landscape. So making something which takes 20% more energy and yields more greenhouse gas emissions might seem rather counterproductive. But when both vehicles roll off the production line with 0.0 km on the odometer, the emissions and energy efficiency race really starts.
Environmental Impact in Operation
The average Australian ICE passenger vehicle mileage is about 10 litres/100 km. Diesel engines are a generally a bit more efficient, although the majority of diesels are heavy SUVs and four wheel drives, so any efficiency gains are soon lost. Assuming full combustion, a well tuned engine converts 10 litres of fuel into approximately 19.2 kg of CO2, water vapour, carbon monoxide and nitrogen oxides for every 100 km travelled. The release of energy is harnessed by the moving pistons which convert the exploding hot gases into forward motion. Considering the average Australian motor vehicle travels 14,000 km per year, that’s about 2700 kg of CO2e every single year.
By comparison, an electric sedan like the Hyundai Ioniq is a very efficient vehicle. It averages about 14.5 kWh per 100 km. It can be hard to compare electricity to petrol, but we’ll do our best; 14.5 kWh is enough energy to run a small household for a day. It’s the same amount of energy as vacuuming the floor for 20 hours straight (no thanks) or leaving a toaster on from morning to evening. It’s the amount of energy added to a battery after two hours of charging at 7 kW, or only about 15 minutes on a DC fast charger. 14.5 kWh will silently push a 1.5 ton car down the road at highway speeds for 100 km. No greenhouse gases are emitted by the car ever.
Hang on, what about the energy source?
This is where the numbers get interesting. Australia’s main electricity grid, the NEM is a mixture of generators but predominantly black coal (50%) brown coal (15%) natural gas (20%) and ~15% renewable generation from solar, wind and hydro. Each of these sources has a corresponding CO2e intensity – brown coal is highest at over 1.1 kg CO2e/kWh, black coal about 0.85 kg CO2/kWh and natural gas is about 0.6 kg CO2e/kWh. Solar, wind and hydro are effectively 0 kg CO2e/kWh. Based on the current mixture of generators, it’s fair to say the NEM emits 0.8 kg CO2e/kWh.
Therefore if the Ioniq EV were charged only from grid electricity, it emits 11.6 kg CO2e per 100 km, or 1600 kg per year – almost half that of the average petrol or diesel car. Even the most efficient diesel passenger car at 4 litres per 100 km will emit over 12 kg CO2e per 100 km. But unlike a petrol or diesel car, the EV can be charged from 100% renewable energy – by charging in the middle of the day while the sun shines and wind blows, or perhaps it was stored in a household battery. This brings the emissions down to practically zero. A recent straw poll on Twitter suggested more than 75% of Australian EV drivers either charge directly from solar, or they buy green power from their electricity retailer. So without any prompting, most EV drivers are already choosing to reduce emissions and save money when they charge their vehicles.
Considering the emissions of manufacture and those from operation over a 10 year period, the two vehicles can be compared. An EV charged entirely on Australia’s main grid with its current mixture of renewable energy and fossil fuel generators tracks a different path to that of a typical petrol vehicle. By year 8, both vehicles have emitted the same amount of CO2 as each other. But from this point on, the ICE car will continue to pollute. If the EV were to be charged entirely on renewable energy from day one, the chart looks even better with emissions equivalence reached after just three years.
Greenhouse gas emissions over time for an EV, an EV charged on 100% renewable energy, and an ICE vehicle.
Petrol production also produces emissions (and oil spills)
Internal combustion engine vehicles run on petrol or diesel. They cannot run on anything but liquid fuels*. A thick, smelly liquid hydrocarbon mixture is extracted from the ground or the sea floor and is shipped around the world to a refinery where vast amounts of energy are consumed in order to yield volatile fractions, a part of which is suitable for these vehicles. ‘Vast’ is no exaggeration – it takes 4.6 MJ of heat energy to refine a litre of crude. Crude oil packs 30 MJ of chemical energy per litre, so from 100 litres of crude oil, roughly 15 litres is burned just to refine the remaining 85 litres. This would typically yield 34 litres of petrol, 22 litres of diesel and 24 litres of light fractions. Somewhat ironically, many refineries also use electricity to pre-heat many stages in the process. Before it’s even trucked it to a filling station, vast amounts of energy and greenhouse gases are expended. Some sources of crude oil are more energy and emissions intensive than others – Saudi Arabian crude is one of the more ready-to-burn sources, while Canadian tar-sands are as difficult as they sound to extract. Indeed, the refining of tar-sand derived fuels results in up to 40% more emissions than Arabian oil. This is the concept of ‘well-to-wheel emissions’. When considering the CO2-e emissions of an ICE vehicle per km travelled, it often starts at the fuel tank. Should you include the full emissions intensity of its life cycle that 19.2 kg CO2/100 km will be more like 23.0 kg CO2/100 km.
The impact of the BP oil spill in the Gulf of Mexico in 2010 is still being felt (Image by Sean Gardner)
* Some vehicles can run on natural gas or bio-fuels, but the environmental impact of these fuels and their production is for another day. For now, it’s safe to assume your 2015 Camry can’t run on anything but unleaded petrol.
End of Life Impact (the old toxic battery waste question)
At some point in the future, maybe in 10 or 15 years time, the battery in your car might need replacing. The lithium ion battery will start to show signs of degradation; usually in the form of reduced range and/or reduced power output. Three things will cause ongoing degradation to a battery: Heat, high states of charge, and time. The product of all three is a shorter battery life. This is normal, although for some early models it was quite significant. Most manufacturers will warranty their battery for 8 years or 160,000 km, whichever comes first.
The most common situation is where the underperforming battery is removed and replaced with a new one, returning the driving range to its original specification. Ideally, the incoming battery is current technology; in Quebec and New Zealand, some clever engineers have replaced a 2012 Nissan Leaf battery with one from a 2019 Leaf, effectively doubling the range. The old battery is typically pulled apart and the laggard cells are discarded while the remaining good cells are re-configured into a home storage battery for household solar storage. This is called “second lifeing” or “repurposing” and is arguably the most environmentally benign way of dealing with battery waste. The second hand and used EV battery market is white-hot right now, particularly given battery prices are still high. A used Leaf or Tesla battery may power a home solar-storage system for another 5 or 10 years depending on the climate.
But sometimes the battery is no longer suitable for even home storage. The battery must be sent off for recycling. Li-ion battery recycling has been possible since the first cells were manufactured in the 1980s, but like most recycling it’s often not economically viable. The battery cells are not toxic in their final form and do not present a contamination risk in most municipal landfills. However this is a poor outcome, and should be discouraged. The battery still consists of valuable materials – steel, copper, aluminium, nickel, manganese cobalt and lithium. These elements represent battery chemicals which do not need to be dug up from the earth, and should therefore afford a convenient source for new battery chemical feedstocks. At the moment, lithium ion battery recycling as a business is still small scale, but it will soon become a critical component of manufacturer’s product stewardship.
Almost all materials may be recycled and purified to a point where they may re-enter the manufacturing process. Chemists are working on ways of recycling the battery in the most cost effective way. Most approaches involve shredding the battery to small particles, separating plastics from metals then separating the three main native metals (steel, aluminium and copper). The copper and aluminium fraction need to be cleaned of their anode and cathode coatings respectively, which is currently done by either ultrasonic agitation in water or by solvent action. Alternatively the aluminium may be dissolved in alkali and discarded. The cathode material is then acid leached, and precipitated to extract valuable cobalt, nickel and manganese hydroxide, which may be used as precursors for new batteries. Finally the remaining liquid may be precipitated to extract the remaining lithium in solution. Lithium is relatively inexpensive and abundant and this step may not prove viable. New cathodes are made in high temperature calcining ovens which is where the bulk of the energy and potential emissions stem from in battery manufacturing. If the electricity was sourced from renewable or low-emission generators, the impact is massively reduced.
Image from Rothermel, S.; Evertz, M.; Kasnatscheew, J.; Qi, X.; Grützke, M.; Winter, M.; Nowak, S. ChemSusChem, 9, 3473-3484 (2016)
As for the remainder of the car, it’s just like an ICE car – the chassis is crushed and separated into steel, glass, plastic and aluminium, and these are melted down to make new cars. The process of crushing, grinding and separating is energy intensive, but arguably no worse than pulling new ores fresh from the ground.