I’ve been thinking about whether the right thing to do is to buy an electric car or a petrol car with carbon offsetting by tree planting.
My car is now 10 years old and has done over 90, 000 miles. It’s starting to show its age and I’ve started thinking about replacing it. I want to do what I can to reduce my personal carbon footprint so I’ve been wondering about an electric car.
Now, of course, you might say just give up your car and travel by public transport (or don’t travel at all). However, although we use public transport almost exclusively for local journeys in Edinburgh, my wife has mobility problems and can only really walk short distances. This is something many no-car advocates don’t think about - choosing to ban cars from certain areas discriminates against those who are not disabled but who are not completely mobile. So, we are not giving up our car yet.
I reckon we now drive about 5000 miles per year, mostly on journeys of more than 20 miles. In a modern medium-sized petrol engine car such as a VW Golf, I would expect to get about 50 miles/gallon so will use approximately 100 gallons (450 litres) of petrol per year. The figures I have seen are that with unleaded fuel, the carbon dioxide emissions are 2.1kg/litre so our annual emissions from driving are about 945 kg/CO2. For the sake of easy arithmetic, let’s assume 1000kg/CO2 per year.
If I buy an electric car and all electricity is from renewable sources, then this will be reduced to zero.
So, a no-brainer? An electric car will make a big dent in my personal carbon footprint. But wait?
Electric cars are much more expensive than petrol cars. I don’t know the specifics but let’s say that I can lease an electric Golf for £400/month (I think it will be more but take this as a working assumption). I can lease a petrol Golf for considerably less - details don’t matter but let’s say £300/month. So, I save £1200/year from the petrol option. In practice, I would actually save more as I’d buy a second-hand petrol model but let’s ignore this. Running costs for electric cars are lower but we don’t do a high mileage so let’s say the actual saving is £750 year.
Now let’s assume I can afford to spend £400/month on a car. I can either buy an electric car or, alternatively, buy a petrol-engined car and offset the carbon generated. It’s quite difficult to be precise about offsetting but some figures suggest that a mature tree can absorb about 20kg of carbon dioxide per year. Young trees are much less but let’s assume over a 60 year lifetime, the mean CO2 absorption is 15kg/year. This means that, over 60 years, a single tree will absorb 900kg of CO2.
Say it costs £5 to plant a tree (National Trust figures) so for £750/year, I can plant 150 trees. If I keep a petrol-engined car for 3 years, which is the typical life of a lease, then I can plant 450 trees for the same cost as an electric car. Over their lifetime, 450 trees will absorb 405,000kg of CO2, considerably more than the emissions saved from an electric car (3000kg). The difference here is so great that, even if some of my offset figures are ambitious, there still seems to be a significant net saving on CO2 for the same financial outlay.
Obviously, this is not an approach that scales as there isn’t enough land or tree planters to plant that trees to offset all petrol and diesel cars. So, for sure, we need electric cars in the medium-term. But, for the moment, maybe an electric car isn’t the best way for individuals to reduce their net carbon footprint?
This is not something that I’ve ever seen considered in discussions about electric cars. Have I missed something obvious?
Update: January 2023
I have bought an electric car. I had several helpful responses to this that convinced me that there is so much uncertainty in offsetting that any calculations I make are unreliable.