Environmental comparison of transport – CO₂e footprints

In recent years the debate over the most environmentally friendly modes of passenger and goods transport has been raging and will continue to do so as different types of vehicle and planes make new innovations to improve their efficiency.

This is further complicated by the number of passengers being transported, the fuel type and the distance between stops. 

The best way to compare the efficiency of a mode of transport is to look at the grams of CO₂e output per kilometre per passenger or g CO₂e /km

1. Here is a simple list showing the Carbon intensity of various forms of transport from lowest to highest:

Type of transport	Passengers	G CO₂e / km per passenger From least to most	Total CO₂e per person per journey
Land travel
Cycling, this includes making the bicycle and food required by the cyclist	1	21g
Coaches	Average	26g
Trains	Average	34g
Nissan Leaf Medium car electric	4	35g
Medium saloon car diesel	4	52g
Nissan Leaf –  Medium car electric	1	140g
Medium saloon car diesel	1	210g
Air travel
Return flight London to New York 11,100km	Average	162g	1,800kg
Economy return flight London to Perth Australia 29,100km	Average	172g	5,000kg
Return flight London to Rome 2900km	Average	187g	545kg
Return flight Bristol to Newcastle UK	Average	340g	272kg
1st Class flight London to Perth Australia 29,100km	Average	515g	15,000kg

Its very interesting to see that coach and train travel has less impact on climate change than an electric car with 4 passengers, and if that same car is driven with just one passenger, then unsurprisingly the greenhouse gas emissions leap dramatically.

Flying takes the top spots with large CO₂e emissions and with the current climate crisis this may be a time to consider alternative modes of transport where possible.

We all have to make a change so try walking or cycling short distances, try to avoid the car for medium to long distances by hopping on a train or coach, only fly as a last resort.

Of course, I appreciate time and money are important and it is not always possible to take the least environmentally impactful mode of transport but whenever possible give it a go.

Note: the figures in the table above are based on average train, bus and aeroplane passenger capacity however if the numbers fall below this level then of course the figures for G CO₂e /km per passenger rise.

I thought it was interesting to include a 1^st class flight from London to Perth Australia to show the huge leap in relative emissions compared to an economy flight. Shocking!! This one flight is around 1.5 x the annual CO₂e footprint of an individual in UK.

2. We also thought it may be interesting to show you the total CO₂e footprints of various transport methods for a round trip between Bristol and Newcastle in UK, a distance of around 960km – please see below

When you think of all the people travelling by the various modes of transport shown above, then the overall tonnage of  CO₂e being sent into our atmosphere every day is frightening and so finally we will look at the annual CO₂e emissions coming from UK transport and the relative impact of each mode of transport on this total.

In UK, transport produced about 122 MT CO₂e in 2019 which is 27% of all our greenhouse gas emissions. Break this down one more level and we see that 91% of these emissions came from road transport – 111 MtCO₂e

The biggest contributors were cars and taxis at 61% of emissions (68 MtCO₂e)

Next Heavy Goods Vehicles at 18.5% emissions (19.5 MTCO₂e)                                   

Lastly Vans at 17% emissions (19 MTCO₂e)

All other modes of transport including rail and flying make up the rest.

On a national level if we want to reduce our overall greenhouse gas emissions produced by transport then we need to look at reducing our dependency on cars, lorries and vans. This we can do by a) reducing our individual car miles and b) transferring more freight to rail.

On a personal level, the greatest impact we can make is to stop flying.

Explanations:

CO₂e  – I often hear the question ‘Why is the carbon footprint of a commodity sometimes referred to as CO₂e?’

The reasons being –

1. There are seven greenhouse gases GHG) covered under the Kyoto Protocol: carbon dioxide (CO₂), methane (NH4), nitrous oxide (N2O), hydrofuorocarbons (HFCs), perfuorocarbons (PFCs), sulphur hexafluoride (SF6) and nitogren trifuroide (NF3). These are all greenhouse gases but some have a higher global warming potential than others and the largest contributor is carbon dioxide, so to simplify greenhouse gas emissions they are expressed as carbon dioxide equivalent (CO₂e).
2. There are also GHG emissions produced during the extraction, refining, and transportation of the fuel used to power the vehicle. For electric vehicles, this includes the generation and transmission of electricity.
3. In addition there are GHG emissions produced during the manufacture, transport, and marketing of a vehicle which must be included in the overall CO₂e.

The figures above are an average taken from a range of sources and although they can never be exact, they give an indication of the CO₂e output from various forms of transport and hopefully help individuals to understand the impact of their travelling preference on climate change.

Note: flight numbers are taken from the following website