This story comes from the BBC Sport website. It was then picked up by other news outlets. Sky Sports included much of the same material, but the final bullet-point comes from their version of the story.
Man Utd defend decision to
fly 100 miles to Leicester for Premier League game
United say they
would not normally fly to the game but plans changed due to
"circumstances". There were reports of traffic congestion on the M6.
Flying is a
significant contributor to global warming and world leaders are meeting later
this month in an attempt to avoid a climate
catastrophe.
Aviation actually
only contributes about 3.5% of the world's global carbon emissions, according to
Carbon Brief, but only a very small
percentage of the world flies frequently, meaning those who do
are disproportionately responsible for these emissions.
Domestic flights are the least energy-efficient way to travel, as shown by the graphic below. France has moved to ban all short-haul domestic flights.
In response to BBC questions around the travel plans, United said they:
§ Have a policy to
purchase certified green electricity for all club buildings and facilities.
§ Achieved the Carbon
Trust Standard certification for a sixth consecutive year in 2020.
§ Achieved 12
consecutive years of energy and carbon reductions through the Manchester United
Energy & Carbon Reduction Programme.
- Since
the programme's launch in 2008, they have reduced annual carbon emissions
by over 2,700 tonnes, a reduction equivalent to emissions produced by 540
homes for a year.
Questions:
1) In the table, what hasn’t been explained?
2) What is the link between the two figures in the table for cars?
3) Why might the figure for a bus be less than for a car, but more than for a coach?
4) Look at the final bullet point. How many km driven by car are equivalent to the emissions produced by a home in a day?
Here are the figures used in the table (taken from a government document):
|
|
|
|
Diesel |
|
Activity |
Type |
Unit |
kg CO2 |
|
Cars (by size) |
Small car |
km |
0.14024 |
|
miles |
0.2257
|
||
|
Medium car |
km |
0.16877 |
|
|
miles |
0.27161 |
||
|
Large car |
km |
0.20763 |
|
|
miles |
0.33415 |
||
|
Average car |
km |
0.17152 |
|
|
miles |
0.27603 |
5) From the graphic in the story, a diesel car uses
171g per km. Where is that figure?
6) What is the conversion factor between km and miles (it’s not exactly 1.6) ?
7) Find the average of the km figures for the small, medium and large cars. Is this the same as the average car? Comment!
|
|
kg CO2 |
|
Diesel |
0.17152 |
|
Petrol |
0.18014 |
|
Hybrid |
0.11346 |
|
Battery Electric Vehicle |
0.05973 |
8) Comment on the choice to use diesel cars in the graphic.
9) Do hybrid cars use their batteries exactly half the time?
10) In the bus data (not yet shown), there is data about Local bus (not-London), Local London bus, Average local bus. Do you expect the London or the not-London figure to be higher? Will the average figure be halfway between the London and not-London figures, or closer to one of them (which one)?
Here is the bus data:
|
Type |
Unit |
kg CO2 |
|
Local bus (not London) |
passenger.km |
0.11974 |
|
Local London bus |
passenger.km |
0.08163 |
|
Average local bus |
passenger.km |
0.10391 |
|
Coach |
passenger.km |
0.02728 |
Questions:
11) Were you right?
12) How many days of extra CO2 did each player use?
Answers:
1) These are presumably average figures. Some cars will be more polluting than others because they have a bigger engine or are older, etc. The same will be true for planes. They haven’t explained why they used Diesel cars; I assume there are more petrol cars on the road. They haven’t explained the +121g fully. Does that give an equivalent total CO2 rating for a domestic flight of 254g per km?
2) A car with 1 passenger emits 171g per km. Dividing this by 4 for a car with 4 people in it, which gives 42.75g per person – which has been rounded to 43g here. Does this work? A car with an additional 3 people in it will be heavier and will therefore presumably emit more…
3) I guess: a bus will emit a lot more than a car, but carries a lot more people, so the amount per person is less. A coach stops less often than a bus (wasting fuel while idling), and is more likely to have a higher occupancy.
4) 2700 tonnes is the amount of CO2 produced by 540 homes in a year, so that is 5 tonnes = 5000kg per year. This is 5000kg / 365 per day = 13.7kg = 13700g. Dividing this by 171g, gives us 80km. (I don’t know whether ‘produced by 540 homes’ includes the CO2 the occupants emit in their cars, or whether this is just the CO2 emitted by the building itself, for heating, cooking, food, etc.)
5) It looks like they have used the ‘average car’ figure (which seems fair enough). This is 0.17152. It should be rounded to 172g.
6) Dividing the miles figure by the km one gives 1.609 every time. The next digit is either a 3 or a 4, so this is accurate to 4sf.
7) Working out the average of the small/medium/large, we get 0.172213. The ‘average car’ value given is 0.17152, which is slightly different. Presumably they didn’t work out this average but took into account that there are more medium cars on the road than small cars, etc. The figures given for each size of car are already averages and it is sometimes problematic to take an average of averages.
8) Presumably there are more petrol cars on the road than any other type. Did they choose diesel cars because it made cars look better (and therefore made flying look even worse)? Or did they note that hybrids and electric cars and even better, so it would be fair to use diesel as a kind of average figure?
9) Using half petrol and half electric gives 0.11994, whereas the hybrid figure is 0.11346, so it doesn’t use battery for half the km. (Using diesel and electric doesn’t work either.)
10) I expect not-London to be higher, because rural buses will have fewer passengers on them than city buses and London is a big city. There are many more not-London buses though, so I think the ‘average local bus’ figure will be closer to not-London and won’t be halfway between.
11) Halfway between the not-London and London figures is 0.100685 The average is more than this, so it is closer to not-London.
I wonder whether they will drive or fly home ...
Sources:
https://www.bbc.co.uk/sport/football/58938198
https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2019
