Carbon pollution: trams vs cars - think about it.

I thought I saw every argument against trams in the context of Gold Coast tram extension to Burleigh, including such ridiculous ones as "trams are ugly" and "trams are outdated technology", but this is something new:

The comment appeared under this post:

I followed up to make sure I understood the argument, made by a retired "electronics technician & field application engineer" from North Carolina: 

Ok, so Wayne did not want to go back to his original "think about it" scenario, but also did not recant it.

Let's look at it, as if it was a "what if" question: 

What generates more carbon pollution for a typical commuter, a petrol car or an electric grid that powers an electric tram?

Let's assume that we have x commuters who can either go from A to B and back by their car or by a tram. Let's assume that they spend the same amount of time commuting: 30 minutes each way. This may happen in a city like Gold Coast between some locations (very few, because there is only one tram line) and during some times of the day:

 

Trams usually don't run at night, but since the argument uses a period of 24 hours, let's take that. The carbon intensity of electricity may vary greatly between countries/cities and times of day. At one end there is France with nuclear power plants supplanted by solar and wind, with carbon intensity of about 20 g/kWh throughout the day and night:

At the other is Poland with coal generation supplanted by wind, solar and gas, with carbon intensity between 600 and 900 g/kWh, let's say 800 on average on that day:

Queensland is perhaps more typical for the world. The electrical grid here is running on coal, solar and gas. Data from 20 April shows carbon intensity of 400-700, let's assume average of 600 g/kWh:

For the car, let's take my last petrol car, which was a 2012 Toyota Camry with average fuel consumption of 8.6 litres per 100 km. In Australia, on one hand the three most popular new cars are stupidly big petrol utes (pickups) with Ford Ranger burning 11.5 litres of petrol per 100 km on average, but on the other, the electric cars finally showed up and are growing quickly:

 

The trip distance was 11 km one way, 22 km total, which would burn 1.9 litres of petrol, times 2.3 kg of CO2 per litre =  4.8 kg of CO2.

Gold Coast uses Flexity 2 trams. For their energy consumption let's use the Energy Efficiency Assessment of Rail Freight Transport: Freight Tram in Berlin study, which calculated the use at 3.2 MJ for a fully loaded tram (47 tonnes), flat terrain and traveling for a distance of 250 m between two stops. In Gold Coast the stops are much farther apart (about 1 km), but let's assume the 3.2 MJ per 0.25 km stands. In one hour our tram would travel 22 km, and use 282 MJ of energy, which is 78 kWh, which at 600 g/kWh emits 47 kg of CO2, about 10x the amount of CO2 of a Toyota Camry. According to the argument that the energy needs to be available 24 hours per day, the total CO2 per tram is 1128 kg.

The Gold Coast tram patronage for the last 2 quarters of 2023 was 5.8 million, 32 thousand trips per day, using max 18 trams, gives us 1800 trips per day per tram, 900 passengers. The maximum distance one way is 20 km, with max travel time of 45 minutes, so 11 km, 30 minute trip seems like an acceptable average per commuter. When we divide the 1128 kg of CO2 per 900 passengers, we get 1.2 kg per passenger, compared to 4.8 kg when that person is driving a car. The tram, in this scenario emits 4 times less CO2 than a car... not "minuscule".

Things that may change these calculations: the energy mix is changing towards renewables; the energy generation when trams are not running should not be counted; the patronage/ridership per tram, the car fuel efficiency.

Things that will not change: geometry hates cars. Each car needs about 14 m2 parking space at each end of the trip. If the 16,000 people traveling by trams each day would drive instead, the city would need 16,000 extra car parking spaces in the city centre taking up at least 224,000 m2 of space.

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Update: patronage is defined as "A single one way movement of a person from an origin to a destination.", so the number of people per tram per day is half of what I had originally.