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Comment by Kiro | Hacker News Reader

That's just ridiculous and no-one thinks that.

That is certainly the implication :-

"Environmental website ecopassenger.org calculates that Greta’s train journey to Davos, Switzerland, emitted just 44 kilograms of CO2, compared to an expected 262 kilograms had gone by plane."

They are trying to suggest that she chose this trip, because it is environmentally better, but actually irrespective of her choice, there was most likely a total of emmission of 306kg of CO2.

There could certainly a benefit, if the aim is to just fund transport that is more efficient and less pollutant. However, as mentioned earlier, it is unclear how the calculation is made and whether it is actually true when considering the wider requirements for the services - e.g. maintenance.

> Greta’s train journey to Davos

a journey that took around 25 hours

> compared to an expected 262 kilograms had gone by plane.

I still very much doubt that 262kg is per person. There's no way a plane emits tens of thousands of kilos of CO2 on a trip.

A passenger jet burns 10-15 liters of fuel pr km. Stockholm-Geneva is about 1600 km, so 3200 km round trip. So the numbers seem at least to be in the right ball park.

Here's a bunch of physics if you're into that sort of thing: https://therocketscienceblog.wordpress.com/2016/08/01/how-mu...

262 might be a high estimate. At 750 gallons/hour[0] and 9.57 kg CO2/gallon[1] that's about 18000kg for a 2.5 hour flight.

[0] https://eu.usatoday.com/story/travel/columnist/cox/2014/10/1...

[1] https://www.eia.gov/environment/emissions/co2_vol_mass.php

The 262 number was for total trip there and back. So about 5 hours of flight time in total.

There is a way :) Don't forget that each atom of carbon combines with two oxygens from the air.

I think you're going to be surprised.

A Boeing 747F has a fuel capacity of c.200,000kg, 200 metric tons (http://www.airliners.net/forum/viewtopic.php?t=738927).

It's mostly heptane (C7H16) and octane (C8H18). Rough calculation, that's 15x12 : 34x1 ratio of C to H (180:34).

So let's say 86% by mass, of 90% is Carbon.

But CO2 is mostly Oxygen from the air, about 12:32 ratio. So the Carbon is a quarter of the total mass.

This gives us (0.86 x 0.90 x 200tons) x4 as a ball park figure.

That's 600,000kg of CO2 produced by 200,000kg of fuel.

With 400 passengers that's 1500kg of CO2 per passenger if they burnt the full fuel capacity; ie that's a top bound estimate.

So ...

Meanwhile you might be surprised to find trees are made of CO2 with the oxygen removed. A large oak tree weighs c.5000kg and half of that is Carbon.

So very, very roughly you'll want to plant and grow to full size a large tree for every couple of long haul flights (to account for fuel only).

That's interesting. My assumption was that they were using individual examples to show the aggregate effect of large numbers of people making such choices, at a scale great enough to influence flight planning, but in a way that seems relevant to us as individuals. After all, there are hundreds of millions of people in Europe. If 1% of them make a small but material change in their travel habits that's millions of people taking fewer flights, which clearly could have a material effect on flight schedules. It would never have occurred to me that, in fact, they literally meant us to think that one person making that choice would individually have that effect.

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