Coal is the key to the worldwide structure of energy

[caraher]

6. shouldn't be too hard to guesstimate

If you take coal to be basically all carbon C + O2 --> CO2 means multiply coal mass consumed by the ratio of CO2 molecular mass (44 g/mol) to carbon mass per mol (12 g/mol).

Further simplifying by assuming the rate is in metric tons per day, for Titanic we get

825,000 kg coal/day * (44/12) = 3 million kg/day CO2

Some Googling reveals Titanic cruised at 21 knots, just shy of 40 km/hour. So in 25 hours Titanic could travel 40 * 21 = 840 km. This means it spewed 3 million kg/840 km = 3600 kg CO2/km

It's not clear precisely how many people were on the Titanic; one source puts the total at 2229 of whom 1316 were passengers. That works out to 3600/2229 = 1.6 kg/(person km) for all aboard and 2.7 kg/(passenger km) looking just at passengers.

That's quite a lot worse than most modern forms of transportation.