Train costs from L'Aldea(next station after Tortosa) are about 13.50 one way and about 26euros return. You have to change at either Barcelona Sants or Franca but if you bought a ticket at the station to the airport it's all the same ticket. Just change platform for the airport shuttle. It takes between 2.5 to 3hours. Seats are comfy. Toilets. Often elec sockets to recharge stuff. I'm a big fan. The airport shuttle is usually very busy is about the worst I can say about it and if there's a gap between the train and the shuttle there are plenty of shops and cafés in Barcelona Sants with free wifi at mcd's too. I understand the attraction of Tortosa direct to the airport but there's no journey time difference and the bus seems expensive in comparison. Oh and parking is plentiful,easy and free at L'Aldea station. I've left my vehicle for a week at a time with no problem as have other friends.
I await rebuttals from bus groupies.
Bruixot