Which is more economical with resources, an e-tick or a paper ticket? I always get an e-ticket on my mobile, to save the environment and so on.

But then I thought well, am I really saving trees? I have to give my phone a full charge in order that it doesn't run out just when the conductor asks for my ticket. Which means that it needs electricity and a powerstation is burning some fosil fuels somewhere no doubt.

So that got me wondering, which would be better for the environment, if everyone got e-tickets on their phones. Or everyone got a paper ticket.

We shall assume:


We don't count manufacture of phone. (We assume we will have one
anyway). 
When phone is not used for buying tickets it is not charged up.
One ticket per day. 
Paper ticket is on A4 paper with ink.
E-ticket needs a full battery charge for the day.


My intuition is that an e-ticket is worse because to get the energy needed to power a phone a would think it wold require burning many hundreds of paper tickets. Is this intutition correct?
According to this study by the IATA, it costs \$1 to process an e-ticket, versus \$10 to process paper ticket. I assume this is only from the airline's point of view. You could argue that this is not the "environmental cost" you care about, but I just wanted to point it out.

I'm a bit confused by your phone charging assumptions, but according to this post, it costs close to 1 cent to charge a phone (10,000 mAh, at least). Also, you won't need your phone at full charge to use e-ticket.

On top of that, paper tickets also have a lot of costs associated with it, from the manufacturing process, logistics of getting the paper to your local store, getting it from the store to your home. Then we need to talk about recycling costs, etc.

So without the cost of the phone taken into account, I still think it's more efficient to use e-ticket.