At the port, have they thought about using giant winch to pull the container ship in?

Question

Can someone calculate the effect on pollution and gas?

Answer 1

Pulling in the ship, which is only half of the process, is not the problem when docking a big ship to pier side. The problem is how  to arrest the inertia of the vessel so that it would not ram the pier. Even at a docking velocity of only 5 knots the kinetic energy of the vessel is still very large such that allowing it to bear on the pier without reducing the approach velocity can damage the pier and the vessel.Thus tug boats are needed to pull the vessel slightly outward to break that inertia as the ship gets closer to the pier side.

The question on pollution due to the use of tugboats therefore is irrelevant to the problem of docking a vessel.,

Answer 2

It would be impractical.  You'd have to send a boat out, attach the line, winch it in, find some way to stop the container ship so it doesn't crash into the dock, then move the winch to another pier and repeat the process for another ship.  A lot of wasted manpower, while the crew of the containership is basically sitting on their bums.  

Nowadays, large ships are equipped with bow and stern thrusters and can function and maneuver at low speeds without tugboats.  Besides, the dock workers are busy enough trying to unload all those containers and get the ships reloaded to be bothered with 'winch duty'.