Using electrical power for ships at berth instead of diesel-burning engines, ‘cold ironing’ can greatly reduce air pollution from ships. When ships use shore power, they connect into landside electricity for their power needs at berth, avoiding to run diesel-fueled auxiliary on-board engines.
According to estimations, shore power is able to limit air pollution from ships at berth by 95%.
Regarding the Port of Long Beach, it has completed over $185 million worth of dockside power hookups and other...
https://safety4sea.com/how-does-cold-ironing-affect-the-environment/