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Ship Exhaust, Port Noise and Local Cruise Ship Conflicts
Cruise ship calls can lead to local conflicts when energy needs and operations at berth clash with neighborhood interests in clean air and low noise. Air pollutants, greenhouse gas emissions and noise are separate issues. Their causes differ, and a measure taken at the quay does not automatically change the footprint of the entire voyage.
Exhaust emissions and noise at berth
Even when a ship is not moving in port, it needs energy to run systems such as ventilation, heating, cooling, pumps and controls. Without shore power, onboard generators may be used for this purpose. The IMO describes the associated local air emissions and noise. Air pollutants affect the surrounding air quality; noise affects people who live or work within earshot of port operations.
These local impacts are not the same as the ship’s contribution to greenhouse gas emissions. Air pollutants, audible noise and climate-impacting emissions are different impact categories. That is why discussion of a port call cannot usefully be summed up in a single general statement about “environmental impact.”
What shore power changes at the quay
A suitably equipped ship can draw electricity from shore while in port, replacing its onboard generators. The IMO identifies reduced local air pollution and noise as possible benefits when the main and auxiliary engines are switched off during this time. This describes a possibility at berth, not all emissions or noise from the ship and its entire voyage.
The impact also depends on whether the ship and port are equipped for the connection. For larger ships, both shore-side and onboard installations have to be specially designed; the IMO notes that only some ships and ports can use shore power. The reduction in climate-impacting emissions also depends on the source of the electricity supplied. The IMO explains the requirements for and potential effects of shore power.
Why local assessments differ
At least three questions therefore matter in any specific debate: Which impact is being considered—air pollution, noise or greenhouse gases? Does it occur during the ship’s stay at the quay or elsewhere during the voyage? And is the ship actually using shore power, or are its generators running? Different answers lead to different assessments. A possible reduction in impacts at berth matters for local air quality and noise levels, but on its own says nothing about the overall impact of the cruise.
Photo: Alesia Belaya
