While OPS eliminates onboard emissions at berth, consideration needs to be given to the emissions associated with power generation as such, as the source of this power will have a major influence on the overall emissions reduction achieved.
In particular, if renewable energy is used, near-zero emissions of all kinds of air pollutants can be achieved. Studies suggest that the average carbon dioxide emissions from the EU energy mix are around 50% lower than emissions from diesel engines. While coal-fired power plants emit more CO2, though, they have lower emissions of nitrogen oxides (compared with those associated with burning diesel with a 0.1 or 2.7 % sulphur content), particulate matter (ditto) and sulphur oxides (compared with diesel with a 2.7 % sulphur content).
In addition, stationary power plants are typically located some distance from densely populated areas, whereas dockside shipping emissions will often occur close to city centres as a consequence of a port´s typical location. Human exposure to air pollutants therefore also needs to be considered.
More information on emission factors of air pollutants and CO2 can be found in the Environment and Health section.