So is shipping really to blame for NOx increase?

Malcolm Latarche
Malcolm Latarche

22 June 2016


When it comes to emissions, shipping is often marked out for particular criticism by regulators and environmentalists alike with reports claiming that shipping’s share of pollutants is increasing as other sources are reducing. But is this really the case? In an article on the BBC today, a report by testing company Emissions Analytics suggests that motor vehicles are not quite as clean as they are touted and it is the newest models that are mostly at fault. Since the sources of NOx are not identifiable during air pollution testing, the argument that shipping must be to blame for increasing NOx measurements in cities near the coast may well be suspect. The report suggests that motor vehicle engine manufacturers (213 models from 13 different makers were used in compiling the report) are taking advantage of legal loopholes in the European regulations covering emissions and that most EGR systems on vehicles work at reduced capacity below ambient temperatures of 18°C in order to give better fuel economy figures. Emissions Analytics found that, in 2015, average mpg dropped for the first time in years. Probably because the car firms are concentrating more on cleaning up NOx. The Emissions Analytics data found the average Euro 5 vehicle was 3.6 times over the legal limit for NOx when it was above 18C. But that increased to 4.6 times over the limit, when the air temperature dropped. The latest generation of Euro 6 cars, on sale from September last year, were better averaging 2.9 times the limit above 18°C rising to 4.2 times the limit at lower temperatures, but the figures were skewed by three especially bad performers. Recent testing by the German, French and UK governments uncovered a similar trend. The article on the BBC website highlights a fact often reported by marine media that pollution control is a delicate balancing act and that regardless of engine type dealing with exhaust gas components separately often means that the result is increased pollution by another component. The down side of cutting NOx gases is that the engine uses more fuel resulting in higher CO2 output and cutting SOx removes an atmospheric refrigerant that some studies suggest could be deliberately released into the atmosphere to reduce global warming. It is probably unrealistic to hope that those blaming shipping for increased NOx in Europe will now moderate their attacks or even to rethink the need for the Baltic and North Sea SECAs being extended to cover NOx as well but at least the image of shipping as being the main source of pollution can now be questioned by industry representatives and perhaps some of the heat taken off.