Stavanger-headquartered shipping company Solvang has publicly submitted five years of sampling data from its exhaust gas cleaning (EGC) systems on board 13 vessels; the documentation, verified by Sintef, is said to firmly overrule a recent German report presenting figures heavily inflated by inaccurate emission factors and methodological errors.
Recent discussions about negative impact from open-loop exhaust gas cleaning systems in special areas like ports has made IMO call for validated sampling data. Such data have now been submitted by Solvang, via the Norwegian Maritime Authorities.
The dataset and scientific procedure have been verified by independent research institute Sintef before being handed over to Norwegian maritime authorities for processing to IMO for high-level environmental risk assessment. The validated figures show an EGC contamination at a fraction of the output brought by a recent report from a German institution.
The scientific methods used in detecting and determining elusive substances in water, imply advanced measurements and validation.
Solvang fleet director Tor Øyvind Ask said: “To get a valid product of one microgram (1µg = 1/1,000,000g) multiplied with a 45,000 to 100,000 litre flow, requires extreme accuracy. If you measure 2µg instead of 1µg of a substance, the emission factor will double and completely destroy the outcome. The main problem of the German report is the wrongly specified detection limits, which lead to non-detection values being wrongly assessed. Secondly, the contamination from other sources in the washwater has been disregarded. Thirdly, the level of substances in the outlet water has not been corrected for levels in the inlet water. The report cannot pass as a piece of scientific work.”
Ask, who is a member of several research bodies dealing with maritime pollution from ships’ engines. His first scientific project assessing EGC washwater was completed in 2016, investigating Solvang’s gas carrier Clipper Harald (Marintek report MT2016 F-152). Ask cites an example from the German report.
Ask said: “The detection of zinc in the outlet discharge water has no possible origin in the system. Still, the report assigns zinc to the exhaust gas cleaning process, instead of the inlet water, which is the obvious explanation. And shown beyond doubt in Solvang’s data submission.”
Since 2013, Solvang has sampled inlet sea water and outlet washwater from the EGC, comparing output with water quality standards published by the Norwegian Environment Agency (Miljødirektoratet). The method follows IMO guidelines for the vessels’ IAPP certificates. The results show similar figures for the predicted effect (PEC) and no-effect concentration (PNEC), pertaining to metals, PAH components, hydrocarbons, nitrate/nitrite, turbidity and PH. In total 41 components plus PH and turbidity for each sample, all according to official Norwegian criteria.
Ask continued: “Samples and analyses strongly acquit EGC washwater from any effect on the water surrounding our ships or anywhere beyond. Consistent data from 2013 to 2024 confirm that all traceable metals in EGC washwater independently exist in ambient seawater.”
The documents submitted to IMO discuss all elements measured in the washwater together with a detailed description of the complete water system, from the sea chest to overboard. The only concern Solvang evaluates in relation to the open-loop EGC is the possible accumulation of nickel and vanadium in closed ports. As for copper, a smart control of marine growth systems would very easily bring the values within acceptable limits. For a shorter period and in closed ports, MGP could also be switched off.
As part of the unburnt fuel (THC) in exhaust, PAH is being condensed in the scrubber and contained in sea water instead of being released to the atmosphere. Well-maintained diesel engines running on HFO or MGO emit 0.1-0.2 g/kWh. Shipping is estimated to contribute 0.5% of the total PAH emissions in Norway (newest data from 2015). Whether PAH emissions with the use of HFO is higher or lower than MGO and 0.5 % HFO, remains unsettled. In any case, the values are negligible.
Solvang’s washwater analyses show less than 10% of the maximum ∆PAH levels, and PAH carcinogenics close to or below detection levels.
Solvang’s description of the company’s environmental impact below sea and on land can be read here.
Image: Solvang refutes claims that scrubber washwater is harmful to the ocean environment, even in ports (source: Solvang)
