Performance assessment of state-of-the-art and novel methods for remote compliance monitoring of sulphur emissions from shipping

Abstract. Sulphur emissions to the air from sea-going and inland vessels were measured simultaneously by eight different, state-of-the-art and novel, monitoring systems during a six-week campaign at the Elbe River, at about 10 km distance to the port of Hamburg, Germany. Both, stationary, and airborne systems on unmanned aerial vehicles (UAV) were operated by four participating partners in a side-by-side measurement setup to observe the same emission sources under similar conditions. A novel laser spectrometer with significantly better precision specifications as compared to the other instruments was used for the first time for emission monitoring regarding MARPOL Annex VI regulations. The comparison took place in the Northern European Sulphur Emission Control Area (SECA) where the allowed Fuel Sulphur Content (FSC) is limited to 0.10 %Sm/m. In total, 966 plumes that originated from 436 different vessels were analysed in this study. At the same time, fuel samples, obtained from 34 different vessels, and bunker delivery notes (BDN) from five frequently monitored vessels were used as references to assess the uncertainties of the different systems. Most measurement systems tended to underestimate the FSC found from fuel samples and BDNs. A possible relation was seen to high relative humidities above 80 %. The lowest systematic deviations were observed for the airborne systems and the novel laser spectrometer. The latter showed the lowest total uncertainty of 0.05 %Sm/m (confidence level: 95 %) compared to other stationary sniffer systems whose total uncertainties range from 0.08 to 0.09 %Sm/m. The two UAV-borne systems showed total uncertainties of 0.07 and 0.09 %Sm/m, respectively. Overall, it was found that non-compliant vessels with an actual FSC of the combusted fuel above 0.15 to 0.19 %Sm/m can be detected by the compared systems with 95 % confidence.