Protocol development for real-time ship fuel sulfur content determination using drone based plume sniffing microsensor system

Abstract Pollutants from the navigation sector are key contributors to emission inventories of most coastal cities with heavy port activities. The use of high fuel sulfur content (FSC) bunker oil by the ocean going vessels (OGVs) has been identified as a major source of sulfur dioxide (SO2). Many governments authorities all over the world, including Hong Kong government, have implemented the air pollution control regulations to cap FSC of fuel used by OGVs to 0.5%, from the existing 3.5%, to reduce SO2 emissions. However, the lack of efficient screening tools to identify non-compliant OGVs has prevented effective enforcement. This study developed and evaluated an unmanned aerial vehicle (UAV)-borne lightweight (750 g) microsensor system (MSS), which is capable of measuring ship plume SO2, NO2, NO, CO2, CO, and particulate matter in real-time. Extensive experiments were conducted on the sensor system performance in the laboratory and during field operations. The effects of cross-sensitivity and meteorological conditions were studied and incorporated to account for the measurement conditions in dispersed ship plumes. The SO2 to CO2 concentration ratio-based FSC expression was formulated as per the 2016 European Union Directive and Regulations. Furthermore, the impact of plume dilution on the accuracy of FSC measurement was investigated at different stages using the MSS, with and without the UAV in both simulated conditions and real-world scenarios at a safe distance from the OGV exhaust stacks. The study demonstrates the robustness of using UAV-borne sensor system for ship emissions sniffing and FSC determination. The results will assist the development of a technological framework for effective enforcement of ship emission control.